commit 0d85fceb1f1a6ce5a417d669df7f43ac562d88cd
Author: cat <zkdream@protonmail.com>
Date:   Mon Mar 11 20:20:28 2024 +0200

    push

diff --git a/.agda-lib b/.agda-lib
new file mode 100644
index 0000000..84329d8
--- /dev/null
+++ b/.agda-lib
@@ -0,0 +1,4 @@
+name: agda-symmetries
+depend:
+  .
+  cubical
diff --git a/Cubical/Structures/Arity.agda b/Cubical/Structures/Arity.agda
new file mode 100644
index 0000000..6c5a9c0
--- /dev/null
+++ b/Cubical/Structures/Arity.agda
@@ -0,0 +1,91 @@
+{-# OPTIONS --cubical --safe --exact-split #-}
+
+module Cubical.Structures.Arity where
+
+import Cubical.Data.Empty as ⊥
+open import Cubical.Foundations.Everything
+open import Cubical.Data.Fin public renaming (Fin to Arity)
+open import Cubical.Data.Fin.Recursive public using (rec)
+open import Cubical.Data.Nat
+open import Cubical.Data.Nat.Order
+open import Cubical.Data.List
+open import Cubical.Data.Sigma
+
+private
+  variable
+    ℓ : Level
+    A B : Type ℓ
+    k : ℕ
+
+ftwo : Arity (suc (suc (suc k)))
+ftwo = fsuc fone
+
+lookup : ∀ (xs : List A) -> Arity (length xs) -> A
+lookup [] num = ⊥.rec (¬Fin0 num)
+lookup (x ∷ xs) (zero , prf) = x
+lookup (x ∷ xs) (suc num , prf) = lookup xs (num , pred-≤-pred prf)
+
+tabulate : ∀ n -> (Arity n -> A) -> List A
+tabulate zero ^a = []
+tabulate (suc n) ^a = ^a fzero ∷ tabulate n (^a ∘ fsuc)
+
+length-tabulate : ∀ n -> (^a : Arity n → A) -> length (tabulate n ^a) ≡ n
+length-tabulate zero ^a = refl
+length-tabulate (suc n) ^a = cong suc (length-tabulate n (^a ∘ fsuc))
+
+tabulate-lookup : ∀ (xs : List A) -> tabulate (length xs) (lookup xs) ≡ xs
+tabulate-lookup [] = refl
+tabulate-lookup (x ∷ xs) =
+   _ ≡⟨ cong (λ z -> x ∷ tabulate (length xs) z) (funExt λ _ -> cong (lookup xs) (Σ≡Prop (λ _ -> isProp≤) refl)) ⟩
+   _ ≡⟨ cong (x ∷_) (tabulate-lookup xs) ⟩
+   _ ∎
+
+arity-n≡m : ∀ {n m} -> (a : Arity n) -> (b : Arity m) -> (p : n ≡ m) -> a .fst ≡ b .fst -> PathP (λ i -> Arity (p i)) a b
+arity-n≡m (v , a) (w , b) p q = ΣPathP (q , toPathP (isProp≤ _ _))
+
+lookup-tabulate : ∀ n (^a : Arity n -> A) -> PathP (λ i -> (Arity (length-tabulate n ^a i) -> A)) (lookup (tabulate n ^a)) ^a
+lookup-tabulate zero ^a = funExt (⊥.rec ∘ ¬Fin0)
+lookup-tabulate (suc n) ^a = toPathP (funExt lemma) i (zero , p) =  ^a (0 , toPathP {A = λ j -> 0 < suc (length-tabulate n (^a ∘ fsuc) (~ j))} {!   !} i) toPathP (sym (transport-filler _ _) ∙ cong ^a (Σ≡Prop (λ _ -> isProp≤) refl)) i suc-≤-suc (zero-≤ {n = n}) toPathP {x = suc-≤-suc (zero-≤ {n = n})} {!   !} i
+  where
+  lemma : _
+  lemma (zero , p) = sym (transport-filler _ _) ∙ cong ^a (Σ≡Prop (λ _ -> isProp≤) refl)
+  TODO: Cleanup this mess
+  lemma (suc w , p) =
+    _ ≡⟨ sym (transport-filler _ _) ⟩
+    _ ≡⟨ congP (λ i f -> f (arity-n≡m (w ,
+       pred-≤-pred
+       (transp
+        (λ i → suc w < suc (length-tabulate n (λ x → ^a (fsuc x)) (~ i)))
+        i0 p)) (w , pred-≤-pred p) (length-tabulate n (^a ∘ fsuc)) refl i)) (lookup-tabulate n (^a ∘ fsuc)) ⟩
+    _ ≡⟨ cong ^a (Σ≡Prop (λ _ -> isProp≤) refl) ⟩
+    _ ∎
+
+lookup2≡i : ∀ (i : Arity 2 -> A) -> lookup (i fzero ∷ i fone ∷ []) ≡ i
+lookup2≡i i = funExt lemma
+  where
+  lemma : _
+  lemma (zero , p) = cong i (Σ≡Prop (λ _ -> isProp≤) refl)
+  lemma (suc zero , p) = cong i (Σ≡Prop (λ _ -> isProp≤) refl)
+  lemma (suc (suc n) , p) = ⊥.rec (¬m+n<m {m = 2} p)
+
+◼ : Arity 0 -> A
+◼ = ⊥.rec ∘ ¬Fin0
+
+infixr 30 _▸_
+
+_▸_ : ∀ {n} -> A -> (Arity n -> A) -> Arity (suc n) -> A
+_▸_ {n = zero} x f i = x
+_▸_ {n = suc n} x f i = lookup (x ∷ tabulate (suc n) f) (subst Arity (congS (suc ∘ suc) (sym (length-tabulate n (f ∘ fsuc)))) i)
+
+⟪⟫ : Arity 0 -> A
+⟪⟫ = lookup []
+
+⟪_⟫ : (a : A) -> Arity 1 -> A
+⟪ a ⟫ = lookup [ a ]
+
+⟪_⨾_⟫ : (a b : A) -> Arity 2 -> A
+⟪ a ⨾ b ⟫ = lookup (a ∷ b ∷ [])
+
+⟪_⨾_⨾_⟫ : (a b c : A) -> Arity 3 -> A
+⟪ a ⨾ b ⨾ c ⟫ = lookup (a ∷ b ∷ c ∷ [])
+ 
\ No newline at end of file
diff --git a/Cubical/Structures/Coh.agda b/Cubical/Structures/Coh.agda
new file mode 100644
index 0000000..16199d6
--- /dev/null
+++ b/Cubical/Structures/Coh.agda
@@ -0,0 +1,34 @@
+{-# OPTIONS --cubical --safe --exact-split #-}
+
+module Cubical.Structures.Coh where
+
+open import Cubical.Foundations.Everything
+open import Cubical.Foundations.Equiv
+open import Cubical.Functions.Image
+open import Cubical.HITs.PropositionalTruncation as P
+open import Cubical.Data.Nat
+open import Cubical.Data.Fin
+open import Cubical.Data.List as L
+open import Cubical.Data.Sigma
+open import Cubical.Reflection.RecordEquiv
+open import Cubical.HITs.SetQuotients as Q
+open import Agda.Primitive
+
+open import Cubical.Structures.Sig
+open import Cubical.Structures.Str
+open import Cubical.Structures.Tree
+open import Cubical.Structures.Eq
+
+record CohSig (e n : Level) : Type (ℓ-max (ℓ-suc e) (ℓ-suc n)) where
+  field
+    name : Type e
+    free : name -> Type n
+open CohSig public
+
+data EqSeq {a} {A : Type a} : A -> A -> Type a where
+  nil : ∀ {a} -> EqSeq a a
+  cons : ∀ {a b c} -> a ≡ b -> EqSeq b c -> EqSeq a c
+
+evalEqSeq : ∀ {a} {A : Type a} -> {a b : A} -> EqSeq a b -> a ≡ b
+evalEqSeq nil = refl
+evalEqSeq (cons p e) = p ∙ evalEqSeq e
diff --git a/Cubical/Structures/Eq.agda b/Cubical/Structures/Eq.agda
new file mode 100644
index 0000000..a1bf776
--- /dev/null
+++ b/Cubical/Structures/Eq.agda
@@ -0,0 +1,60 @@
+{-# OPTIONS --cubical --safe --exact-split #-}
+
+module Cubical.Structures.Eq where
+
+open import Cubical.Foundations.Everything
+open import Cubical.Foundations.Equiv
+open import Cubical.Functions.Image
+open import Cubical.HITs.PropositionalTruncation as P
+open import Cubical.Data.Nat
+open import Cubical.Data.Fin
+open import Cubical.Data.List as L
+open import Cubical.Data.Sigma
+open import Cubical.Data.Empty as ⊥
+open import Cubical.Data.Sum as ⊎
+open import Cubical.Reflection.RecordEquiv
+open import Cubical.HITs.SetQuotients as Q
+open import Agda.Primitive
+
+open import Cubical.Structures.Sig
+open import Cubical.Structures.Str
+open import Cubical.Structures.Tree
+
+record EqSig (e n : Level) : Type (ℓ-max (ℓ-suc e) (ℓ-suc n)) where
+  field
+    name : Type e
+    free : name -> Type n
+open EqSig public
+
+FinEqSig : (e : Level) -> Type (ℓ-max (ℓ-suc e) (ℓ-suc ℓ-zero))
+FinEqSig = FinSig
+
+finEqSig : {e : Level} -> FinEqSig e -> EqSig e ℓ-zero
+name (finEqSig σ) = σ .fst
+free (finEqSig σ) = Fin ∘ σ .snd
+
+emptyEqSig : EqSig ℓ-zero ℓ-zero
+name emptyEqSig = ⊥.⊥
+free emptyEqSig = ⊥.rec
+
+sumEqSig : {e n e' n' : Level} -> EqSig e n -> EqSig e' n' -> EqSig (ℓ-max e e') (ℓ-max n n')
+name (sumEqSig σ τ) = (name σ) ⊎ (name τ)
+free (sumEqSig {n' = n} σ τ) (inl x) = Lift {j = n} ((free σ) x)
+free (sumEqSig {n = n} σ τ) (inr x) = Lift {j = n} ((free τ) x)
+
+module _ {f a e n : Level} (σ : Sig f a) (τ : EqSig e n) where
+  TODO: refactor as (Tree σ Unit -> Tree σ X) × (Tree σ Unit -> Tree σ X) ?
+  seq : Type (ℓ-max (ℓ-max (ℓ-max f a) e) n)
+  seq = (e : τ .name) -> Tree σ (τ .free e) × Tree σ (τ .free e)
+
+emptySEq : seq emptySig emptyEqSig
+emptySEq n = ⊥.rec n
+
+module _ {f a e n s : Level} {σ : Sig f a} {τ : EqSig e n} where
+  type of structure satisfying equations
+  TODO: refactor as a coequaliser
+  infix 30 _⊨_
+  _⊨_ : struct s σ -> (ε : seq σ τ) -> Type (ℓ-max s (ℓ-max e n))
+  𝔛 ⊨ ε = (eqn : τ .name) (ρ : τ .free eqn -> 𝔛 .car)
+       -> sharp σ 𝔛 ρ (ε eqn .fst) ≡ sharp σ 𝔛 ρ (ε eqn .snd)
+
diff --git a/Cubical/Structures/Free.agda b/Cubical/Structures/Free.agda
new file mode 100644
index 0000000..97fde55
--- /dev/null
+++ b/Cubical/Structures/Free.agda
@@ -0,0 +1,192 @@
+{-# OPTIONS --cubical --safe --exact-split #-}
+
+module Cubical.Structures.Free where
+
+open import Cubical.Foundations.Everything
+open import Cubical.Foundations.Equiv
+open import Cubical.Functions.Image
+open import Cubical.HITs.PropositionalTruncation as P
+open import Cubical.Data.Nat
+open import Cubical.Data.List as L
+open import Cubical.Data.Sigma
+open import Cubical.Reflection.RecordEquiv
+open import Cubical.HITs.SetQuotients as Q
+open import Agda.Primitive
+
+open import Cubical.Structures.Sig
+open import Cubical.Structures.Str
+open import Cubical.Structures.Tree
+open import Cubical.Structures.Eq
+
+module Definition {f a e n s : Level} (σ : Sig f a) (τ : EqSig e (ℓ-max n s)) (ε : seq {n = ℓ-max n s} σ τ) where
+  ns : Level
+  ns = ℓ-max n s
+
+  record Free (ℓ ℓ' : Level) (h : HLevel) : Type (ℓ-suc (ℓ-max ℓ' (ℓ-max ℓ (ℓ-max f (ℓ-max a (ℓ-max e ns)))))) where
+    field
+      F : (X : Type ℓ) -> Type (ℓ-max ℓ ns)
+      η : {X : Type ℓ} -> X -> F X
+      α : {X : Type ℓ} -> sig σ (F X) -> F X
+      sat : {X : Type ℓ} -> < F X , α > ⊨ ε
+      isFree : {X : Type ℓ}
+        {𝔜 : struct (ℓ-max ℓ' ns) σ}
+        (H : isOfHLevel h (𝔜 .car)) (ϕ : 𝔜 ⊨ ε)
+        -> isEquiv (\(f : structHom {x = ℓ-max ℓ ns} < F X , α > 𝔜) -> f .fst ∘ η)
+
+    ext : {X : Type ℓ} {𝔜 : struct (ℓ-max ℓ' ns) σ}
+          (H : isOfHLevel h (𝔜 .car)) (ϕ : 𝔜 ⊨ ε)
+       -> (hom : X -> 𝔜 .car) -> structHom < F X , α > 𝔜
+    ext H ϕ = invIsEq (isFree H ϕ)
+
+    ext-β : {X : Type ℓ} {𝔜 : struct (ℓ-max ℓ' ns) σ}
+            (H : isOfHLevel h (𝔜 .car)) (ϕ : 𝔜 ⊨ ε) (Hom : structHom < F X , α > 𝔜)
+         -> ext H ϕ (Hom .fst ∘ η) ≡ Hom
+    ext-β H ϕ = retIsEq (isFree H ϕ)
+
+    ext-η : {X : Type ℓ} {𝔜 : struct (ℓ-max ℓ' ns) σ}
+            (H : isOfHLevel h (𝔜 .car)) (ϕ : 𝔜 ⊨ ε) (h : X -> 𝔜 .car)
+         -> (ext H ϕ h .fst) ∘ η ≡ h
+    ext-η H ϕ = secIsEq (isFree H ϕ)
+
+    hom≡ : {X : Type ℓ} {𝔜 : struct (ℓ-max ℓ' ns) σ}
+        -> (H : isOfHLevel h (𝔜 .car)) (ϕ : 𝔜 ⊨ ε)
+        -> (H1 H2 : structHom < F X , α > 𝔜)
+        -> H1 .fst ∘ η ≡ H2 .fst ∘ η
+        -> H1 ≡ H2
+    hom≡ H ϕ H1 H2 α = sym (ext-β H ϕ H1) ∙ cong (ext H ϕ) α ∙ ext-β H ϕ H2
+
+  open Free
+  module _ {ℓ} {A : Type ℓ} (𝔛 : Free ℓ ℓ 2) (𝔜 : Free ℓ ℓ 2) (isSet𝔛 : isSet (𝔛 .F A)) (isSet𝔜 : isSet (𝔜 .F A)) where
+    private
+      str𝔛 : struct (ℓ-max (ℓ-max n s) ℓ) σ
+      str𝔛 = < 𝔛 .F A , 𝔛 .α >
+
+      str𝔜 : struct (ℓ-max (ℓ-max n s) ℓ) σ
+      str𝔜 = < 𝔜 .F A , 𝔜 .α >
+    
+      ϕ1 : structHom str𝔛 str𝔜
+      ϕ1 = ext 𝔛 isSet𝔜 (𝔜 .sat) (𝔜 .η)
+
+      ϕ2 : structHom str𝔜 str𝔛
+      ϕ2 = ext 𝔜 isSet𝔛 (𝔛 .sat) (𝔛 .η)
+
+      ϕ1∘ϕ2 : structHom str𝔜 str𝔜
+      ϕ1∘ϕ2 = structHom∘ str𝔜 str𝔛 str𝔜 ϕ1 ϕ2
+
+      ϕ2∘ϕ1 : structHom str𝔛 str𝔛
+      ϕ2∘ϕ1 = structHom∘ str𝔛 str𝔜 str𝔛 ϕ2 ϕ1
+
+      ϕ1∘ϕ2≡ : ϕ1∘ϕ2 .fst ∘ 𝔜 .η ≡ idHom str𝔜 .fst ∘ 𝔜 .η
+      ϕ1∘ϕ2≡ =
+          ϕ1 .fst ∘ ((ext 𝔜 isSet𝔛 (𝔛 .sat) (𝔛 .η) .fst) ∘ 𝔜 .η)
+        ≡⟨ congS (ϕ1 .fst ∘_) (ext-η 𝔜 isSet𝔛 (𝔛 .sat) (𝔛 .η)) ⟩
+          ext 𝔛 isSet𝔜 (𝔜 .sat) (𝔜 .η) .fst ∘ 𝔛 .η
+        ≡⟨ ext-η 𝔛 isSet𝔜 (𝔜 .sat) (𝔜 .η) ⟩
+          𝔜 .η ∎
+
+      ϕ2∘ϕ1≡ : ϕ2∘ϕ1 .fst ∘ 𝔛 .η ≡ idHom str𝔛 .fst ∘ 𝔛 .η
+      ϕ2∘ϕ1≡ =
+          ϕ2 .fst ∘ ((ext 𝔛 isSet𝔜 (𝔜 .sat) (𝔜 .η) .fst) ∘ 𝔛 .η)
+        ≡⟨ congS (ϕ2 .fst ∘_) (ext-η 𝔛 isSet𝔜 (𝔜 .sat) (𝔜 .η)) ⟩
+          ext 𝔜 isSet𝔛 (𝔛 .sat) (𝔛 .η) .fst ∘ 𝔜 .η
+        ≡⟨ ext-η 𝔜 isSet𝔛 (𝔛 .sat) (𝔛 .η) ⟩
+          𝔛 .η ∎
+
+    freeIso : Iso (𝔛 .F A) (𝔜 .F A)
+    freeIso = iso (ϕ1 .fst) (ϕ2 .fst)
+      (λ x -> congS (λ f -> f .fst x) (hom≡ 𝔜 isSet𝔜 (𝔜 .sat) ϕ1∘ϕ2 (idHom str𝔜) ϕ1∘ϕ2≡))
+      (λ x -> congS (λ f -> f .fst x) (hom≡ 𝔛 isSet𝔛 (𝔛 .sat) ϕ2∘ϕ1 (idHom str𝔛) ϕ2∘ϕ1≡))
+
+  record FreeAux (ℓ ℓ' : Level) (h : HLevel) (F : (X : Type ℓ) -> Type (ℓ-max ℓ ns)) : Type (ℓ-suc (ℓ-max ℓ' (ℓ-max ℓ (ℓ-max f (ℓ-max a (ℓ-max e ns)))))) where
+    field
+      η : {X : Type ℓ} -> X -> F X
+      α : {X : Type ℓ} -> sig σ (F X) -> F X
+      sat : {X : Type ℓ} -> < F X , α > ⊨ ε
+      isFree : {X : Type ℓ}
+        {𝔜 : struct (ℓ-max ℓ' ns) σ}
+        (H : isOfHLevel h (𝔜 .car)) (ϕ : 𝔜 ⊨ ε)
+        -> isEquiv (\(f : structHom {x = ℓ-max ℓ ns} < F X , α > 𝔜) -> f .fst ∘ η)
+
+  isoAux : {ℓ ℓ' : Level} {h : HLevel} ->
+           Iso (Σ[ F ∈ ((X : Type ℓ) -> Type (ℓ-max ℓ ns)) ] FreeAux ℓ ℓ' h F) (Free ℓ ℓ' h)
+  isoAux {ℓ = ℓ} {ℓ' = ℓ'} {h = h} = iso to from (λ _ -> refl) (λ _ -> refl)
+    where
+    to : Σ[ F ∈ ((X : Type ℓ) -> Type (ℓ-max ℓ ns)) ] FreeAux ℓ ℓ' h F -> Free ℓ ℓ' h
+    Free.F (to (F , aux)) = F
+    Free.η (to (F , aux)) = FreeAux.η aux
+    Free.α (to (F , aux)) = FreeAux.α aux
+    Free.sat (to (F , aux)) = FreeAux.sat aux
+    Free.isFree (to (F , aux)) = FreeAux.isFree aux
+
+    from : Free ℓ ℓ' h -> Σ[ F ∈ ((X : Type ℓ) -> Type (ℓ-max ℓ ns)) ] FreeAux ℓ ℓ' h F
+    fst (from free) = Free.F free
+    FreeAux.η (snd (from free)) = Free.η free
+    FreeAux.α (snd (from free)) = Free.α free
+    FreeAux.sat (snd (from free)) = Free.sat free
+    FreeAux.isFree (snd (from free)) = Free.isFree free
+
+
+constructions of a free structure on a signature and equations
+TODO: generalise the universe levels!!
+using a HIT
+ module Construction {f a e n : Level} (σ : Sig f a) (τ : EqSig e n) (ε : seq σ τ) where
+ 
+   data Free (X : Type n) : Type (ℓ-suc (ℓ-max f (ℓ-max a (ℓ-max e n)))) where
+       η : X -> Free X
+       α : sig σ (Free X) -> Free X
+       sat : mkStruct (Free X) α ⊨ ε
+
+  freeStruct : (X : Type) -> struct σ
+  car (freeStruct X) = Free X
+  alg (freeStruct _) = α
+
+  module _ (X : Type) (𝔜 : struct σ) (ϕ : 𝔜 ⊨ ε) where
+
+     private
+       Y = 𝔜 .fst
+       β = 𝔜 .snd
+
+     ext : (h : X -> Y) -> Free X -> Y
+     ext h (η x) = h x
+     ext h (α (f , o)) = β (f , (ext h ∘ o))
+     ext h (sat e ρ i) = ϕ e (ext h ∘ ρ) {!i!}
+
+     module _  where
+       postulate
+         Fr : Type (ℓ-max (ℓ-max f a) n)
+         Fα : sig σ Fr -> Fr
+         Fs : sat σ τ ε (Fr , Fα)
+
+       module _ (Y : Type (ℓ-max (ℓ-max f a) n)) (α : sig σ Y -> Y) where
+         postulate
+           Frec : sat σ τ ε (Y , α) -> Fr -> Y
+           Fhom : (p : sat σ τ ε (Y , α)) -> walgIsH σ (Fr , Fα) (Y , α) (Frec p)
+           Feta : (p : sat σ τ ε (Y , α)) (h : Fr -> Y) -> walgIsH σ (Fr , Fα) (Y , α) h -> Frec p ≡ h
+    
+module Construction2 (σ : Sig ℓ-zero ℓ-zero) (τ : EqSig ℓ-zero ℓ-zero) (ε : seq σ τ) where 
+data _≈_ {X : Type} : Tree σ X -> Tree σ X -> Type (ℓ-suc ℓ-zero) where
+    ≈-refl : ∀ t -> t ≈ t
+    ≈-sym : ∀ t s -> t ≈ s -> s ≈ t
+    ≈-trans : ∀ t s r -> t ≈ s -> s ≈ r -> t ≈ r
+    ≈-cong : (f : σ .symbol) -> {t s : σ .arity f -> Tree σ X}
+          -> ((a : σ .arity f) -> t a ≈ s a)
+          -> node (f , t) ≈ node (f , s)
+    ≈-eqs : (𝔜 : struct {ℓ-zero} {ℓ-zero} {ℓ-zero} σ) (ϕ : 𝔜 ⊨ ε)
+         -> (e : τ .name) (ρ : X -> 𝔜 .car)
+         -> ∀ t s -> sharp σ {𝔜 = 𝔜} ρ t ≡ sharp σ {𝔜 = 𝔜} ρ s
+         -> t ≈ s
+
+Free : Type -> Type₁
+Free X = Tree σ X / _≈_
+
+freeAlg : (X : Type) -> sig σ (Free X) -> Free X
+freeAlg X (f , i) = Q.[ node (f , {!!}) ] needs choice?
+
+freeStruct : (X : Type) -> struct σ
+freeStruct X = Free X , freeAlg X
+
+module _ (X : Type) (𝔜 : struct σ) (ϕ : 𝔜 ⊨ ε) where
+
+  private
+    Y = 𝔜 .fst
+    β = 𝔜 .snd
diff --git a/Cubical/Structures/Gpd/Mon/Free.agda b/Cubical/Structures/Gpd/Mon/Free.agda
new file mode 100644
index 0000000..e7390b3
--- /dev/null
+++ b/Cubical/Structures/Gpd/Mon/Free.agda
@@ -0,0 +1,4 @@
+TODO: Define free monoidal groupoids as a HIT
+
+{-# OPTIONS --cubical --safe --exact-split #-}
+module Cubical.Structures.Gpd.Mon.Free where
diff --git a/Cubical/Structures/Gpd/Mon/List.agda b/Cubical/Structures/Gpd/Mon/List.agda
new file mode 100644
index 0000000..ec1f1ba
--- /dev/null
+++ b/Cubical/Structures/Gpd/Mon/List.agda
@@ -0,0 +1,4 @@
+TODO: Show that List A has all the monoidal coherences
+
+{-# OPTIONS --cubical --safe --exact-split #-}
+module Cubical.Structures.Gpd.Mon.List where
\ No newline at end of file
diff --git a/Cubical/Structures/Gpd/SMon/Free.agda b/Cubical/Structures/Gpd/SMon/Free.agda
new file mode 100644
index 0000000..62c455c
--- /dev/null
+++ b/Cubical/Structures/Gpd/SMon/Free.agda
@@ -0,0 +1,4 @@
+TODO: Define free symmetric monoidal groupoids as a HIT
+
+{-# OPTIONS --cubical --safe --exact-split #-}
+module Cubical.Structures.Gpd.SMon.Free where
diff --git a/Cubical/Structures/Gpd/SMon/SList.agda b/Cubical/Structures/Gpd/SMon/SList.agda
new file mode 100644
index 0000000..09f60f5
--- /dev/null
+++ b/Cubical/Structures/Gpd/SMon/SList.agda
@@ -0,0 +1,115 @@
+{-# OPTIONS --cubical --safe --exact-split #-}
+
+module Cubical.Structures.Gpd.SMon.SList where
+
+open import Cubical.Foundations.Everything
+open import Cubical.Data.Sigma
+
+infixr 20 _∷_
+
+data SList {a} (A : Type a) : Type a where
+  [] : SList A
+  _∷_ : (a : A) -> (as : SList A) -> SList A
+  swap : (a b : A) (cs : SList A)
+      -> a ∷ b ∷ cs ≡ b ∷ a ∷ cs
+  swap⁻¹ : (a b : A) (cs : SList A)
+       -> swap a b cs ≡ sym (swap b a cs)
+  hexagon– : (a b c : A) (cs : SList A)
+          -> a ∷ b ∷ c ∷ cs ≡ c ∷ b ∷ a ∷ cs
+  hexagon↑ : (a b c : A) (cs : SList A)
+           -> Square (\i -> b ∷ swap a c cs i) (hexagon– a b c cs)
+                     (swap b a (c ∷ cs)) (swap b c (a ∷ cs))
+  hexagon↓ : (a b c : A) (cs : SList A)
+           -> Square (hexagon– a b c cs) (swap a c (b ∷ cs))
+                     (\i -> a ∷ swap b c cs i) (\i -> c ∷ swap b a cs i)
+  isGpdSList : isGroupoid (SList A)
+
+pattern [_] a = a ∷ []
+
+private
+  variable
+    ℓ : Level
+    A : Type ℓ
+
+swap² : (a b : A) (cs : SList A)
+     -> swap a b cs ∙ swap b a cs ≡ refl
+swap² a b cs = cong (_∙ swap b a cs) (swap⁻¹ a b cs) ∙ lCancel (swap b a cs)
+
+hexagon : (a b c : A) (cs : SList A)
+       -> (swap a b (c ∷ cs) ∙ cong (b ∷_) (swap a c cs) ∙ swap b c (a ∷ cs))
+        ≡ cong (a ∷_) (swap b c cs) ∙ swap a c (b ∷ cs) ∙ cong (c ∷_) (swap a b cs)
+hexagon a b c cs =
+  let hex-up = PathP→compPathL (hexagon↑ a b c cs)
+      hex-dn = PathP→compPathR (hexagon↓ a b c cs)
+  in
+    swap a b (c ∷ cs) ∙ cong (b ∷_) (swap a c cs) ∙ swap b c (a ∷ cs)
+  ≡⟨ cong (_∙ cong (b ∷_) (swap a c cs) ∙ swap b c (a ∷ cs)) (swap⁻¹ a b (c ∷ cs)) ⟩
+    sym (swap b a (c ∷ cs)) ∙ cong (b ∷_) (swap a c cs) ∙ swap b c (a ∷ cs)
+  ≡⟨ hex-up ⟩
+    hexagon– a b c cs
+  ≡⟨ hex-dn ⟩
+    cong (a ∷_) (swap b c cs) ∙ swap a c (b ∷ cs) ∙ cong (c ∷_) (sym (swap b a cs))
+  ≡⟨ assoc (cong (a ∷_) (swap b c cs)) (swap a c (b ∷ cs)) (cong (c ∷_) (sym (swap b a cs))) ⟩
+    (cong (a ∷_) (swap b c cs) ∙ swap a c (b ∷ cs)) ∙ cong (c ∷_) (sym (swap b a cs))
+  ≡⟨ cong ((cong (a ∷_) (swap b c cs) ∙ swap a c (b ∷ cs)) ∙_) (cong (cong (c ∷_)) (sym (swap⁻¹ a b cs))) ⟩
+    (cong (a ∷_) (swap b c cs) ∙ swap a c (b ∷ cs)) ∙ cong (c ∷_) (swap a b cs)
+  ≡⟨ sym (assoc (cong (a ∷_) (swap b c cs)) (swap a c (b ∷ cs)) (cong (c ∷_) (swap a b cs))) ⟩
+    cong (a ∷_) (swap b c cs) ∙ swap a c (b ∷ cs) ∙ cong (c ∷_) (swap a b cs)
+  ∎
+
+_++_ : SList A -> SList A -> SList A
+[] ++ bs = bs
+(a ∷ as) ++ bs = a ∷ (as ++ bs)
+swap a b as i ++ bs = swap a b (as ++ bs) i
+swap⁻¹ a b as i j ++ bs = swap⁻¹ a b (as ++ bs) i j
+hexagon– a b c as i ++ bs = hexagon– a b c (as ++ bs) i
+hexagon↑ a b c as i j ++ bs = hexagon↑ a b c (as ++ bs) i j
+hexagon↓ a b c as i j ++ bs = hexagon↓ a b c (as ++ bs) i j
+isGpdSList as cs p q u v i j k ++ bs =
+  isGpdSList (as ++ bs) (cs ++ bs) (cong (_++ bs) p) (cong (_++ bs) q)
+             (cong (cong (_++ bs)) u) (cong (cong (_++ bs)) v) i j k
+
+++-unitl : (as : SList A) -> [] ++ as ≡ as
+++-unitl as = refl
+
+++-unitr : (as : SList A) -> as ++ [] ≡ as
+++-unitr [] = refl
+++-unitr (a ∷ as) = cong (a ∷_) (++-unitr as)
+++-unitr (swap a b as i) j = swap a b (++-unitr as j) i
+++-unitr (swap⁻¹ a b as i j) k = swap⁻¹ a b (++-unitr as k) i j
+++-unitr (hexagon– a b c as i) j = hexagon– a b c (++-unitr as j) i
+++-unitr (hexagon↑ a b c as i j) k = hexagon↑ a b c (++-unitr as k) i j
+++-unitr (hexagon↓ a b c as i j) k = hexagon↓ a b c (++-unitr as k) i j
+++-unitr (isGpdSList as cs p q u v i j k) l =
+  isGpdSList (++-unitr as l) (++-unitr cs l) (cong (\z -> ++-unitr z l) p) (cong (\z -> ++-unitr z l) q)
+             (cong (cong (\z -> ++-unitr z l)) u) (cong (cong (\z -> ++-unitr z l)) v) i j k
+
+++-assocr : (as bs cs : SList A) -> (as ++ bs) ++ cs ≡ as ++ (bs ++ cs)
+++-assocr [] bs cs = refl
+++-assocr (a ∷ as) bs cs = cong (a ∷_) (++-assocr as bs cs)
+++-assocr (swap a b as i) bs cs j = swap a b (++-assocr as bs cs j) i
+++-assocr (swap⁻¹ a b as i j) bs cs k = swap⁻¹ a b (++-assocr as bs cs k) i j
+++-assocr (hexagon– a b c as i) bs cs j = hexagon– a b c (++-assocr as bs cs j) i
+++-assocr (hexagon↑ a b c as i j) bs cs k = hexagon↑ a b c (++-assocr as bs cs k) i j
+++-assocr (hexagon↓ a b c as i j) bs cs k = hexagon↓ a b c (++-assocr as bs cs k) i j
+++-assocr (isGpdSList as ds p q u v i j k) bs cs l =
+  isGpdSList (++-assocr as bs cs l) (++-assocr ds bs cs l) (cong (\z -> ++-assocr z bs cs l) p) (cong (\z -> ++-assocr z bs cs l) q)
+             (cong (cong (\z -> ++-assocr z bs cs l)) u) (cong (cong (\z -> ++-assocr z bs cs l)) v) i j k
+
+TODO: Define commutativity for SList directly or after truncation
+ To do this directly will probably need coherence for swap
+ ++-∷ : (a : A) (as : SList A) -> a ∷ as ≡ as ++ [ a ]
+ ++-∷ a [] = refl
+ ++-∷ a (b ∷ as) = swap a b as ∙ cong (b ∷_) (++-∷ a as)
+ ++-∷ a (swap b c as i) =
+   {!!}
+
+ ++-comm : (as bs : SList A) -> as ++ bs ≡ bs ++ as
+ ++-comm [] bs = sym (++-unitr bs)
+ ++-comm (a ∷ as) bs = cong (a ∷_) (++-comm as bs)
+                     ∙ cong (_++ as) (++-∷ a bs)
+                     ∙ ++-assocr bs [ a ] as
+++-comm (swap a b as i) bs = {!!}
+
+TODO: Prove SList is free symmetric monoidal on groupoids
+--
diff --git a/Cubical/Structures/Set/CMon/Bag.agda b/Cubical/Structures/Set/CMon/Bag.agda
new file mode 100644
index 0000000..5eebfac
--- /dev/null
+++ b/Cubical/Structures/Set/CMon/Bag.agda
@@ -0,0 +1,8 @@
+{-# OPTIONS --cubical --safe --exact-split #-}
+
+module Cubical.Structures.Set.CMon.Bag where
+
+open import Cubical.Structures.Set.CMon.Bag.Base public
+open import Cubical.Structures.Set.CMon.Bag.Free public
+open import Cubical.Structures.Set.CMon.Bag.ToCList public
+
diff --git a/Cubical/Structures/Set/CMon/Bag/Base.agda b/Cubical/Structures/Set/CMon/Bag/Base.agda
new file mode 100644
index 0000000..39717e3
--- /dev/null
+++ b/Cubical/Structures/Set/CMon/Bag/Base.agda
@@ -0,0 +1,41 @@
+{-# OPTIONS --cubical --safe --exact-split #-}
+
+module Cubical.Structures.Set.CMon.Bag.Base where
+
+open import Cubical.Core.Everything
+open import Cubical.Foundations.Everything
+open import Cubical.Foundations.Isomorphism
+open import Cubical.Data.List renaming (_∷_ to _∷ₗ_)
+open import Cubical.Data.Nat
+open import Cubical.Data.Nat.Order
+open import Cubical.Data.Fin
+open import Cubical.Data.Sum as ⊎
+open import Cubical.Data.Sigma
+import Cubical.Data.Empty as ⊥
+
+import Cubical.Structures.Set.Mon.Desc as M
+import Cubical.Structures.Set.CMon.Desc as M
+import Cubical.Structures.Free as F
+open import Cubical.Structures.Set.Mon.Array as A
+open import Cubical.Structures.Set.Mon.List as L
+open import Cubical.Structures.Sig
+open import Cubical.Structures.Str public
+open import Cubical.Structures.Tree
+open import Cubical.Structures.Eq
+open import Cubical.Structures.Arity hiding (_/_)
+open import Cubical.HITs.SetQuotients as Q
+open import Cubical.Structures.Set.CMon.QFreeMon
+open import Cubical.Relation.Nullary
+
+open Iso
+
+private
+  variable
+    ℓ ℓ' ℓ'' : Level
+    A : Type ℓ
+
+_≈_ : ∀ {A : Type ℓ} -> Array A -> Array A -> Type ℓ
+_≈_ (n , v) (m , w) = Σ[ σ ∈ Iso (Fin n) (Fin m) ] v ≡ w ∘ σ .fun
+
+Bag : Type ℓ -> Type ℓ
+Bag A = Array A Q./ _≈_
diff --git a/Cubical/Structures/Set/CMon/Bag/FinExcept.agda b/Cubical/Structures/Set/CMon/Bag/FinExcept.agda
new file mode 100644
index 0000000..845a8db
--- /dev/null
+++ b/Cubical/Structures/Set/CMon/Bag/FinExcept.agda
@@ -0,0 +1,311 @@
+{-# OPTIONS --cubical --safe --exact-split #-}
+
+module Cubical.Structures.Set.CMon.Bag.FinExcept where
+
+open import Cubical.Core.Everything
+open import Cubical.Foundations.Everything
+open import Cubical.Foundations.Isomorphism
+open Iso
+open import Cubical.Data.List renaming (_∷_ to _∷ₗ_)
+open import Cubical.Data.Nat
+open import Cubical.Data.Nat.Order
+open import Cubical.Data.Fin
+open import Cubical.Data.Sum as ⊎
+open import Cubical.Data.Sigma
+import Cubical.Data.Empty as ⊥
+
+import Cubical.Structures.Set.Mon.Desc as M
+import Cubical.Structures.Set.CMon.Desc as M
+import Cubical.Structures.Free as F
+open import Cubical.Structures.Set.Mon.Array as A
+open import Cubical.Structures.Set.Mon.List as L
+open import Cubical.Structures.Sig
+open import Cubical.Structures.Str public
+open import Cubical.Structures.Tree
+open import Cubical.Structures.Eq
+open import Cubical.Structures.Arity hiding (_/_)
+open import Cubical.Structures.Set.CMon.QFreeMon
+open import Cubical.Structures.Set.CMon.Bag.Base
+open import Cubical.Structures.Set.CMon.Bag.Free
+open import Cubical.Relation.Nullary
+open import Cubical.Data.Fin.LehmerCode as E
+
+private
+  variable
+    ℓ : Level
+    A : Type ℓ
+    n : ℕ
+
+abstract
+  <-not-dense : ∀ {a b c} -> a < b -> b < suc c -> a < c
+  <-not-dense {a} {b} {c} p q with a ≟ c
+  ... | lt r = r
+  ... | eq r = ⊥.rec (¬n<m<suc-n p (subst (b <_) (congS suc (sym r)) q))
+  ... | gt r = ⊥.rec (<-asym (suc-≤-suc r) (≤-trans (≤-suc p) q))
+
+  a>b→a≠0 : ∀ {a b} -> a > b -> ¬ a ≡ 0
+  a>b→a≠0 {a} {b} (k , p) a≡0 = snotz (sym (+-suc k b) ∙ p ∙ a≡0)
+
+  predℕa<b : ∀ {e a b} -> a < suc b -> e < a -> predℕ a < b
+  predℕa<b {e} {a} {b} p q = subst (_≤ b) (suc-predℕ a (a>b→a≠0 q)) (predℕ-≤-predℕ p)
+
+  _<?_on_ : ∀ (a b : ℕ) -> ¬ a ≡ b -> (a < b) ⊎ (b < a)
+  a <? b on p with a ≟ b
+  ... | lt q = inl q
+  ... | gt q = inr q
+  ... | eq q = ⊥.rec (p q)
+  
+  <?-beta-inl : ∀ (a b : ℕ) -> (p : ¬ a ≡ b) -> (q : a < b) -> a <? b on p ≡ inl q
+  <?-beta-inl a b p q with a ≟ b
+  ... | lt r = congS inl (isProp≤ _ _)
+  ... | eq r = ⊥.rec (p r)
+  ... | gt r = ⊥.rec (<-asym r (<-weaken q))
+  
+  <?-beta-inr : ∀ (a b : ℕ) -> (p : ¬ a ≡ b) -> (q : a > b) -> a <? b on p ≡ inr q
+  <?-beta-inr a b p q with a ≟ b
+  ... | lt r = ⊥.rec (<-asym r (<-weaken q))
+  ... | eq r = ⊥.rec (p r)
+  ... | gt r = congS inr (isProp≤ _ _)
+  
+  ≤?-beta-inl : ∀ (a b : ℕ) -> (p : a < b) -> a ≤? b ≡ inl p
+  ≤?-beta-inl a b p with a ≤? b
+  ... | inl q = congS inl (isProp≤ _ _)
+  ... | inr q = ⊥.rec (<-asym p q)
+  
+  ≤?-beta-inr : ∀ (a b : ℕ) -> (p : b ≤ a) -> a ≤? b ≡ inr p
+  ≤?-beta-inr a b p with a ≤? b
+  ... | inl q = ⊥.rec (<-asym q p)
+  ... | inr q = congS inr (isProp≤ _ _)
+
+  FinExcept≡ : ∀ {n k} -> {a b : FinExcept {n = n} k} -> a .fst .fst ≡ b .fst .fst -> a ≡ b
+  FinExcept≡ p = Σ≡Prop (λ _ -> isProp¬ _) (Fin-fst-≡ p)
+
+pOut : ∀ {n} -> (k : Fin (suc n)) -> FinExcept k -> Fin n
+pOut {n} (k , p) ((j , q) , r) =
+  ⊎.rec
+    (λ j<k -> j , <-not-dense j<k p)
+    (λ k<j -> predℕ j , predℕa<b q k<j)
+    (j <? k on j≠k)
+  where
+    abstract DO NOT MOVE THIS OUT OF ABSTRACT OR IT WILL TAKE FOREVER TO TYPE CHECK
+      j≠k : ¬ j ≡ k
+      j≠k = r ∘ Fin-fst-≡ ∘ sym
+
+pIn : (k : Fin (suc n)) -> Fin n -> FinExcept k
+pIn (k , p) (j , q) =
+  ⊎.rec
+    (λ j<k -> (j , ≤-suc q) , <→≢ j<k ∘ sym ∘ congS fst)
+    (λ k≤j -> fsuc (j , q) , λ r -> ¬m<m (subst (_≤ j) (congS fst r) k≤j))
+    (j ≤? k)
+
+_∼ : {k : Fin n} -> (Fin n -> A) -> FinExcept k -> A
+f ∼ = f ∘ toFinExc
+
+1+_ : {k : Fin n} -> FinExcept k -> FinExcept (fsuc k)
+1+_ {k = k} (j , p) = (fsuc j) , fsuc≠
+  where
+    abstract
+      fsuc≠ : ¬ fsuc k ≡ fsuc j
+      fsuc≠ r = p (fsuc-inj r)
+
+pIn∘Out : (k : Fin (suc n)) -> ∀ j -> pIn k (pOut k j) ≡ j
+pIn∘Out (k , p) ((j , q) , r) =
+  ⊎.rec
+    (λ j<k ->
+        pIn (k , p) (pOut (k , p) ((j , q) , r))
+      ≡⟨⟩
+        pIn (k , p) (⊎.rec (λ j<k -> j , _) _ (j <? k on _))
+      ≡⟨ congS (pIn (k , p) ∘ ⊎.rec _ _) (<?-beta-inl j k _ j<k) ⟩
+        pIn (k , p) (j , <-not-dense j<k p)
+      ≡⟨⟩
+        ⊎.rec (λ j<k -> (j , _) , _) _ (j ≤? k)
+      ≡⟨ congS (⊎.rec (λ j<k -> (j , _) , _) _) (≤?-beta-inl j k j<k) ⟩
+        (j , ≤-suc (<-not-dense j<k p)) , _
+      ≡⟨ FinExcept≡ refl ⟩
+        ((j , q) , r)
+    ∎)
+    (λ k<j ->
+        pIn (k , p) (pOut (k , p) ((j , q) , r))
+      ≡⟨⟩
+        pIn (k , p) (⊎.rec _ (λ k<j -> predℕ j , predℕa<b q k<j) (j <? k on _))
+      ≡⟨ congS (pIn (k , p) ∘ ⊎.rec _ _) (<?-beta-inr j k _ k<j) ⟩
+        pIn (k , p) (predℕ j , predℕa<b q k<j)
+      ≡⟨⟩
+        ⊎.rec _ (λ k≤predℕj -> fsuc (predℕ j , _) , _) (predℕ j ≤? k)
+      ≡⟨ congS (⊎.rec _ _) (≤?-beta-inr (predℕ j) k (predℕ-≤-predℕ k<j)) ⟩
+        (fsuc (predℕ j , predℕa<b q k<j) , _)
+      ≡⟨ FinExcept≡ (sym (suc-predℕ j (a>b→a≠0 k<j))) ⟩
+        ((j , q) , r)
+    ∎)
+    (j <? k on (r ∘ Fin-fst-≡ ∘ sym))
+
+pOut∘In : (k : Fin (suc n)) -> ∀ j -> pOut k (pIn k j) ≡ j
+pOut∘In (k , p) (j , q) =
+  ⊎.rec
+    (λ j<k ->
+        pOut (k , p) (pIn (k , p) (j , q))
+      ≡⟨⟩
+        pOut (k , p) (⊎.rec (λ j<k -> (j , ≤-suc q) , _) _ (j ≤? k))
+      ≡⟨ congS (pOut (k , p) ∘ ⊎.rec _ _) (≤?-beta-inl j k j<k) ⟩
+        pOut (k , p) ((j , ≤-suc q) , _)
+      ≡⟨⟩
+        ⊎.rec (λ j<k -> j , <-not-dense j<k p) _ (j <? k on _)
+      ≡⟨ congS (⊎.rec _ _) (<?-beta-inl j k _ j<k) ⟩
+        (j , <-not-dense j<k p)
+      ≡⟨ Fin-fst-≡ refl ⟩
+         (j , q)
+    ∎)
+    (λ k≤j ->
+        pOut (k , p) (pIn (k , p) (j , q))
+      ≡⟨⟩
+        pOut (k , p) (⊎.rec _ (λ k≤j -> fsuc (j , q) , _) (j ≤? k))
+      ≡⟨ congS (pOut (k , p) ∘ ⊎.rec _ _) (≤?-beta-inr j k k≤j) ⟩
+        pOut (k , p) (fsuc (j , q) , _)
+      ≡⟨⟩
+        ⊎.rec _ (λ k<sucj -> predℕ (suc j) , _) (suc j <? k on _)
+      ≡⟨ congS (⊎.rec _ _) (<?-beta-inr (suc j) k _ (suc-≤-suc k≤j)) ⟩
+        (j , predℕa<b (snd (fsuc (j , q))) (suc-≤-suc k≤j))
+      ≡⟨ Fin-fst-≡ refl ⟩
+        (j , q)
+    ∎)
+    (j ≤? k)
+
+module _ {k : Fin (suc n)} where
+  pIso : Iso (FinExcept k) (Fin n)
+  Iso.fun pIso = pOut k
+  Iso.inv pIso = pIn k
+  Iso.rightInv pIso = pOut∘In k
+  Iso.leftInv pIso = pIn∘Out k
+
+pInZ≡fsuc : (k : Fin n) -> fst (pIn fzero k) ≡ fsuc k
+pInZ≡fsuc k = congS (fst ∘ ⊎.rec _ _) (≤?-beta-inr (fst k) 0 zero-≤)
+
+pIn-fsuc-nat : {k : Fin (suc n)} -> 1+_ ∘ pIn k ≡ pIn (fsuc k) ∘ fsuc
+pIn-fsuc-nat {n = zero} {k = k} = funExt \j -> ⊥.rec (¬Fin0 j)
+pIn-fsuc-nat {n = suc n} {k = k} = funExt (pIn-fsuc-nat-htpy k)
+  where
+    pIn-fsuc-nat-htpy : (k : Fin (suc (suc n))) (j : Fin (suc n))
+                      -> 1+ (pIn k j) ≡ pIn (fsuc k) (fsuc j)
+    pIn-fsuc-nat-htpy (k , p) (j , q) =
+      ⊎.rec
+        (λ j<k ->
+          let
+            r =
+                1+ pIn (k , p) (j , q)
+              ≡⟨⟩
+                1+ (⊎.rec (λ j<k -> (j , ≤-suc q) , _) _ (j ≤? k))
+              ≡⟨ congS (1+_ ∘ ⊎.rec _ _) (≤?-beta-inl j k j<k) ⟩
+                1+ ((j , ≤-suc q) , _)
+              ≡⟨⟩
+                fsuc (j , ≤-suc q) , _ ∎
+            s =
+                pIn (fsuc (k , p)) (fsuc (j , q))
+              ≡⟨⟩
+                ⊎.rec (λ sj<sk -> fsuc (j , _) , _) _ (suc j ≤? suc k)
+              ≡⟨ congS (⊎.rec _ _) (≤?-beta-inl (suc j) (suc k) (suc-≤-suc j<k)) ⟩
+                fsuc (j , _) , _
+              ≡⟨ FinExcept≡ refl ⟩
+                fsuc (j , ≤-suc q) , _ ∎
+          in r ∙ (sym s)
+        )
+        (λ k≤j ->
+          let
+            r =
+                1+ pIn (k , p) (j , q)
+              ≡⟨⟩
+                1+ (⊎.rec _ (λ k≤j -> fsuc (j , q) , _) (j ≤? k))
+              ≡⟨ congS (1+_ ∘ ⊎.rec _ _) (≤?-beta-inr j k k≤j) ⟩
+                1+ (fsuc (j , q) , _)
+              ≡⟨⟩
+                fsuc (fsuc (j , q)) , _ ∎
+            s =
+                pIn (fsuc (k , p)) (fsuc (j , q))
+              ≡⟨⟩
+                ⊎.rec _ (λ sk≤sj -> fsuc (fsuc (j , q)) , _) (suc j ≤? suc k)
+              ≡⟨ congS (⊎.rec _ _) (≤?-beta-inr (suc j) (suc k) (suc-≤-suc k≤j)) ⟩
+                fsuc (fsuc (j , q)) , _
+              ≡⟨ FinExcept≡ refl ⟩
+                fsuc (fsuc (j , q)) , _ ∎
+          in r ∙ (sym s)
+        )
+        (j ≤? k)
+
+
+Aut : (A : Type ℓ) -> Type ℓ
+Aut A = Iso A A
+
+projectIso : {i : Fin n} -> Iso (Unit ⊎ FinExcept i) (Fin n)
+fun (projectIso {i = i}) (inl _) = i
+fun (projectIso {i = i}) (inr m) = fst m
+inv (projectIso {i = i}) m =
+  decRec (λ i≡m -> inl tt) (λ i≠m -> inr (m , i≠m)) (discreteFin i m)
+rightInv (projectIso {i = i}) m with discreteFin i m
+... | yes i≡m = i≡m
+... | no ¬i≡m = refl
+leftInv (projectIso {i = i}) (inl _) with discreteFin i i
+... | yes i≡m = refl
+... | no ¬i≡m = ⊥.rec (¬i≡m refl)
+leftInv (projectIso {i = i}) (inr m) with discreteFin i (fst m)
+... | yes i≡m = ⊥.rec (m .snd i≡m)
+... | no ¬i≡m = congS inr (FinExcept≡ refl)
+
+module _ {n : ℕ} where
+  equivIn : (σ : Aut (Fin (suc n))) -> Iso (FinExcept fzero) (FinExcept (σ .fun fzero))
+  Iso.fun (equivIn σ) (k , p) = σ .fun k , p ∘ isoFunInjective σ _ _
+  Iso.inv (equivIn σ) (k , p) = σ .inv k , p ∘ isoInvInjective σ _ _ ∘ σ .leftInv fzero ∙_
+  Iso.rightInv (equivIn σ) (k , p) = FinExcept≡ (congS fst (σ .rightInv k))
+  Iso.leftInv (equivIn σ) (k , p) = FinExcept≡ (congS fst (σ .leftInv k))
+
+  equivOut : ∀ {k} -> Iso (FinExcept fzero) (FinExcept k) -> Aut (Fin (suc n))
+  equivOut {k = k} σ =
+    Fin (suc n) Iso⟨ invIso projectIso ⟩
+    Unit ⊎ FinExcept fzero Iso⟨ ⊎Iso idIso σ ⟩
+    Unit ⊎ FinExcept k Iso⟨ projectIso ⟩
+    Fin (suc n) ∎Iso
+
+  equivOut-beta-α : ∀ {k} {σ} (x : FinExcept fzero) -> (equivOut {k = k} σ) .fun (fst x) ≡ fst (σ .fun x)
+  equivOut-beta-α {σ = σ} x with discreteFin fzero (fst x)
+  ... | yes p = ⊥.rec (x .snd p)
+  ... | no ¬p = congS (fst ∘ σ .fun) (FinExcept≡ refl)
+
+  equivOut-beta-β : ∀ {k} {σ} (x : FinExcept (equivOut {k = k} σ .fun fzero)) -> equivOut σ .inv (fst x) ≡ σ .inv x .fst
+  equivOut-beta-β {k = k} {σ = σ} x with discreteFin k (fst x)
+  ... | yes p = ⊥.rec (x .snd p)
+  ... | no ¬p = congS (fst ∘ σ .inv) (FinExcept≡ refl)
+
+  equivIn∘Out : ∀ {k} -> (τ : Iso (FinExcept fzero) (FinExcept k)) -> equivIn (equivOut τ) ≡ τ
+  equivIn∘Out τ =
+    Iso≡Set isSetFinExcept isSetFinExcept _ _
+      (FinExcept≡ ∘ congS fst ∘ equivOut-beta-α)
+      (FinExcept≡ ∘ congS fst ∘ equivOut-beta-β)
+
+  equivOut∘In : (σ : Aut (Fin (suc n))) -> equivOut (equivIn σ) ≡ σ
+  equivOut∘In σ = Iso≡Set isSetFin isSetFin _ _ lemma-α lemma-β
+    where
+    lemma-α : (x : Fin (suc n)) -> equivOut (equivIn σ) .fun x ≡ σ .fun x
+    lemma-α x with discreteFin fzero x
+    ... | yes p = congS (σ .fun) p
+    ... | no ¬p = refl
+    lemma-β : (x : Fin (suc n)) -> equivOut (equivIn σ) .inv x ≡ σ .inv x
+    lemma-β x with discreteFin (σ .fun fzero) x
+    ... | yes p = sym (σ .leftInv fzero) ∙ congS (σ .inv) p
+    ... | no ¬p = refl
+
+  G : Iso (Aut (Fin (suc n))) (Σ[ k ∈ Fin (suc n) ] (Iso (FinExcept (fzero {k = n})) (FinExcept k)))
+  fun G σ = σ .fun fzero , equivIn σ
+  inv G (k , τ) = equivOut τ
+  rightInv G (k , τ) = ΣPathP (refl , equivIn∘Out τ)
+  leftInv G = equivOut∘In 
+
+  punch-σ : (σ : Aut (Fin (suc n))) -> Aut (Fin n)
+  punch-σ σ =
+    Fin n Iso⟨ invIso pIso ⟩
+    FinExcept (fzero {k = n}) Iso⟨ (G .fun σ) .snd ⟩
+    FinExcept (σ .fun fzero) Iso⟨ pIso ⟩
+    Fin n ∎Iso
+
+  fill-σ : ∀ k -> Aut (Fin (suc n))
+  fill-σ k = equivOut $
+    FinExcept fzero Iso⟨ pIso ⟩
+    Fin n Iso⟨ invIso pIso ⟩
+    FinExcept k ∎Iso
diff --git a/Cubical/Structures/Set/CMon/Bag/Free.agda b/Cubical/Structures/Set/CMon/Bag/Free.agda
new file mode 100644
index 0000000..3093d0b
--- /dev/null
+++ b/Cubical/Structures/Set/CMon/Bag/Free.agda
@@ -0,0 +1,390 @@
+{-# OPTIONS --cubical --safe --exact-split #-}
+
+module Cubical.Structures.Set.CMon.Bag.Free where
+
+open import Cubical.Core.Everything
+open import Cubical.Foundations.Everything
+open import Cubical.Foundations.Isomorphism
+open import Cubical.Data.List renaming (_∷_ to _∷ₗ_)
+open import Cubical.Data.Nat
+open import Cubical.Data.Nat.Order
+open import Cubical.Data.Fin
+open import Cubical.Data.Sum as ⊎
+open import Cubical.Data.Sigma
+import Cubical.Data.Empty as ⊥
+
+import Cubical.Structures.Set.Mon.Desc as M
+import Cubical.Structures.Set.CMon.Desc as M
+import Cubical.Structures.Free as F
+open import Cubical.Structures.Set.Mon.Array as A
+open import Cubical.Structures.Set.Mon.List as L
+open import Cubical.Structures.Sig
+open import Cubical.Structures.Str public
+open import Cubical.Structures.Tree
+open import Cubical.Structures.Eq
+open import Cubical.Structures.Arity hiding (_/_)
+open import Cubical.Structures.Set.CMon.QFreeMon
+open import Cubical.Structures.Set.CMon.Bag.Base
+open import Cubical.Relation.Nullary
+
+open Iso
+
+private
+  variable
+    ℓ ℓ' ℓ'' : Level
+    A : Type ℓ
+
+Bag≈ = _≈_
+
+refl≈ : {as : Array A} -> as ≈ as
+refl≈ {as = as} = idIso , refl
+
+sym≈ : {as bs : Array A} -> as ≈ bs -> bs ≈ as
+sym≈ {as = (n , f)} {bs = (m , g)} (σ , p) =
+  invIso σ , congS (g ∘_) (sym (funExt (σ .rightInv)))
+           ∙ congS (_∘ σ .inv) (sym p)
+
+trans≈ : {as bs cs : Array A} -> as ≈ bs -> bs ≈ cs -> as ≈ cs
+trans≈ {as = (n , f)} {bs = (m , g)} {cs = (o , h)} (σ , p) (τ , q) =
+  compIso σ τ , sym
+    ((h ∘ τ .fun) ∘ σ .fun ≡⟨ congS (_∘ σ .fun) (sym q) ⟩
+    g ∘ σ .fun ≡⟨ sym p ⟩
+    f ∎)
+
+Fin+-cong : {n m n' m' : ℕ} -> Iso (Fin n) (Fin n') -> Iso (Fin m) (Fin m') -> Iso (Fin (n + m)) (Fin (n' + m'))
+Fin+-cong {n} {m} {n'} {m'} σ τ =
+  compIso (Fin≅Fin+Fin n m) (compIso (⊎Iso σ τ) (invIso (Fin≅Fin+Fin n' m')))
+
+⊎Iso-eta : {A B A' B' : Type ℓ} {C : Type ℓ'} (f : A' -> C) (g : B' -> C)
+        -> (σ : Iso A A') (τ : Iso B B')
+        -> ⊎.rec (f ∘ σ .fun) (g ∘ τ .fun) ≡ ⊎.rec f g ∘ ⊎Iso σ τ .fun
+⊎Iso-eta f g σ τ = ⊎-eta (⊎.rec f g ∘ ⊎Iso σ τ .fun) refl refl
+
+⊎Swap-eta : {A B : Type ℓ} {C : Type ℓ'} (f : A -> C) (g : B -> C)
+        -> ⊎.rec f g ≡ ⊎.rec g f ∘ ⊎-swap-Iso .fun
+⊎Swap-eta f g = ⊎-eta (⊎.rec g f ∘ ⊎-swap-Iso .fun) refl refl
+
+cong≈ : {as bs cs ds : Array A} -> as ≈ bs -> cs ≈ ds -> (as ⊕ cs) ≈ (bs ⊕ ds)
+cong≈ {as = n , f} {bs = n' , f'} {m , g} {m' , g'} (σ , p) (τ , q) =
+  Fin+-cong σ τ ,
+  (
+    combine n m f g
+  ≡⟨ cong₂ (combine n m) p q ⟩
+    combine n m (f' ∘ σ .fun) (g' ∘ τ .fun)
+  ≡⟨⟩
+    ⊎.rec (f' ∘ σ .fun) (g' ∘ τ .fun) ∘ finSplit n m
+  ≡⟨ congS (_∘ finSplit n m) (⊎Iso-eta f' g' σ τ) ⟩
+    ⊎.rec f' g' ∘ ⊎Iso σ τ .fun ∘ finSplit n m
+  ≡⟨⟩
+    ⊎.rec f' g' ∘ idfun _ ∘ ⊎Iso σ τ .fun ∘ finSplit n m
+  ≡⟨ congS (\h -> ⊎.rec f' g' ∘ h ∘ ⊎Iso σ τ .fun ∘ finSplit n m) (sym (funExt (Fin≅Fin+Fin n' m' .rightInv))) ⟩
+    ⊎.rec f' g' ∘ (Fin≅Fin+Fin n' m' .fun ∘ Fin≅Fin+Fin n' m' .inv) ∘ ⊎Iso σ τ .fun ∘ finSplit n m
+  ≡⟨⟩
+    (⊎.rec f' g' ∘ Fin≅Fin+Fin n' m' .fun) ∘ (Fin≅Fin+Fin n' m' .inv ∘ ⊎Iso σ τ .fun ∘ finSplit n m)
+  ≡⟨⟩
+    combine n' m' f' g' ∘ Fin+-cong σ τ .fun
+  ∎)
+
+Fin+-comm : (n m : ℕ) -> Iso (Fin (n + m)) (Fin (m + n))
+Fin+-comm n m = compIso (Fin≅Fin+Fin n m) (compIso ⊎-swap-Iso (invIso (Fin≅Fin+Fin m n)))
+
+comm≈ : {as bs : Array A} -> (as ⊕ bs) ≈ (bs ⊕ as)
+comm≈ {as = n , f} {bs = m , g} =
+  Fin+-comm n m , sym
+    (
+      ⊎.rec g f ∘ finSplit m n ∘ Fin≅Fin+Fin m n .inv ∘ ⊎-swap-Iso .fun ∘ Fin≅Fin+Fin n m .fun
+    ≡⟨⟩
+      ⊎.rec g f ∘ (Fin≅Fin+Fin m n .fun ∘ Fin≅Fin+Fin m n .inv) ∘ ⊎-swap-Iso .fun ∘ Fin≅Fin+Fin n m .fun
+    ≡⟨ congS (λ h -> ⊎.rec g f ∘ h ∘ ⊎-swap-Iso .fun ∘ Fin≅Fin+Fin n m .fun) (funExt (Fin≅Fin+Fin m n .rightInv)) ⟩
+      ⊎.rec g f ∘ ⊎-swap-Iso .fun ∘ Fin≅Fin+Fin n m .fun
+    ≡⟨ congS (_∘ Fin≅Fin+Fin n m .fun) (sym (⊎Swap-eta f g)) ⟩
+      ⊎.rec f g ∘ Fin≅Fin+Fin n m .fun
+    ∎)
+
+fpred' : ∀ {n} -> (x : Fin (suc n)) -> ¬ x ≡ fzero -> Fin n
+fpred' (zero , p) q = ⊥.rec (q (Fin-fst-≡ refl))
+fpred' (suc w , p) q = w , pred-≤-pred p
+
+fpred : ∀ {n} -> Fin (suc (suc n)) -> Fin (suc n)
+fpred (zero , p) = fzero
+fpred (suc w , p) = w , pred-≤-pred p
+
+fsuc∘fpred : ∀ {n} -> (x : Fin (suc (suc n))) -> ¬ x ≡ fzero -> fsuc (fpred x) ≡ x
+fsuc∘fpred (zero , p) q = ⊥.rec (q (Fin-fst-≡ refl))
+fsuc∘fpred (suc k , p) q = Fin-fst-≡ refl
+
+fpred∘fsuc : ∀ {n} -> (x : Fin (suc n)) -> fpred (fsuc x) ≡ x
+fpred∘fsuc (k , p) = Fin-fst-≡ refl
+
+isoFunInv : ∀ {A B : Type ℓ} {x y} -> (σ : Iso A B) -> σ .fun x ≡ y -> σ .inv y ≡ x
+isoFunInv σ p = congS (σ .inv) (sym p) ∙ σ .leftInv _
+
+isoFunInvContra : ∀ {A B : Type ℓ} {x y z} -> (σ : Iso A B) -> σ .fun x ≡ y -> ¬ (z ≡ y) -> ¬ (σ .inv z ≡ x)
+isoFunInvContra σ p z≠y q = z≠y (sym (σ .rightInv _) ∙ congS (σ .fun) q ∙ p)
+
+autInvIs0 : ∀ {n} -> (σ : Iso (Fin (suc (suc n))) (Fin (suc (suc n))))
+          -> σ .fun fzero ≡ fzero -> σ .inv fzero ≡ fzero
+autInvIs0 = isoFunInv
+
+autSucNot0 : ∀ {n} -> (σ : Iso (Fin (suc (suc n))) (Fin (suc (suc n))))
+          -> (x : Fin (suc n)) -> σ .fun fzero ≡ fzero -> ¬ σ .fun (fsuc x) ≡ fzero
+autSucNot0 σ x p = isoFunInvContra (invIso σ) (isoFunInv σ p) (snotz ∘ congS fst)
+
+punchOutZero : ∀ {n} (σ : Iso (Fin (suc (suc n))) (Fin (suc (suc n)))) -> σ .fun fzero ≡ fzero
+              -> Iso (Fin (suc n)) (Fin (suc n))
+punchOutZero {n = n} σ p =
+  iso (punch σ) (punch (invIso σ)) (punch∘punch σ p) (punch∘punch (invIso σ) (autInvIs0 σ p))
+  where
+  punch : Iso (Fin (suc (suc n))) (Fin (suc (suc n))) -> Fin (suc n) -> Fin (suc n)
+  punch σ = fpred ∘ σ .fun ∘ fsuc
+  punch∘punch : (σ : Iso (Fin (suc (suc n))) (Fin (suc (suc n))))
+              -> σ .fun fzero ≡ fzero
+              -> (x : Fin (suc n))
+              -> punch σ (punch (invIso σ) x) ≡ x
+  punch∘punch σ p x =
+      punch σ (punch (invIso σ) x)
+    ≡⟨⟩
+      fpred (σ .fun ((fsuc ∘ fpred) (σ .inv (fsuc x))))
+    ≡⟨ congS (fpred ∘ σ .fun) (fsuc∘fpred (σ .inv (fsuc x)) (autSucNot0 (invIso σ) x (autInvIs0 σ p))) ⟩
+      fpred (σ .fun (σ .inv (fsuc x)))
+    ≡⟨ congS fpred (σ .rightInv (fsuc x)) ⟩
+      fpred (fsuc x)
+    ≡⟨ fpred∘fsuc x ⟩
+      x ∎
+
+punchOutZero≡fsuc : ∀ {n} (σ : Iso (Fin (suc (suc n))) (Fin (suc (suc n)))) -> (σ-0≡0 : σ .fun fzero ≡ fzero)
+                  -> (w : Fin (suc n)) -> σ .fun (fsuc w) ≡ fsuc (punchOutZero σ σ-0≡0 .fun w)
+punchOutZero≡fsuc σ σ-0≡0 w = sym (fsuc∘fpred _ (autSucNot0 σ w σ-0≡0))
+
+finSubst : ∀ {n m} -> n ≡ m -> Fin n -> Fin m
+finSubst {n = n} {m = m} p (k , q) = k , (subst (k <_) p q)
+
+Fin≅ : ∀ {n m} -> n ≡ m -> Iso (Fin n) (Fin m)
+Fin≅ {n = n} {m = m} p = iso
+  (finSubst p)
+  (finSubst (sym p))
+  (λ (k , q) -> Fin-fst-≡ refl)
+  (λ (k , q) -> Fin-fst-≡ refl)
+
+Fin≅-inj : {n m : ℕ} -> Iso (Fin n) (Fin m) -> n ≡ m
+Fin≅-inj {n = n} {m = m} σ = Fin-inj n m (isoToPath σ)
+
+≈-length : {n m : ℕ} -> Iso (Fin n) (Fin m) -> n ≡ m 
+≈-length {n = n} {m = m} σ = Fin-inj n m (isoToPath σ)
+
+module _ {n} (σ : Iso (Fin (suc n)) (Fin (suc n))) where
+  private
+    m : ℕ
+    m = suc n
+
+    cutoff : ℕ
+    cutoff = (σ .inv fzero) .fst
+
+    cutoff< : cutoff < m
+    cutoff< = (σ .inv fzero) .snd
+
+    cutoff+- : cutoff + (m ∸ cutoff) ≡ m
+    cutoff+- = ∸-lemma (<-weaken cutoff<)
+
+    0<m-cutoff : 0 < m ∸ cutoff
+    0<m-cutoff = n∸l>0 m cutoff cutoff<
+
+  swapAut : Iso (Fin (suc n)) (Fin (suc n))
+  swapAut = compIso (Fin≅ (sym cutoff+- ∙ +-comm cutoff _)) (compIso (Fin+-comm (m ∸ cutoff) cutoff) (compIso (Fin≅ cutoff+-) σ))
+
+  swapAut0≡0 : swapAut .fun fzero ≡ fzero
+  swapAut0≡0 =
+      σ .fun (finSubst cutoff+- (⊎.rec finCombine-inl finCombine-inr (fun ⊎-swap-Iso (finSplit (m ∸ cutoff) cutoff (0 , _)))))
+    ≡⟨ congS (λ z -> σ .fun (finSubst cutoff+- (⊎.rec (finCombine-inl {m = cutoff}) (finCombine-inr {m = cutoff}) (fun ⊎-swap-Iso z)))) (finSplit-beta-inl 0 0<m-cutoff _) ⟩
+      σ .fun (σ .inv fzero .fst + 0 , _)
+    ≡⟨ congS (σ .fun) (Fin-fst-≡ (+-zero (σ .inv (0 , suc-≤-suc zero-≤) .fst) ∙ congS (fst ∘ σ .inv) (Fin-fst-≡ refl))) ⟩
+      σ .fun (σ .inv fzero)
+    ≡⟨ σ .rightInv fzero ⟩
+      fzero ∎
+
+module _ {ℓA ℓB} {A : Type ℓA} {𝔜 : struct ℓB M.MonSig} (isSet𝔜 : isSet (𝔜 .car)) (𝔜-cmon : 𝔜 ⊨ M.CMonSEq) (f : A -> 𝔜 .car) where
+  module 𝔜 = M.CMonSEq 𝔜 𝔜-cmon
+
+  f♯-hom = ArrayDef.Free.ext arrayDef isSet𝔜 (M.cmonSatMon 𝔜-cmon) f
+
+  f♯ : Array A -> 𝔜 .car
+  f♯ = f♯-hom .fst
+
+  f♯-η : (a : A) -> f♯ (η a) ≡ f a
+  f♯-η a i = ArrayDef.Free.ext-η arrayDef isSet𝔜 (M.cmonSatMon 𝔜-cmon) f i a
+
+  f♯-hom-⊕ : (as bs : Array A) -> f♯ (as ⊕ bs) ≡ f♯ as 𝔜.⊕ f♯ bs
+  f♯-hom-⊕ as bs =
+    f♯ (as ⊕ bs) ≡⟨ sym ((f♯-hom .snd) M.`⊕ ⟪ as ⨾ bs ⟫) ⟩
+    𝔜 .alg (M.`⊕ , (λ w -> f♯ (⟪ as ⨾ bs ⟫ w))) ≡⟨ 𝔜.⊕-eta ⟪ as ⨾ bs ⟫ f♯ ⟩
+    f♯ as 𝔜.⊕ f♯ bs ∎
+
+  f♯-comm : (as bs : Array A) -> f♯ (as ⊕ bs) ≡ f♯ (bs ⊕ as)
+  f♯-comm as bs =
+    f♯ (as ⊕ bs) ≡⟨ f♯-hom-⊕ as bs ⟩
+    f♯ as 𝔜.⊕ f♯ bs ≡⟨ 𝔜.comm (f♯ as) (f♯ bs) ⟩
+    f♯ bs 𝔜.⊕ f♯ as ≡⟨ sym (f♯-hom-⊕ bs as) ⟩
+    f♯ (bs ⊕ as) ∎
+
+  swapAutToAut : ∀ {n} (zs : Fin (suc (suc n)) -> A) (σ : Iso (Fin (suc (suc n))) (Fin (suc (suc n))))
+               -> f♯ (suc (suc n) , zs ∘ swapAut σ .fun) ≡ f♯ (suc (suc n) , zs ∘ σ .fun)
+  swapAutToAut {n = n} zs σ =
+      f♯ (m , zs ∘ swapAut σ .fun)
+    ≡⟨ congS f♯ lemma-α ⟩
+      f♯ (((m ∸ cutoff) , (zs ∘ σ .fun ∘ finSubst cutoff+- ∘ finCombine cutoff _ ∘ inr))
+        ⊕ (cutoff , (zs ∘ σ .fun ∘ finSubst cutoff+- ∘ finCombine cutoff _ ∘ inl)))
+    ≡⟨ f♯-comm ((m ∸ cutoff) , (zs ∘ σ .fun ∘ finSubst cutoff+- ∘ finCombine cutoff _ ∘ inr)) _ ⟩
+      f♯ ((cutoff , (zs ∘ σ .fun ∘ finSubst cutoff+- ∘ finCombine cutoff _ ∘ inl))
+        ⊕ ((m ∸ cutoff) , (zs ∘ σ .fun ∘ finSubst cutoff+- ∘ finCombine cutoff _ ∘ inr)))
+    ≡⟨ congS f♯ lemma-β ⟩
+      f♯ (m , zs ∘ σ .fun) ∎
+    where
+    m : ℕ
+    m = suc (suc n)
+
+    cutoff : ℕ
+    cutoff = (σ .inv fzero) .fst
+
+    cutoff< : cutoff < m
+    cutoff< = (σ .inv fzero) .snd
+
+    cutoff+- : cutoff + (m ∸ cutoff) ≡ m
+    cutoff+- = ∸-lemma (<-weaken cutoff<)
+
+    lemma-α : Path (Array A) (m , zs ∘ swapAut σ .fun) ((m ∸ cutoff) + cutoff , _)
+    lemma-α = Array≡ (sym cutoff+- ∙ +-comm cutoff _) λ k k<m∸cutoff+cutoff -> ⊎.rec
+      (λ k<m∸cutoff ->
+          zs (σ .fun (finSubst cutoff+- (⊎.rec finCombine-inl finCombine-inr (fun ⊎-swap-Iso (finSplit (m ∸ cutoff) cutoff (k , _))))))
+        ≡⟨ congS (λ z -> zs (σ .fun (finSubst cutoff+- (⊎.rec (finCombine-inl {m = cutoff}) finCombine-inr (fun ⊎-swap-Iso z))))) (finSplit-beta-inl k k<m∸cutoff _) ⟩
+          zs (σ .fun (cutoff + k , _))
+        ≡⟨ congS (zs ∘ σ .fun) (Fin-fst-≡ refl) ⟩
+          zs (σ .fun (finSubst cutoff+- (finCombine cutoff (m ∸ cutoff) (inr (k , k<m∸cutoff)))))
+        ≡⟨⟩
+          ⊎.rec
+            (zs ∘ σ .fun ∘ finSubst cutoff+- ∘ finCombine cutoff (m ∸ cutoff) ∘ inr)
+            (zs ∘ σ .fun ∘ finSubst cutoff+- ∘ finCombine cutoff (m ∸ cutoff) ∘ inl)
+            (inl (k , k<m∸cutoff))
+        ≡⟨ congS (⊎.rec _ _) (sym (finSplit-beta-inl k k<m∸cutoff k<m∸cutoff+cutoff)) ⟩
+          ⊎.rec
+            (zs ∘ σ .fun ∘ finSubst cutoff+- ∘ finCombine cutoff (m ∸ cutoff) ∘ inr)
+            (zs ∘ σ .fun ∘ finSubst cutoff+- ∘ finCombine cutoff (m ∸ cutoff) ∘ inl)
+            (finSplit (m ∸ cutoff) cutoff (k , k<m∸cutoff+cutoff))
+      ∎)
+      (λ m∸cutoff≤k ->
+          zs (σ .fun (finSubst cutoff+- (⊎.rec finCombine-inl finCombine-inr (fun ⊎-swap-Iso (finSplit (m ∸ cutoff) cutoff (k , _))))))
+        ≡⟨ congS (λ z -> zs (σ .fun (finSubst cutoff+- (⊎.rec (finCombine-inl {m = cutoff}) finCombine-inr (fun ⊎-swap-Iso z))))) (finSplit-beta-inr k _ m∸cutoff≤k (∸-<-lemma (m ∸ cutoff) cutoff k k<m∸cutoff+cutoff m∸cutoff≤k)) ⟩
+          zs (σ .fun (finSubst cutoff+- (finCombine-inl (k ∸ (m ∸ cutoff) , ∸-<-lemma (m ∸ cutoff) cutoff k k<m∸cutoff+cutoff m∸cutoff≤k))))
+        ≡⟨ congS (zs ∘ σ .fun ∘ finSubst cutoff+-) (Fin-fst-≡ refl) ⟩
+          zs (σ .fun (finSubst cutoff+- (finCombine cutoff (m ∸ cutoff) (inl (k ∸ (m ∸ cutoff) , ∸-<-lemma (m ∸ cutoff) cutoff k k<m∸cutoff+cutoff m∸cutoff≤k)))))
+        ≡⟨ congS (⊎.rec _ _) (sym (finSplit-beta-inr k k<m∸cutoff+cutoff m∸cutoff≤k (∸-<-lemma (m ∸ cutoff) cutoff k k<m∸cutoff+cutoff m∸cutoff≤k))) ⟩
+          ⊎.rec
+            (zs ∘ σ .fun ∘ finSubst cutoff+- ∘ finCombine cutoff (m ∸ cutoff) ∘ inr)
+            (zs ∘ σ .fun ∘ finSubst cutoff+- ∘ finCombine cutoff (m ∸ cutoff) ∘ inl)
+            (finSplit (m ∸ cutoff) cutoff (k , k<m∸cutoff+cutoff))
+      ∎)
+      (k ≤? (m ∸ cutoff))
+    
+    lemma-β : Path (Array A) (cutoff + (m ∸ cutoff) , _) (m , zs ∘ σ .fun)
+    lemma-β = Array≡ cutoff+- λ k k<m -> ⊎.rec
+      (λ k<cutoff ->
+          ⊎.rec
+            (zs ∘ σ .fun ∘ finSubst cutoff+- ∘ finCombine cutoff (m ∸ cutoff) ∘ inl)
+            (zs ∘ σ .fun ∘ finSubst cutoff+- ∘ finCombine cutoff (m ∸ cutoff) ∘ inr)
+            (finSplit cutoff (m ∸ cutoff) (k , _))
+        ≡⟨ congS (⊎.rec _ _) (finSplit-beta-inl k k<cutoff _) ⟩
+          ⊎.rec  
+            (zs ∘ σ .fun ∘ finSubst cutoff+- ∘ finCombine cutoff (m ∸ cutoff) ∘ inl)
+            (zs ∘ σ .fun ∘ finSubst cutoff+- ∘ finCombine cutoff (m ∸ cutoff) ∘ inr)
+            (inl (k , _))
+        ≡⟨⟩
+          zs (σ .fun (finSubst cutoff+- (finCombine cutoff (m ∸ cutoff) (inl (k , _)))))
+        ≡⟨ congS (zs ∘ σ .fun) (Fin-fst-≡ refl) ⟩
+          zs (σ .fun (k , k<m))
+      ∎)
+      (λ cutoff≤k ->
+          ⊎.rec
+            (zs ∘ σ .fun ∘ finSubst cutoff+- ∘ finCombine cutoff (m ∸ cutoff) ∘ inl)
+            (zs ∘ σ .fun ∘ finSubst cutoff+- ∘ finCombine cutoff (m ∸ cutoff) ∘ inr)
+            (finSplit cutoff (m ∸ cutoff) (k , _))
+        ≡⟨ congS (⊎.rec _ _) (finSplit-beta-inr k _ cutoff≤k (<-∸-< k m cutoff k<m cutoff<)) ⟩
+          ⊎.rec
+            (zs ∘ σ .fun ∘ finSubst cutoff+- ∘ finCombine cutoff (m ∸ cutoff) ∘ inl)
+            (zs ∘ σ .fun ∘ finSubst cutoff+- ∘ finCombine cutoff (m ∸ cutoff) ∘ inr)
+            (inr (k ∸ cutoff , _))
+        ≡⟨⟩
+          zs (σ .fun (finSubst cutoff+- (finCombine cutoff (m ∸ cutoff) (inr (k ∸ cutoff , _)))))
+        ≡⟨ congS (zs ∘ σ .fun) (Fin-fst-≡ (+-comm cutoff (k ∸ cutoff) ∙ ≤-∸-+-cancel cutoff≤k)) ⟩
+          zs (σ .fun (k , k<m))
+      ∎)
+      (k ≤? cutoff)
+
+  permuteInvariant : ∀ n (zs : Fin n -> A) (σ : Iso (Fin n) (Fin n)) -> f♯ (n , zs ∘ σ .fun) ≡ f♯ (n , zs)
+  permuteInvariant zero zs σ =
+    congS f♯ (Array≡ {f = zs ∘ σ .fun} {g = zs} refl \k k<0 -> ⊥.rec (¬-<-zero k<0))
+  permuteInvariant (suc zero) zs σ =
+    congS f♯ (Array≡ {f = zs ∘ σ .fun} {g = zs} refl \k k<1 -> congS zs (isContr→isProp isContrFin1 _ _))
+  permuteInvariant (suc (suc n)) zs σ =
+    let τ = swapAut σ ; τ-0≡0 = swapAut0≡0 σ
+        IH = permuteInvariant (suc n) (zs ∘ fsuc) (punchOutZero τ τ-0≡0)
+    in
+      f♯ (suc (suc n) , zs ∘ σ .fun)
+    ≡⟨ sym (swapAutToAut zs σ) ⟩
+      f♯ (suc (suc n) , zs ∘ τ .fun)
+    ≡⟨ permuteInvariantOnZero τ τ-0≡0 IH ⟩
+      f♯ (suc (suc n) , zs) ∎
+      where
+        permuteInvariantOnZero : (τ : Iso (Fin (suc (suc n))) (Fin (suc (suc n)))) (τ-0≡0 : τ .fun fzero ≡ fzero) -> (IH : _)
+                              -> f♯ (suc (suc n) , zs ∘ τ .fun) ≡ f♯ (suc (suc n) , zs)
+        permuteInvariantOnZero τ τ-0≡0 IH =
+            f♯ (suc (suc n) , zs ∘ τ .fun)
+          ≡⟨⟩
+            f (zs (τ .fun fzero)) 𝔜.⊕ f♯ (suc n , zs ∘ τ .fun ∘ fsuc)
+          ≡⟨ congS (\z -> f (zs z) 𝔜.⊕ f♯ (suc n , zs ∘ τ .fun ∘ fsuc)) (Fin-fst-≡ (congS fst τ-0≡0)) ⟩
+            f (zs fzero) 𝔜.⊕ f♯ (suc n , zs ∘ τ .fun ∘ fsuc)
+          ≡⟨ congS (\z -> f (zs fzero) 𝔜.⊕ f♯ z)
+                   (Array≡ {f = zs ∘ τ .fun ∘ fsuc} refl \k k≤n ->
+                           congS (zs ∘ τ .fun ∘ fsuc) (Fin-fst-≡ refl) ∙ congS zs (punchOutZero≡fsuc τ τ-0≡0 (k , k≤n))) ⟩
+            f (zs fzero) 𝔜.⊕ f♯ (suc n , zs ∘ fsuc ∘ punchOutZero τ τ-0≡0 .fun)
+          ≡⟨ cong₂ 𝔜._⊕_ (sym (f♯-η (zs fzero))) IH ⟩
+            f♯ (η (zs fzero)) 𝔜.⊕ f♯ (suc n , zs ∘ fsuc)
+          ≡⟨ sym (f♯-hom-⊕ (η (zs fzero)) (suc n , zs ∘ fsuc)) ⟩
+            f♯ (η (zs fzero) ⊕ (suc n , zs ∘ fsuc))
+          ≡⟨ congS f♯ (η+fsuc zs) ⟩
+            f♯ (suc (suc n) , zs)
+          ∎
+
+  ≈-resp-♯ : {as bs : Array A} -> as ≈ bs -> f♯ as ≡ f♯ bs
+  ≈-resp-♯ {as = n , g} {bs = m , h} (σ , p) =
+      f♯ (n , g)
+    ≡⟨ congS (λ z -> f♯ (n , z)) p ⟩
+      f♯ (n , h ∘ σ .fun)
+    ≡⟨ congS f♯ (Array≡ n≡m λ _ _ -> refl) ⟩
+      f♯ (m , h ∘ σ .fun ∘ (Fin≅ (sym n≡m)) .fun)
+    ≡⟨⟩
+      f♯ (m , h ∘ (compIso (Fin≅ (sym n≡m)) σ) .fun)
+    ≡⟨ permuteInvariant m h (compIso (Fin≅ (sym n≡m)) σ) ⟩
+      f♯ (m , h) ∎
+    where
+    n≡m : n ≡ m
+    n≡m = Fin≅-inj σ
+
+module _ {ℓ} (A : Type ℓ) where
+  open import Cubical.Relation.Binary
+  module P = BinaryRelation {A = Array A} _≈_
+  module R = isPermRel
+
+  isPermRelPerm : isPermRel arrayDef (_≈_ {A = A})
+  P.isEquivRel.reflexive (R.isEquivRel isPermRelPerm) _ = refl≈
+  P.isEquivRel.symmetric (R.isEquivRel isPermRelPerm) _ _ = sym≈
+  P.isEquivRel.transitive (R.isEquivRel isPermRelPerm) _ _ cs = trans≈ {cs = cs}
+  R.isCongruence isPermRelPerm {as} {bs} {cs} {ds} p q = cong≈ p q
+  R.isCommutative isPermRelPerm = comm≈
+  R.resp-♯ isPermRelPerm {isSet𝔜 = isSet𝔜} 𝔜-cmon f p = ≈-resp-♯ isSet𝔜 𝔜-cmon f p
+
+  PermRel : PermRelation arrayDef A
+  PermRel = _≈_ , isPermRelPerm
+
+module BagDef = F.Definition M.MonSig M.CMonEqSig M.CMonSEq
+
+bagFreeDef : ∀ {ℓ} -> BagDef.Free ℓ ℓ 2
+bagFreeDef = qFreeMonDef (PermRel _)
diff --git a/Cubical/Structures/Set/CMon/Bag/ToCList.agda b/Cubical/Structures/Set/CMon/Bag/ToCList.agda
new file mode 100644
index 0000000..fc48462
--- /dev/null
+++ b/Cubical/Structures/Set/CMon/Bag/ToCList.agda
@@ -0,0 +1,313 @@
+{-# OPTIONS --cubical --safe --exact-split #-}
+
+module Cubical.Structures.Set.CMon.Bag.ToCList where
+
+open import Cubical.Core.Everything
+open import Cubical.Foundations.Everything
+open import Cubical.Foundations.Isomorphism
+open import Cubical.Data.List renaming (_∷_ to _∷ₗ_)
+open import Cubical.Data.Nat
+open import Cubical.Data.Nat.Order
+open import Cubical.Data.Fin
+open import Cubical.Data.Sum as ⊎
+open import Cubical.Data.Sigma
+import Cubical.Data.Empty as ⊥
+
+import Cubical.Structures.Set.Mon.Desc as M
+import Cubical.Structures.Set.CMon.Desc as M
+import Cubical.Structures.Free as F
+open import Cubical.Structures.Set.Mon.Array as A
+open import Cubical.Structures.Set.Mon.List as L
+open import Cubical.Structures.Sig
+open import Cubical.Structures.Str public
+open import Cubical.Structures.Tree
+open import Cubical.Structures.Eq
+open import Cubical.Structures.Arity hiding (_/_)
+open import Cubical.Structures.Set.CMon.QFreeMon
+open import Cubical.Structures.Set.CMon.CList
+open import Cubical.Structures.Set.CMon.Bag.Base
+open import Cubical.Structures.Set.CMon.Bag.Free
+open import Cubical.Relation.Nullary
+open import Cubical.Data.Fin.LehmerCode hiding (LehmerCode; _∷_; [])
+
+open import Cubical.Structures.Set.CMon.Bag.FinExcept
+
+open Iso
+
+private
+  variable
+    ℓ ℓ' ℓ'' : Level
+    A : Type ℓ
+    n : ℕ
+
+module IsoToCList {ℓ} (A : Type ℓ) where
+  open import Cubical.Structures.Set.CMon.CList as CL
+  open import Cubical.HITs.SetQuotients as Q
+  open BagDef.Free
+
+  module 𝔄 = M.MonSEq < Array A , array-α > array-sat
+  module 𝔅 = M.CMonSEq < Bag A , bagFreeDef .α > (bagFreeDef .sat)
+  module ℭ = M.CMonSEq < CList A , clist-α > clist-sat
+
+  abstract needed so Agda wouldn't get stuck
+    fromCListHom : structHom < CList A , clist-α > < Bag A , bagFreeDef .α >
+    fromCListHom = ext clistDef squash/ (bagFreeDef .sat) (BagDef.Free.η bagFreeDef)
+
+    fromCList : CList A -> Bag A
+    fromCList = fromCListHom .fst
+
+    fromCListIsHom : structIsHom < CList A , clist-α > < Bag A , bagFreeDef .α > fromCList
+    fromCListIsHom = fromCListHom .snd
+
+    fromCList-e : fromCList [] ≡ 𝔅.e
+    fromCList-e = refl
+
+    fromCList-++ : ∀ xs ys -> fromCList (xs ℭ.⊕ ys) ≡ fromCList xs 𝔅.⊕ fromCList ys
+    fromCList-++ xs ys =
+      fromCList (xs ℭ.⊕ ys) ≡⟨ sym (fromCListIsHom M.`⊕ ⟪ xs ⨾ ys ⟫) ⟩
+      _ ≡⟨ 𝔅.⊕-eta ⟪ xs ⨾ ys ⟫ fromCList ⟩
+      _ ∎
+
+    fromCList-η : ∀ x -> fromCList (CL.[ x ]) ≡ Q.[ A.η x ]
+    fromCList-η x = congS (λ f -> f x)
+      (ext-η clistDef squash/ (bagFreeDef .sat) (BagDef.Free.η bagFreeDef))
+
+  ListToCListHom : structHom < List A , list-α > < CList A , clist-α >
+  ListToCListHom = ListDef.Free.ext listDef isSetCList (M.cmonSatMon clist-sat) CL.[_]
+
+  ListToCList : List A -> CList A
+  ListToCList = ListToCListHom .fst
+
+  ArrayToCListHom : structHom < Array A , array-α > < CList A , clist-α >
+  ArrayToCListHom = structHom∘ < Array A , array-α > < List A , list-α > < CList A , clist-α >
+    ListToCListHom ((arrayIsoToList .fun) , arrayIsoToListHom)
+
+  ArrayToCList : Array A -> CList A
+  ArrayToCList = ArrayToCListHom .fst
+
+  tab : ∀ n -> (Fin n -> A) -> CList A
+  tab = curry ArrayToCList
+
+  isContr≅ : ∀ {ℓ} {A : Type ℓ} -> isContr A -> isContr (Iso A A)
+  isContr≅ ϕ = inhProp→isContr idIso \σ1 σ2 ->
+    SetsIso≡ (isContr→isOfHLevel 2 ϕ) (isContr→isOfHLevel 2 ϕ)
+             (funExt \x -> isContr→isProp ϕ (σ1 .fun x) (σ2 .fun x))
+             (funExt \x -> isContr→isProp ϕ (σ1 .inv x) (σ2 .inv x))
+
+  isContrFin1≅ : isContr (Iso (Fin 1) (Fin 1))
+  isContrFin1≅ = isContr≅ isContrFin1
+
+  fsuc∘punchOutZero≡ : ∀ {n}
+          -> (f g : Fin (suc (suc n)) -> A)
+          -> (σ : Iso (Fin (suc (suc n))) (Fin (suc (suc n)))) (p : f ≡ g ∘ σ .fun)
+          -> (q : σ .fun fzero ≡ fzero)
+          -> f ∘ fsuc ≡ g ∘ fsuc ∘ punchOutZero σ q .fun
+  fsuc∘punchOutZero≡ f g σ p q =
+    f ∘ fsuc ≡⟨ congS (_∘ fsuc) p ⟩
+    g ∘ σ .fun ∘ fsuc ≡⟨ congS (g ∘_) (funExt (punchOutZero≡fsuc σ q)) ⟩
+    g ∘ fsuc ∘ punchOutZero σ q .fun ∎
+
+  toCList-eq : ∀ n
+             -> (f : Fin n -> A) (g : Fin n -> A) (σ : Iso (Fin n) (Fin n)) (p : f ≡ g ∘ σ .fun)
+             -> tab n f ≡ tab n g
+  toCList-eq zero f g σ p =
+    refl
+  toCList-eq (suc zero) f g σ p =
+    let q : σ ≡ idIso
+        q = isContr→isProp isContrFin1≅ σ idIso
+    in congS (tab 1) (p ∙ congS (g ∘_) (congS Iso.fun q))
+  toCList-eq (suc (suc n)) f g σ p =
+    ⊎.rec
+      (λ 0≡σ0 ->
+        let IH = toCList-eq (suc n) (f ∘ fsuc) (g ∘ fsuc) (punchOutZero σ (sym 0≡σ0)) (fsuc∘punchOutZero≡ f g σ p (sym 0≡σ0))
+        in case1 IH (sym 0≡σ0)
+      )
+      (λ (k , Sk≡σ0) ->
+        case2 k (sym Sk≡σ0)
+          (toCList-eq (suc n) (f ∘ fsuc) ((g ∼) ∘ pIn (fsuc k)) (punch-σ σ) (sym (IH1-lemma k Sk≡σ0)))
+          (toCList-eq (suc n) (g-σ k) (g ∘ fsuc) (fill-σ k) (sym (funExt (IH2-lemma k Sk≡σ0))))
+      )
+      (fsplit (σ .fun fzero))
+    where
+      g-σ : ∀ k -> Fin (suc n) -> A
+      g-σ k (zero , p) = g (σ .fun fzero)
+      g-σ k (suc j , p) = (g ∼) (1+ (pIn k (j , predℕ-≤-predℕ p)))
+
+      IH1-lemma : ∀ k -> fsuc k ≡ σ .fun fzero -> (g ∼) ∘ pIn (fsuc k) ∘ punch-σ σ .fun ≡ f ∘ fsuc
+      IH1-lemma k Sk≡σ0 =
+          (g ∼) ∘ pIn (fsuc k) ∘ punch-σ σ .fun
+        ≡⟨ congS (λ z -> (g ∼) ∘ pIn z ∘ punch-σ σ .fun) Sk≡σ0 ⟩
+          (g ∼) ∘ pIn (σ .fun fzero) ∘ punch-σ σ .fun
+        ≡⟨⟩
+          (g ∼) ∘ pIn (σ .fun fzero) ∘ pOut (σ .fun fzero) ∘ ((G .fun σ) .snd) .fun ∘ pIn fzero
+        ≡⟨ congS (λ h -> (g ∼) ∘ h ∘ ((G .fun σ) .snd) .fun ∘ (invIso pIso) .fun) (funExt (pIn∘Out (σ .fun fzero))) ⟩
+          (g ∼) ∘ equivIn σ .fun ∘ pIn fzero
+        ≡⟨⟩
+          g ∘ σ .fun ∘ fst ∘ pIn fzero
+        ≡⟨ congS (_∘ fst ∘ pIn fzero) (sym p) ⟩
+          f ∘ fst ∘ pIn fzero
+        ≡⟨ congS (f ∘_) (funExt pInZ≡fsuc) ⟩
+          f ∘ fsuc ∎
+
+      IH2-lemma : ∀ k -> fsuc k ≡ σ .fun fzero -> (j : Fin (suc n)) -> g (fsuc (fill-σ k .fun j)) ≡ (g-σ k) j
+      IH2-lemma k Sk≡σ0 (zero , r) = congS g Sk≡σ0
+      IH2-lemma k Sk≡σ0 (suc j , r) =
+          g (fsuc (equivOut {k = k} (compIso pIso (invIso pIso)) .fun (suc j , r)))
+        ≡⟨⟩
+          g (fsuc (equivOut {k = k} (compIso pIso (invIso pIso)) .fun (j' .fst)))
+        ≡⟨ congS (g ∘ fsuc) (equivOut-beta-α {σ = compIso pIso (invIso pIso)} j') ⟩
+          g (fsuc (fst (pIn k (pOut fzero j'))))
+        ≡⟨⟩
+          g (fsuc (fst (pIn k (⊎.rec _ (λ k<j -> predℕ (suc j) , _) (suc j <? 0 on _)))))
+        ≡⟨ congS (g ∘ fsuc ∘ fst ∘ pIn k ∘ ⊎.rec _ _) (<?-beta-inr (suc j) 0 _ (suc-≤-suc zero-≤)) ⟩
+          (g ∘ fsuc ∘ fst ∘ pIn k) (predℕ (suc j) , _)
+        ≡⟨ congS {x = predℕ (suc j) , _} {y = j , predℕ-≤-predℕ r} (g ∘ fsuc ∘ fst ∘ pIn k) (Fin-fst-≡ refl) ⟩
+          (g ∘ fsuc ∘ fst ∘ pIn k) (j , predℕ-≤-predℕ r) ∎
+        where
+        j' : FinExcept fzero
+        j' = (suc j , r) , znots ∘ (congS fst)
+
+      case1 : (tab (suc n) (f ∘ fsuc) ≡ tab (suc n) (g ∘ fsuc))
+            -> σ .fun fzero ≡ fzero
+            -> tab (suc (suc n)) f ≡ tab (suc (suc n)) g
+      case1 IH σ0≡0 =
+        tab (suc (suc n)) f ≡⟨⟩
+        f fzero ∷ tab (suc n) (f ∘ fsuc) ≡⟨ congS (_∷ tab (suc n) (f ∘ fsuc)) (funExt⁻ p fzero) ⟩
+        g (σ .fun fzero) ∷ tab (suc n) (f ∘ fsuc) ≡⟨ congS (\k -> g k ∷ tab (suc n) (f ∘ fsuc)) σ0≡0 ⟩
+        g fzero ∷ tab (suc n) (f ∘ fsuc) ≡⟨ congS (g fzero ∷_) IH ⟩
+        g fzero ∷ tab (suc n) (g ∘ fsuc) ≡⟨⟩
+        tab (suc (suc n)) g ∎
+      case2 : (k : Fin (suc n))
+            -> σ .fun fzero ≡ fsuc k
+            -> tab (suc n) (f ∘ fsuc) ≡ tab (suc n) ((g ∼) ∘ pIn (fsuc k))
+            -> tab (suc n) (g-σ k) ≡ tab (suc n) (g ∘ fsuc)
+            -> tab (suc (suc n)) f ≡ tab (suc (suc n)) g
+      case2 k σ0≡Sk IH1 IH2 =
+        comm (f fzero) (g fzero) (tab n ((g ∼) ∘ pIn (fsuc k) ∘ fsuc))
+          (sym (eqn1 IH1)) (sym (eqn2 IH2))
+        where
+        eqn1 : tab (suc n) (f ∘ fsuc) ≡ tab (suc n) ((g ∼) ∘ pIn (fsuc k))
+              -> g fzero ∷ tab n ((g ∼) ∘ pIn (fsuc k) ∘ fsuc) ≡ tab (suc n) (f ∘ fsuc)
+        eqn1 IH =
+            g fzero ∷ tab n ((g ∼) ∘ pIn (fsuc k) ∘ fsuc)
+          ≡⟨ congS (λ z -> g z ∷ tab n ((g ∼) ∘ pIn (fsuc k) ∘ fsuc)) (Fin-fst-≡ refl) ⟩
+            ((g ∼) ∘ pIn (fsuc k)) fzero ∷ tab n ((g ∼) ∘ pIn (fsuc k) ∘ fsuc)
+          ≡⟨⟩
+            tab (suc n) ((g ∼) ∘ pIn (fsuc k))
+          ≡⟨ sym IH ⟩
+            tab (suc n) (f ∘ fsuc) ∎
+
+        g-σ≡ : tab (suc n) (g-σ k) ≡ g (σ .fun fzero) ∷ tab n ((g ∼) ∘ 1+_ ∘ pIn k)
+        g-σ≡ = congS (λ z -> g (σ .fun fzero) ∷ tab n z)
+          (funExt λ z -> congS {x = (fst z , pred-≤-pred (snd (fsuc z)))} ((g ∼) ∘ 1+_ ∘ pIn k) (Fin-fst-≡ refl))
+
+        eqn2 : tab (suc n) (g-σ k) ≡ tab (suc n) (g ∘ fsuc)
+            -> f fzero ∷ tab n ((g ∼) ∘ pIn (fsuc k) ∘ fsuc) ≡ tab (suc n) (g ∘ fsuc)
+        eqn2 IH2 =
+            f fzero ∷ tab n ((g ∼) ∘ pIn (fsuc k) ∘ fsuc)
+          ≡⟨ congS (λ h -> h fzero ∷ tab n ((g ∼) ∘ pIn (fsuc k) ∘ fsuc)) p ⟩
+            g (σ .fun fzero) ∷ tab n ((g ∼) ∘ pIn (fsuc k) ∘ fsuc)
+          ≡⟨ congS (λ h -> g (σ .fun fzero) ∷ tab n ((g ∼) ∘ h)) (sym pIn-fsuc-nat) ⟩
+            g (σ .fun fzero) ∷ tab n ((g ∼) ∘ 1+_ ∘ pIn k)
+          ≡⟨ sym g-σ≡ ⟩
+            tab (suc n) (g-σ k)
+          ≡⟨ IH2 ⟩
+            tab (suc n) (g ∘ fsuc) ∎
+
+  abstract
+    toCList-eq' : ∀ n m f g -> (r : (n , f) ≈ (m , g)) -> tab n f ≡ tab m g
+    toCList-eq' n m f g (σ , p) =
+      tab n f ≡⟨ toCList-eq n f (g ∘ (finSubst n≡m)) (compIso σ (Fin≅ (sym n≡m))) (sym lemma-α) ⟩
+      (uncurry tab) (n , g ∘ finSubst n≡m) ≡⟨ congS (uncurry tab) (Array≡ n≡m λ _ _ -> congS g (Fin-fst-≡ refl)) ⟩
+      (uncurry tab) (m , g) ∎
+      where
+      n≡m : n ≡ m
+      n≡m = ≈-length σ
+      lemma-α : g ∘ finSubst n≡m ∘ (Fin≅ (sym n≡m)) .fun ∘ σ .fun ≡ f
+      lemma-α =
+          g ∘ finSubst n≡m ∘ finSubst (sym n≡m) ∘ σ .fun
+        ≡⟨ congS {x = finSubst n≡m ∘ finSubst (sym n≡m)} {y = idfun _} (λ h -> g ∘ h ∘ σ .fun) (funExt (λ x -> Fin-fst-≡ refl)) ⟩
+          g ∘ σ .fun
+        ≡⟨ sym p ⟩
+          f ∎
+
+  abstract
+    toCList : Bag A -> CList A
+    toCList Q.[ (n , f) ] = tab n f
+    toCList (eq/ (n , f) (m , g) r i) = toCList-eq' n m f g r i
+    toCList (squash/ xs ys p q i j) =
+      isSetCList (toCList xs) (toCList ys) (congS toCList p) (congS toCList q) i j
+
+    toCList-η : (xs : Array A) -> toCList Q.[ xs ] ≡ ArrayToCList xs
+    toCList-η xs = refl
+
+    toCList-e : toCList 𝔅.e ≡ CL.[]
+    toCList-e = refl
+
+    toCList-++ : ∀ xs ys -> toCList (xs 𝔅.⊕ ys) ≡ toCList xs ℭ.⊕ toCList ys
+    toCList-++ =
+      elimProp (λ _ -> isPropΠ (λ _ -> isSetCList _ _)) λ xs ->
+        elimProp (λ _ -> isSetCList _ _) λ ys ->
+          sym (ArrayToCListHom .snd M.`⊕ ⟪ xs ⨾ ys ⟫)
+
+    toCList∘fromCList-η : ∀ x -> toCList (fromCList CL.[ x ]) ≡ CL.[ x ]
+    toCList∘fromCList-η x = refl
+
+    fromCList∘toCList-η : ∀ x -> fromCList (toCList Q.[ A.η x ]) ≡ Q.[ A.η x ]
+    fromCList∘toCList-η x = fromCList-η x
+
+  toCList-fromCList : ∀ xs -> toCList (fromCList xs) ≡ xs
+  toCList-fromCList =
+    elimCListProp.f _
+      (congS toCList fromCList-e ∙ toCList-e) 
+      (λ x {xs} p ->
+        toCList (fromCList (x ∷ xs)) ≡⟨ congS toCList (fromCList-++ CL.[ x ] xs) ⟩
+        toCList (fromCList CL.[ x ] 𝔅.⊕ fromCList xs) ≡⟨ toCList-++ (fromCList CL.[ x ]) (fromCList xs) ⟩
+        toCList (fromCList CL.[ x ]) ℭ.⊕ toCList (fromCList xs) ≡⟨ congS (toCList (fromCList CL.[ x ]) ℭ.⊕_) p ⟩
+        toCList (fromCList CL.[ x ]) ℭ.⊕ xs ≡⟨ congS {x = toCList (fromCList CL.[ x ])} {y = CL.[ x ]} (ℭ._⊕ xs) (toCList∘fromCList-η x) ⟩
+        CL.[ x ] ℭ.⊕ xs
+      ∎)
+      (isSetCList _ _)
+
+  fromList-toCList : ∀ xs -> fromCList (toCList xs) ≡ xs
+  fromList-toCList = elimProp (λ _ -> squash/ _ _) (uncurry lemma)
+    where
+    lemma : (n : ℕ) (f : Fin n -> A) -> fromCList (toCList Q.[ n , f ]) ≡ Q.[ n , f ]
+    lemma zero f =
+      fromCList (toCList Q.[ zero , f ]) ≡⟨ congS fromCList (toCList-η (zero , f)) ⟩
+      fromCList [] ≡⟨ fromCList-e ⟩
+      𝔅.e ≡⟨ congS Q.[_] (e-eta _ (zero , f) refl refl) ⟩
+      Q.[ zero , f ] ∎
+    lemma (suc n) f =
+        fromCList (toCList Q.[ suc n , f ])
+      ≡⟨ congS fromCList (toCList-η (suc n , f)) ⟩
+        fromCList (ArrayToCList (suc n , f))
+      ≡⟨ congS (fromCList ∘ ArrayToCList) (sym (η+fsuc f)) ⟩
+        fromCList (ArrayToCList (A.η (f fzero) ⊕ (n , f ∘ fsuc)))
+      ≡⟨ congS fromCList $ sym (ArrayToCListHom .snd M.`⊕ ⟪ A.η (f fzero) ⨾ (n , f ∘ fsuc) ⟫) ⟩
+        fromCList (f fzero ∷ ArrayToCList (n , f ∘ fsuc))
+      ≡⟨ fromCList-++ CL.[ f fzero ] (ArrayToCList (n , f ∘ fsuc)) ⟩
+        fromCList CL.[ f fzero ] 𝔅.⊕ fromCList (ArrayToCList (n , f ∘ fsuc))
+      ≡⟨ congS (𝔅._⊕ fromCList (ArrayToCList (n , f ∘ fsuc))) (fromCList-η (f fzero)) ⟩
+        Q.[ A.η (f fzero) ] 𝔅.⊕ fromCList (ArrayToCList (n , f ∘ fsuc))
+      ≡⟨ congS (λ zs -> Q.[ A.η (f fzero) ] 𝔅.⊕ fromCList zs) (sym (toCList-η (n , f ∘ fsuc))) ⟩
+        Q.[ A.η (f fzero) ] 𝔅.⊕ fromCList (toCList Q.[ n , f ∘ fsuc ])
+      ≡⟨ congS (Q.[ A.η (f fzero) ] 𝔅.⊕_) (lemma n (f ∘ fsuc)) ⟩
+        Q.[ A.η (f fzero) ] 𝔅.⊕ Q.[ n , f ∘ fsuc ]
+      ≡⟨ QFreeMon.[ A ]-isMonHom (PermRel A) .snd M.`⊕ ⟪ _ ⨾ _ ⟫ ⟩
+        Q.[ A.η (f fzero) 𝔄.⊕ (n , f ∘ fsuc) ]
+      ≡⟨ congS Q.[_] (η+fsuc f) ⟩
+        Q.[ suc n , f ] ∎
+
+  BagToCList : Iso (Bag A) (CList A)
+  BagToCList = iso toCList fromCList toCList-fromCList fromList-toCList
+
+bagDef' : ∀ {ℓ ℓ'} -> BagDef.Free ℓ ℓ' 2
+bagDef' {ℓ = ℓ} {ℓ' = ℓ'} = BagDef.isoAux .fun (Bag , bagFreeAux)
+  where
+  clistFreeAux : BagDef.FreeAux ℓ ℓ' 2 CList
+  clistFreeAux = (inv BagDef.isoAux clistDef) .snd
+
+  bagFreeAux : BagDef.FreeAux ℓ ℓ' 2 Bag
+  bagFreeAux = subst (BagDef.FreeAux ℓ ℓ' 2)
+    (funExt λ X -> isoToPath $ invIso (IsoToCList.BagToCList X)) clistFreeAux
diff --git a/Cubical/Structures/Set/CMon/CList.agda b/Cubical/Structures/Set/CMon/CList.agda
new file mode 100644
index 0000000..7de6c5f
--- /dev/null
+++ b/Cubical/Structures/Set/CMon/CList.agda
@@ -0,0 +1,178 @@
+{-# OPTIONS --cubical --safe --exact-split #-}
+
+module Cubical.Structures.Set.CMon.CList where
+
+open import Cubical.Foundations.Everything
+open import Cubical.Data.Sigma
+open import Cubical.Data.Nat
+open import Cubical.Data.Nat.Order
+open import Cubical.Data.Empty as ⊥
+import Cubical.Data.List as L
+
+import Cubical.Structures.Set.Mon.Desc as M
+import Cubical.Structures.Set.CMon.Desc as M
+import Cubical.Structures.Free as F
+open import Cubical.Structures.Sig
+open import Cubical.Structures.Str public
+open import Cubical.Structures.Tree
+open import Cubical.Structures.Eq
+open import Cubical.Structures.Arity
+
+infixr 20 _∷_
+
+data CList {a} (A : Type a) : Type a where
+  [] : CList A
+  _∷_ : (a : A) -> (as : CList A) -> CList A
+  comm : (a b : A)
+      -> {as bs : CList A} (cs : CList A)
+      -> (p : as ≡ b ∷ cs) (q : bs ≡ a ∷ cs)
+      -> a ∷ as ≡ b ∷ bs
+  isSetCList : isSet (CList A)
+
+pattern [_] a = a ∷ []
+
+module elimCListSet {ℓ p : Level} {A : Type ℓ} (P : CList A -> Type p)
+                   ([]* : P [])
+                   (_∷*_ : (x : A) {xs : CList A} -> P xs -> P (x ∷ xs))
+                   (comm* : (a b : A)
+                            -> {as bs : CList A} {cs : CList A}
+                            -> {as* : P as}
+                            -> {bs* : P bs}
+                            -> (cs* : P cs)
+                            -> {p : as ≡ b ∷ cs} {q : bs ≡ a ∷ cs}
+                            -> (bp : PathP (λ i -> P (p i)) as* (b ∷* cs*))
+                            -> (bq : PathP (λ i -> P (q i)) bs* (a ∷* cs*))
+                            -> PathP (λ i -> P (comm a b cs p q i)) (a ∷* as*) (b ∷* bs*)
+                   )
+                   (isSetCList* : {xs : CList A} -> isSet (P xs))
+                   where
+  f : (xs : CList A) -> P xs
+  f [] = []*
+  f (a ∷ as) = a ∷* f as
+  f (comm a b {as} {bs} cs p q i) =
+    comm* a b (f cs) (cong f p) (cong f q) i
+  f (isSetCList xs ys p q i j) =
+    isOfHLevel→isOfHLevelDep 2 (λ xs -> isSetCList* {xs = xs}) (f xs) (f ys) (cong f p) (cong f q) (isSetCList xs ys p q) i j
+
+module elimCListProp {ℓ p : Level} {A : Type ℓ} (P : CList A -> Type p)
+                   ([]* : P [])
+                   (_∷*_ : (x : A) {xs : CList A} -> P xs -> P (x ∷ xs))
+                   (isSetCList* : {xs : CList A} -> isProp (P xs))
+                   where
+  f : (xs : CList A) -> P xs
+  f = elimCListSet.f P []* _∷*_
+    (λ a b {as} {bs} {cs} {as*} {bs*} cs* bp bq -> toPathP (isSetCList* _ (b ∷* bs*)))
+    (isProp→isSet isSetCList*)
+
+private
+  variable
+    ℓ : Level
+    A : Type ℓ
+
+_++_ : CList A -> CList A -> CList A
+[] ++ bs = bs
+(a ∷ as) ++ bs = a ∷ (as ++ bs)
+comm a b cs p q i ++ bs = comm a b (cs ++ bs) (cong (_++ bs) p) (cong (_++ bs) q) i
+isSetCList a b p q i j ++ bs = isSetCList (a ++ bs) (b ++ bs) (cong (_++ bs) p) (cong (_++ bs) q) i j
+
+++-unitl : (as : CList A) -> [] ++ as ≡ as
+++-unitl as = refl
+
+++-unitr : (as : CList A) -> as ++ [] ≡ as
+++-unitr = elimCListProp.f _ refl (λ a p -> cong (a ∷_) p) (isSetCList _ _)
+
+++-assocr : (as bs cs : CList A) -> (as ++ bs) ++ cs ≡ as ++ (bs ++ cs)
+++-assocr = elimCListProp.f _
+  (λ _ _ -> refl)
+  (λ x p bs cs -> cong (x ∷_) (p bs cs))
+  (isPropΠ λ _ -> isPropΠ λ _ -> isSetCList _ _)
+
+swap : (a b : A) (cs : CList A) -> a ∷ b ∷ cs ≡ b ∷ a ∷ cs
+swap a b cs = comm a b cs refl refl
+
+++-∷ : (a : A) (as : CList A) -> a ∷ as ≡ as ++ [ a ]
+++-∷ a = elimCListProp.f (λ as -> a ∷ as ≡ as ++ [ a ])
+  refl
+  (λ b {as} p -> swap a b as ∙ cong (b ∷_) p)
+  (isSetCList _ _) 
+
+++-comm : (as bs : CList A) -> as ++ bs ≡ bs ++ as
+++-comm = elimCListProp.f _
+  (sym ∘ ++-unitr)
+  (λ a {as} p bs -> cong (a ∷_) (p bs) ∙ cong (_++ as) (++-∷ a bs) ∙ ++-assocr bs [ a ] as)
+  (isPropΠ λ _ -> isSetCList _ _)
+
+clist-α : ∀ {n : Level} {X : Type n} -> sig M.MonSig (CList X) -> CList X
+clist-α (M.`e , i) = []
+clist-α (M.`⊕ , i) = i fzero ++ i fone
+
+module Free {x y : Level} {A : Type x} {𝔜 : struct y M.MonSig} (isSet𝔜 : isSet (𝔜 .car)) (𝔜-cmon : 𝔜 ⊨ M.CMonSEq) where
+  module 𝔜 = M.CMonSEq 𝔜 𝔜-cmon
+
+  𝔛 : M.CMonStruct
+  𝔛 = < CList A , clist-α >
+
+  module _ (f : A -> 𝔜 .car) where
+    _♯ : CList A -> 𝔜 .car
+    _♯ = elimCListSet.f _
+      𝔜.e
+      (λ a p -> f a 𝔜.⊕ p)
+      (λ a b {ab} {bs} {cs} {as*} {bs*} cs* bp bq ->
+        f a 𝔜.⊕ as* ≡⟨ cong (f a 𝔜.⊕_) bp ⟩
+        f a 𝔜.⊕ f b 𝔜.⊕ cs* ≡⟨ sym (𝔜.assocr _ _ _) ⟩
+        (f a 𝔜.⊕ f b) 𝔜.⊕ cs* ≡⟨ cong (𝔜._⊕ cs*) (𝔜.comm _ _) ⟩
+        (f b 𝔜.⊕ f a) 𝔜.⊕ cs* ≡⟨ 𝔜.assocr _ _ _ ⟩
+        f b 𝔜.⊕ (f a 𝔜.⊕ cs*) ≡⟨ cong (f b 𝔜.⊕_) (sym bq) ⟩
+        f b 𝔜.⊕ bs* ∎
+      )
+      isSet𝔜
+
+    private
+      ♯-++ : ∀ xs ys -> (xs ++ ys) ♯ ≡ (xs ♯) 𝔜.⊕ (ys ♯)
+      ♯-++ = elimCListProp.f _
+        (λ ys -> sym (𝔜.unitl (ys ♯)))
+        (λ a {xs} p ys ->
+          f a 𝔜.⊕ ((xs ++ ys) ♯) ≡⟨ cong (f a 𝔜.⊕_) (p ys) ⟩
+          f a 𝔜.⊕ ((xs ♯) 𝔜.⊕ (ys ♯)) ≡⟨ sym (𝔜.assocr (f a) (xs ♯) (ys ♯)) ⟩
+          _ ∎
+        )
+        (isPropΠ λ _ -> isSet𝔜 _ _)
+
+    ♯-isMonHom : structHom 𝔛 𝔜
+    fst ♯-isMonHom = _♯
+    snd ♯-isMonHom M.`e i = 𝔜.e-eta
+    snd ♯-isMonHom M.`⊕ i = 𝔜.⊕-eta i _♯ ∙ sym (♯-++ (i fzero) (i fone))
+
+  private
+    clistEquivLemma : (g : structHom 𝔛 𝔜) -> (x : CList A) -> g .fst x ≡ ((g .fst ∘ [_]) ♯) x
+    clistEquivLemma (g , homMonWit) = elimCListProp.f _
+      (sym (homMonWit M.`e (lookup L.[])) ∙ 𝔜.e-eta)
+      (λ x {xs} p ->
+        g (x ∷ xs) ≡⟨ sym (homMonWit M.`⊕ (lookup ([ x ] L.∷ xs L.∷ L.[]))) ⟩
+        _ ≡⟨ 𝔜.⊕-eta (lookup ([ x ] L.∷ xs L.∷ L.[])) g ⟩
+        _ ≡⟨ cong (g [ x ] 𝔜.⊕_) p ⟩
+        _ ∎
+      )
+      (isSet𝔜 _ _)
+
+    clistEquivLemma-β : (g : structHom 𝔛 𝔜) -> g ≡ ♯-isMonHom (g .fst ∘ [_])
+    clistEquivLemma-β g = structHom≡ 𝔛 𝔜 g (♯-isMonHom (g .fst ∘ [_])) isSet𝔜 (funExt (clistEquivLemma g))
+
+  clistMonEquiv : structHom 𝔛 𝔜 ≃ (A -> 𝔜 .car)
+  clistMonEquiv =
+    isoToEquiv (iso (λ g -> g .fst ∘ [_]) ♯-isMonHom (λ g -> funExt (𝔜.unitr ∘ g)) (sym ∘ clistEquivLemma-β))
+
+module CListDef = F.Definition M.MonSig M.CMonEqSig M.CMonSEq
+
+clist-sat : ∀ {n} {X : Type n} -> < CList X , clist-α > ⊨ M.CMonSEq
+clist-sat (M.`mon M.`unitl) ρ = ++-unitl (ρ fzero)
+clist-sat (M.`mon M.`unitr) ρ = ++-unitr (ρ fzero)
+clist-sat (M.`mon M.`assocr) ρ = ++-assocr (ρ fzero) (ρ fone) (ρ ftwo)
+clist-sat M.`comm ρ = ++-comm (ρ fzero) (ρ fone)
+
+clistDef : ∀ {ℓ ℓ'} -> CListDef.Free ℓ ℓ' 2
+F.Definition.Free.F clistDef = CList
+F.Definition.Free.η clistDef = [_]
+F.Definition.Free.α clistDef = clist-α
+F.Definition.Free.sat clistDef = clist-sat
+F.Definition.Free.isFree clistDef isSet𝔜 satMon = (Free.clistMonEquiv isSet𝔜 satMon) .snd
diff --git a/Cubical/Structures/Set/CMon/Desc.agda b/Cubical/Structures/Set/CMon/Desc.agda
new file mode 100644
index 0000000..614685f
--- /dev/null
+++ b/Cubical/Structures/Set/CMon/Desc.agda
@@ -0,0 +1,103 @@
+{-# OPTIONS --cubical --safe --exact-split #-}
+
+module Cubical.Structures.Set.CMon.Desc where
+
+open import Cubical.Foundations.Everything
+open import Cubical.Data.Nat
+open import Cubical.Data.Nat.Order
+open import Cubical.Data.List
+open import Cubical.Data.Sigma
+open import Cubical.Data.Empty as ⊥
+open import Cubical.Functions.Logic as L
+open import Cubical.Structures.Arity as F public
+
+open import Cubical.Structures.Sig
+open import Cubical.Structures.Str public
+open import Cubical.Structures.Tree
+open import Cubical.Structures.Eq
+
+import Cubical.Structures.Set.Mon.Desc as M
+
+open M.MonSym
+
+CMonSym = M.MonSym
+CMonAr = M.MonAr
+CMonFinSig = M.MonFinSig
+CMonSig = M.MonSig
+
+CMonStruct : ∀ {n} -> Type (ℓ-suc n)
+CMonStruct {n} = struct n CMonSig
+
+CMon→Mon : ∀ {ℓ} -> CMonStruct {ℓ} -> M.MonStruct {ℓ}
+car (CMon→Mon 𝔛) = 𝔛 .car
+alg (CMon→Mon 𝔛) = 𝔛 .alg
+
+module CMonStruct {ℓ} (𝔛 : CMonStruct {ℓ}) where
+  open M.MonStruct (CMon→Mon 𝔛) public
+
+data CMonEq : Type where
+  `mon : M.MonEq -> CMonEq
+  `comm : CMonEq
+
+CMonEqFree : CMonEq -> ℕ
+CMonEqFree (`mon eqn) = M.MonEqFree eqn
+CMonEqFree `comm = 2
+
+CMonEqSig : EqSig ℓ-zero ℓ-zero
+CMonEqSig = finEqSig (CMonEq , CMonEqFree)
+
+cmonEqLhs : (eq : CMonEq) -> FinTree CMonFinSig (CMonEqFree eq)
+cmonEqLhs (`mon eqn) = M.monEqLhs eqn
+cmonEqLhs `comm = node (`⊕ , lookup (leaf fzero ∷ leaf fone ∷ []))
+
+cmonEqRhs : (eq : CMonEq) -> FinTree CMonFinSig (CMonEqFree eq)
+cmonEqRhs (`mon eqn) = M.monEqRhs eqn
+cmonEqRhs `comm = node (`⊕ , lookup (leaf fone ∷ leaf fzero ∷ []))
+
+CMonSEq : seq CMonSig CMonEqSig
+CMonSEq n = cmonEqLhs n , cmonEqRhs n
+
+cmonSatMon : ∀ {s} {str : struct s CMonSig} -> str ⊨ CMonSEq -> str ⊨ M.MonSEq
+cmonSatMon {_} {str} cmonSat eqn ρ = cmonSat (`mon eqn) ρ
+
+module CMonSEq {ℓ} (𝔛 : CMonStruct {ℓ}) (ϕ : 𝔛 ⊨ CMonSEq) where
+  open M.MonSEq (CMon→Mon 𝔛) (cmonSatMon ϕ) public
+
+  comm : ∀ m n -> m ⊕ n ≡ n ⊕ m
+  comm m n =
+      m ⊕ n
+    ≡⟨⟩
+      𝔛 .alg (`⊕ , lookup (m ∷ n ∷ []))
+    ≡⟨ cong (λ z -> 𝔛 .alg (`⊕ , z)) (funExt lemma1) ⟩
+      𝔛 .alg (`⊕ , (λ x -> sharp CMonSig 𝔛 (lookup (m ∷ n ∷ [])) (lookup (leaf fzero ∷ leaf fone ∷ []) x)))
+    ≡⟨ ϕ `comm (lookup (m ∷ n ∷ [])) ⟩
+      𝔛 .alg (`⊕ , (λ x -> sharp CMonSig 𝔛 (lookup (m ∷ n ∷ [])) (lookup (leaf fone ∷ leaf fzero ∷ []) x)))
+    ≡⟨ cong (λ z -> 𝔛 .alg (`⊕ , z)) (sym (funExt lemma2)) ⟩
+      𝔛 .alg (`⊕ , lookup (n ∷ m ∷ []))
+    ≡⟨⟩
+      n ⊕ m ∎
+    where
+      lemma1 : (w : CMonSig .arity `⊕) -> lookup (m ∷ n ∷ []) w ≡ sharp CMonSig 𝔛 (lookup (m ∷ n ∷ [])) (lookup (leaf fzero ∷ leaf fone ∷ []) w)
+      lemma1 (zero , p) = refl
+      lemma1 (suc zero , p) = refl
+      lemma1 (suc (suc n) , p) = ⊥.rec (¬m+n<m {m = 2} p)
+
+      lemma2 : (w : CMonSig .arity `⊕) -> lookup (n ∷ m ∷ []) w ≡ sharp CMonSig 𝔛 (lookup (m ∷ n ∷ [])) (lookup (leaf fone ∷ leaf fzero ∷ []) w)
+      lemma2 (zero , p) = refl
+      lemma2 (suc zero , p) = refl
+      lemma2 (suc (suc n) , p) = ⊥.rec (¬m+n<m {m = 2} p)
+
+ℕ-CMonStr : CMonStruct
+ℕ-CMonStr = M.ℕ-MonStr
+
+ℕ-CMonStr-MonSEq : ℕ-CMonStr ⊨ CMonSEq
+ℕ-CMonStr-MonSEq (`mon eqn) ρ = M.ℕ-MonStr-MonSEq eqn ρ
+ℕ-CMonStr-MonSEq `comm ρ = +-comm (ρ fzero) (ρ fone)
+
+⊔-MonStr-CMonSEq : (ℓ : Level) -> M.⊔-MonStr ℓ ⊨ CMonSEq
+⊔-MonStr-CMonSEq ℓ (`mon eqn) ρ = M.⊔-MonStr-MonSEq ℓ eqn ρ
+⊔-MonStr-CMonSEq ℓ `comm ρ = ⊔-comm (ρ fzero) (ρ fone)
+
+⊓-MonStr-CMonSEq : (ℓ : Level) -> M.⊓-MonStr ℓ ⊨ CMonSEq
+⊓-MonStr-CMonSEq ℓ (`mon eqn) ρ = M.⊓-MonStr-MonSEq ℓ eqn ρ
+⊓-MonStr-CMonSEq ℓ `comm ρ = ⊓-comm (ρ fzero) (ρ fone)
\ No newline at end of file
diff --git a/Cubical/Structures/Set/CMon/Free.agda b/Cubical/Structures/Set/CMon/Free.agda
new file mode 100644
index 0000000..f131770
--- /dev/null
+++ b/Cubical/Structures/Set/CMon/Free.agda
@@ -0,0 +1,142 @@
+{-# OPTIONS --cubical --safe --exact-split #-}
+
+module Cubical.Structures.Set.CMon.Free where
+
+open import Cubical.Foundations.Everything
+open import Cubical.Data.Sigma
+open import Cubical.Data.List
+open import Cubical.Data.Nat
+open import Cubical.Data.Nat.Order
+import Cubical.Data.Empty as ⊥
+
+import Cubical.Structures.Set.Mon.Desc as M
+import Cubical.Structures.Set.Mon.Free as FM
+import Cubical.Structures.Set.CMon.Desc as M
+import Cubical.Structures.Free as F
+open import Cubical.Structures.Sig
+open import Cubical.Structures.Str public
+open import Cubical.Structures.Tree
+open import Cubical.Structures.Eq
+open import Cubical.Structures.Arity
+
+data FreeCMon {ℓ : Level} (A : Type ℓ) : Type ℓ where
+  η : (a : A) -> FreeCMon A
+  e : FreeCMon A
+  _⊕_ : FreeCMon A -> FreeCMon A -> FreeCMon A
+  unitl : ∀ m -> e ⊕ m ≡ m
+  unitr : ∀ m -> m ⊕ e ≡ m
+  assocr : ∀ m n o -> (m ⊕ n) ⊕ o ≡ m ⊕ (n ⊕ o)
+  comm : ∀ m n -> m ⊕ n ≡ n ⊕ m
+  trunc : isSet (FreeCMon A)
+
+module elimFreeCMonSet {p n : Level} {A : Type n} (P : FreeCMon A -> Type p)
+                    (η* : (a : A) -> P (η a))
+                    (e* : P e)
+                    (_⊕*_ : {m n : FreeCMon A} -> P m -> P n -> P (m ⊕ n))
+                    (unitl* : {m : FreeCMon A} (m* : P m) -> PathP (λ i → P (unitl m i)) (e* ⊕* m*) m*)
+                    (unitr* : {m : FreeCMon A} (m* : P m) -> PathP (λ i → P (unitr m i)) (m* ⊕* e*) m*)
+                    (assocr* : {m n o : FreeCMon A}
+                               (m* : P m) ->
+                               (n* : P n) ->
+                               (o* : P o) ->
+                               PathP (λ i → P (assocr m n o i)) ((m* ⊕* n*) ⊕* o*) (m* ⊕* (n* ⊕* o*)))
+                    (comm* : {m n : FreeCMon A}
+                               (m* : P m) ->
+                               (n* : P n) ->  
+                               PathP (λ i → P (comm m n i)) (m* ⊕* n*) (n* ⊕* m*))
+                    (trunc* : {xs : FreeCMon A} -> isSet (P xs))
+                    where
+  f : (x : FreeCMon A) -> P x
+  f (η a) = η* a
+  f e = e*
+  f (x ⊕ y) = f x ⊕* f y
+  f (unitl x i) = unitl* (f x) i
+  f (unitr x i) = unitr* (f x) i
+  f (assocr x y z i) = assocr* (f x) (f y) (f z) i
+  f (comm x y i) = comm* (f x) (f y) i
+  f (trunc xs ys p q i j) =
+     isOfHLevel→isOfHLevelDep 2 (\xs -> trunc* {xs = xs}) (f xs) (f ys) (cong f p) (cong f q) (trunc xs ys p q) i j
+
+module elimFreeCMonProp {p n : Level} {A : Type n} (P : FreeCMon A -> Type p)
+                    (η* : (a : A) -> P (η a))
+                    (e* : P e)
+                    (_⊕*_ : {m n : FreeCMon A} -> P m -> P n -> P (m ⊕ n))
+                    (trunc* : {xs : FreeCMon A} -> isProp (P xs))
+                    where
+  f : (x : FreeCMon A) -> P x
+  f = elimFreeCMonSet.f P η* e* _⊕*_ unitl* unitr* assocr* comm* (isProp→isSet trunc*)
+    where
+      abstract
+        unitl* : {m : FreeCMon A} (m* : P m) -> PathP (λ i → P (unitl m i)) (e* ⊕* m*) m*
+        unitl* {m} m* = toPathP (trunc* (transp (λ i -> P (unitl m i)) i0 (e* ⊕* m*)) m*)
+        unitr* : {m : FreeCMon A} (m* : P m) -> PathP (λ i → P (unitr m i)) (m* ⊕* e*) m*
+        unitr* {m} m* = toPathP (trunc* (transp (λ i -> P (unitr m i)) i0 (m* ⊕* e*)) m*)
+        assocr* : {m n o : FreeCMon A}
+                  (m* : P m) ->
+                  (n* : P n) ->
+                  (o* : P o) -> PathP (λ i → P (assocr m n o i)) ((m* ⊕* n*) ⊕* o*) (m* ⊕* (n* ⊕* o*))
+        assocr* {m} {n} {o} m* n* o* =
+          toPathP (trunc* (transp (λ i -> P (assocr m n o i)) i0 ((m* ⊕* n*) ⊕* o*)) (m* ⊕* (n* ⊕* o*)))
+        comm* : {m n : FreeCMon A} (m* : P m) (n* : P n) -> PathP (λ i → P (comm m n i)) (m* ⊕* n*) (n* ⊕* m*)
+        comm* {m} {n} m* n* = toPathP (trunc* (transp (λ i -> P (comm m n i)) i0 (m* ⊕* n*)) (n* ⊕* m*))
+
+freeCMon-α : ∀ {ℓ} {X : Type ℓ} -> sig M.MonSig (FreeCMon X) -> FreeCMon X
+freeCMon-α (M.`e , _) = e
+freeCMon-α (M.`⊕ , i) = i fzero ⊕ i fone
+
+module Free {x y : Level} {A : Type x} {𝔜 : struct y M.MonSig} (isSet𝔜 : isSet (𝔜 .car)) (𝔜-cmon : 𝔜 ⊨ M.CMonSEq) where
+  module 𝔜 = M.CMonSEq 𝔜 𝔜-cmon
+
+  𝔉 : struct x M.MonSig
+  𝔉 = < FreeCMon A , freeCMon-α >
+
+  module _ (f : A -> 𝔜 .car) where
+    _♯ : FreeCMon A -> 𝔜 .car
+    _♯ (η a) = f a
+    _♯ e = 𝔜.e
+    _♯ (m ⊕ n) = (m ♯) 𝔜.⊕ (n ♯)
+    _♯ (unitl m i) = 𝔜.unitl (m ♯) i
+    _♯ (unitr m i) = 𝔜.unitr (m ♯) i
+    _♯ (assocr m n o i) = 𝔜.assocr (m ♯) (n ♯) (o ♯) i
+    comm m n i ♯ = 𝔜.comm (m ♯) (n ♯) i
+    (trunc m n p q i j) ♯ = isSet𝔜 (m ♯) (n ♯) (cong _♯ p) (cong _♯ q) i j
+
+    ♯-isMonHom : structHom 𝔉 𝔜
+    fst ♯-isMonHom = _♯
+    snd ♯-isMonHom M.`e i = 𝔜.e-eta
+    snd ♯-isMonHom M.`⊕ i = 𝔜.⊕-eta i _♯
+
+  private
+    freeCMonEquivLemma : (g : structHom 𝔉 𝔜) -> (x : FreeCMon A) -> g .fst x ≡ ((g .fst ∘ η) ♯) x
+    freeCMonEquivLemma (g , homMonWit) = elimFreeCMonProp.f (λ x -> g x ≡ ((g ∘ η) ♯) x)
+      (λ _ -> refl)
+      (sym (homMonWit M.`e (lookup [])) ∙ 𝔜.e-eta)
+      (λ {m} {n} p q ->
+        g (m ⊕ n) ≡⟨ sym (homMonWit M.`⊕ (lookup (m ∷ n ∷ []))) ⟩
+        𝔜 .alg (M.`⊕ , (λ w -> g (lookup (m ∷ n ∷ []) w))) ≡⟨ 𝔜.⊕-eta (lookup (m ∷ n ∷ [])) g ⟩
+        g m 𝔜.⊕ g n ≡⟨ cong₂ 𝔜._⊕_ p q ⟩
+        _ ∎
+      )
+      (isSet𝔜 _ _)
+
+    freeCMonEquivLemma-β : (g : structHom 𝔉 𝔜) -> g ≡ ♯-isMonHom (g .fst ∘ η)
+    freeCMonEquivLemma-β g = structHom≡ 𝔉 𝔜 g (♯-isMonHom (g .fst ∘ η)) isSet𝔜 (funExt (freeCMonEquivLemma g))
+
+  freeCMonEquiv : structHom 𝔉 𝔜 ≃ (A -> 𝔜 .car)
+  freeCMonEquiv =
+    isoToEquiv (iso (λ g -> g .fst ∘ η) ♯-isMonHom (λ _ -> refl) (sym ∘ freeCMonEquivLemma-β))
+
+module FreeCMonDef = F.Definition M.MonSig M.CMonEqSig M.CMonSEq
+
+freeCMon-sat : ∀ {n} {X : Type n} -> < FreeCMon X , freeCMon-α > ⊨ M.CMonSEq
+freeCMon-sat (M.`mon M.`unitl) ρ = unitl (ρ fzero)
+freeCMon-sat (M.`mon M.`unitr) ρ = unitr (ρ fzero)
+freeCMon-sat (M.`mon M.`assocr) ρ = assocr (ρ fzero) (ρ fone) (ρ ftwo)
+freeCMon-sat M.`comm ρ = comm (ρ fzero) (ρ fone)
+
+freeMonDef : ∀ {ℓ ℓ'} -> FreeCMonDef.Free ℓ ℓ' 2
+F.Definition.Free.F freeMonDef = FreeCMon
+F.Definition.Free.η freeMonDef = η
+F.Definition.Free.α freeMonDef = freeCMon-α
+F.Definition.Free.sat freeMonDef = freeCMon-sat
+F.Definition.Free.isFree freeMonDef isSet𝔜 satMon = (Free.freeCMonEquiv isSet𝔜 satMon) .snd
diff --git a/Cubical/Structures/Set/CMon/PList.agda b/Cubical/Structures/Set/CMon/PList.agda
new file mode 100644
index 0000000..f17a339
--- /dev/null
+++ b/Cubical/Structures/Set/CMon/PList.agda
@@ -0,0 +1,115 @@
+{-# OPTIONS --cubical --safe --exact-split #-}
+
+Definition taken from https://drops.dagstuhl.de/opus/volltexte/2023/18395/pdf/LIPIcs-ITP-2023-20.pdf
+module Cubical.Structures.Set.CMon.PList where
+
+open import Cubical.Core.Everything
+open import Cubical.Foundations.Everything
+open import Cubical.Data.List as L
+
+import Cubical.Structures.Set.Mon.Desc as M
+import Cubical.Structures.Set.Mon.List as LM
+import Cubical.Structures.Set.CMon.Desc as M
+import Cubical.Structures.Free as F
+open import Cubical.Structures.Sig
+open import Cubical.Structures.Str public
+open import Cubical.Structures.Tree
+open import Cubical.Structures.Eq
+open import Cubical.Structures.Arity hiding (_/_)
+open import Cubical.Structures.Set.CMon.QFreeMon
+
+data Perm {ℓ : Level} {A : Type ℓ} : List A -> List A -> Type ℓ where
+  perm-refl : ∀ {xs} -> Perm xs xs
+  perm-swap : ∀ {x y xs ys zs} -> Perm (xs ++ x ∷ y ∷ ys) zs -> Perm (xs ++ y ∷ x ∷ ys) zs 
+
+private
+  variable
+    ℓ ℓ₁ ℓ₂ : Level
+    A B : Type ℓ
+
+infixr 30 _∙ₚ_
+_∙ₚ_ : ∀ {xs ys zs} -> Perm xs ys -> Perm ys zs -> Perm {A = A} xs zs
+perm-refl ∙ₚ q = q
+(perm-swap p) ∙ₚ q = perm-swap (p ∙ₚ q)
+
+perm-sym : ∀ {xs ys} -> Perm xs ys -> Perm {A = A} ys xs
+perm-sym perm-refl = perm-refl
+perm-sym (perm-swap p) = perm-sym p ∙ₚ perm-swap perm-refl
+
+perm-subst : ∀ {xs ys} -> xs ≡ ys -> Perm {A = A} xs ys
+perm-subst {xs = xs} p = subst (Perm xs) p perm-refl
+
+perm-∷ : ∀ {x xs ys} -> Perm xs ys -> Perm {A = A} (x ∷ xs) (x ∷ ys)
+perm-∷ perm-refl = perm-refl
+perm-∷ {x = x} (perm-swap {xs = xs} p) = perm-swap {xs = x ∷ xs} (perm-∷ p)
+
+perm-prepend : (xs : List A) {ys zs : List A} -> Perm ys zs -> Perm (xs ++ ys) (xs ++ zs)
+perm-prepend [] p = p
+perm-prepend (x ∷ xs) p = perm-∷ (perm-prepend xs p)
+
+perm-append : ∀ {xs ys} -> Perm xs ys -> (zs : List A) -> Perm (xs ++ zs) (ys ++ zs)
+perm-append perm-refl _ = perm-refl
+perm-append (perm-swap {xs = xs} p) _ =
+  perm-subst (++-assoc xs _ _) ∙ₚ perm-swap (perm-subst (sym (++-assoc xs _ _)) ∙ₚ perm-append p _)
+
+perm-movehead : (x : A) (xs : List A) {ys : List A} -> Perm (x ∷ xs ++ ys) (xs ++ x ∷ ys)
+perm-movehead x [] = perm-refl
+perm-movehead x (y ∷ xs) = perm-swap {xs = []} (perm-∷ (perm-movehead x xs))
+
+⊕-commₚ : (xs ys : List A) -> Perm (xs ++ ys) (ys ++ xs)
+⊕-commₚ xs [] = perm-subst (++-unit-r xs)
+⊕-commₚ xs (y ∷ ys) = perm-sym (perm-movehead y xs {ys = ys}) ∙ₚ perm-∷ (⊕-commₚ xs ys)
+
+module _ {ℓA ℓB} {A : Type ℓA} {𝔜 : struct ℓB M.MonSig} {isSet𝔜 : isSet (𝔜 .car)} (𝔜-cmon : 𝔜 ⊨ M.CMonSEq) (f : A -> 𝔜 .car) where
+  module 𝔜 = M.CMonSEq 𝔜 𝔜-cmon
+
+  f♯-hom = LM.Free.♯-isMonHom isSet𝔜 (M.cmonSatMon 𝔜-cmon) f
+
+  f♯ : List A -> 𝔜 .car
+  f♯ = f♯-hom .fst
+
+  f♯-++ : ∀ xs ys -> f♯ (xs ++ ys) ≡ f♯ xs 𝔜.⊕ f♯ ys
+  f♯-++ xs ys =
+    f♯ (xs ++ ys) ≡⟨ sym ((f♯-hom .snd) M.`⊕ (lookup (xs ∷ ys ∷ []))) ⟩
+    𝔜 .alg (M.`⊕ , (λ w -> f♯ (lookup (xs ∷ ys ∷ []) w))) ≡⟨ 𝔜.⊕-eta (lookup (xs ∷ ys ∷ [])) f♯ ⟩
+    _ ∎
+
+  f♯-swap : ∀ {x y : A} (xs ys : List A) -> f♯ (xs ++ x ∷ y ∷ ys) ≡ f♯ (xs ++ y ∷ x ∷ ys)
+  f♯-swap {x} {y} [] ys =
+    f♯ ((L.[ x ] ++ L.[ y ]) ++ ys) ≡⟨ f♯-++ (L.[ x ] ++ L.[ y ]) ys  ⟩
+    f♯ (L.[ x ] ++ L.[ y ]) 𝔜.⊕ f♯ ys ≡⟨ cong (𝔜._⊕ f♯ ys) (f♯-++ L.[ x ] L.[ y ]) ⟩
+    (f♯ L.[ x ] 𝔜.⊕ f♯ L.[ y ]) 𝔜.⊕ f♯ ys ≡⟨ cong (𝔜._⊕ f♯ ys) (𝔜.comm _ _) ⟩
+    (f♯ L.[ y ] 𝔜.⊕ f♯ L.[ x ]) 𝔜.⊕ f♯ ys ≡⟨ cong (𝔜._⊕ f♯ ys) (sym (f♯-++ L.[ y ] L.[ x ])) ⟩
+    f♯ (L.[ y ] ++ L.[ x ]) 𝔜.⊕ f♯ ys ≡⟨ sym (f♯-++ (L.[ y ] ++ L.[ x ]) ys) ⟩
+    f♯ ((L.[ y ] ++ L.[ x ]) ++ ys) ∎
+  f♯-swap {x} {y} (a ∷ as) ys =
+    f♯ (L.[ a ] ++ (as ++ x ∷ y ∷ ys)) ≡⟨ f♯-++ L.[ a ] (as ++ x ∷ y ∷ ys) ⟩
+    f♯ L.[ a ] 𝔜.⊕ f♯ (as ++ x ∷ y ∷ ys) ≡⟨ cong (f♯ L.[ a ] 𝔜.⊕_) (f♯-swap as ys) ⟩
+    f♯ L.[ a ] 𝔜.⊕ f♯ (as ++ y ∷ x ∷ ys) ≡⟨ sym (f♯-++ L.[ a ] (as ++ y ∷ x ∷ ys)) ⟩
+    f♯ (L.[ a ] ++ (as ++ y ∷ x ∷ ys)) ≡⟨⟩
+    f♯ ((a ∷ as) ++ y ∷ x ∷ ys) ∎
+
+  perm-resp-f♯ : {a b : List A} -> Perm a b -> f♯ a ≡ f♯ b
+  perm-resp-f♯ perm-refl = refl
+  perm-resp-f♯ (perm-swap {xs = xs} {ys = ys} p) = f♯-swap xs ys ∙ perm-resp-f♯ p
+
+module _ {ℓ} (A : Type ℓ) where
+  open import Cubical.Relation.Binary
+  module P = BinaryRelation {A = List A} Perm
+  open isPermRel
+
+  isPermRelPerm : isPermRel LM.listDef (Perm {A = A})
+  P.isEquivRel.reflexive (isEquivRel isPermRelPerm) _ = perm-refl
+  P.isEquivRel.symmetric (isEquivRel isPermRelPerm) _ _ = perm-sym
+  P.isEquivRel.transitive (isEquivRel isPermRelPerm) _ _ _ = _∙ₚ_
+  isCongruence isPermRelPerm {a} {b} {c} {d} p q = perm-prepend a q ∙ₚ perm-append p d
+  isCommutative isPermRelPerm {a} {b} = ⊕-commₚ a b
+  resp-♯ isPermRelPerm {isSet𝔜 = isSet𝔜} 𝔜-cmon f p = perm-resp-f♯ {isSet𝔜 = isSet𝔜} 𝔜-cmon f p
+
+  PermRel : PermRelation LM.listDef A
+  PermRel = Perm , isPermRelPerm
+
+module PListDef = F.Definition M.MonSig M.CMonEqSig M.CMonSEq
+
+plistFreeDef : ∀ {ℓ} -> PListDef.Free ℓ ℓ 2
+plistFreeDef = qFreeMonDef (PermRel _)
diff --git a/Cubical/Structures/Set/CMon/QFreeMon.agda b/Cubical/Structures/Set/CMon/QFreeMon.agda
new file mode 100644
index 0000000..9670aa3
--- /dev/null
+++ b/Cubical/Structures/Set/CMon/QFreeMon.agda
@@ -0,0 +1,195 @@
+{-# OPTIONS --cubical --safe --exact-split #-}
+
+module Cubical.Structures.Set.CMon.QFreeMon where
+
+open import Cubical.Core.Everything
+open import Cubical.Foundations.Everything
+open import Cubical.HITs.PropositionalTruncation as P
+open import Cubical.HITs.SetQuotients as Q
+open import Cubical.Data.List as L
+open import Cubical.Relation.Binary
+
+import Cubical.Structures.Set.Mon.Desc as M
+import Cubical.Structures.Set.CMon.Desc as M
+import Cubical.Structures.Free as F
+open import Cubical.Structures.Sig
+open import Cubical.Structures.Str public
+open import Cubical.Structures.Tree
+open import Cubical.Structures.Eq
+open import Cubical.Structures.Arity hiding (_/_)
+open import Cubical.Relation.Nullary hiding (⟪_⟫)
+
+open F.Definition M.MonSig M.MonEqSig M.MonSEq
+open F.Definition.Free
+
+module _ {ℓ ℓ' : Level} (freeMon : Free ℓ ℓ' 2) where
+
+  private
+    ℱ : Type ℓ -> Type ℓ
+    ℱ A = freeMon .F A
+
+  PRel : Type ℓ -> Type (ℓ-max ℓ (ℓ-suc ℓ'))
+  PRel A = Rel (ℱ A) (ℱ A) ℓ'
+
+  record isPermRel {A : Type ℓ} (R : PRel A) : Type (ℓ-max ℓ (ℓ-suc ℓ')) where
+    constructor permRel
+    infix 3 _≈_
+    _≈_ : Rel (ℱ A) (ℱ A) ℓ' ; _≈_ = R
+    TODO: Add ⊕ as a helper in Mon.Desc
+    infixr 10 _⊕_
+    _⊕_ : ℱ A -> ℱ A -> ℱ A
+    a ⊕ b = freeMon .α (M.`⊕ , ⟪ a ⨾ b ⟫)
+    module R = BinaryRelation R
+    field
+      isEquivRel : R.isEquivRel
+      isCongruence : {a b c d : ℱ A}
+                  -> a ≈ b -> c ≈ d
+                  -> a ⊕ c ≈ b ⊕ d
+      isCommutative : {a b : ℱ A}
+                   -> a ⊕ b ≈ b ⊕ a
+      resp-♯ : {a b : ℱ A} {𝔜 : struct ℓ' M.MonSig} {isSet𝔜 : isSet (𝔜 .car)} (𝔜-cmon : 𝔜 ⊨ M.CMonSEq)
+            -> (f : A -> 𝔜 .car)
+            -> a ≈ b
+            -> let f♯ = ext freeMon isSet𝔜 (M.cmonSatMon 𝔜-cmon) f .fst in f♯ a ≡ f♯ b
+
+    refl≈ = isEquivRel .R.isEquivRel.reflexive
+    trans≈ = isEquivRel .R.isEquivRel.transitive
+    cong≈ = isCongruence
+    comm≈ = isCommutative
+    subst≈-left : {a b c : ℱ A} -> a ≡ b -> a ≈ c -> b ≈ c
+    subst≈-left {c = c} = subst (_≈ c)
+    subst≈-right : {a b c : ℱ A} -> b ≡ c -> a ≈ b -> a ≈ c
+    subst≈-right {a = a} = subst (a ≈_)
+    subst≈ : {a b c d : ℱ A} -> a ≡ b -> c ≡ d -> a ≈ c -> b ≈ d
+    subst≈ {a} {b} {c} {d} p q r = trans≈ b c d (subst≈-left p r) (subst≈-right q (refl≈ c))
+
+  PermRelation : Type ℓ -> Type (ℓ-max ℓ (ℓ-suc ℓ'))
+  PermRelation A = Σ (PRel A) isPermRel
+
+module QFreeMon {ℓr ℓB} {freeMon : Free ℓr ℓB 2} (A : Type ℓr) ((R , isPermRelR) : PermRelation freeMon A) where
+  private
+    ℱ = freeMon .F A
+  open isPermRel isPermRelR
+
+  𝒬 : Type (ℓ-max ℓr ℓB)
+  𝒬 = ℱ / _≈_
+
+  𝔉 : M.MonStruct
+  𝔉 = < ℱ , freeMon .α >
+
+  module 𝔉 = M.MonSEq 𝔉 (freeMon .sat)
+
+  e : ℱ
+  e = 𝔉.e
+
+  e/ : 𝒬
+  e/ = Q.[ e ]
+
+  η/ : A -> 𝒬
+  η/ x = Q.[ freeMon .η x ]
+
+  _⊕/_ : 𝒬 -> 𝒬 -> 𝒬
+  _⊕/_ = Q.rec2 squash/
+    (\a b -> Q.[ a ⊕ b ])
+    (\a b c r -> eq/ (a ⊕ c) (b ⊕ c) (cong≈ r (refl≈ c)))
+    (\a b c r -> eq/ (a ⊕ b) (a ⊕ c) (cong≈ (refl≈ a) r))
+
+  ⊕-unitl : (a : 𝒬) -> e/ ⊕/ a ≡ a
+  ⊕-unitl = Q.elimProp
+    (\_ -> squash/ _ _)
+    (\a -> eq/ (e ⊕ a) a (subst≈-right (𝔉.unitl a) (refl≈ (e ⊕ a))))
+
+  ⊕-unitr : (a : 𝒬) -> a ⊕/ e/ ≡ a
+  ⊕-unitr = Q.elimProp
+    (\_ -> squash/ _ _)
+    (\a -> eq/ (a ⊕ e) a (subst≈-right (𝔉.unitr a) (refl≈ (a ⊕ e))))
+
+  ⊕-assocr : (a b c : 𝒬) -> (a ⊕/ b) ⊕/ c ≡ a ⊕/ (b ⊕/ c)
+  ⊕-assocr = Q.elimProp
+    (\_ -> isPropΠ (\_ -> isPropΠ (\_ -> squash/ _ _)))
+    (\a -> elimProp
+      (\_ -> isPropΠ (\_ -> squash/ _ _))
+      (\b -> elimProp
+        (\_ -> squash/ _ _)
+        (\c -> eq/ ((a ⊕ b) ⊕ c) (a ⊕ (b ⊕ c)) (subst≈-right (𝔉.assocr a b c) (refl≈ ((a ⊕ b) ⊕ c))))))
+
+  ⊕-comm : (a b : 𝒬) -> a ⊕/ b ≡ b ⊕/ a
+  ⊕-comm = elimProp
+    (\_ -> isPropΠ (\_ -> squash/ _ _))
+    (\a -> elimProp
+      (\_ -> squash/ _ _)
+      (\b -> eq/ (a ⊕ b) (b ⊕ a) comm≈))
+
+  qFreeMon-α : sig M.MonSig 𝒬 -> 𝒬
+  qFreeMon-α (M.`e , i) = Q.[ e ]
+  qFreeMon-α (M.`⊕ , i) = i fzero ⊕/ i fone
+
+  qFreeMon-sat : < 𝒬 , qFreeMon-α > ⊨ M.CMonSEq
+  qFreeMon-sat (M.`mon M.`unitl) ρ = ⊕-unitl (ρ fzero)
+  qFreeMon-sat (M.`mon M.`unitr) ρ = ⊕-unitr (ρ fzero)
+  qFreeMon-sat (M.`mon M.`assocr) ρ = ⊕-assocr (ρ fzero) (ρ fone) (ρ ftwo)
+  qFreeMon-sat M.`comm ρ = ⊕-comm (ρ fzero) (ρ fone)
+
+  private
+    𝔛 : M.CMonStruct
+    𝔛 = < 𝒬 , qFreeMon-α >
+    
+    module 𝔛 = M.CMonSEq 𝔛 qFreeMon-sat
+
+  [_]-isMonHom : structHom 𝔉 𝔛
+  fst [_]-isMonHom = Q.[_]
+  snd [_]-isMonHom M.`e i = cong _/_.[_] 𝔉.e-eta
+  snd [_]-isMonHom M.`⊕ i =
+    𝔛 .alg (M.`⊕ , (λ x -> Q.[ i x ])) ≡⟨ 𝔛.⊕-eta i Q.[_] ⟩
+    Q.[ freeMon .α (M.`⊕ , _) ] ≡⟨ cong (λ z -> Q.[_] {R = _≈_} (freeMon .α (M.`⊕ , z))) (lookup2≡i i) ⟩
+    Q.[ freeMon .α (M.`⊕ , i) ] ∎
+
+  module IsFree {𝔜 : struct ℓB M.MonSig} (isSet𝔜 : isSet (𝔜 .car)) (𝔜-cmon : 𝔜 ⊨ M.CMonSEq) where
+    module 𝔜 = M.CMonSEq 𝔜 𝔜-cmon
+
+    module _ (f : A -> 𝔜 .car) where
+      f♯ : structHom 𝔉 𝔜
+      f♯ = ext (freeMon) isSet𝔜 (M.cmonSatMon 𝔜-cmon) f
+
+      _♯ : 𝒬 -> 𝔜 .car
+      _♯ = Q.rec isSet𝔜 (f♯ .fst) (\_ _ -> resp-♯ 𝔜-cmon f)
+
+      private
+        ♯-++ : ∀ xs ys -> (xs ⊕/ ys) ♯ ≡ (xs ♯) 𝔜.⊕ (ys ♯)
+        ♯-++ =
+          elimProp (λ _ -> isPropΠ λ _ -> isSet𝔜 _ _) λ xs ->
+            elimProp (λ _ -> isSet𝔜 _ _) λ ys ->
+              f♯ .fst (xs ⊕ ys) ≡⟨ sym (f♯ .snd M.`⊕ (lookup (xs ∷ ys ∷ []))) ⟩
+              _ ≡⟨ 𝔜.⊕-eta (lookup (xs ∷ ys ∷ [])) (f♯ .fst) ⟩
+              _ ∎
+
+      ♯-isMonHom : structHom 𝔛 𝔜
+      fst ♯-isMonHom = _♯
+      snd ♯-isMonHom M.`e i = 𝔜.e-eta ∙ f♯ .snd M.`e (lookup [])
+      snd ♯-isMonHom M.`⊕ i = 𝔜.⊕-eta i _♯ ∙ sym (♯-++ (i fzero) (i fone))
+
+    private
+      qFreeMonEquivLemma : (g : structHom 𝔛 𝔜) (x : 𝔛 .car) -> g .fst x ≡ ((g .fst ∘ η/) ♯) x
+      qFreeMonEquivLemma g = elimProp (λ _ -> isSet𝔜 _ _) λ x i -> lemma (~ i) x
+        where
+        lemma : (f♯ (((g .fst) ∘ Q.[_]) ∘ freeMon .η)) .fst ≡ (g .fst) ∘ Q.[_]
+        lemma = cong fst (ext-β (freeMon) isSet𝔜 (M.cmonSatMon 𝔜-cmon) (structHom∘ 𝔉 𝔛 𝔜 g [_]-isMonHom))
+
+    qFreeMonEquiv : structHom 𝔛 𝔜 ≃ (A -> 𝔜 .car)
+    qFreeMonEquiv =
+      isoToEquiv
+        ( iso
+          (λ g -> g .fst ∘ η/)
+          ♯-isMonHom
+          (ext-η (freeMon) isSet𝔜 (M.cmonSatMon 𝔜-cmon))
+          (λ g -> sym (structHom≡ 𝔛 𝔜 g (♯-isMonHom (g .fst ∘ η/)) isSet𝔜 (funExt (qFreeMonEquivLemma g))))
+        )
+
+module QFreeMonDef = F.Definition M.MonSig M.CMonEqSig M.CMonSEq
+
+qFreeMonDef : ∀ {ℓ : Level} {freeMon : Free ℓ ℓ 2} (R : {A : Type ℓ} -> PermRelation freeMon A) -> QFreeMonDef.Free ℓ ℓ 2
+F (qFreeMonDef R) A = QFreeMon.𝒬 A R
+η (qFreeMonDef R) = QFreeMon.η/ _ R
+α (qFreeMonDef R) = QFreeMon.qFreeMon-α _ R
+sat (qFreeMonDef R) = QFreeMon.qFreeMon-sat _ R
+isFree (qFreeMonDef R) isSet𝔜 𝔜-cmon = (QFreeMon.IsFree.qFreeMonEquiv _ R isSet𝔜 𝔜-cmon) .snd
diff --git a/Cubical/Structures/Set/CMon/SList.agda b/Cubical/Structures/Set/CMon/SList.agda
new file mode 100644
index 0000000..1df4c1d
--- /dev/null
+++ b/Cubical/Structures/Set/CMon/SList.agda
@@ -0,0 +1,7 @@
+{-# OPTIONS --cubical --safe --exact-split #-}
+
+module Cubical.Structures.Set.CMon.SList where
+
+open import Cubical.Structures.Set.CMon.SList.Base public
+open import Cubical.Structures.Set.CMon.SList.Length public
+open import Cubical.Structures.Set.CMon.SList.Membership public
diff --git a/Cubical/Structures/Set/CMon/SList/Base.agda b/Cubical/Structures/Set/CMon/SList/Base.agda
new file mode 100644
index 0000000..c169444
--- /dev/null
+++ b/Cubical/Structures/Set/CMon/SList/Base.agda
@@ -0,0 +1,98 @@
+{-# OPTIONS --cubical --safe --exact-split #-}
+
+module Cubical.Structures.Set.CMon.SList.Base where
+
+open import Cubical.Foundations.Everything
+open import Cubical.Data.Sigma
+open import Cubical.Data.Nat
+open import Cubical.Data.Nat.Order
+open import Cubical.Data.Empty as ⊥
+open import Cubical.Induction.WellFounded
+import Cubical.Data.List as L
+
+import Cubical.Structures.Set.Mon.Desc as M
+import Cubical.Structures.Set.CMon.Desc as M
+import Cubical.Structures.Free as F
+open import Cubical.Structures.Sig
+open import Cubical.Structures.Str public
+open import Cubical.Structures.Tree
+open import Cubical.Structures.Eq
+open import Cubical.Structures.Arity
+open import Cubical.HITs.FiniteMultiset public renaming (FMSet to SList; comm to swap)
+
+pattern [_] a = a ∷ []
+
+private
+  variable
+    ℓ : Level
+    A : Type ℓ
+
+slist-α : ∀ {n : Level} {X : Type n} -> sig M.MonSig (SList X) -> SList X
+slist-α (M.`e , i) = []
+slist-α (M.`⊕ , i) = i fzero ++ i fone
+
+module Free {x y : Level} {A : Type x} {𝔜 : struct y M.MonSig} (isSet𝔜 : isSet (𝔜 .car)) (𝔜-cmon : 𝔜 ⊨ M.CMonSEq) where
+  module 𝔜 = M.CMonSEq 𝔜 𝔜-cmon
+
+  𝔛 : M.CMonStruct
+  𝔛 = < SList A , slist-α >
+
+  module _ (f : A -> 𝔜 .car) where
+    _♯ : SList A -> 𝔜 .car    
+    _♯ = Elim.f 𝔜.e
+      (λ x xs -> (f x) 𝔜.⊕ xs)
+      (λ a b xs i ->
+        ( sym (𝔜.assocr (f a) (f b) xs)
+        ∙ cong (𝔜._⊕ xs) (𝔜.comm (f a) (f b))
+        ∙ 𝔜.assocr (f b) (f a) xs
+        ) i
+      )
+      (λ _ -> isSet𝔜)
+
+    private
+      ♯-++ : ∀ xs ys -> (xs ++ ys) ♯ ≡ (xs ♯) 𝔜.⊕ (ys ♯)
+      ♯-++ = ElimProp.f (isPropΠ λ _ -> isSet𝔜 _ _)
+        (λ ys -> sym (𝔜.unitl (ys ♯)))
+        (λ a {xs} p ys ->
+          f a 𝔜.⊕ ((xs ++ ys) ♯) ≡⟨ cong (f a 𝔜.⊕_) (p ys) ⟩
+          f a 𝔜.⊕ ((xs ♯) 𝔜.⊕ (ys ♯)) ≡⟨ sym (𝔜.assocr (f a) (xs ♯) (ys ♯)) ⟩
+          _
+        ∎)
+
+    ♯-isMonHom : structHom 𝔛 𝔜
+    fst ♯-isMonHom = _♯
+    snd ♯-isMonHom M.`e i = 𝔜.e-eta
+    snd ♯-isMonHom M.`⊕ i = 𝔜.⊕-eta i _♯ ∙ sym (♯-++ (i fzero) (i fone))
+  
+  private
+    slistEquivLemma : (g : structHom 𝔛 𝔜) -> (x : SList A) -> g .fst x ≡ ((g .fst ∘ [_]) ♯) x
+    slistEquivLemma (g , homMonWit) = ElimProp.f (isSet𝔜 _ _)
+      (sym (homMonWit M.`e (lookup L.[])) ∙ 𝔜.e-eta)
+      (λ x {xs} p ->
+        g (x ∷ xs) ≡⟨ sym (homMonWit M.`⊕ (lookup ([ x ] L.∷ xs L.∷ L.[]))) ⟩
+        _ ≡⟨ 𝔜.⊕-eta (lookup ([ x ] L.∷ xs L.∷ L.[])) g ⟩
+        _ ≡⟨ cong (g [ x ] 𝔜.⊕_) p ⟩
+        _ ∎
+      )
+  
+    slistEquivLemma-β : (g : structHom 𝔛 𝔜) -> g ≡ ♯-isMonHom (g .fst ∘ [_])
+    slistEquivLemma-β g = structHom≡ 𝔛 𝔜 g (♯-isMonHom (g .fst ∘ [_])) isSet𝔜 (funExt (slistEquivLemma g))
+
+  slistMonEquiv : structHom 𝔛 𝔜 ≃ (A -> 𝔜 .car)
+  slistMonEquiv =
+    isoToEquiv (iso (λ g -> g .fst ∘ [_]) ♯-isMonHom (λ g -> funExt (𝔜.unitr ∘ g)) (sym ∘ slistEquivLemma-β))
+
+module SListDef = F.Definition M.MonSig M.CMonEqSig M.CMonSEq
+
+slist-sat : ∀ {n} {X : Type n} -> < SList X , slist-α > ⊨ M.CMonSEq
+slist-sat (M.`mon M.`unitl) ρ = unitl-++ (ρ fzero)
+slist-sat (M.`mon M.`unitr) ρ = unitr-++ (ρ fzero)
+slist-sat (M.`mon M.`assocr) ρ = sym (assoc-++ (ρ fzero) (ρ fone) (ρ ftwo))
+slist-sat M.`comm ρ = comm-++ (ρ fzero) (ρ fone)
+
+slistDef : ∀ {ℓ ℓ'} -> SListDef.Free ℓ ℓ' 2
+F.Definition.Free.F slistDef = SList
+F.Definition.Free.η slistDef = [_]
+F.Definition.Free.α slistDef = slist-α
+F.Definition.Free.sat slistDef = slist-sat
+F.Definition.Free.isFree slistDef isSet𝔜 satMon = (Free.slistMonEquiv isSet𝔜 satMon) .snd
diff --git a/Cubical/Structures/Set/CMon/SList/Length.agda b/Cubical/Structures/Set/CMon/SList/Length.agda
new file mode 100644
index 0000000..5941b6f
--- /dev/null
+++ b/Cubical/Structures/Set/CMon/SList/Length.agda
@@ -0,0 +1,148 @@
+{-# OPTIONS --cubical --exact-split --safe #-}
+
+module Cubical.Structures.Set.CMon.SList.Length where
+
+open import Cubical.Core.Everything
+open import Cubical.Foundations.Everything
+open import Cubical.Data.Sum
+open import Cubical.Data.Prod
+open import Cubical.Data.Empty as E
+open import Cubical.Data.Unit
+open import Cubical.Data.Nat
+open import Cubical.Data.Sigma
+open import Cubical.Functions.Embedding
+
+open import Cubical.Structures.Set.CMon.SList.Base as SList
+
+private
+  variable
+    ℓ : Level
+    A B : Type ℓ
+    ϕ : isSet A
+    a x : A
+    xs ys : SList A
+
+disj-nil-cons : x ∷ xs ≡ [] -> ⊥
+disj-nil-cons p = transport (λ i → fst (code (p i))) tt
+  where code : SList A -> hProp ℓ-zero
+        code = Elim.f (⊥ , isProp⊥)
+          (λ _ _ -> Unit , isPropUnit)
+          (λ _ _ _ _ -> Unit , isPropUnit)
+          (λ _ -> isSetHProp)
+
+disj-cons-nil : [] ≡ x ∷ xs -> ⊥
+disj-cons-nil p = disj-nil-cons (sym p)
+
+length : SList A → ℕ
+length = Elim.f 0 (λ _ n -> suc n) (λ _ _ _ -> refl) (λ _ -> isSetℕ)
+
+length-++ : (x y : SList A) → length (x ++ y) ≡ length x + length y
+length-++ x y = ElimProp.f {B = λ xs → length (xs ++ y) ≡ length xs + length y}
+  (isSetℕ _ _) refl (λ a p -> cong suc p) x
+  
+lenZero-out : (xs : SList A) → length xs ≡ 0 → [] ≡ xs
+lenZero-out = ElimProp.f (isPropΠ λ _ → trunc _ _)
+  (λ _ -> refl)
+  (λ x p q -> E.rec (snotz q))
+
+lenZero-eqv : (xs : SList A) → (length xs ≡ 0) ≃ ([] ≡ xs)
+lenZero-eqv xs = propBiimpl→Equiv (isSetℕ _ _) (trunc _ _) (lenZero-out xs) (λ p i → length (p (~ i)))
+
+is-sing-pred : SList A → A → Type _
+is-sing-pred xs a = [ a ] ≡ xs
+
+is-sing-pred-prop : (xs : SList A) (z : A) → isProp (is-sing-pred xs z)
+is-sing-pred-prop xs a = trunc [ a ] xs
+
+is-sing : SList A → Type _
+is-sing xs = Σ _ (is-sing-pred xs)
+
+Sing : Type ℓ → Type ℓ
+Sing A = Σ (SList A) is-sing
+
+[_]-is-sing : (a : A) → is-sing [ a ]
+[ a ]-is-sing = a , refl
+
+sing=isProp : ∀ {x y : A} → isProp ([ x ] ≡ [ y ])
+sing=isProp {x = x} {y = y} = trunc [ x ] [ y ]
+
+sing=-in : ∀ {x y : A} → x ≡ y → [ x ] ≡ [ y ]
+sing=-in p i = [ p i ]
+
+sing=isContr : ∀ {x y : A} → x ≡ y → isContr ([ x ] ≡ [ y ])
+sing=isContr p = sing=-in p , sing=isProp (sing=-in p)
+
+lenOne-down : (x : A) (xs : SList A) → length (x ∷ xs) ≡ 1 → [] ≡ xs
+lenOne-down x xs p = lenZero-out xs (injSuc p)
+
+lenOne-cons : (x : A) (xs : SList A) → length (x ∷ xs) ≡ 1 → is-sing (x ∷ xs)
+lenOne-cons x xs p =
+  let q = lenOne-down x xs p
+  in transport (λ i → is-sing (x ∷ q i)) [ x ]-is-sing
+
+lenTwo-⊥ : (x y : A) (xs : SList A) → (length (y ∷ x ∷ xs) ≡ 1) ≃ ⊥
+lenTwo-⊥ x y xs = (λ p → E.rec (snotz (injSuc p))) , record { equiv-proof = E.elim }
+
+isContrlenTwo-⊥→X : (X : Type ℓ) (x y : A) (xs : SList A) → isContr (length (y ∷ x ∷ xs) ≡ 1 → X)
+isContrlenTwo-⊥→X X x y xs = subst (λ Z → isContr (Z → X)) (sym (ua (lenTwo-⊥ x y xs))) (isContr⊥→A {A = X})
+
+lenOne-swap : {A : Type ℓ} (x y : A) (xs : SList A)
+            → PathP (λ i → length (SList.swap x y xs i) ≡ 1 → is-sing (SList.swap x y xs i))
+                    (λ p → lenOne-cons x (y ∷ xs) p)
+                    (λ p → lenOne-cons y (x ∷ xs) p)
+lenOne-swap {A = A} x y xs =
+  transport (sym (PathP≡Path (λ i → length (SList.swap x y xs i) ≡ 1 → is-sing (SList.swap x y xs i)) _ _))
+            (isContr→isProp (isContrlenTwo-⊥→X _ x y xs) _ _)
+
+lenOne : Type ℓ → Type _
+lenOne A = Σ (SList A) (λ xs → length xs ≡ 1)
+
+module _ {ϕ : isSet A} where
+
+  is-sing-set : (xs : SList A) → isSet (is-sing xs)
+  is-sing-set xs = isSetΣ ϕ λ x → isProp→isSet (is-sing-pred-prop xs x)
+
+  lenOne-out : (xs : SList A) → length xs ≡ 1 → is-sing xs
+  lenOne-out = Elim.f (λ p → E.rec (znots p))
+    (λ x {xs} f p → lenOne-cons x xs p)
+    (λ x y {xs} f → lenOne-swap x y xs)
+    λ xs → isSetΠ (λ p → is-sing-set xs)
+ 
+  head : lenOne A → A
+  head (xs , p) = lenOne-out xs p .fst
+
+  head-β : (a : A) → head ([ a ] , refl) ≡ a
+  head-β a i = transp (λ _ → A) i a
+
+  lenOnePath : (a b : A) → Type _
+  lenOnePath a b = Path (lenOne A) ([ a ] , refl) ([ b ] , refl)
+
+  lenOnePath-in : {a b : A} → [ a ] ≡ [ b ] → lenOnePath a b
+  lenOnePath-in = Σ≡Prop (λ xs → isSetℕ _ _)
+
+  [-]-inj : {a b : A} → [ a ] ≡ [ b ] → a ≡ b
+  [-]-inj {a = a} {b = b} p = aux (lenOnePath-in p)
+    where aux : lenOnePath a b → a ≡ b
+          aux p = sym (head-β a) ∙ cong head p ∙ head-β b
+
+  is-sing-prop : (xs : SList A) → isProp (is-sing xs)
+  is-sing-prop xs (a , ψ) (b , ξ) = Σ≡Prop (is-sing-pred-prop xs) ([-]-inj (ψ ∙ sym ξ))
+
+  lenOne-eqv : (xs : SList A) → (length xs ≡ 1) ≃ (is-sing xs)
+  lenOne-eqv xs = propBiimpl→Equiv (isSetℕ _ _) (is-sing-prop xs) (lenOne-out xs) (λ χ → cong length (sym (χ .snd)))
+
+  lenOne-set-eqv : lenOne A ≃ A
+  lenOne-set-eqv = isoToEquiv (iso head g head-β g-f)
+    where g : A → lenOne A
+          g a = [ a ] , refl
+          g-f : (as : lenOne A) → g (head as) ≡ as
+          g-f (as , ϕ) =
+            let (a , ψ) = lenOne-out as ϕ
+            in Σ≡Prop (λ xs → isSetℕ _ _) {u = ([ a ] , refl)} {v = (as , ϕ)} ψ
+
+  sing-set-eqv : Sing A ≃ A
+  sing-set-eqv = isoToEquiv (iso f (λ a → [ a ] , [ a ]-is-sing) (λ _ → refl) ret)
+    where f : Sing A → A
+          f s = s .snd .fst
+          ret : (s : Sing A) → ([ f s ] , f s , refl) ≡ s
+          ret (s , ψ) = Σ≡Prop is-sing-prop (ψ .snd)
diff --git a/Cubical/Structures/Set/CMon/SList/Membership.agda b/Cubical/Structures/Set/CMon/SList/Membership.agda
new file mode 100644
index 0000000..1fdc1c6
--- /dev/null
+++ b/Cubical/Structures/Set/CMon/SList/Membership.agda
@@ -0,0 +1,82 @@
+{-# OPTIONS --cubical --exact-split --safe #-}
+
+module Cubical.Structures.Set.CMon.SList.Membership where
+
+open import Cubical.Foundations.Everything
+open import Cubical.Data.Sigma
+open import Cubical.Data.Nat
+open import Cubical.Data.Nat.Order
+open import Cubical.Data.Empty as ⊥
+open import Cubical.Induction.WellFounded
+import Cubical.Data.List as L
+open import Cubical.Functions.Logic as L
+open import Cubical.HITs.PropositionalTruncation as P
+open import Cubical.Data.Sum as ⊎
+
+import Cubical.Structures.Set.Mon.Desc as M
+import Cubical.Structures.Set.CMon.Desc as M
+import Cubical.Structures.Free as F
+open import Cubical.Structures.Sig
+open import Cubical.Structures.Str public
+open import Cubical.Structures.Tree
+open import Cubical.Structures.Eq
+open import Cubical.Structures.Arity
+open import Cubical.Structures.Set.Mon.List
+
+open import Cubical.Structures.Set.CMon.SList.Base as SList
+
+private
+  variable
+    ℓ : Level
+    A : Type ℓ
+
+list→slist-Hom : structHom < L.List A , list-α > < SList A , slist-α >
+list→slist-Hom = ListDef.Free.ext listDef trunc (M.cmonSatMon slist-sat) [_]
+
+list→slist : L.List A -> SList A
+list→slist = list→slist-Hom .fst
+
+module Membership* {ℓ} {A : Type ℓ} (isSetA : isSet A) where
+  open SList.Free {A = A} isSetHProp (M.⊔-MonStr-CMonSEq ℓ)
+  
+  ∈*Prop : A -> SList A -> hProp ℓ 
+  ∈*Prop x = (λ y -> (x ≡ y) , isSetA x y) ♯
+
+  _∈*_ : A -> SList A -> Type ℓ
+  x ∈* xs = ∈*Prop x xs .fst
+  
+  isProp-∈* : (x : A) -> (xs : SList A) -> isProp (x ∈* xs)
+  isProp-∈* x xs = (∈*Prop x xs) .snd
+  
+  x∈*xs : ∀ x xs -> x ∈* (x ∷ xs)
+  x∈*xs x xs = L.inl refl
+
+  x∈*[x] : ∀ x -> x ∈* [ x ]
+  x∈*[x] x = x∈*xs x []
+
+  ∈*-∷ : ∀ x y xs -> x ∈* xs -> x ∈* (y ∷ xs)
+  ∈*-∷ x y xs p = L.inr p
+
+  ∈*-++ : ∀ x xs ys -> x ∈* ys -> x ∈* (xs ++ ys)
+  ∈*-++ x xs ys p =
+    ElimProp.f {B = λ zs -> x ∈* (zs ++ ys)} (λ {zs} -> isProp-∈* x (zs ++ ys)) p
+      (λ a {zs} q -> ∈*-∷ x a (zs ++ ys) q)
+      xs
+
+  ¬∈*[] : ∀ x -> (x ∈* []) -> ⊥.⊥
+  ¬∈*[] x = ⊥.rec*
+
+  x∈*[y]→x≡y : ∀ x y -> x ∈* [ y ] -> x ≡ y
+  x∈*[y]→x≡y x y = P.rec (isSetA x y) $ ⊎.rec (idfun _) ⊥.rec*
+
+  open Membership isSetA
+
+  ∈→∈* : ∀ x xs -> x ∈ xs -> x ∈* (list→slist xs)
+  ∈→∈* x (y L.∷ ys) = P.rec
+    (isProp-∈* x (list→slist (y L.∷ ys)))
+    (⊎.rec L.inl (L.inr ∘ ∈→∈* x ys))
+
+  ∈*→∈ : ∀ x xs -> x ∈* (list→slist xs) -> x ∈ xs
+  ∈*→∈ x (y L.∷ ys) = P.rec
+    (isProp-∈ x (y L.∷ ys))
+    (⊎.rec L.inl (L.inr ∘ ∈*→∈ x ys))
\ No newline at end of file
diff --git a/Cubical/Structures/Set/CMon/SList/Seely.agda b/Cubical/Structures/Set/CMon/SList/Seely.agda
new file mode 100644
index 0000000..c77e446
--- /dev/null
+++ b/Cubical/Structures/Set/CMon/SList/Seely.agda
@@ -0,0 +1,141 @@
+{-# OPTIONS --cubical --exact-split --safe #-}
+
+module Cubical.Structures.Set.CMon.SList.Seely where
+
+open import Cubical.Foundations.Everything
+open import Cubical.Data.Sigma
+open import Cubical.Data.Nat
+open import Cubical.Data.Nat.Order
+open import Cubical.Data.Empty as ⊥
+open import Cubical.Induction.WellFounded
+import Cubical.Data.List as L
+open import Cubical.HITs.PropositionalTruncation as P
+open import Cubical.Data.Sum as ⊎
+
+import Cubical.Structures.Set.Mon.Desc as M
+import Cubical.Structures.Set.CMon.Desc as M
+import Cubical.Structures.Free as F
+open import Cubical.Structures.Sig
+open import Cubical.Structures.Str public
+open import Cubical.Structures.Tree
+open import Cubical.Structures.Eq
+open import Cubical.Structures.Arity
+open import Cubical.Structures.Set.Mon.List
+
+open import Cubical.Structures.Set.CMon.SList.Base as SList
+
+module _ {ℓ} {A B : Type ℓ} where
+
+  open SListDef.Free
+
+  isSetSList× : isSet (SList A × SList B)
+  isSetSList× = isSet× trunc trunc
+
+  slist×-α : sig M.MonSig (SList A × SList B) -> (SList A × SList B)
+  slist×-α (M.`e , i) = [] , []
+  slist×-α (M.`⊕ , i) = (i fzero) .fst ++ (i fone) .fst , (i fzero) .snd ++ (i fone) .snd
+
+  slist×-sat : < (SList A × SList B) , slist×-α > ⊨ M.CMonSEq
+  slist×-sat (M.`mon M.`unitl) ρ = refl
+  slist×-sat (M.`mon M.`unitr) ρ = ≡-× (slist-sat (M.`mon M.`unitr) (fst ∘ ρ)) ((slist-sat (M.`mon M.`unitr) (snd ∘ ρ)))
+  slist×-sat (M.`mon M.`assocr) ρ = ≡-× (slist-sat (M.`mon M.`assocr) (fst ∘ ρ)) ((slist-sat (M.`mon M.`assocr) (snd ∘ ρ)))
+  slist×-sat M.`comm ρ = ≡-× (slist-sat M.`comm (fst ∘ ρ)) ((slist-sat M.`comm (snd ∘ ρ)))
+
+  f-η : A ⊎ B -> SList A × SList B
+  f-η (inl x) = [ x ] , []
+  f-η (inr x) = [] , [ x ]
+  
+  f-hom : structHom < SList (A ⊎ B) , slist-α > < (SList A × SList B) , slist×-α >
+  f-hom = ext slistDef isSetSList× slist×-sat f-η
+  
+  f : SList (A ⊎ B) -> SList A × SList B
+  f = f-hom .fst
+
+  mmap : ∀ {X Y : Type ℓ} -> (X -> Y) -> SList X -> SList Y
+  mmap f = ext slistDef trunc slist-sat ([_] ∘ f) .fst
+
+  mmap-++ : ∀ {X Y : Type ℓ} -> ∀ f xs ys -> mmap {X = X} {Y = Y} f (xs ++ ys) ≡ mmap f xs ++ mmap f ys 
+  mmap-++ f xs ys = sym (ext slistDef trunc slist-sat ([_] ∘ f) .snd M.`⊕ ⟪ xs ⨾ ys ⟫)
+
+  mmap-∷ : ∀ {X Y : Type ℓ} -> ∀ f x xs -> mmap {X = X} {Y = Y} f (x ∷ xs) ≡ f x ∷ mmap f xs 
+  mmap-∷ f x xs = mmap-++ f [ x ] xs
+
+  g : SList A × SList B -> SList (A ⊎ B)
+  g (as , bs) = mmap inl as ++ mmap inr bs
+
+  g-++ : ∀ xs ys -> g xs ++ g ys ≡ g (xs .fst ++ ys .fst , xs .snd ++ ys .snd)
+  g-++ (as , bs) (cs , ds) = sym $
+      g (as ++ cs , bs ++ ds)
+    ≡⟨ cong (_++ mmap inr (bs ++ ds)) (mmap-++ inl as cs) ⟩
+      (mmap inl as ++ mmap inl cs) ++ (mmap inr (bs ++ ds))
+    ≡⟨ cong ((mmap inl as ++ mmap inl cs) ++_) (mmap-++ inr bs ds) ⟩
+      (mmap inl as ++ mmap inl cs) ++ (mmap inr bs ++ mmap inr ds)
+    ≡⟨ assoc-++ (mmap inl as ++ mmap inl cs) (mmap inr bs) (mmap inr ds) ⟩
+      ((mmap inl as ++ mmap inl cs) ++ mmap inr bs) ++ mmap inr ds
+    ≡⟨ cong (_++ mmap inr ds) (sym (assoc-++ (mmap inl as) (mmap inl cs) (mmap inr bs))) ⟩
+      (mmap inl as ++ (mmap inl cs ++ mmap inr bs)) ++ mmap inr ds
+    ≡⟨ cong (λ z → (mmap inl as ++ z) ++ mmap inr ds) (comm-++ (mmap inl cs) (mmap inr bs)) ⟩
+      (mmap inl as ++ (mmap inr bs ++ mmap inl cs)) ++ mmap inr ds
+    ≡⟨ cong (_++ mmap inr ds) (assoc-++ (mmap inl as) (mmap inr bs) (mmap inl cs)) ⟩
+      ((mmap inl as ++ mmap inr bs) ++ mmap inl cs) ++ mmap inr ds
+    ≡⟨ sym (assoc-++ (mmap inl as ++ mmap inr bs) (mmap inl cs) (mmap inr ds)) ⟩
+      (mmap inl as ++ mmap inr bs) ++ (mmap inl cs ++ mmap inr ds)
+    ≡⟨⟩
+      g (as , bs) ++ g (cs , ds)
+    ∎
+
+  g-hom : structHom < (SList A × SList B) , slist×-α > < SList (A ⊎ B) , slist-α > 
+  g-hom = g , g-is-hom
+    where
+    g-is-hom : structIsHom < SList A × SList B , slist×-α > < SList (A ⊎ B) , slist-α > g
+    g-is-hom M.`e i = refl
+    g-is-hom M.`⊕ i = g-++ (i fzero) (i fone)
+
+  module _ {ℓ} {X : Type ℓ} (h : structHom < SList X , slist-α > < SList X , slist-α >) (h-η : ∀ x -> h .fst [ x ] ≡ [ x ]) where
+    univ-htpy : ∀ xs -> h .fst xs ≡ xs
+    univ-htpy xs = h~η♯ xs ∙ η♯~id xs
+      where
+      h~η♯ : ∀ xs -> h .fst xs ≡ ext slistDef trunc slist-sat [_] .fst xs
+      h~η♯ = ElimProp.f (trunc _ _) (sym (h .snd M.`e ⟪⟫)) λ x {xs} p ->
+        h .fst (x ∷ xs) ≡⟨ sym (h .snd M.`⊕ ⟪ [ x ] ⨾ xs ⟫) ⟩
+        h .fst [ x ] ++ h .fst xs ≡⟨ congS (_++ h .fst xs) (h-η x) ⟩
+        x ∷ h .fst xs ≡⟨ congS (x ∷_) p ⟩
+        x ∷ ext slistDef trunc slist-sat [_] .fst xs ∎
+      η♯~id : ∀ xs -> ext slistDef trunc slist-sat [_] .fst xs ≡ xs
+      η♯~id xs = congS (λ h -> h .fst xs) (ext-β slistDef trunc slist-sat (idHom < SList X , slist-α >))
+  
+  g-f : ∀ xs -> g (f xs) ≡ xs
+  g-f = univ-htpy (structHom∘ _ _ < SList (A ⊎ B) , slist-α > g-hom f-hom) lemma
+    where
+    lemma : ∀ x -> g (f [ x ]) ≡ [ x ]
+    lemma (inl x) = refl
+    lemma (inr x) = refl
+
+  f-mmap-inl : ∀ as -> f (mmap inl as) ≡ (as , [])
+  f-mmap-inl = ElimProp.f (isSetSList× _ _) refl λ x {xs} p ->
+    f (mmap inl (x ∷ xs)) ≡⟨ cong f (mmap-∷ inl x xs) ⟩
+    f (inl x ∷ mmap inl xs) ≡⟨ sym (f-hom .snd M.`⊕ ⟪ [ inl x ] ⨾ mmap inl xs ⟫) ⟩
+    x ∷ f (mmap inl xs) .fst , f (mmap inl xs) .snd ≡⟨ congS (λ z -> x ∷ z .fst , z .snd) p ⟩
+    x ∷ xs , [] ∎
+
+  f-mmap-inr : ∀ as -> f (mmap inr as) ≡ ([] , as)
+  f-mmap-inr = ElimProp.f (isSetSList× _ _) refl λ x {xs} p ->
+    f (mmap inr (x ∷ xs)) ≡⟨ cong f (mmap-∷ inr x xs) ⟩
+    f (inr x ∷ mmap inr xs) ≡⟨ sym (f-hom .snd M.`⊕ ⟪ [ inr x ] ⨾ mmap inr xs ⟫) ⟩
+    f (mmap inr xs) .fst , x ∷ f (mmap inr xs) .snd ≡⟨ congS (λ z -> z .fst , x ∷ z .snd) p ⟩
+    [] , x ∷ xs ∎
+
+  f-g : ∀ xs -> f (g xs) ≡ xs
+  f-g (as , bs) =
+      f (g (as , bs))
+    ≡⟨ sym (f-hom .snd M.`⊕ ⟪ mmap inl as ⨾ mmap inr bs ⟫) ⟩
+      (f (mmap inl as) .fst ++ f (mmap inr bs) .fst) , (f (mmap inl as) .snd ++ f (mmap inr bs) .snd)
+    ≡⟨ congS (λ z -> (z .fst ++ f (mmap inr bs) .fst) , (z .snd ++ f (mmap inr bs) .snd)) (f-mmap-inl as) ⟩
+      as ++ f (mmap inr bs) .fst , [] ++ f (mmap inr bs) .snd
+    ≡⟨ congS (λ z -> as ++ z .fst , [] ++ z .snd) (f-mmap-inr bs) ⟩
+      as ++ [] , bs
+    ≡⟨ congS (λ zs -> zs , bs) (unitr-++ as) ⟩
+      as , bs ∎
+
+  seely : SList (A ⊎ B) ≃ SList A × SList B
+  seely = isoToEquiv (iso f g f-g g-f)
\ No newline at end of file
diff --git a/Cubical/Structures/Set/CMon/SList/Sort.agda b/Cubical/Structures/Set/CMon/SList/Sort.agda
new file mode 100644
index 0000000..c44b539
--- /dev/null
+++ b/Cubical/Structures/Set/CMon/SList/Sort.agda
@@ -0,0 +1,8 @@
+{-# OPTIONS --cubical --safe --exact-split #-}
+
+module Cubical.Structures.Set.CMon.SList.Sort where
+
+open import Cubical.Structures.Set.CMon.SList.Sort.Base public
+open import Cubical.Structures.Set.CMon.SList.Sort.Order public
+open import Cubical.Structures.Set.CMon.SList.Sort.Sort public
+open import Cubical.Structures.Set.CMon.SList.Sort.Equiv public
diff --git a/Cubical/Structures/Set/CMon/SList/Sort/Base.agda b/Cubical/Structures/Set/CMon/SList/Sort/Base.agda
new file mode 100644
index 0000000..8bb7f5e
--- /dev/null
+++ b/Cubical/Structures/Set/CMon/SList/Sort/Base.agda
@@ -0,0 +1,165 @@
+{-# OPTIONS --cubical --safe --exact-split -WnoUnsupportedIndexedMatch #-}
+
+module Cubical.Structures.Set.CMon.SList.Sort.Base where
+
+open import Cubical.Foundations.Everything
+open import Cubical.Data.Sigma
+open import Cubical.Data.Nat
+open import Cubical.Data.Nat.Order renaming (_≤_ to _≤ℕ_; _<_ to _<ℕ_)
+open import Cubical.Data.Sum as ⊎
+open import Cubical.Data.Maybe as Maybe
+open import Cubical.Data.Empty as ⊥
+open import Cubical.Induction.WellFounded
+open import Cubical.Relation.Binary
+open import Cubical.Relation.Binary.Order 
+open import Cubical.Relation.Nullary
+open import Cubical.Relation.Nullary.HLevels
+open import Cubical.Data.List
+open import Cubical.HITs.PropositionalTruncation as P
+import Cubical.Data.List as L
+open import Cubical.Functions.Logic as L hiding (¬_; ⊥) 
+
+import Cubical.Structures.Set.Mon.Desc as M
+import Cubical.Structures.Set.CMon.Desc as M
+import Cubical.Structures.Free as F
+open import Cubical.Structures.Sig
+open import Cubical.Structures.Str public
+open import Cubical.Structures.Tree
+open import Cubical.Structures.Eq
+open import Cubical.Structures.Arity
+open import Cubical.Structures.Set.Mon.List
+open import Cubical.Structures.Set.CMon.SList.Base renaming (_∷_ to _∷*_; [] to []*; [_] to [_]*; _++_ to _++*_)
+import Cubical.Structures.Set.CMon.SList.Base as S
+open import Cubical.Structures.Set.CMon.SList.Length as S
+open import Cubical.Structures.Set.CMon.SList.Membership as S
+
+open Iso
+
+private
+  variable
+    ℓ : Level
+    A : Type ℓ
+
+head-maybe : List A -> Maybe A
+head-maybe [] = nothing
+head-maybe (x ∷ xs) = just x
+
+module Sort {A : Type ℓ} (isSetA : isSet A) (sort : SList A -> List A) where
+  open Membership isSetA
+
+  is-sorted : List A -> Type _
+  is-sorted list = ∥ fiber sort list ∥₁
+
+  is-section : Type _
+  is-section = ∀ xs -> list→slist (sort xs) ≡ xs
+
+  isProp-is-section : isProp is-section
+  isProp-is-section = isPropΠ (λ _ -> trunc _ _)
+
+  is-head-least : Type _
+  is-head-least = ∀ x y xs -> is-sorted (x ∷ xs) -> y ∈ (x ∷ xs) -> is-sorted (x ∷ y ∷ [])
+
+  is-tail-sort : Type _
+  is-tail-sort = ∀ x xs -> is-sorted (x ∷ xs) -> is-sorted xs
+
+  is-sort : Type _
+  is-sort = is-head-least × is-tail-sort
+
+  isProp-is-head-least : isProp is-head-least
+  isProp-is-head-least = isPropΠ5 λ _ _ _ _ _ -> squash₁
+
+  isProp-is-tail-sort : isProp is-tail-sort
+  isProp-is-tail-sort = isPropΠ3 (λ _ _ _ -> squash₁)
+
+  isProp-is-sort : isProp is-sort
+  isProp-is-sort = isProp× isProp-is-head-least isProp-is-tail-sort
+
+  is-sort-section : Type _
+  is-sort-section = is-section × is-sort
+
+  isProp-is-sort-section : isProp is-sort-section
+  isProp-is-sort-section = isOfHLevelΣ 1 isProp-is-section (λ _ -> isProp-is-sort)
+
+  module Section (sort≡ : is-section) where
+    open Membership* isSetA
+
+    list→slist-η : ∀ xs -> (x : A) -> list→slist xs ≡ [ x ]* -> xs ≡ [ x ]
+    list→slist-η [] x p = ⊥.rec (znots (congS S.length p))
+    list→slist-η (x ∷ []) y p = congS [_] ([-]-inj {ϕ = isSetA} p)
+    list→slist-η (x ∷ y ∷ xs) z p = ⊥.rec (snotz (injSuc (congS S.length p)))
+
+    sort-length≡-α : ∀ (xs : List A) -> L.length xs ≡ S.length (list→slist xs)
+    sort-length≡-α [] = refl
+    sort-length≡-α (x ∷ xs) = congS suc (sort-length≡-α xs)
+
+    sort-length≡ : ∀ xs -> L.length (sort xs) ≡ S.length xs
+    sort-length≡ xs = sort-length≡-α (sort xs) ∙ congS S.length (sort≡ xs)
+
+    length-0 : ∀ (xs : List A) -> L.length xs ≡ 0 -> xs ≡ []
+    length-0 [] p = refl
+    length-0 (x ∷ xs) p = ⊥.rec (snotz p)
+
+    sort-[] : ∀ xs -> sort xs ≡ [] -> xs ≡ []*
+    sort-[] xs p = sym (sort≡ xs) ∙ congS list→slist p
+
+    sort-[]' : sort []* ≡ []
+    sort-[]' = length-0 (sort []*) (sort-length≡ []*)
+
+    sort-[-] : ∀ x -> sort [ x ]* ≡ [ x ]
+    sort-[-] x = list→slist-η (sort [ x ]*) x (sort≡ [ x ]*)
+
+    sort-∈ : ∀ x xs -> x ∈* xs -> x ∈ sort xs
+    sort-∈ x xs p = ∈*→∈ x (sort xs) (subst (x ∈*_) (sym (sort≡ xs)) p)
+
+    sort-∈* : ∀ x xs -> x ∈ sort xs -> x ∈* xs
+    sort-∈* x xs p = subst (x ∈*_) (sort≡ xs) (∈→∈* x (sort xs) p)
+
+    sort-unique : ∀ xs -> is-sorted xs -> sort (list→slist xs) ≡ xs
+    sort-unique xs = P.rec (isOfHLevelList 0 isSetA _ xs) λ (ys , p) ->
+      sym (congS sort (sym (sort≡ ys) ∙ congS list→slist p)) ∙ p
+
+    sort-choice-lemma : ∀ x -> sort (x ∷* x ∷* []*) ≡ x ∷ x ∷ []
+    sort-choice-lemma x with sort (x ∷* x ∷* []*) | inspect sort (x ∷* x ∷* []*)
+    ... | []                | [ p ]ᵢ = ⊥.rec (snotz (sym (sort-length≡ (x ∷* x ∷* []*)) ∙ congS L.length p))
+    ... | x₁ ∷ []           | [ p ]ᵢ = ⊥.rec (snotz (injSuc (sym (sort-length≡ (x ∷* x ∷* []*)) ∙ congS L.length p)))
+    ... | x₁ ∷ x₂ ∷ x₃ ∷ xs | [ p ]ᵢ = ⊥.rec (znots (injSuc (injSuc (sym (sort-length≡ (x ∷* x ∷* []*)) ∙ congS L.length p))))
+    ... | a ∷ b ∷ [] | [ p ]ᵢ =
+      P.rec (isOfHLevelList 0 isSetA _ _)
+        (⊎.rec lemma1 (lemma1 ∘ x∈[y]→x≡y a x))
+        (sort-∈* a (x ∷* x ∷* []*) (subst (a ∈_) (sym p) (x∈xs a [ b ])))
+      where
+      lemma2 : a ≡ x -> b ≡ x -> a ∷ b ∷ [] ≡ x ∷ x ∷ []
+      lemma2 q r = cong₂ (λ u v -> u ∷ v ∷ []) q r
+      lemma1 : a ≡ x -> a ∷ b ∷ [] ≡ x ∷ x ∷ []
+      lemma1 q =
+          P.rec (isOfHLevelList 0 isSetA _ _)
+            (⊎.rec (lemma2 q) (lemma2 q ∘ x∈[y]→x≡y b x))
+            (sort-∈* b (x ∷* x ∷* []*) (subst (b ∈_) (sym p) (L.inr (L.inl refl))))
+
+    sort-choice : ∀ x y -> (sort (x ∷* y ∷* []*) ≡ x ∷ y ∷ []) ⊔′ (sort (x ∷* y ∷* []*) ≡ y ∷ x ∷ [])
+    sort-choice x y with sort (x ∷* y ∷* []*) | inspect sort (x ∷* y ∷* []*) 
+    ... | []                | [ p ]ᵢ = ⊥.rec (snotz (sym (sort-length≡ (x ∷* y ∷* []*)) ∙ congS L.length p))
+    ... | x₁ ∷ []           | [ p ]ᵢ = ⊥.rec (snotz (injSuc (sym (sort-length≡ (x ∷* y ∷* []*)) ∙ congS L.length p)))
+    ... | x₁ ∷ x₂ ∷ x₃ ∷ xs | [ p ]ᵢ = ⊥.rec (znots (injSuc (injSuc (sym (sort-length≡ (x ∷* y ∷* []*)) ∙ congS L.length p))))
+    ... | a ∷ b ∷ [] | [ p ]ᵢ =
+      P.rec squash₁
+        (⊎.rec
+          (λ x≡a -> P.rec squash₁
+            (⊎.rec
+              (λ y≡a -> L.inl (sym p ∙ subst (λ u -> sort (x ∷* [ u ]*) ≡ x ∷ u ∷ []) (x≡a ∙ sym y≡a) (sort-choice-lemma x)))
+              (λ y∈[b] -> L.inl (cong₂ (λ u v → u ∷ v ∷ []) (sym x≡a) (sym (x∈[y]→x≡y y b y∈[b]))))
+            )
+            (subst (y ∈_) p (sort-∈ y (x ∷* y ∷* []*) (L.inr (L.inl refl))))
+          )
+          (λ x∈[b] -> P.rec squash₁
+            (⊎.rec
+              (λ y≡a -> L.inr (cong₂ (λ u v → u ∷ v ∷ []) (sym y≡a) (sym (x∈[y]→x≡y x b x∈[b]))))
+              (λ y∈[b] ->
+                let x≡y = (x∈[y]→x≡y x b x∈[b]) ∙ sym (x∈[y]→x≡y y b y∈[b])
+                in L.inl (sym p ∙ subst (λ u -> sort (x ∷* [ u ]*) ≡ x ∷ u ∷ []) x≡y (sort-choice-lemma x))
+              )
+            )
+            (subst (y ∈_) p (sort-∈ y (x ∷* y ∷* []*) (L.inr (L.inl refl))))
+          )
+        )
+        (subst (x ∈_) p (sort-∈ x (x ∷* y ∷* []*) (L.inl refl)))
diff --git a/Cubical/Structures/Set/CMon/SList/Sort/Equiv.agda b/Cubical/Structures/Set/CMon/SList/Sort/Equiv.agda
new file mode 100644
index 0000000..dc05969
--- /dev/null
+++ b/Cubical/Structures/Set/CMon/SList/Sort/Equiv.agda
@@ -0,0 +1,172 @@
+{-# OPTIONS --cubical --exact-split -WnoUnsupportedIndexedMatch --safe #-}
+
+module Cubical.Structures.Set.CMon.SList.Sort.Equiv where
+
+open import Cubical.Foundations.Everything
+open import Cubical.Data.Sigma
+open import Cubical.Data.Nat
+open import Cubical.Data.Nat.Order renaming (_≤_ to _≤ℕ_; _<_ to _<ℕ_)
+open import Cubical.Data.Sum as ⊎
+open import Cubical.Data.Maybe as Maybe
+open import Cubical.Data.Empty as ⊥
+open import Cubical.Induction.WellFounded
+open import Cubical.Relation.Binary
+open import Cubical.Relation.Binary.Order 
+open import Cubical.Relation.Nullary
+open import Cubical.Relation.Nullary.HLevels
+open import Cubical.Data.List
+open import Cubical.HITs.PropositionalTruncation as P
+open import Cubical.Functions.Embedding
+import Cubical.Data.List as L
+open import Cubical.Functions.Logic as L hiding (¬_; ⊥) 
+
+import Cubical.Structures.Set.Mon.Desc as M
+import Cubical.Structures.Set.CMon.Desc as M
+import Cubical.Structures.Free as F
+open import Cubical.Structures.Sig
+open import Cubical.Structures.Str public
+open import Cubical.Structures.Tree
+open import Cubical.Structures.Eq
+open import Cubical.Structures.Arity
+open import Cubical.Structures.Set.Mon.List
+open import Cubical.Structures.Set.CMon.SList.Base renaming (_∷_ to _∷*_; [] to []*; [_] to [_]*; _++_ to _++*_)
+import Cubical.Structures.Set.CMon.SList.Base as S
+open import Cubical.Structures.Set.CMon.SList.Length as S
+open import Cubical.Structures.Set.CMon.SList.Membership as S
+open import Cubical.Structures.Set.CMon.SList.Sort.Base
+open import Cubical.Structures.Set.CMon.SList.Sort.Sort
+open import Cubical.Structures.Set.CMon.SList.Sort.Order
+
+open Iso
+
+private
+  variable
+    ℓ : Level
+    A : Type ℓ
+
+module Sort↔Order {ℓ : Level} {A : Type ℓ} (isSetA : isSet A) where
+  open Sort isSetA
+  open Sort.Section isSetA
+  open Sort→Order isSetA
+  open Order→Sort
+  open IsToset
+
+  IsDecOrder : (A -> A -> Type ℓ) -> Type _
+  IsDecOrder _≤_ = IsToset _≤_ × (∀ x y -> Dec (x ≤ y))
+
+  HasDecOrder : Type _
+  HasDecOrder = Σ _ IsDecOrder
+
+  IsHeadLeastSection : (SList A -> List A) -> Type _
+  IsHeadLeastSection q = is-section q × is-head-least q
+
+  IsSortSection : (SList A -> List A) -> Type _
+  IsSortSection q = is-section q × is-head-least q × is-tail-sort q
+
+  HasHeadLeastSectionAndIsDiscrete : Type _
+  HasHeadLeastSectionAndIsDiscrete = (Σ _ IsHeadLeastSection) × (Discrete A)
+
+  HasSortSectionAndIsDiscrete : Type _
+  HasSortSectionAndIsDiscrete = (Σ _ IsSortSection) × (Discrete A)
+
+  IsSortSection→IsHeadLeastSection : ∀ q -> IsSortSection q -> IsHeadLeastSection q
+  IsSortSection→IsHeadLeastSection q (section , head-least , _) = section , head-least
+
+  order→sort : HasDecOrder -> HasSortSectionAndIsDiscrete
+  order→sort (_≤_ , isToset , isDec) =
+    (sort _≤_ isToset isDec , subst (λ isSetA' -> Sort.is-sort-section isSetA' (sort _≤_ isToset isDec)) (isPropIsSet _ _) (Order→Sort.sort-is-sort-section _≤_ isToset isDec)) , isDiscreteA _≤_ isToset isDec
+  
+  order→head-least : HasDecOrder -> HasHeadLeastSectionAndIsDiscrete
+  order→head-least p = let ((q , q-is-sort) , r) = order→sort p in (q , IsSortSection→IsHeadLeastSection q q-is-sort) , r
+
+  head-least→order : HasHeadLeastSectionAndIsDiscrete -> HasDecOrder
+  head-least→order ((s , s-is-section , s-is-sort) , discA) =
+    _≤_ s s-is-section , ≤-isToset s s-is-section s-is-sort , dec-≤ s s-is-section discA
+
+  sort→order : HasSortSectionAndIsDiscrete -> HasDecOrder
+  sort→order ((q , q-is-sort) , r) = head-least→order ((q , IsSortSection→IsHeadLeastSection q q-is-sort) , r)
+
+  order→head-least→order : ∀ x -> head-least→order (order→head-least x) ≡ x
+  order→head-least→order (_≤_ , isToset , isDec) =
+    Σ≡Prop (λ _≤'_ -> isOfHLevelΣ 1 (isPropIsToset _) (λ p -> isPropΠ2 λ x y -> isPropDec (is-prop-valued p x y))) (sym ≤-≡)
+    where
+    _≤*_ : A -> A -> Type _
+    _≤*_ = head-least→order (order→head-least (_≤_ , isToset , isDec)) .fst
+
+    ≤*-isToset : IsToset _≤*_
+    ≤*-isToset = head-least→order (order→head-least (_≤_ , isToset , isDec)) .snd .fst
+
+    iso-to : ∀ x y -> x ≤ y -> x ≤* y
+    iso-to x y x≤y with isDec x y
+    ... | yes p = refl
+    ... | no ¬p = ⊥.rec (¬p x≤y)
+
+    iso-from : ∀ x y -> x ≤* y -> x ≤ y
+    iso-from x y x≤y with isDec x y
+    ... | yes p = p
+    ... | no ¬p = ⊥.rec (¬p (subst (_≤ y) (just-inj y x x≤y) (is-refl isToset y)))
+
+    iso-≤ : ∀ x y -> Iso (x ≤ y) (x ≤* y)
+    iso-≤ x y = iso (iso-to x y) (iso-from x y) (λ p -> is-prop-valued ≤*-isToset x y _ p) (λ p -> is-prop-valued isToset x y _ p)
+    ≤-≡ : _≤_ ≡ _≤*_  
+    ≤-≡ = funExt λ x -> funExt λ y -> isoToPath (iso-≤ x y) 
+
+  sort→order→sort : ∀ x -> order→sort (sort→order x) ≡ x
+  sort→order→sort ((s , s-is-section , s-is-sort) , discA) =
+    Σ≡Prop (λ _ -> isPropDiscrete)
+    $ Σ≡Prop isProp-is-sort-section
+    $ sym
+    $ funExt λ xs -> unique-sort' _≤*_ ≤*-isToset ≤*-dec s xs (s-is-section , ∣_∣₁ ∘ s-is-sort')
+    where
+    s' : SList A -> List A
+    s' = order→sort (sort→order ((s , s-is-section , s-is-sort) , discA)) .fst .fst
+
+    s'-is-sort-section : is-sort-section s'
+    s'-is-sort-section = order→sort (sort→order ((s , s-is-section , s-is-sort) , discA)) .fst .snd
+
+    _≤*_ : A -> A -> Type _
+    _≤*_ = _≤_ s s-is-section
+
+    ≤*-isToset : IsToset _≤*_
+    ≤*-isToset = ≤-isToset s s-is-section (s-is-sort .fst)
+
+    ≤*-dec : ∀ x y -> Dec (x ≤* y)
+    ≤*-dec = dec-≤ s s-is-section discA
+
+    Sorted* : List A -> Type _
+    Sorted* = Sorted _≤*_ ≤*-isToset ≤*-dec
+
+    s-is-sort'' : ∀ xs n -> n ≡ L.length (s xs) -> Sorted* (s xs)
+    s-is-sort'' xs n p with n | s xs | inspect s xs
+    ... | zero  | []     | _ = sorted-nil
+    ... | zero  | y ∷ ys | _ = ⊥.rec (znots p)
+    ... | suc _ | []     | _ = ⊥.rec (snotz p)
+    ... | suc _ | y ∷ [] | _ = sorted-one y
+    ... | suc m | y ∷ z ∷ zs | [ q ]ᵢ = induction (s-is-sort'' (list→slist (z ∷ zs)) m (injSuc p ∙ wit))
+      where
+      wit : suc (L.length zs) ≡ L.length (s (list→slist (z ∷ zs)))
+      wit = sym $
+        L.length (s (list→slist (z ∷ zs))) ≡⟨ sort-length≡ s s-is-section (list→slist (z ∷ zs)) ⟩
+        S.length (list→slist (z ∷ zs)) ≡⟨ sym (sort-length≡-α s s-is-section (z ∷ zs)) ⟩
+        L.length (z ∷ zs) ∎
+
+      z∷zs-sorted : s (list→slist (z ∷ zs)) ≡ z ∷ zs
+      z∷zs-sorted = sort-unique s s-is-section (z ∷ zs) (s-is-sort .snd y (z ∷ zs) ∣ _ , q ∣₁)
+
+      induction : Sorted* (s (list→slist (z ∷ zs))) -> Sorted* (y ∷ z ∷ zs)  
+      induction IH =
+        sorted-cons y z zs
+          (is-sorted→≤ s s-is-section y z (s-is-sort .fst y z _ ∣ _ , q ∣₁ (L.inr (L.inl refl))))
+          (subst Sorted* z∷zs-sorted IH)
+
+    s-is-sort' : ∀ xs -> Sorted* (s xs)
+    s-is-sort' xs = s-is-sort'' xs (L.length (s xs)) refl helps with termination checking
+
+  without tail sort, we cannot construct a full equivalence
+  order⊂head-least : isEmbedding order→head-least
+  order⊂head-least = injEmbedding (isSet× (isSetΣ (isSetΠ (λ _ -> isOfHLevelList 0 isSetA)) λ q -> isProp→isSet (isProp× (isProp-is-section q) (isProp-is-head-least q))) (isProp→isSet isPropDiscrete))
+    (λ p -> sym (order→head-least→order _) ∙ congS head-least→order p ∙ order→head-least→order _)
+
+  with tail sort, we can construct a full equivalence
+  sort↔order : Iso HasDecOrder HasSortSectionAndIsDiscrete
+  sort↔order = iso order→sort sort→order sort→order→sort order→head-least→order
diff --git a/Cubical/Structures/Set/CMon/SList/Sort/Order.agda b/Cubical/Structures/Set/CMon/SList/Sort/Order.agda
new file mode 100644
index 0000000..dd6ad06
--- /dev/null
+++ b/Cubical/Structures/Set/CMon/SList/Sort/Order.agda
@@ -0,0 +1,410 @@
+{-# OPTIONS --cubical --safe --exact-split -WnoUnsupportedIndexedMatch #-}
+
+module Cubical.Structures.Set.CMon.SList.Sort.Order where
+
+open import Cubical.Foundations.Everything
+open import Cubical.Data.Sigma
+open import Cubical.Data.Nat
+open import Cubical.Data.Nat.Order renaming (_≤_ to _≤ℕ_; _<_ to _<ℕ_)
+open import Cubical.Data.Sum as ⊎
+open import Cubical.Data.Maybe as Maybe
+open import Cubical.Data.Empty as ⊥
+open import Cubical.Induction.WellFounded
+open import Cubical.Relation.Binary
+open import Cubical.Relation.Binary.Order 
+open import Cubical.Relation.Nullary
+open import Cubical.Relation.Nullary.HLevels
+open import Cubical.Data.List
+open import Cubical.HITs.PropositionalTruncation as P
+import Cubical.Data.List as L
+open import Cubical.Functions.Logic as L hiding (¬_; ⊥) 
+
+import Cubical.Structures.Set.Mon.Desc as M
+import Cubical.Structures.Set.CMon.Desc as M
+import Cubical.Structures.Free as F
+open import Cubical.Structures.Sig
+open import Cubical.Structures.Str public
+open import Cubical.Structures.Tree
+open import Cubical.Structures.Eq
+open import Cubical.Structures.Arity
+open import Cubical.Structures.Set.Mon.List
+open import Cubical.Structures.Set.CMon.SList.Base renaming (_∷_ to _∷*_; [] to []*; [_] to [_]*; _++_ to _++*_)
+import Cubical.Structures.Set.CMon.SList.Base as S
+open import Cubical.Structures.Set.CMon.SList.Length as S
+open import Cubical.Structures.Set.CMon.SList.Membership as S
+open import Cubical.Structures.Set.CMon.SList.Sort.Base
+
+open Iso
+
+private
+  variable
+    ℓ : Level
+    A : Type ℓ
+
+module Order→Sort {A : Type ℓ} (_≤_ : A -> A -> Type ℓ) (≤-isToset : IsToset _≤_) (_≤?_ : ∀ x y -> Dec (x ≤ y)) where
+  open IsToset ≤-isToset
+  open Membership is-set
+  open Membership* is-set
+
+  isDiscreteA : Discrete A
+  isDiscreteA x y with x ≤? y | y ≤? x
+  ... | yes p | yes q = yes (is-antisym x y p q)
+  ... | yes p | no ¬q = no λ r -> ¬q (subst (_≤ x) r (is-refl x))
+  ... | no ¬p | yes q = no λ r -> ¬p (subst (x ≤_) r (is-refl x))
+  ... | no ¬p | no ¬q = ⊥.rec $ P.rec isProp⊥ (⊎.rec ¬p ¬q) (is-strongly-connected x y)
+
+  A-is-loset : Loset _ _
+  A-is-loset = Toset→Loset (A , tosetstr _≤_ ≤-isToset) isDiscreteA
+
+  _<_ : A -> A -> Type ℓ
+  _<_ = LosetStr._<_ (A-is-loset .snd)
+
+  <-isLoset : IsLoset _<_
+  <-isLoset = LosetStr.isLoset (A-is-loset .snd)
+
+  insert : A -> List A -> List A
+  insert x [] = [ x ]
+  insert x (y ∷ ys) with x ≤? y
+  ... | yes p = x ∷ y ∷ ys
+  ... | no ¬p = y ∷ insert x ys
+
+  insert-β-1 : ∀ x y ys -> x ≤ y -> insert x (y ∷ ys) ≡ x ∷ y ∷ ys
+  insert-β-1 x y ys p with x ≤? y
+  ... | yes _ = refl
+  ... | no ¬p = ⊥.rec (¬p p)
+
+  insert-β-2 : ∀ x y ys -> ¬ (x ≤ y) -> insert x (y ∷ ys) ≡ y ∷ insert x ys
+  insert-β-2 x y ys ¬p with x ≤? y
+  ... | yes p = ⊥.rec (¬p p)
+  ... | no ¬_ = refl
+
+  insert-≤ : ∀ x y xs ys -> insert x (insert y xs) ≡ x ∷ y ∷ ys -> x ≤ y
+  insert-≤ x y [] ys p with x ≤? y
+  ... | yes x≤y = x≤y
+  ... | no ¬x≤y = subst (_≤ y) (cons-inj₁ p) (is-refl y)
+  insert-≤ x y (z ∷ zs) ys p with y ≤? z
+  ... | yes y≤z = lemma
+    where
+    lemma : x ≤ y
+    lemma with x ≤? y
+    ... | yes x≤y = x≤y
+    ... | no ¬x≤y = subst (_≤ y) (cons-inj₁ p) (is-refl y)
+  ... | no ¬y≤z = lemma
+    where
+    lemma : x ≤ y
+    lemma with x ≤? z
+    ... | yes x≤z = subst (x ≤_) (cons-inj₁ (cons-inj₂ p)) x≤z
+    ... | no ¬x≤z = ⊥.rec (¬x≤z (subst (_≤ z) (cons-inj₁ p) (is-refl z)))
+
+  insert-cons : ∀ x xs ys -> x ∷ xs ≡ insert x ys -> xs ≡ ys
+  insert-cons x xs [] p = cons-inj₂ p
+  insert-cons x xs (y ∷ ys) p with x ≤? y
+  ... | yes x≤y = cons-inj₂ p
+  ... | no ¬x≤y = ⊥.rec (¬x≤y (subst (x ≤_) (cons-inj₁ p) (is-refl x)))
+
+  private
+    not-total-impossible : ∀ {x y} -> ¬(x ≤ y) -> ¬(y ≤ x) -> ⊥
+    not-total-impossible {x} {y} p q =
+      P.rec isProp⊥ (⊎.rec p q) (is-strongly-connected x y)
+
+  insert-insert : ∀ x y xs -> insert x (insert y xs) ≡ insert y (insert x xs)
+  insert-insert x y [] with x ≤? y | y ≤? x
+  ... | yes x≤y | no ¬y≤x = refl
+  ... | no ¬x≤y | yes y≤x = refl
+  ... | no ¬x≤y | no ¬y≤x = ⊥.rec (not-total-impossible ¬x≤y ¬y≤x)
+  ... | yes x≤y | yes y≤x = let x≡y = is-antisym x y x≤y y≤x in cong₂ (λ u v -> u ∷ v ∷ []) x≡y (sym x≡y)
+  insert-insert x y (z ∷ zs) with y ≤? z | x ≤? z
+  ... | yes y≤z | yes x≤z = case1 y≤z x≤z
+    where
+    case1 : y ≤ z -> x ≤ z -> insert x (y ∷ z ∷ zs) ≡ insert y (x ∷ z ∷ zs)
+    case1 y≤z x≤z with x ≤? y | y ≤? x
+    ... | yes x≤y | yes y≤x = let x≡y = is-antisym x y x≤y y≤x in cong₂ (λ u v -> (u ∷ v ∷ z ∷ zs)) x≡y (sym x≡y)
+    ... | yes x≤y | no ¬y≤x = sym (congS (x ∷_) (insert-β-1 y z zs y≤z))
+    ... | no ¬x≤y | yes y≤x = congS (y ∷_) (insert-β-1 x z zs x≤z)
+    ... | no ¬x≤y | no ¬y≤x = ⊥.rec (not-total-impossible ¬x≤y ¬y≤x)
+  ... | yes y≤z | no ¬x≤z = case2 y≤z ¬x≤z
+    where
+    case2 : y ≤ z -> ¬(x ≤ z) -> insert x (y ∷ z ∷ zs) ≡ insert y (z ∷ insert x zs)
+    case2 y≤z ¬x≤z with x ≤? y
+    ... | yes x≤y = ⊥.rec (¬x≤z (is-trans x y z x≤y y≤z))
+    ... | no ¬x≤y = congS (y ∷_) (insert-β-2 x z zs ¬x≤z) ∙ sym (insert-β-1 y z _ y≤z)
+  ... | no ¬y≤z | yes x≤z = case3 ¬y≤z x≤z
+    where
+    case3 : ¬(y ≤ z) -> x ≤ z -> insert x (z ∷ insert y zs) ≡ insert y (x ∷ z ∷ zs)
+    case3 ¬y≤z x≤z with y ≤? x
+    ... | yes y≤x = ⊥.rec (¬y≤z (is-trans y x z y≤x x≤z))
+    ... | no ¬y≤x = insert-β-1 x z _ x≤z ∙ congS (x ∷_) (sym (insert-β-2 y z zs ¬y≤z))
+  ... | no ¬y≤z | no ¬x≤z =
+    insert x (z ∷ insert y zs) ≡⟨ insert-β-2 x z _ ¬x≤z ⟩
+    z ∷ insert x (insert y zs) ≡⟨ congS (z ∷_) (insert-insert x y zs) ⟩
+    z ∷ insert y (insert x zs) ≡⟨ sym (insert-β-2 y z _ ¬y≤z) ⟩
+    insert y (z ∷ insert x zs) ∎
+
+  sort : SList A -> List A
+  sort = Elim.f []
+    (λ x xs -> insert x xs)
+    (λ x y xs -> insert-insert x y xs)
+    (λ _ -> isOfHLevelList 0 is-set)
+
+  insert-is-permute : ∀ x xs -> list→slist (x ∷ xs) ≡ list→slist (insert x xs)
+  insert-is-permute x [] = refl
+  insert-is-permute x (y ∷ ys) with x ≤? y
+  ... | yes p = refl
+  ... | no ¬p =
+    x ∷* y ∷* list→slist ys ≡⟨ swap x y _ ⟩
+    y ∷* x ∷* list→slist ys ≡⟨ congS (y ∷*_) (insert-is-permute x ys) ⟩
+    y ∷* list→slist (insert x ys) ∎
+
+  open Sort is-set
+
+  sort-is-permute : is-section sort
+  sort-is-permute = ElimProp.f (trunc _ _) refl lemma
+    where
+    lemma : ∀ x {xs} p -> list→slist (sort (x ∷* xs)) ≡ x ∷* xs
+    lemma x {xs} p = sym $
+      x ∷* xs ≡⟨ congS (x ∷*_) (sym p) ⟩
+      list→slist (x ∷ sort xs) ≡⟨ insert-is-permute x (sort xs) ⟩
+      list→slist (insert x (sort xs)) ≡⟨⟩
+      list→slist (sort (x ∷* xs)) ∎
+
+  tail-is-sorted : ∀ x xs -> is-sorted sort (x ∷ xs) -> is-sorted sort xs
+  tail-is-sorted x xs = P.rec squash₁ (uncurry lemma)
+    where
+    lemma : ∀ ys p -> is-sorted sort xs
+    lemma ys p = ∣ (list→slist xs) , sym (insert-cons x _ _ sort-proof) ∣₁
+      where
+      ys-proof : ys ≡ x ∷* list→slist xs
+      ys-proof = sym (sort-is-permute ys) ∙ (congS list→slist p)
+      sort-proof : x ∷ xs ≡ insert x (sort (list→slist xs))
+      sort-proof = sym p ∙ congS sort ys-proof
+
+  data Sorted : List A -> Type ℓ where
+    sorted-nil : Sorted []
+    sorted-one : ∀ x -> Sorted [ x ]
+    sorted-cons : ∀ x y zs -> x ≤ y -> Sorted (y ∷ zs) -> Sorted (x ∷ y ∷ zs)
+
+  open Sort.Section is-set
+
+  is-sort' : (SList A -> List A) -> Type _
+  is-sort' f = (∀ xs -> list→slist (f xs) ≡ xs) × (∀ xs -> ∥ Sorted (f xs) ∥₁)
+
+  tail-sorted' : ∀ {x xs} -> Sorted (x ∷ xs) -> Sorted xs 
+  tail-sorted' (sorted-one ._) = sorted-nil
+  tail-sorted' (sorted-cons ._ _ _ _ p) = p
+
+  ≤-tail : ∀ {x y ys} -> y ∈ (x ∷ ys) -> Sorted (x ∷ ys) -> x ≤ y
+  ≤-tail {y = y} p (sorted-one x) = subst (_≤ y) (x∈[y]→x≡y y x p) (is-refl y)
+  ≤-tail {x} {y = z} p (sorted-cons x y zs q r) =
+    P.rec (is-prop-valued x z)
+      (⊎.rec
+        (λ z≡x -> subst (x ≤_) (sym z≡x) (is-refl x))
+        (λ z∈ys -> is-trans x y z q (≤-tail z∈ys r))
+      ) p
+  
+  smallest-sorted : ∀ x xs -> (∀ y -> y ∈ xs -> x ≤ y) -> Sorted xs -> Sorted (x ∷ xs)
+  smallest-sorted x .[] p sorted-nil =
+    sorted-one x
+  smallest-sorted x .([ y ]) p (sorted-one y) =
+    sorted-cons x y [] (p y (x∈[x] y)) (sorted-one y)
+  smallest-sorted x .(_ ∷ _ ∷ _) p (sorted-cons y z zs y≤z r) =
+    sorted-cons x y (z ∷ zs) (p y (x∈xs y (z ∷ zs))) (smallest-sorted y (z ∷ zs) lemma r)
+    where
+    lemma : ∀ a -> a ∈ (z ∷ zs) -> y ≤ a
+    lemma a = P.rec (is-prop-valued y a) $ ⊎.rec
+      (λ a≡z -> subst (y ≤_) (sym a≡z) y≤z)
+      (λ a∈zs -> is-trans y z a y≤z (≤-tail (L.inr a∈zs) r))
+
+  insert-∈ : ∀ {x} {y} ys -> x ∈ insert y ys -> x ∈ (y ∷ ys)
+  insert-∈ {x} {y} ys p = ∈*→∈ x (y ∷ ys)
+    (subst (x ∈*_) (sym (insert-is-permute y ys)) (∈→∈* x (insert y ys) p))
+
+  insert-is-sorted : ∀ x xs -> Sorted xs -> Sorted (insert x xs)
+  insert-is-sorted x [] p = sorted-one x
+  insert-is-sorted x (y ∷ ys) p with x ≤? y
+  ... | yes q = sorted-cons x y ys q p
+  ... | no ¬q = smallest-sorted y (insert x ys) (lemma ys p) IH
+    where
+    IH : Sorted (insert x ys)
+    IH = insert-is-sorted x ys (tail-sorted' p)
+    y≤x : y ≤ x
+    y≤x = P.rec (is-prop-valued y x) (⊎.rec (idfun _) (⊥.rec ∘ ¬q)) (is-strongly-connected y x)
+    lemma : ∀ zs -> Sorted (y ∷ zs) -> ∀ z -> z ∈ insert x zs → y ≤ z
+    lemma zs p z r = P.rec (is-prop-valued y z)
+      (⊎.rec (λ z≡x -> subst (y ≤_) (sym z≡x) y≤x) (λ z∈zs -> ≤-tail (L.inr z∈zs) p)) (insert-∈ zs r)
+
+  sort-is-sorted' : ∀ xs -> ∥ Sorted (sort xs) ∥₁
+  sort-is-sorted' = ElimProp.f squash₁ ∣ sorted-nil ∣₁
+    λ x -> P.rec squash₁ λ p -> ∣ (insert-is-sorted x _ p) ∣₁
+
+  sort-is-sorted'' : ∀ xs -> is-sorted sort xs -> ∥ Sorted xs ∥₁
+  sort-is-sorted'' xs = P.rec squash₁ λ (ys , p) ->
+    P.map (subst Sorted p) (sort-is-sorted' ys)
+
+  Step 1. show both sort xs and sort->order->sort xs give sorted list
+  Step 2. apply this lemma
+  Step 3. get sort->order->sort = sort
+  unique-sorted-xs : ∀ xs ys -> list→slist xs ≡ list→slist ys -> Sorted xs -> Sorted ys -> xs ≡ ys
+  unique-sorted-xs [] [] p xs-sorted ys-sorted = refl
+  unique-sorted-xs [] (y ∷ ys) p xs-sorted ys-sorted = ⊥.rec (znots (congS S.length p))
+  unique-sorted-xs (x ∷ xs) [] p xs-sorted ys-sorted = ⊥.rec (snotz (congS S.length p))
+  unique-sorted-xs (x ∷ xs) (y ∷ ys) p xs-sorted ys-sorted =
+    cong₂ _∷_ x≡y (unique-sorted-xs xs ys xs≡ys (tail-sorted' xs-sorted) (tail-sorted' ys-sorted))
+    where
+    x≤y : x ≤ y
+    x≤y = ≤-tail (∈*→∈ y (x ∷ xs) (subst (y ∈*_) (sym p) (L.inl refl))) xs-sorted
+    y≤x : y ≤ x
+    y≤x = ≤-tail (∈*→∈ x (y ∷ ys) (subst (x ∈*_) p (L.inl refl))) ys-sorted
+    x≡y : x ≡ y
+    x≡y = is-antisym x y x≤y y≤x
+    xs≡ys : list→slist xs ≡ list→slist ys
+    xs≡ys =
+      list→slist xs ≡⟨ remove1-≡-lemma isDiscreteA (list→slist xs) refl ⟩
+      remove1 isDiscreteA x (list→slist (x ∷ xs)) ≡⟨ congS (remove1 isDiscreteA x) p ⟩
+      remove1 isDiscreteA x (list→slist (y ∷ ys)) ≡⟨ sym (remove1-≡-lemma isDiscreteA (list→slist ys) x≡y) ⟩
+      list→slist ys ∎
+  
+  unique-sort : ∀ f -> is-sort' f -> f ≡ sort
+  unique-sort f (f-is-permute , f-is-sorted) = funExt λ xs ->
+    P.rec2 (isOfHLevelList 0 is-set _ _)
+      (unique-sorted-xs (f xs) (sort xs) (f-is-permute xs ∙ sym (sort-is-permute xs)))
+      (f-is-sorted xs)
+      (sort-is-sorted' xs)
+
+  unique-sort' : ∀ f xs -> is-sort' f -> f xs ≡ sort xs
+  unique-sort' f xs p = congS (λ g -> g xs) (unique-sort f p)
+
+  private
+    sort→order-lemma : ∀ x y xs -> is-sorted sort (x ∷ y ∷ xs) -> x ≤ y
+    sort→order-lemma x y xs = P.rec (is-prop-valued x y) (uncurry lemma)
+      where
+      lemma : ∀ ys p -> x ≤ y
+      lemma ys p = insert-≤ x y (sort tail) xs (congS sort tail-proof ∙ p)
+        where
+        tail : SList A
+        tail = list→slist xs
+        tail-proof : x ∷* y ∷* tail ≡ ys
+        tail-proof = sym (congS list→slist p) ∙ sort-is-permute ys
+
+    sort→order : ∀ x y xs -> is-sorted sort (x ∷ xs) -> y ∈ (x ∷ xs) -> x ≤ y
+    sort→order x y [] p y∈xs = subst (_≤ y) (x∈[y]→x≡y y x y∈xs) (is-refl y)
+    sort→order x y (z ∷ zs) p y∈x∷z∷zs with isDiscreteA x y
+    ... | yes x≡y = subst (x ≤_) x≡y (is-refl x)
+    ... | no ¬x≡y =
+      P.rec (is-prop-valued x y) (⊎.rec (⊥.rec ∘ ¬x≡y ∘ sym) lemma) y∈x∷z∷zs
+      where
+      lemma : y ∈ (z ∷ zs) -> x ≤ y
+      lemma y∈z∷zs = is-trans x z y
+        (sort→order-lemma x z zs p)
+        (sort→order z y zs (tail-is-sorted x (z ∷ zs) p) y∈z∷zs)
+
+  sort-is-head-least : is-head-least sort
+  sort-is-head-least x y xs p y∈xs = ∣ (x ∷* y ∷* []* , insert-β-1 x y [] (sort→order x y xs p y∈xs)) ∣₁
+
+  sort-is-sort-section : is-sort-section sort
+  sort-is-sort-section = sort-is-permute , sort-is-head-least , tail-is-sorted
+
+
+  swap1-2 : List A -> List A
+  swap1-2 [] = []
+  swap1-2 (x ∷ []) = x ∷ []
+  swap1-2 (x ∷ y ∷ xs) = y ∷ x ∷ xs
+
+  swap1-2-id : ∀ xs -> swap1-2 (swap1-2 xs) ≡ xs
+  swap1-2-id [] = refl
+  swap1-2-id (x ∷ []) = refl
+  swap1-2-id (x ∷ y ∷ xs) = refl
+
+  swap2-3 : List A -> List A
+  swap2-3 [] = []
+  swap2-3 (x ∷ xs) = x ∷ swap1-2 xs
+
+  swap2-3-id : ∀ xs -> swap2-3 (swap2-3 xs) ≡ xs
+  swap2-3-id [] = refl
+  swap2-3-id (x ∷ xs) = congS (x ∷_) (swap1-2-id xs)
+
+  swap2-3-is-permute : ∀ f -> is-section f -> is-section (swap2-3 ∘ f)
+  swap2-3-is-permute f f-is-permute xs with f xs | inspect f xs
+  ... | [] | [ p ]ᵢ = sym (congS list→slist p) ∙ f-is-permute xs
+  ... | x ∷ [] | [ p ]ᵢ = sym (congS list→slist p) ∙ f-is-permute xs
+  ... | x ∷ y ∷ [] | [ p ]ᵢ = sym (congS list→slist p) ∙ f-is-permute xs
+  ... | x ∷ y ∷ z ∷ ys | [ p ]ᵢ =
+    x ∷* z ∷* y ∷* list→slist ys ≡⟨ congS (x ∷*_) (swap z y (list→slist ys)) ⟩
+    x ∷* y ∷* z ∷* list→slist ys ≡⟨ sym (congS list→slist p) ⟩
+    list→slist (f xs) ≡⟨ f-is-permute xs ⟩
+    xs ∎
+
+  head-least-only : SList A -> List A
+  head-least-only = swap2-3 ∘ sort
+
+  head-least-only-is-permute : is-section head-least-only
+  head-least-only-is-permute = swap2-3-is-permute sort sort-is-permute
+
+  private
+    head-least-is-same-for-2 : ∀ u v -> is-sorted sort (u ∷ v ∷ []) -> is-sorted head-least-only (u ∷ v ∷ [])
+    head-least-is-same-for-2 u v = P.map λ (ys , q) -> ys , congS swap2-3 q
+
+    head-least→sorted : ∀ x xs -> is-sorted head-least-only (x ∷ xs) -> is-sorted sort (x ∷ swap1-2 xs)
+    head-least→sorted x [] =
+      P.map λ (ys , q) -> ys , sym (swap2-3-id (sort ys)) ∙ congS swap2-3 q
+    head-least→sorted x (y ∷ []) =
+      P.map λ (ys , q) -> ys , sym (swap2-3-id (sort ys)) ∙ congS swap2-3 q
+    head-least→sorted x (y ∷ z ∷ xs) =
+      P.map λ (ys , q) -> ys , sym (swap2-3-id (sort ys)) ∙ congS swap2-3 q
+
+    swap1-2-∈ : ∀ x xs -> x ∈ xs -> x ∈ swap1-2 xs
+    swap1-2-∈ x [] x∈ = x∈
+    swap1-2-∈ x (y ∷ []) x∈ = x∈
+    swap1-2-∈ x (y ∷ z ∷ xs) = P.rec squash₁
+      (⊎.rec (L.inr ∘ L.inl) (P.rec squash₁ (⊎.rec L.inl (L.inr ∘ L.inr))))
+
+    swap2-3-∈ : ∀ x xs -> x ∈ xs -> x ∈ swap2-3 xs
+    swap2-3-∈ x (y ∷ xs) = P.rec squash₁ (⊎.rec L.inl (L.inr ∘ swap1-2-∈ x xs))
+
+    is-sorted→≤ : ∀ {x y} -> is-sorted sort (x ∷ y ∷ []) -> x ≤ y
+    is-sorted→≤ {x} {y} p = P.rec (is-prop-valued x y)
+      (≤-tail {ys = y ∷ []} (L.inr (L.inl refl)))
+      (sort-is-sorted'' (x ∷ y ∷ []) p)
+
+    head-least-tail-sort→x≡y : ∀ x y -> is-tail-sort head-least-only -> x ≤ y -> x ≡ y
+    head-least-tail-sort→x≡y x y h-tail-sort x≤y =
+      is-antisym x y x≤y (is-sorted→≤ (lemma1 ∣ x ∷* x ∷* y ∷* []* , lemma2 ∣₁))
+      where
+      [1, 2, 3] sorted by sort -> [1, 3, 2] sorted by head-least -> [3, 2] sorted by head-least -> [3, 2] sorted by sort
+      lemma1 : is-sorted sort (x ∷ x ∷ y ∷ []) -> is-sorted sort (y ∷ x ∷ [])
+      lemma1 = P.rec squash₁ λ (ys , q) -> head-least→sorted y [ x ] (h-tail-sort x _ ∣ ys , congS swap2-3 q ∣₁) 
+      lemma2 : sort (x ∷* x ∷* [ y ]*) ≡ x ∷ x ∷ y ∷ []
+      lemma2 =
+        insert x (insert x [ y ]) ≡⟨ congS (insert x) (insert-β-1 x y [] x≤y) ⟩
+        insert x (x ∷ y ∷ []) ≡⟨ insert-β-1 x x [ y ] (is-refl x) ⟩
+        x ∷ x ∷ [ y ] ∎
+
+  head-least-only-is-head-least : is-head-least head-least-only
+  head-least-only-is-head-least x y xs p y∈xs = head-least-is-same-for-2 x y
+    (sort-is-head-least x y (swap1-2 xs) (head-least→sorted x xs p) (swap2-3-∈ y (x ∷ xs) y∈xs))
+
+  head-least-tail-sort→isProp-A : is-tail-sort head-least-only -> isProp A
+  head-least-tail-sort→isProp-A h-tail-sort x y = P.rec (is-set _ _)
+    (⊎.rec (head-least-tail-sort→x≡y x y h-tail-sort) (sym ∘ (head-least-tail-sort→x≡y y x h-tail-sort)))
+    (is-strongly-connected x y)
+
+module Order→Sort-Example where
+
+  ≤ℕ-isToset : IsToset _≤ℕ_
+  ≤ℕ-isToset = istoset isSetℕ
+    (λ _ _ -> isProp≤)
+    (λ _ -> ≤-refl)
+    (λ _ _ _ -> ≤-trans)
+    (λ _ _ -> ≤-antisym)
+    lemma
+    where
+    <→≤ : ∀ {n m} -> n <ℕ m -> n ≤ℕ m
+    <→≤ (k , p) = suc k , sym (+-suc k _) ∙ p
+    lemma : BinaryRelation.isStronglyConnected _≤ℕ_
+    lemma x y = ∣ ⊎.rec ⊎.inl (_⊎_.inr ∘ <→≤) (splitℕ-≤ x y) ∣₁
+
+  open Order→Sort _≤ℕ_ ≤ℕ-isToset ≤Dec
+ 
+  _ : sort (4 ∷* 6 ∷* 1 ∷* 2 ∷* []*) ≡ (1 ∷ 2 ∷ 4 ∷ 6 ∷ [])
+  _ = refl
+   
+   
\ No newline at end of file
diff --git a/Cubical/Structures/Set/CMon/SList/Sort/Sort.agda b/Cubical/Structures/Set/CMon/SList/Sort/Sort.agda
new file mode 100644
index 0000000..3dfbb86
--- /dev/null
+++ b/Cubical/Structures/Set/CMon/SList/Sort/Sort.agda
@@ -0,0 +1,178 @@
+{-# OPTIONS --cubical --safe --exact-split -WnoUnsupportedIndexedMatch #-}
+
+module Cubical.Structures.Set.CMon.SList.Sort.Sort where
+
+open import Cubical.Foundations.Everything
+open import Cubical.Data.Sigma
+open import Cubical.Data.Nat
+open import Cubical.Data.Nat.Order renaming (_≤_ to _≤ℕ_; _<_ to _<ℕ_)
+open import Cubical.Data.Sum as ⊎
+open import Cubical.Data.Maybe as Maybe
+open import Cubical.Data.Empty as ⊥
+open import Cubical.Induction.WellFounded
+open import Cubical.Relation.Binary
+open import Cubical.Relation.Binary.Order 
+open import Cubical.Relation.Nullary
+open import Cubical.Relation.Nullary.HLevels
+open import Cubical.Data.List
+open import Cubical.HITs.PropositionalTruncation as P
+import Cubical.Data.List as L
+open import Cubical.Functions.Logic as L hiding (¬_; ⊥) 
+
+import Cubical.Structures.Set.Mon.Desc as M
+import Cubical.Structures.Set.CMon.Desc as M
+import Cubical.Structures.Free as F
+open import Cubical.Structures.Sig
+open import Cubical.Structures.Str public
+open import Cubical.Structures.Tree
+open import Cubical.Structures.Eq
+open import Cubical.Structures.Arity
+open import Cubical.Structures.Set.Mon.List
+open import Cubical.Structures.Set.CMon.SList.Base renaming (_∷_ to _∷*_; [] to []*; [_] to [_]*; _++_ to _++*_)
+import Cubical.Structures.Set.CMon.SList.Base as S
+open import Cubical.Structures.Set.CMon.SList.Length as S
+open import Cubical.Structures.Set.CMon.SList.Membership as S
+open import Cubical.Structures.Set.CMon.SList.Sort.Base
+
+open Iso
+
+private
+  variable
+    ℓ : Level
+    A : Type ℓ
+
+module Sort→Order (isSetA : isSet A) (sort : SList A -> List A) (sort≡ : ∀ xs -> list→slist (sort xs) ≡ xs) where
+
+  isSetMaybeA : isSet (Maybe A)
+  isSetMaybeA = isOfHLevelMaybe 0 isSetA
+
+  isSetListA : isSet (List A)
+  isSetListA = isOfHLevelList 0 isSetA
+
+  private
+    module 𝔖 = M.CMonSEq < SList A , slist-α > slist-sat
+  
+  open Membership isSetA
+  open Membership* isSetA
+  open Sort isSetA sort
+  open Sort.Section isSetA sort sort≡
+
+  least : SList A -> Maybe A
+  least xs = head-maybe (sort xs)
+
+  least-nothing : ∀ xs -> least xs ≡ nothing -> xs ≡ []*
+  least-nothing xs p with sort xs | inspect sort xs
+  ... | []     | [ q ]ᵢ = sort-[] xs q
+  ... | y ∷ ys | [ q ]ᵢ = ⊥.rec (¬just≡nothing p)
+
+  least-Σ : ∀ x xs -> least xs ≡ just x -> Σ[ ys ∈ List A ] (sort xs ≡ x ∷ ys)
+  least-Σ x xs p with sort xs
+  ... | []     = ⊥.rec (¬nothing≡just p)
+  ... | y ∷ ys = ys , congS (_∷ ys) (just-inj y x p)
+
+  least-in : ∀ x xs -> least xs ≡ just x -> x ∈* xs
+  least-in x xs p =
+    let (ys , q) = least-Σ x xs p
+        x∷ys≡xs = congS list→slist (sym q) ∙ sort≡ xs
+    in subst (x ∈*_) x∷ys≡xs (x∈*xs x (list→slist ys))
+
+  least-choice : ∀ x y -> (least (x ∷* [ y ]*) ≡ just x) ⊔′ (least (x ∷* [ y ]*) ≡ just y)
+  least-choice x y = P.rec squash₁
+    (⊎.rec
+      (L.inl ∘ congS head-maybe)
+      (L.inr ∘ congS head-maybe)
+    )
+    (sort-choice x y)
+
+  _≤_ : A -> A -> Type _
+  x ≤ y = least (x ∷* y ∷* []*) ≡ just x
+
+  isProp-≤ : ∀ {a} {b} -> isProp (a ≤ b)
+  isProp-≤  = isSetMaybeA _ _
+
+  ≤-Prop : ∀ x y -> hProp _
+  ≤-Prop x y = (x ≤ y) , isProp-≤
+
+  refl-≤ : ∀ x -> x ≤ x
+  refl-≤ x = P.rec isProp-≤ (⊎.rec (idfun _) (idfun _)) (least-choice x x)
+
+  antisym-≤ : ∀ x y -> x ≤ y -> y ≤ x -> x ≡ y
+  antisym-≤ x y p q = P.rec (isSetA x y)
+    (⊎.rec
+      (λ xy -> just-inj x y $
+        just x ≡⟨ sym xy ⟩
+        least (x ∷* y ∷* []*) ≡⟨ congS least (swap x y []*) ⟩
+        least (y ∷* x ∷* []*) ≡⟨ q ⟩
+        just y
+      ∎)
+      (λ yx -> just-inj x y $
+        just x ≡⟨ sym p ⟩
+        least (x ∷* [ y ]*) ≡⟨ yx ⟩
+        just y
+      ∎))
+     (least-choice x y)
+
+  total-≤ : ∀ x y -> (x ≤ y) ⊔′ (y ≤ x)
+  total-≤ x y = P.rec squash₁
+    (⊎.rec
+      L.inl
+      (λ p -> L.inr $
+        least (y ∷* [ x ]*) ≡⟨ congS least (swap y x []*) ⟩
+        least (x ∷* [ y ]*) ≡⟨ p ⟩
+        just y
+      ∎))
+    (least-choice x y)
+
+  dec-≤ : (discA : Discrete A) -> ∀ x y -> Dec (x ≤ y)
+  dec-≤ discA x y = discreteMaybe discA _ _
+
+  is-sorted→≤ : ∀ x y -> is-sorted (x ∷ y ∷ []) -> x ≤ y
+  is-sorted→≤ x y = P.rec (isSetMaybeA _ _) λ (xs , p) ->
+    congS head-maybe (congS sort (sym (sym (sort≡ xs) ∙ congS list→slist p)) ∙ p)
+
+  module _ (sort-is-sort : is-head-least) where
+    trans-≤ : ∀ x y z -> x ≤ y -> y ≤ z -> x ≤ z
+    trans-≤ x y z x≤y y≤z with least (x ∷* y ∷* z ∷* []*) | inspect least (x ∷* y ∷* z ∷* []*)
+    ... | nothing | [ p ]ᵢ = ⊥.rec (snotz (congS S.length (least-nothing _ p)))
+    ... | just u | [ p ]ᵢ =
+      P.rec (isSetMaybeA _ _)
+        (⊎.rec case1 
+          (P.rec (isSetMaybeA _ _)
+            (⊎.rec case2 (case3 ∘ x∈[y]→x≡y _ _))
+          )
+        )
+        (least-in u (x ∷* y ∷* z ∷* []*) p)
+      where
+      tail' : Σ[ xs ∈ List A ] u ∷ xs ≡ sort (x ∷* y ∷* z ∷* []*)
+      tail' with sort (x ∷* y ∷* z ∷* []*)
+      ... | [] = ⊥.rec (¬nothing≡just p)
+      ... | v ∷ xs = xs , congS (_∷ xs) (just-inj _ _ (sym p))
+      tail : List A
+      tail = tail' .fst
+      tail-proof : u ∷ tail ≡ sort (x ∷* y ∷* z ∷* []*)
+      tail-proof = tail' .snd
+      u∷tail-is-sorted : is-sorted (u ∷ tail)
+      u∷tail-is-sorted = ∣ ((x ∷* y ∷* z ∷* []*) , sym tail-proof) ∣₁
+      u-is-smallest : ∀ v -> v ∈* (x ∷* y ∷* z ∷* []*) -> u ≤ v
+      u-is-smallest v q =
+        is-sorted→≤ u v (sort-is-sort u v tail u∷tail-is-sorted (subst (v ∈_) (sym tail-proof) (sort-∈ v _ q)))
+      case1 : u ≡ x -> x ≤ z
+      case1 u≡x = subst (_≤ z) u≡x (u-is-smallest z (L.inr (L.inr (L.inl refl))))
+      case2 : u ≡ y -> x ≤ z
+      case2 u≡y = subst (_≤ z) (antisym-≤ y x y≤x x≤y) y≤z
+        where
+        y≤x : y ≤ x
+        y≤x = subst (_≤ x) u≡y (u-is-smallest x (L.inl refl))
+      case3 : u ≡ z -> x ≤ z
+      case3 u≡z = subst (x ≤_) (antisym-≤ y z y≤z z≤y) x≤y
+        where
+        z≤y : z ≤ y
+        z≤y = subst (_≤ y) u≡z (u-is-smallest y (L.inr (L.inl refl)))
+
+    ≤-isToset : IsToset _≤_
+    IsToset.is-set ≤-isToset = isSetA
+    IsToset.is-prop-valued ≤-isToset x y = isOfHLevelMaybe 0 isSetA _ _
+    IsToset.is-refl ≤-isToset = refl-≤
+    IsToset.is-trans ≤-isToset = trans-≤ 
+    IsToset.is-antisym ≤-isToset = antisym-≤                
+    IsToset.is-strongly-connected ≤-isToset = total-≤
diff --git a/Cubical/Structures/Set/Empty.agda b/Cubical/Structures/Set/Empty.agda
new file mode 100644
index 0000000..6ae37e0
--- /dev/null
+++ b/Cubical/Structures/Set/Empty.agda
@@ -0,0 +1,65 @@
+{-# OPTIONS --cubical --safe --exact-split #-}
+
+module Cubical.Structures.Set.Empty where
+
+open import Cubical.Foundations.Everything
+open import Cubical.Data.Sigma
+open import Cubical.Data.Nat
+open import Cubical.Data.Nat.Order
+open import Cubical.Data.Empty as ⊥
+import Cubical.Data.List as L
+
+import Cubical.Structures.Free as F
+open import Cubical.Structures.Sig
+open import Cubical.Structures.Str public
+open import Cubical.Structures.Tree
+open import Cubical.Structures.Eq
+open import Cubical.Structures.Arity
+
+private
+  variable
+    ℓ ℓ' : Level
+    A : Type ℓ
+
+empty-α : ∀ (A : Type ℓ) -> sig emptySig A -> A
+empty-α _ (x , _) = ⊥.rec x
+
+emptyHomDegen : (𝔜 : struct ℓ' emptySig) -> structHom < A , empty-α A > 𝔜 ≃ (A -> 𝔜 .car)
+emptyHomDegen _ = Σ-contractSnd λ _ -> isContrΠ⊥
+
+module EmptyDef = F.Definition emptySig emptyEqSig emptySEq
+
+empty-sat : ∀ (A : Type ℓ) -> < A , empty-α A > ⊨ emptySEq
+empty-sat _ eqn ρ = ⊥.rec eqn
+
+treeEmpty≃  : Tree emptySig A ≃ A
+treeEmpty≃ = isoToEquiv (iso from leaf (λ _ -> refl) leaf∘from)
+  where
+  from : Tree emptySig A -> A
+  from (leaf x) = x
+
+  leaf∘from : retract from leaf
+  leaf∘from (leaf x) = refl
+
+treeDef : ∀ {ℓ ℓ'} -> EmptyDef.Free ℓ ℓ' 2
+F.Definition.Free.F treeDef = Tree emptySig
+F.Definition.Free.η treeDef = leaf
+F.Definition.Free.α treeDef = empty-α (Tree emptySig _)
+F.Definition.Free.sat treeDef = empty-sat (Tree emptySig _)
+F.Definition.Free.isFree (treeDef {ℓ = ℓ}) {X = A} {𝔜 = 𝔜} H ϕ = lemma .snd
+  where
+  𝔗 : struct ℓ emptySig
+  𝔗 = < Tree emptySig A , empty-α (Tree emptySig A) >
+
+  lemma : structHom 𝔗 𝔜 ≃ (A -> 𝔜 .car)
+  lemma =
+    structHom 𝔗 𝔜 ≃⟨ emptyHomDegen 𝔜 ⟩
+    (𝔗 .car -> 𝔜 .car) ≃⟨ equiv→ treeEmpty≃ (idEquiv (𝔜 .car)) ⟩
+    (A -> 𝔜 .car) ■
+    
+anyDef : ∀ {ℓ ℓ'} -> EmptyDef.Free ℓ ℓ' 2
+F.Definition.Free.F anyDef A = A
+F.Definition.Free.η anyDef a = a
+F.Definition.Free.α anyDef = empty-α _
+F.Definition.Free.sat anyDef = empty-sat _
+F.Definition.Free.isFree anyDef {𝔜 = 𝔜} _ _ = emptyHomDegen 𝔜 .snd 
\ No newline at end of file
diff --git a/Cubical/Structures/Set/Mon/Array.agda b/Cubical/Structures/Set/Mon/Array.agda
new file mode 100644
index 0000000..7b32b17
--- /dev/null
+++ b/Cubical/Structures/Set/Mon/Array.agda
@@ -0,0 +1,493 @@
+{-# OPTIONS --cubical --safe --exact-split #-}
+
+module Cubical.Structures.Set.Mon.Array where
+
+open import Cubical.Foundations.Everything
+open import Cubical.Data.Sigma
+open import Cubical.Data.List renaming (_∷_ to _∷ₗ_)
+open import Cubical.Data.Fin
+open import Cubical.Data.Nat
+open import Cubical.Data.Nat.Order
+open import Cubical.Data.Sum as ⊎
+import Cubical.Data.Empty as ⊥
+
+import Cubical.Structures.Set.Mon.Desc as M
+import Cubical.Structures.Free as F
+open import Cubical.Structures.Sig
+open import Cubical.Structures.Str public
+open import Cubical.Structures.Tree
+open import Cubical.Structures.Eq
+open import Cubical.Structures.Arity
+
+open Iso
+
+private
+  variable
+    ℓ ℓ₁ ℓ₂ : Level
+    A B C : Type ℓ
+    n m : ℕ
+
+Array : Type ℓ -> Type ℓ
+Array A = Σ[ n ∈ ℕ ] (Fin n -> A)
+
+isSetArray : isSet A -> isSet (Array A)
+isSetArray isSetA = isOfHLevelΣ 2 isSetℕ λ _ -> isOfHLevelΠ 2 λ _ -> isSetA
+
+tptLemma : ∀ {ℓ ℓ' ℓ''} (A : Type ℓ) (B : Type ℓ') (P : A -> Type ℓ'') {a b : A} (p : a ≡ b) (f : P a -> B) (k : P b)
+        -> transport (\i -> P (p i) -> B) f k ≡ f (transport (\i -> P (p (~ i))) k)
+tptLemma A B P {a} p f k = sym (transport-filler (λ _ -> B) (f (transport (\i -> P (p (~ i))) k)))
+
+Array≡ : ∀ {ℓ} {A : Type ℓ} {n m} {f : Fin n -> A} {g : Fin m -> A}
+      -> (n=m : n ≡ m)
+      -> (∀ (k : ℕ) (k<m : k < m) -> f (k , subst (k <_) (sym n=m) k<m) ≡ g (k , k<m))
+      -> Path (Array A) (n , f) (m , g)
+Array≡ {A = A} {n = n} {m} {f} {g} p h = ΣPathP (p , toPathP (funExt lemma))
+  where
+    lemma : (k : Fin m) -> transport (\i -> Fin (p i) -> A) f k ≡ g k
+    lemma k = tptLemma ℕ A Fin p f k ∙ h (k .fst) (k .snd)
+
+ℕ≡→Fin̄≅ : ∀ {n m} -> n ≡ m -> Fin n ≃ Fin m
+ℕ≡→Fin̄≅ {n = n} {m = m} p = univalence .fst (cong Fin p)
+
+⊎-inl-beta : (B : Type ℓ) (f : A -> C) (g : B -> C) -> (a : A) -> ⊎.rec f g (inl a) ≡ f a
+⊎-inl-beta B f g a = refl
+
+⊎-inr-beta : (A : Type ℓ) (f : A -> C) (g : B -> C) -> (b : B) -> ⊎.rec f g (inr b) ≡ g b
+⊎-inr-beta A f g b = refl
+
+⊎-eta : {f : A -> C} {g : B -> C} -> (h : A ⊎ B -> C) (h1 : f ≡ h ∘ inl) (h2 : g ≡ h ∘ inr) -> ⊎.rec f g ≡ h
+⊎-eta h h1 h2 i (inl a) = h1 i a
+⊎-eta h h1 h2 i (inr b) = h2 i b
+
+∸-<-lemma⁻ : (m n o : ℕ) -> m ≤ o -> o ∸ m < n -> o < m + n
+∸-<-lemma⁻ zero n o m≤o o∸m<n = o∸m<n
+∸-<-lemma⁻ (suc m) n zero m≤o o∸m<n = suc-≤-suc zero-≤
+∸-<-lemma⁻ (suc m) n (suc o) m≤o o∸m<n = suc-≤-suc (∸-<-lemma⁻ m n o (pred-≤-pred m≤o) o∸m<n)
+
+finSplitAux : ∀ m n k -> k < m + n -> (k < m) ⊎ (m ≤ k) -> Fin m ⊎ Fin n
+finSplitAux m n k k<m+n (inl k<m) = inl (k , k<m)
+finSplitAux m n k k<m+n (inr k≥m) = inr (k ∸ m , ∸-<-lemma m n k k<m+n k≥m)
+
+finSplit : ∀ m n -> Fin (m + n) -> Fin m ⊎ Fin n
+finSplit m n (k , k<m+n) = finSplitAux m n k k<m+n (k ≤? m)
+
+finSplit-beta-inl-aux : ∀ {m n} (k : ℕ) (k<m : k < m) -> finSplit m n (k , o<m→o<m+n m n k k<m) ≡ inl (k , k<m)
+finSplit-beta-inl-aux {m} {n} k k<m! with k ≤? m
+... | inl k<m = congS (\p -> inl (k , p)) (isProp≤ k<m k<m!)
+... | inr m≤k = ⊥.rec (¬-<-and-≥ k<m! m≤k)
+
+finSplit-beta-inl : ∀ {m n} (k : ℕ) (k<m : k < m) (k<m+n : k < m + n) -> finSplit m n (k , k<m+n) ≡ inl (k , k<m)
+finSplit-beta-inl {m} {n} k k<m k<m+n =
+  finSplit m n (k , k<m+n) ≡⟨ congS (\ϕ -> finSplit m n (k , ϕ)) (isProp≤ k<m+n (o<m→o<m+n m n k k<m)) ⟩
+  finSplit m n (k , o<m→o<m+n m n k k<m) ≡⟨ finSplit-beta-inl-aux k k<m ⟩
+  inl (k , k<m) ∎
+
+finSplit-beta-inr-aux : ∀ {m n} (k : ℕ) (m≤k : m ≤ k) (k∸m<n : k ∸ m < n) -> finSplit m n (k , ∸-<-lemma⁻ m n k m≤k k∸m<n) ≡ inr (k ∸ m , k∸m<n)
+finSplit-beta-inr-aux {m} {n} k m≤k! k∸m<n with k ≤? m
+... | inl k<m = ⊥.rec (¬-<-and-≥ k<m m≤k!)
+... | inr m≤k = congS (\p -> inr (k ∸ m , p)) (isProp≤ (∸-<-lemma m n k (∸-<-lemma⁻ m n k m≤k! k∸m<n) m≤k) k∸m<n)
+
+n+m∸n=m : ∀ n m -> n + m ∸ n ≡ m
+n+m∸n=m n m = congS (_∸ n) (+-comm n m) ∙ m+n∸n=m n m
+
+finSplit-beta-inr : ∀ {m n} (k : ℕ) (k<m+n : k < m + n) (m≤k : m ≤ k) (k∸m<n : k ∸ m < n) -> finSplit m n (k , k<m+n) ≡ inr (k ∸ m , k∸m<n)
+finSplit-beta-inr {m} {n} k k<m+n m≤k k∸m<n =
+    finSplit m n (k , k<m+n)
+  ≡⟨ congS (\ϕ -> finSplit m n (k , ϕ)) (isProp≤ k<m+n (∸-<-lemma⁻ m n k m≤k k∸m<n)) ⟩
+    finSplit m n (k , ∸-<-lemma⁻ m n k m≤k k∸m<n)
+  ≡⟨ finSplit-beta-inr-aux k m≤k k∸m<n ⟩
+    inr (k ∸ m , k∸m<n)
+  ∎
+
+finSplit-beta-inr-+ : ∀ {m n} (k : ℕ) (k<n : k < n) -> finSplit m n (m + k , <-k+ {k = m} k<n) ≡ inr (k , k<n)
+finSplit-beta-inr-+ {m} {n} k k<n =
+    finSplit m n (m + k , <-k+ {k = m} k<n)
+  ≡⟨ finSplit-beta-inr (m + k) (<-k+ k<n) ≤SumLeft (subst (_< n) (sym (n+m∸n=m m k)) k<n) ⟩
+    inr (m + k ∸ m , subst (_< n) (sym (n+m∸n=m m k)) k<n)
+  ≡⟨ congS inr (Σ≡Prop (\_ -> isProp≤) (n+m∸n=m m k)) ⟩
+     inr (k , k<n)
+  ∎
+
+finCombine-inl : Fin m -> Fin (m + n)
+finCombine-inl {m = m} {n = n} (k , k<m) = k , o<m→o<m+n m n k k<m
+
+finCombine-inr : Fin n -> Fin (m + n)
+finCombine-inr {n = n} {m = m} (k , k<n) = m + k , <-k+ k<n
+
+finCombine : ∀ m n -> Fin m ⊎ Fin n -> Fin (m + n)
+finCombine m n = ⊎.rec finCombine-inl finCombine-inr
+
+finSplit∘finCombine : ∀ m n x -> (finSplit m n ∘ finCombine m n) x ≡ x
+finSplit∘finCombine m n =
+  ⊎.elim (\(k , k<m) ->
+              finSplit m n (finCombine m n (inl (k , k<m)))
+         ≡⟨ congS (finSplit m n) (⊎-inl-beta (Fin n) finCombine-inl finCombine-inr (k , k<m)) ⟩
+              finSplit m n (k , o<m→o<m+n m n k k<m)
+         ≡⟨ finSplit-beta-inl k k<m (o<m→o<m+n m n k k<m) ⟩
+              inl (k , k<m)
+         ∎)
+         (\(k , k<n) ->
+              finSplit m n (finCombine m n (inr (k , k<n)))
+         ≡⟨ congS (finSplit m n) (⊎-inr-beta (Fin m) finCombine-inl finCombine-inr (k , k<n)) ⟩
+              finSplit m n (m + k , <-k+ k<n)
+         ≡⟨ finSplit-beta-inr-+ k k<n ⟩
+              inr (k , k<n)
+         ∎)
+
+finCombine∘finSplit : ∀ m n x -> (finCombine m n ∘ finSplit m n) x ≡ x
+finCombine∘finSplit m n (k , k<m+n) =
+  ⊎.rec (\k<m ->
+              finCombine m n (finSplit m n (k , k<m+n))
+        ≡⟨ congS (finCombine m n) (finSplit-beta-inl k k<m k<m+n) ⟩
+              finCombine m n (inl (k , k<m))
+        ≡⟨ ⊎-inl-beta (Fin n) finCombine-inl finCombine-inr (k , k<m) ⟩
+              (k , o<m→o<m+n m n k k<m)
+        ≡⟨ Σ≡Prop (\_ -> isProp≤) refl ⟩
+              (k , k<m+n)
+        ∎)
+        (\m≤k ->
+              finCombine m n (finSplit m n (k , k<m+n))
+        ≡⟨ congS (finCombine m n) (finSplit-beta-inr k k<m+n m≤k (∸-<-lemma m n k k<m+n m≤k)) ⟩
+              finCombine m n (inr (k ∸ m , ∸-<-lemma m n k k<m+n m≤k))
+        ≡⟨ ⊎-inr-beta (Fin m) finCombine-inl finCombine-inr (k ∸ m , ∸-<-lemma m n k k<m+n m≤k) ⟩
+              finCombine-inr (k ∸ m , ∸-<-lemma m n k k<m+n m≤k)
+        ≡⟨ Σ≡Prop (\_ -> isProp≤) (≤-∸-k m≤k ∙ n+m∸n=m m k) ⟩
+              (k , k<m+n)
+        ∎)
+        (k ≤? m)
+
+Fin≅Fin+Fin : ∀ m n -> Iso (Fin (m + n)) (Fin m ⊎ Fin n)
+Fin≅Fin+Fin m n = iso (finSplit m n) (finCombine m n) (finSplit∘finCombine m n) (finCombine∘finSplit m n)
+
+combine : ∀ n m -> (Fin n -> A) -> (Fin m -> A) -> (Fin (n + m) -> A)
+combine n m as bs w = ⊎.rec as bs (finSplit n m w)
+
+_⊕_ : Array A -> Array A -> Array A
+(n , as) ⊕ (m , bs) = n + m , combine n m as bs
+
+e-fun : Fin 0 -> A
+e-fun = ⊥.rec ∘ ¬Fin0
+
+e : Array A
+e = 0 , e-fun
+
+e-eta : ∀ (xs ys : Array A) -> xs .fst ≡ 0 -> ys .fst ≡ 0 -> xs ≡ ys
+e-eta (n , xs) (m , ys) p q = ΣPathP (p ∙ sym q , toPathP (funExt lemma))
+  where
+  lemma : _
+  lemma x = ⊥.rec (¬Fin0 (subst Fin q x))
+
+η : A -> Array A
+η x = 1 , λ _ -> x
+
+zero-+ : ∀ m → 0 + m ≡ m
+zero-+ m = refl
+
+⊕-unitl : ∀ {ℓ} {A : Type ℓ} -> (xs : Array A) -> e ⊕ xs ≡ xs
+⊕-unitl (n , f) = Array≡ (zero-+ n) \k k<n ->
+    ⊎.rec e-fun f (finSplit 0 n (k , subst (k <_) (sym (zero-+ n)) k<n))
+  ≡⟨ congS (⊎.rec e-fun f) (finSplit-beta-inr k (subst (k <_) (sym (zero-+ n)) k<n) zero-≤ k<n) ⟩
+    ⊎.rec e-fun f (inr (k , k<n))
+  ≡⟨ ⊎-inr-beta (Fin 0) e-fun f (k , k<n) ⟩
+    f (k , k<n)
+  ∎
+
+⊕-unitr : ∀ {ℓ} {A : Type ℓ} -> (xs : Array A) -> xs ⊕ e ≡ xs
+⊕-unitr (n , f) = Array≡ (+-zero n) \k k<n ->
+    ⊎.rec f e-fun (finSplit n 0 (k , subst (k <_) (sym (+-zero n)) k<n))
+  ≡⟨ congS (⊎.rec f e-fun) (finSplit-beta-inl k k<n (subst (k <_) (sym (+-zero n)) k<n)) ⟩
+    ⊎.rec f e-fun (inl (k , k<n))
+  ≡⟨ ⊎-inl-beta (Fin 0) f e-fun (k , k<n) ⟩
+    f (k , k<n)
+  ∎
+
+∸-+-assoc : ∀ m n o → m ∸ n ∸ o ≡ m ∸ (n + o)
+∸-+-assoc m       n       zero    = cong (m ∸_) (sym (+-zero n))
+∸-+-assoc zero    zero    (suc o) = refl
+∸-+-assoc zero    (suc n) (suc o) = refl
+∸-+-assoc (suc m) zero    (suc o) = refl
+∸-+-assoc (suc m) (suc n) (suc o) = ∸-+-assoc m n (suc o)
+
+assocr-then-∸ : ∀ (k n m o : ℕ) -> k < n + (m + o) -> n + m ≤ k -> k ∸ (n + m) < o
+assocr-then-∸ k n m o p q = ∸-<-lemma (n + m) o k (subst (k <_) (+-assoc n m o) p) q
+
+⊕-assocr-left-beta : ∀ {ℓ} {A : Type ℓ} {m n o : ℕ} (as : Fin m -> A) (bs : Fin n -> A) (cs : Fin o -> A)
+                      -> (k : ℕ) (k<m+n : k < m + n) (k<m+n+o : k < m + (n + o))
+                      -> ⊎.rec as (⊎.rec bs cs ∘ finSplit n o) (finSplit m (n + o) (k , k<m+n+o)) ≡ ⊎.rec as bs (finSplit m n (k , k<m+n))
+⊕-assocr-left-beta {m = m} {n = n} {o = o} as bs cs k k<m+n k<m+n+o =
+  ⊎.rec (\k<m ->
+          ⊎.rec as (⊎.rec bs cs ∘ finSplit n o) (finSplit m (n + o) (k , k<m+n+o))
+        ≡⟨ congS (⊎.rec as (⊎.rec bs cs ∘ finSplit n o)) (finSplit-beta-inl k k<m k<m+n+o)  ⟩
+          ⊎.rec as (⊎.rec bs cs ∘ finSplit n o) (inl (k , k<m))
+        ≡⟨ ⊎-inl-beta (Fin (n + o)) as (⊎.rec bs cs ∘ finSplit n o) (k , k<m) ⟩
+          as (k , k<m)
+        ≡⟨ ⊎-inl-beta (Fin n) as bs (k , k<m) ⟩
+          ⊎.rec as bs (inl (k , k<m))
+        ≡⟨ sym (congS (⊎.rec as bs) (finSplit-beta-inl k k<m k<m+n)) ⟩
+          ⊎.rec as bs (finSplit m n (k , k<m+n))
+        ∎)
+        (\m≤k ->
+          ⊎.rec as (⊎.rec bs cs ∘ finSplit n o) (finSplit m (n + o) (k , k<m+n+o))
+        ≡⟨ congS (⊎.rec as (⊎.rec bs cs ∘ finSplit n o)) (finSplit-beta-inr k k<m+n+o m≤k (∸-<-lemma m (n + o) k k<m+n+o m≤k))  ⟩
+          ⊎.rec as (⊎.rec bs cs ∘ finSplit n o) (inr (k ∸ m , ∸-<-lemma m (n + o) k k<m+n+o m≤k))
+        ≡⟨ ⊎-inr-beta (Fin m) as (⊎.rec bs cs ∘ finSplit n o) (k ∸ m , ∸-<-lemma m (n + o) k k<m+n+o m≤k) ⟩
+          ⊎.rec bs cs (finSplit n o (k ∸ m , ∸-<-lemma m (n + o) k k<m+n+o m≤k))  
+        ≡⟨ congS (⊎.rec bs cs) (finSplit-beta-inl (k ∸ m) (∸-<-lemma m n k k<m+n m≤k) (∸-<-lemma m (n + o) k k<m+n+o m≤k)) ⟩
+          ⊎.rec bs cs (inl (k ∸ m , ∸-<-lemma m n k k<m+n m≤k))
+        ≡⟨ ⊎-inl-beta (Fin o) bs cs (k ∸ m , ∸-<-lemma m n k k<m+n m≤k) ⟩
+          bs (k ∸ m , ∸-<-lemma m n k k<m+n m≤k)
+        ≡⟨ ⊎-inr-beta (Fin m) as bs (k ∸ m , ∸-<-lemma m n k k<m+n m≤k) ⟩
+          ⊎.rec as bs (inr (k ∸ m , ∸-<-lemma m n k k<m+n m≤k))
+        ≡⟨ sym (congS (⊎.rec as bs) (finSplit-beta-inr k k<m+n m≤k (∸-<-lemma m n k k<m+n m≤k))) ⟩
+          ⊎.rec as bs (finSplit m n (k , k<m+n))
+        ∎)
+  (k ≤? m)
+
+m+n≤k→m≤k : ∀ n m k -> m + n ≤ k -> m ≤ k
+m+n≤k→m≤k n m k (o , p) = (o + n) , sym (+-assoc o n m) ∙ congS (o +_) (+-comm n m) ∙ p
+
+n+m≤k→m≤k∸n : ∀ n m k -> n + m ≤ k -> m ≤ k ∸ n
+n+m≤k→m≤k∸n n m k p = subst (_≤ k ∸ n) (∸+ m n) (≤-∸-≤ (n + m) k n p)
+
+⊕-assocr : ∀ {ℓ} {A : Type ℓ} (m n o : Array A) -> (m ⊕ n) ⊕ o ≡ m ⊕ (n ⊕ o)
+⊕-assocr (n , as) (m , bs) (o , cs) = Array≡ (sym (+-assoc n m o)) \k k<n+m+o ->
+  ⊎.rec (\k<n+m ->
+          ⊎.rec (⊎.rec as bs ∘ finSplit n m) cs (finSplit (n + m) o (k , subst (k <_) (+-assoc n m o) k<n+m+o))
+        ≡⟨ congS (⊎.rec (⊎.rec as bs ∘ finSplit n m) cs) (finSplit-beta-inl k k<n+m (subst (k <_) (+-assoc n m o) k<n+m+o)) ⟩
+          ⊎.rec (⊎.rec as bs ∘ finSplit n m) cs (inl (k , k<n+m))
+        ≡⟨ ⊎-inl-beta (Fin o) (⊎.rec as bs ∘ finSplit n m) cs (k , k<n+m) ⟩
+          ⊎.rec as bs (finSplit n m (k , k<n+m))
+        ≡⟨ sym (⊕-assocr-left-beta as bs cs k k<n+m k<n+m+o) ⟩
+          ⊎.rec as (⊎.rec bs cs ∘ finSplit m o) (finSplit n (m + o) (k , k<n+m+o))
+        ∎) 
+        (\n+m≤k ->
+          ⊎.rec (⊎.rec as bs ∘ finSplit n m) cs (finSplit (n + m) o (k , subst (k <_) (+-assoc n m o) k<n+m+o))
+        ≡⟨ congS (⊎.rec (⊎.rec as bs ∘ finSplit n m) cs) (finSplit-beta-inr k (subst (k <_) (+-assoc n m o) k<n+m+o) n+m≤k (assocr-then-∸ k n m o k<n+m+o n+m≤k)) ⟩
+          ⊎.rec (⊎.rec as bs ∘ finSplit n m) cs (inr (k ∸ (n + m) , assocr-then-∸ k n m o k<n+m+o n+m≤k))
+        ≡⟨ ⊎-inr-beta (Fin (n + m)) ((⊎.rec as bs ∘ finSplit n m)) cs (k ∸ (n + m) , assocr-then-∸ k n m o k<n+m+o n+m≤k) ⟩
+          cs (k ∸ (n + m) , assocr-then-∸ k n m o k<n+m+o n+m≤k)
+        ≡⟨ congS cs (Σ≡Prop (λ _ -> isProp≤) (sym (∸-+-assoc k n m))) ⟩
+          cs (k ∸ n ∸ m , subst (_< o) (sym (∸-+-assoc k n m)) (assocr-then-∸ k n m o k<n+m+o n+m≤k))
+        ≡⟨ ⊎-inr-beta (Fin m) bs cs (k ∸ n ∸ m , subst (_< o) (sym (∸-+-assoc k n m)) (assocr-then-∸ k n m o k<n+m+o n+m≤k)) ⟩
+          ⊎.rec bs cs (inr (k ∸ n ∸ m , subst (_< o) (sym (∸-+-assoc k n m)) (assocr-then-∸ k n m o k<n+m+o n+m≤k)))
+        ≡⟨ sym (congS (⊎.rec bs cs) (finSplit-beta-inr (k ∸ n) (∸-<-lemma n (m + o) k k<n+m+o (m+n≤k→m≤k m n k n+m≤k)) (n+m≤k→m≤k∸n n m k n+m≤k) _)) ⟩
+          ⊎.rec bs cs (finSplit m o (k ∸ n , ∸-<-lemma n (m + o) k k<n+m+o (m+n≤k→m≤k m n k n+m≤k)))
+        ≡⟨ ⊎-inr-beta (Fin n) as (⊎.rec bs cs ∘ finSplit m o) (k ∸ n , ∸-<-lemma n (m + o) k k<n+m+o (m+n≤k→m≤k m n k n+m≤k)) ⟩
+          ⊎.rec as (⊎.rec bs cs ∘ finSplit m o) (inr (k ∸ n , ∸-<-lemma n (m + o) k k<n+m+o (m+n≤k→m≤k m n k n+m≤k)))
+        ≡⟨ sym (congS (⊎.rec as (⊎.rec bs cs ∘ finSplit m o)) (finSplit-beta-inr k k<n+m+o (m+n≤k→m≤k m n k n+m≤k) (∸-<-lemma n (m + o) k k<n+m+o (m+n≤k→m≤k m n k n+m≤k)))) ⟩
+          ⊎.rec as (⊎.rec bs cs ∘ finSplit m o) (finSplit n (m + o) (k , k<n+m+o))
+        ∎) 
+  (k ≤? (n + m))
+
+η+fsuc : ∀ {n} (xs : Fin (suc n) -> A) -> η (xs fzero) ⊕ (n , xs ∘ fsuc) ≡ (suc n , xs)
+η+fsuc {n = n} xs = Array≡ refl λ k k<sucn -> ⊎.rec 
+  (λ k<1 ->
+      ⊎.rec (λ _ -> xs fzero) _ (finSplit 1 n (k , _))
+    ≡⟨ congS (⊎.rec _ _) (finSplit-beta-inl k k<1 _) ⟩
+      xs fzero  
+    ≡⟨ congS xs (Σ≡Prop (λ _ -> isProp≤) (sym (≤0→≡0 (pred-≤-pred k<1)))) ⟩
+      xs (k , k<sucn) ∎
+  )
+  (λ 1≤k ->
+      ⊎.rec _ (xs ∘ fsuc) (finSplit 1 n (k , _))
+    ≡⟨ congS (⊎.rec _ _) (finSplit-beta-inr k _ 1≤k (<-∸-< k (suc n) 1 k<sucn (≤<-trans 1≤k k<sucn))) ⟩
+      xs (suc (k ∸ 1) , _)
+    ≡⟨ congS xs (Fin-fst-≡ (≤-∸-suc 1≤k)) ⟩
+      xs (k , k<sucn) ∎
+  )
+  (k ≤? 1)
+
+¬n<m<suc-n : ∀ {n m} -> n < m -> m < suc n -> ⊥.⊥
+¬n<m<suc-n {n} {m} (x , p) (y , q) = znots lemma-β
+  where
+  lemma-α : suc n ≡ (y + suc x) + suc n
+  lemma-α =
+    suc n ≡⟨ sym q ⟩
+    y + suc m ≡⟨ cong (λ z -> y + suc z) (sym p) ⟩
+    y + (suc x + suc n) ≡⟨ +-assoc y (suc x) (suc n) ⟩
+    (y + suc x) + suc n ∎
+  lemma-β : 0 ≡ suc (y + x)
+  lemma-β = (sym (n∸n (suc n))) ∙ cong (_∸ suc n) lemma-α ∙ +∸ (y + suc x) (suc n) ∙ +-suc y x
+
+⊕-split : ∀ n m (xs : Fin (suc n) -> A) (ys : Fin m -> A) ->
+  (n + m , (λ w -> combine (suc n) m xs ys (fsuc w)))
+  ≡ ((n , (λ w -> xs (fsuc w))) ⊕ (m , ys))
+⊕-split n m xs ys = Array≡ refl λ k k<n+m -> ⊎.rec
+  (λ sk<sn -> sym $
+    ⊎.rec (xs ∘ fsuc) ys (finSplit n m (k , k<n+m)) ≡⟨ congS (⊎.rec _ _) (finSplit-beta-inl k (pred-≤-pred sk<sn) k<n+m) ⟩
+    xs (fsuc (k , pred-≤-pred sk<sn)) ≡⟨ congS xs (Fin-fst-≡ refl) ⟩
+    xs (suc k , sk<sn) ≡⟨ sym (congS (⊎.rec _ _) (finSplit-beta-inl (suc k) sk<sn _)) ⟩
+    ⊎.rec xs ys (finSplit (suc n) m (suc k , _))
+  ∎)
+  (λ sn≤sk ->
+    let
+      k∸n<m = subst (k ∸ n <_) ((congS (_∸ n) (+-comm n m)) ∙ +∸ m n) (<-∸-< k (n + m) n k<n+m (≤<-trans (pred-≤-pred sn≤sk) k<n+m))
+    in
+      ⊎.rec xs ys (finSplit (suc n) m (suc k , _)) ≡⟨ congS (⊎.rec _ _) (finSplit-beta-inr (suc k) _ sn≤sk k∸n<m) ⟩
+      ys (k ∸ n , k∸n<m) ≡⟨ sym (congS (⊎.rec _ _) (finSplit-beta-inr k k<n+m (pred-≤-pred sn≤sk) k∸n<m)) ⟩
+      ⊎.rec (xs ∘ fsuc) ys (finSplit n m (k , k<n+m))
+  ∎)
+  (suc k ≤? suc n)
+
+array-α : sig M.MonSig (Array A) -> Array A
+array-α (M.`e , i) = e
+array-α (M.`⊕ , i) = i fzero ⊕ i fone
+
+module Free {x y : Level} {A : Type x} {𝔜 : struct y M.MonSig} (isSet𝔜 : isSet (𝔜 .car)) (𝔜-monoid : 𝔜 ⊨ M.MonSEq) where  
+  module 𝔜 = M.MonSEq 𝔜 𝔜-monoid
+
+  𝔄 : M.MonStruct
+  𝔄 = < Array A , array-α >
+
+  module _ (f : A -> 𝔜 .car) where
+    ♯^ : (n : ℕ) -> (Fin n -> A) -> 𝔜 .car
+    ♯^ zero    _  = 𝔜.e
+    ♯^ (suc n) xs = f (xs fzero) 𝔜.⊕ ♯^ n (xs ∘ fsuc)
+
+    _♯ : Array A -> 𝔜 .car
+    _♯ = uncurry ♯^
+
+    ♯-η∘ : ∀ n (xs : Fin (suc n) -> A)
+      -> (η (xs fzero) ♯) 𝔜.⊕ ((n , xs ∘ fsuc) ♯)
+      ≡ ((η (xs fzero) ⊕ (n , xs ∘ fsuc)) ♯)
+    ♯-η∘ n xs =
+      (η (xs fzero) ♯) 𝔜.⊕ ((n , xs ∘ fsuc) ♯) ≡⟨ cong (𝔜._⊕ ((n , xs ∘ fsuc) ♯)) (𝔜.unitr _) ⟩
+      f (xs fzero) 𝔜.⊕ ((n , xs ∘ fsuc) ♯) ≡⟨⟩
+      (suc n , xs) ♯ ≡⟨ cong _♯ (sym (η+fsuc xs)) ⟩
+      ((η (xs fzero) ⊕ (n , xs ∘ fsuc)) ♯) ∎
+
+    ♯-++^ : ∀ n xs m ys -> ((n , xs) ⊕ (m , ys)) ♯ ≡ ((n , xs) ♯) 𝔜.⊕ ((m , ys) ♯)
+    ♯-++^ zero xs m ys =
+      ((zero , xs) ⊕ (m , ys)) ♯ ≡⟨ cong (λ z -> (z ⊕ (m , ys)) ♯) (e-eta (zero , xs) e refl refl) ⟩
+      (e ⊕ (m , ys)) ♯ ≡⟨ cong _♯ (⊕-unitl (m , ys)) ⟩
+      (m , ys) ♯ ≡⟨ sym (𝔜.unitl _) ⟩
+      𝔜.e 𝔜.⊕ ((m , ys) ♯) ∎
+    ♯-++^ (suc n) xs m ys =
+        f (xs fzero) 𝔜.⊕ ((n + m , _) ♯)
+      ≡⟨ cong (λ z -> f (xs fzero) 𝔜.⊕ (z ♯)) (⊕-split n m xs ys) ⟩
+        f (xs fzero) 𝔜.⊕ (((n , xs ∘ fsuc) ⊕ (m , ys)) ♯)
+      ≡⟨ cong (f (xs fzero) 𝔜.⊕_) (♯-++^ n _ m _) ⟩
+        f (xs fzero) 𝔜.⊕ ((n , xs ∘ fsuc) ♯) 𝔜.⊕ ((m , ys) ♯)
+      ≡⟨ sym (𝔜.assocr _ _ _) ⟩
+        (f (xs fzero) 𝔜.⊕ ((n , xs ∘ fsuc) ♯)) 𝔜.⊕ ((m , ys) ♯)
+      ≡⟨ cong (λ z -> (z 𝔜.⊕ ((n , xs ∘ fsuc) ♯)) 𝔜.⊕ ((m , ys) ♯) ) (sym (𝔜.unitr _)) ⟩
+        ((η (xs fzero) ♯) 𝔜.⊕ ((n , xs ∘ fsuc) ♯)) 𝔜.⊕ ((m , ys) ♯)
+      ≡⟨ cong (𝔜._⊕ ((m , ys) ♯)) (♯-η∘ n xs) ⟩
+        ((η (xs fzero) ⊕ (n , xs ∘ fsuc)) ♯) 𝔜.⊕ ((m , ys) ♯)
+      ≡⟨ cong (λ z -> (z ♯) 𝔜.⊕ ((m , ys) ♯)) (η+fsuc xs) ⟩
+        ((suc n , xs) ♯) 𝔜.⊕ ((m , ys) ♯) ∎
+
+    ♯-++ : ∀ xs ys -> (xs ⊕ ys) ♯ ≡ (xs ♯) 𝔜.⊕ (ys ♯)
+    ♯-++ (n , xs) (m , ys) = ♯-++^ n xs m ys
+
+    ♯-isMonHom : structHom 𝔄 𝔜
+    fst ♯-isMonHom = _♯
+    snd ♯-isMonHom M.`e i = 𝔜.e-eta
+    snd ♯-isMonHom M.`⊕ i = 𝔜.⊕-eta i _♯ ∙ sym (♯-++ (i fzero) (i fone))
+
+  private
+    arrayEquivLemma : (g : structHom 𝔄 𝔜) (n : ℕ) (xs : Fin n -> A) -> g .fst (n , xs) ≡ ((g .fst ∘ η) ♯) (n , xs)
+    arrayEquivLemma (g , homMonWit) zero xs =
+      g (0 , xs) ≡⟨ cong g (e-eta _ _ refl refl) ⟩
+      g e ≡⟨ sym (homMonWit M.`e (lookup [])) ∙ 𝔜.e-eta ⟩
+      𝔜.e ≡⟨⟩
+      ((g ∘ η) ♯) (zero , xs) ∎
+    arrayEquivLemma (g , homMonWit) (suc n) xs =
+      g (suc n , xs) ≡⟨ cong g (sym (η+fsuc xs)) ⟩
+      g (η (xs fzero) ⊕ (n , xs ∘ fsuc)) ≡⟨ sym (homMonWit M.`⊕ (lookup (η (xs fzero) ∷ₗ (n , xs ∘ fsuc) ∷ₗ []))) ⟩
+      _ ≡⟨ 𝔜.⊕-eta (lookup ((η (xs fzero)) ∷ₗ (n , xs ∘ fsuc) ∷ₗ [])) g ⟩
+      g (η (xs fzero)) 𝔜.⊕ g (n , xs ∘ fsuc) ≡⟨ cong (g (η (xs fzero)) 𝔜.⊕_) (arrayEquivLemma (g , homMonWit) n (xs ∘ fsuc)) ⟩
+      g (η (xs fzero)) 𝔜.⊕ ((g ∘ η) ♯) (n , xs ∘ fsuc) ∎
+
+    arrayEquivLemma-β : (g : structHom 𝔄 𝔜) -> g ≡ ♯-isMonHom (g .fst ∘ η)
+    arrayEquivLemma-β g = structHom≡ 𝔄 𝔜 g (♯-isMonHom (g .fst ∘ η)) isSet𝔜 (funExt λ (n , p) -> arrayEquivLemma g n p)
+
+  arrayEquiv : structHom 𝔄 𝔜 ≃ (A -> 𝔜 .car)
+  arrayEquiv =
+    isoToEquiv (iso (λ g -> g .fst ∘ η) ♯-isMonHom (λ g -> funExt (𝔜.unitr ∘ g)) (sym ∘ arrayEquivLemma-β))
+
+module ArrayDef = F.Definition M.MonSig M.MonEqSig M.MonSEq
+
+array-str : ∀ {n} (A : Type n) -> struct n M.MonSig
+array-str A = < Array A , array-α >
+
+array-sat : ∀ {n} {X : Type n} -> array-str X ⊨ M.MonSEq
+array-sat M.`unitl ρ = ⊕-unitl (ρ fzero)
+array-sat M.`unitr ρ = ⊕-unitr (ρ fzero)
+array-sat M.`assocr ρ = ⊕-assocr (ρ fzero) (ρ fone) (ρ ftwo)
+
+arrayDef : ∀ {ℓ ℓ'} -> ArrayDef.Free ℓ ℓ' 2
+F.Definition.Free.F arrayDef = Array
+F.Definition.Free.η arrayDef = η
+F.Definition.Free.α arrayDef = array-α
+F.Definition.Free.sat arrayDef = array-sat
+F.Definition.Free.isFree arrayDef isSet𝔜 satMon = (Free.arrayEquiv isSet𝔜 satMon) .snd
+
+direct proof of isomorphism between Array and List
+without using the universal property of Array as a free monoid
+arrayIsoToList : ∀ {ℓ} {A : Type ℓ} -> Iso (Array A) (List A)
+arrayIsoToList {A = A} = iso (uncurry tabulate) from tabulate-lookup from∘to
+  where
+  from : List A -> Array A
+  from xs = length xs , lookup xs
+
+  from∘to : ∀ xs -> from (uncurry tabulate xs) ≡ xs
+  from∘to (n , xs) = ΣPathP (length-tabulate n xs , lookup-tabulate n xs)
+
+array≡List : ∀ {ℓ} -> Array {ℓ = ℓ} ≡ List 
+array≡List = funExt λ _ -> isoToPath arrayIsoToList
+
+import Cubical.Structures.Set.Mon.List as LM
+
+arrayDef' : ∀ {ℓ ℓ'} -> ArrayDef.Free ℓ ℓ' 2
+arrayDef' {ℓ = ℓ} {ℓ' = ℓ'} = fun ArrayDef.isoAux (Array , arrayFreeAux)
+  where
+  listFreeAux : ArrayDef.FreeAux ℓ ℓ' 2 List
+  listFreeAux = (inv ArrayDef.isoAux (LM.listDef {ℓ = ℓ} {ℓ' = ℓ'})) .snd
+
+  arrayFreeAux : ArrayDef.FreeAux ℓ ℓ' 2 Array
+  arrayFreeAux = subst (ArrayDef.FreeAux ℓ ℓ' 2) (sym array≡List) listFreeAux
+
+private
+  arrayIsoToList+η : ∀ {ℓ} {A : Type ℓ} -> (x : A) (ys : Array A)
+                  -> arrayIsoToList .fun (η x ⊕ ys) ≡ arrayIsoToList .fun (η x) ++ arrayIsoToList .fun ys
+  arrayIsoToList+η x ys =
+    congS (λ z -> x ∷ₗ (uncurry tabulate) z) $ Array≡ refl $ λ k k<m ->
+      congS (⊎.rec _ _) (finSplit-beta-inr (suc k) (suc-≤-suc _) (suc-≤-suc zero-≤) k<m)
+
+  arrayIsoToList++ : ∀ {ℓ} {A : Type ℓ} n -> (f : Fin n -> A) (ys : Array A)
+                  -> arrayIsoToList .fun (n , f) ++ arrayIsoToList .fun ys ≡ arrayIsoToList .fun ((n , f) ⊕ ys)
+  arrayIsoToList++ zero f ys = congS (arrayIsoToList .fun) $ sym $
+    (zero , f) ⊕ ys ≡⟨ congS (_⊕ ys) (e-eta (zero , f) e refl refl) ⟩
+    e ⊕ ys ≡⟨ ⊕-unitl ys ⟩
+    ys ∎
+  arrayIsoToList++ (suc n) f ys =
+      arrayIsoToList .fun (suc n , f) ++ arrayIsoToList .fun ys
+    ≡⟨ congS (λ z -> arrayIsoToList .fun z ++ arrayIsoToList .fun ys) $ sym (η+fsuc f) ⟩
+      arrayIsoToList .fun (η (f fzero) ⊕ (n , f ∘ fsuc)) ++ arrayIsoToList .fun ys
+    ≡⟨ congS (_++ arrayIsoToList .fun ys) (arrayIsoToList+η (f fzero) (n , f ∘ fsuc)) ⟩
+      (arrayIsoToList .fun (η (f fzero)) ++ arrayIsoToList .fun (n , f ∘ fsuc)) ++ arrayIsoToList .fun ys
+    ≡⟨ ++-assoc (arrayIsoToList .fun (η (f fzero))) (arrayIsoToList .fun (n , f ∘ fsuc)) _ ⟩
+      arrayIsoToList .fun (η (f fzero)) ++ (arrayIsoToList .fun (n , f ∘ fsuc) ++ arrayIsoToList .fun ys)
+    ≡⟨ congS (arrayIsoToList .fun (η (f fzero)) ++_) (arrayIsoToList++ n (f ∘ fsuc) ys) ⟩
+      arrayIsoToList .fun (η (f fzero)) ++ arrayIsoToList .fun ((n , f ∘ fsuc) ⊕ ys)
+    ≡⟨ sym (arrayIsoToList+η (f fzero) ((n , f ∘ fsuc) ⊕ ys)) ⟩
+      arrayIsoToList .fun (η (f fzero) ⊕ ((n , f ∘ fsuc) ⊕ ys))
+    ≡⟨ congS (arrayIsoToList .fun) (sym (⊕-assocr (η (f fzero)) (n , f ∘ fsuc) ys)) ⟩
+      arrayIsoToList .fun ((η (f fzero) ⊕ (n , f ∘ fsuc)) ⊕ ys)
+    ≡⟨ congS (λ zs -> arrayIsoToList .fun (zs ⊕ ys)) (η+fsuc f) ⟩
+      arrayIsoToList .fun ((suc n , f) ⊕ ys) ∎
+
+module _ {ℓ} {A : Type ℓ} where
+  open ArrayDef.Free
+  private
+    module 𝔄 = M.MonSEq < Array A , array-α > array-sat
+
+  arrayIsoToListHom : structIsHom < Array A , array-α > < List A , LM.list-α > (arrayIsoToList .fun)
+  arrayIsoToListHom M.`e i = refl
+  arrayIsoToListHom M.`⊕ i =
+      arrayIsoToList .fun (i fzero) ++ arrayIsoToList .fun (i fone)
+    ≡⟨ arrayIsoToList++ (fst (i fzero)) (snd (i fzero)) (i fone) ⟩
+      arrayIsoToList .fun (i fzero ⊕ i fone)
+    ≡⟨ congS (arrayIsoToList .fun) (sym (𝔄.⊕-eta i (idfun _))) ⟩
+      arrayIsoToList .fun (i fzero ⊕ i fone) ∎ 
\ No newline at end of file
diff --git a/Cubical/Structures/Set/Mon/Desc.agda b/Cubical/Structures/Set/Mon/Desc.agda
new file mode 100644
index 0000000..1da1e32
--- /dev/null
+++ b/Cubical/Structures/Set/Mon/Desc.agda
@@ -0,0 +1,187 @@
+{-# OPTIONS --cubical --safe --exact-split #-}
+
+module Cubical.Structures.Set.Mon.Desc where
+
+open import Cubical.Foundations.Everything
+open import Cubical.Functions.Logic as L
+open import Cubical.Data.Nat
+open import Cubical.Data.Nat.Order
+open import Cubical.Data.List
+open import Cubical.Data.Sigma
+open import Cubical.Data.Sum
+open import Cubical.Data.Unit
+open import Cubical.Data.Empty as ⊥
+
+open import Cubical.Structures.Sig
+open import Cubical.Structures.Str public
+open import Cubical.Structures.Tree as T
+open import Cubical.Structures.Eq
+open import Cubical.Structures.Arity as F
+
+data MonSym : Type where
+  `e : MonSym
+  `⊕ : MonSym
+
+MonAr : MonSym -> ℕ
+MonAr `e = 0
+MonAr `⊕ = 2
+
+MonFinSig : FinSig ℓ-zero
+MonFinSig = MonSym , MonAr
+
+MonSig : Sig ℓ-zero ℓ-zero
+MonSig = finSig MonFinSig
+
+MonStruct : ∀ {n} -> Type (ℓ-suc n)
+MonStruct {n} = struct n MonSig
+
+module MonStruct {ℓ} (𝔛 : MonStruct {ℓ}) where
+  e : 𝔛 .car
+  e = 𝔛 .alg (`e , lookup [])
+
+  e-eta : {i j : Arity 0 -> 𝔛 .car} -> 𝔛 .alg (`e , i) ≡ 𝔛 .alg (`e , j)
+  e-eta {i} = cong (\j -> 𝔛 .alg (`e , j)) (funExt λ z -> lookup [] z)
+
+  infixr 40 _⊕_
+  _⊕_ : 𝔛 .car -> 𝔛 .car -> 𝔛 .car
+  _⊕_ x y = 𝔛 .alg (`⊕ , lookup (x ∷ y ∷ []))
+
+  ⊕-eta : ∀ {ℓ} {A : Type ℓ} (i : Arity 2 -> A) (_♯ : A -> 𝔛 .car) -> 𝔛 .alg (`⊕ , (λ w -> i w ♯)) ≡ (i fzero ♯) ⊕ (i fone ♯)
+  ⊕-eta i _♯ = cong (λ z -> 𝔛 .alg (`⊕ , z)) (funExt lemma)
+    where
+    lemma : (x : Arity 2) -> (i x ♯) ≡ lookup ((i fzero ♯) ∷ (i fone ♯) ∷ []) x
+    lemma (zero , p) = cong (_♯ ∘ i) (Σ≡Prop (λ _ -> isProp≤) refl)
+    lemma (suc zero , p) = cong (_♯ ∘ i) (Σ≡Prop (λ _ -> isProp≤) refl)
+    lemma (suc (suc n) , p) = ⊥.rec (¬m+n<m {m = 2} p)
+
+data MonEq : Type where
+  `unitl `unitr `assocr : MonEq
+
+MonEqFree : MonEq -> ℕ
+MonEqFree `unitl = 1
+MonEqFree `unitr = 1
+MonEqFree `assocr = 3
+
+MonEqSig : EqSig ℓ-zero ℓ-zero
+MonEqSig = finEqSig (MonEq , MonEqFree)
+
+monEqLhs : (eq : MonEq) -> FinTree MonFinSig (MonEqFree eq)
+monEqLhs `unitl = node (`⊕ , lookup (node (`e , lookup []) ∷ leaf fzero ∷ []))
+monEqLhs `unitr = node (`⊕ , lookup (leaf fzero ∷ node (`e , lookup []) ∷ []))
+monEqLhs `assocr = node (`⊕ , lookup (node (`⊕ , lookup (leaf fzero ∷ leaf fone ∷ [])) ∷ leaf ftwo ∷ []))
+
+monEqRhs : (eq : MonEq) -> FinTree MonFinSig (MonEqFree eq)
+monEqRhs `unitl = leaf fzero
+monEqRhs `unitr = leaf fzero
+monEqRhs `assocr = node (`⊕ , lookup (leaf fzero ∷ node (`⊕ , lookup (leaf fone ∷ leaf ftwo ∷ [])) ∷ []))
+
+MonSEq : seq MonSig MonEqSig
+MonSEq n = monEqLhs n , monEqRhs n
+
+module MonSEq {ℓ} (𝔛 : MonStruct {ℓ}) (ϕ : 𝔛 ⊨ MonSEq) where
+  open MonStruct 𝔛 public
+
+  unitl : ∀ m -> e ⊕ m ≡ m
+  unitl m =
+      e ⊕ m
+    ≡⟨⟩
+      𝔛 .alg (`⊕ , lookup (𝔛 .alg (`e , _) ∷ m ∷ []))
+    ≡⟨ cong (\w -> 𝔛 .alg (`⊕ , w)) (funExt lemma) ⟩
+      𝔛 .alg (`⊕ , (λ x -> sharp (finSig (MonSym , MonAr)) 𝔛 (lookup (m ∷ [])) (lookup (node (`e , _) ∷ leaf fzero ∷ []) x)))
+    ≡⟨ ϕ `unitl (lookup [ m ]) ⟩
+      m ∎
+    where
+      lemma : (w : MonSig .arity `⊕) -> lookup (𝔛 .alg (`e , (λ num → ⊥.rec (¬Fin0 num))) ∷ m ∷ []) w ≡ sharp (finSig (MonSym , MonAr)) 𝔛 (lookup (m ∷ [])) (lookup (node (`e , (λ num → ⊥.rec (¬Fin0 num))) ∷ leaf fzero ∷ []) w)
+      lemma (zero , p) = sym e-eta
+      lemma (suc zero , p) = refl
+      lemma (suc (suc n) , p) = ⊥.rec (¬m+n<m {m = 2} p)
+
+  unitr : ∀ m -> m ⊕ e ≡ m
+  unitr m =
+      m ⊕ e
+    ≡⟨⟩
+      𝔛 .alg (`⊕ , lookup (m ∷ 𝔛 .alg (`e , _) ∷ []))  
+    ≡⟨ cong (\w -> 𝔛 .alg (`⊕ , w)) (funExt lemma) ⟩
+      𝔛 .alg (`⊕ , (λ x -> sharp MonSig 𝔛 (lookup [ m ]) (lookup (leaf fzero ∷ node (`e , (λ num → ⊥.rec (¬Fin0 num))) ∷ []) x)))
+    ≡⟨ ϕ `unitr (lookup [ m ]) ⟩
+      m ∎
+    where
+      lemma : (x : MonSig .arity `⊕) -> lookup (m ∷ 𝔛 .alg (`e , (λ num → ⊥.rec (¬Fin0 num))) ∷ []) x ≡ sharp MonSig 𝔛 (lookup [ m ]) (lookup (leaf fzero ∷ node (`e , (λ num → ⊥.rec (¬Fin0 num))) ∷ []) x)
+      lemma (zero , p) = refl
+      lemma (suc zero , p) = sym e-eta
+      lemma (suc (suc n) , p) = ⊥.rec (¬m+n<m {m = 2} p)
+
+  assocr : ∀ m n o -> (m ⊕ n) ⊕ o ≡ m ⊕ (n ⊕ o)
+  assocr m n o =
+      (m ⊕ n) ⊕ o
+    ≡⟨⟩
+      𝔛 .alg (`⊕ , lookup (𝔛 .alg (`⊕ , lookup (m ∷ n ∷ [])) ∷ o ∷ []))
+    ≡⟨ cong (\w -> 𝔛 .alg (`⊕ , w)) (funExt lemma1) ⟩
+      𝔛 .alg (`⊕ , (\w -> sharp MonSig 𝔛 (lookup (m ∷ n ∷ o ∷ [])) (lookup (node (`⊕ , lookup (leaf fzero ∷ leaf fone ∷ [])) ∷ leaf ftwo ∷ []) w)))
+    ≡⟨ ϕ `assocr (lookup (m ∷ n ∷ o ∷ [])) ⟩
+      𝔛 .alg (`⊕ , (λ w -> sharp MonSig 𝔛 (lookup (m ∷ n ∷ o ∷ [])) (lookup (leaf fzero ∷ node (`⊕ , lookup (leaf fone ∷ leaf ftwo ∷ [])) ∷ []) w)))
+    ≡⟨ cong (\w -> 𝔛 .alg (`⊕ , w)) (sym (funExt lemma3)) ⟩
+      𝔛 .alg (`⊕ , lookup (m ∷ 𝔛 .alg (`⊕ , lookup (n ∷ o ∷ [])) ∷ []))
+    ≡⟨⟩
+      m ⊕ (n ⊕ o) ∎
+    where
+      lemma1 : (w : MonSig .arity `⊕) -> lookup (𝔛 .alg (`⊕ , lookup (m ∷ n ∷ [])) ∷ o ∷ []) w ≡ sharp MonSig 𝔛 (lookup (m ∷ n ∷ o ∷ [])) (lookup (node (`⊕ , lookup (leaf fzero ∷ leaf fone ∷ [])) ∷ leaf ftwo ∷ []) w)
+      lemma2 : (w : MonSig .arity `⊕) -> lookup (m ∷ n ∷ []) w ≡ sharp MonSig 𝔛 (lookup (m ∷ n ∷ o ∷ [])) (lookup (leaf fzero ∷ leaf fone ∷ []) w)
+
+      lemma1 (zero , p) = cong (λ o → 𝔛 .alg (`⊕ , o)) (funExt lemma2)
+      lemma1 (suc zero , p) = refl
+      lemma1 (suc (suc n) , p) = ⊥.rec (¬m+n<m {m = 2} p)
+
+      lemma2 (zero , p) = refl
+      lemma2 (suc zero , p) = refl
+      lemma2 (suc (suc n) , p) = ⊥.rec (¬m+n<m {m = 2} p)
+
+      lemma3 : (w : MonSig .arity `⊕) -> lookup (m ∷ 𝔛 .alg (`⊕ , lookup (n ∷ o ∷ [])) ∷ []) w ≡ sharp MonSig 𝔛 (lookup (m ∷ n ∷ o ∷ [])) (lookup (leaf fzero ∷ node (`⊕ , lookup (leaf fone ∷ leaf ftwo ∷ [])) ∷ []) w)
+      lemma4 : (w : MonSig .arity `⊕) -> lookup (n ∷ o ∷ []) w ≡ sharp MonSig 𝔛 (lookup (m ∷ n ∷ o ∷ [])) (lookup (leaf fone ∷ leaf ftwo ∷ []) w)
+
+      lemma3 (zero , p) = refl
+      lemma3 (suc zero , p) = cong (λ w → 𝔛 .alg (`⊕ , w)) (funExt lemma4)
+      lemma3 (suc (suc n) , p) = ⊥.rec (¬m+n<m {m = 2} p)
+
+      lemma4 (zero , p) = refl
+      lemma4 (suc zero , p) = refl
+      lemma4 (suc (suc n) , p) = ⊥.rec (¬m+n<m {m = 2} p)
+
+  TODO: Write generic lemma about compatibility between lookup and sharp
+  lemma : (f : MonSym) (x : 𝔛 .car) (xs : List (𝔛 .car)) (a : Arity (length xs))
+       -> lookup (x ∷ xs) (fsuc a) ≡ sharp MonSig 𝔛 {!!} (lookup {!!} a)
+  lemma f = {!!}
+
+ℕ-MonStr : MonStruct
+car ℕ-MonStr = ℕ
+alg ℕ-MonStr (`e , _) = 0
+alg ℕ-MonStr (`⊕ , i) = i fzero + i fone
+
+ℕ-MonStr-MonSEq : ℕ-MonStr ⊨ MonSEq
+ℕ-MonStr-MonSEq `unitl ρ = refl
+ℕ-MonStr-MonSEq `unitr ρ = +-zero (ρ fzero)
+ℕ-MonStr-MonSEq `assocr ρ = sym (+-assoc (ρ fzero) (ρ fone) (ρ ftwo))
+
+⊔-MonStr : (ℓ : Level) -> MonStruct {n = ℓ-suc ℓ}
+car (⊔-MonStr ℓ) = hProp ℓ
+alg (⊔-MonStr ℓ) (`e , i) = ⊥* , isProp⊥*
+alg (⊔-MonStr ℓ) (`⊕ , i) = i fzero ⊔ i fone
+
+⊔-MonStr-MonSEq : (ℓ : Level) -> ⊔-MonStr ℓ ⊨ MonSEq
+⊔-MonStr-MonSEq ℓ `unitl ρ =
+  ⇒∶ ⊔-elim (⊥* , isProp⊥*) (ρ fzero) (λ _ -> ρ fzero) ⊥.rec* (idfun _)
+  ⇐∶ L.inr
+⊔-MonStr-MonSEq ℓ `unitr ρ =
+  ⇔toPath (⊔-elim (ρ fzero) (⊥* , isProp⊥*) (λ _ -> ρ fzero) (idfun _) ⊥.rec*) L.inl
+⊔-MonStr-MonSEq ℓ `assocr ρ =
+  sym (⊔-assoc (ρ fzero) (ρ fone) (ρ ftwo))
+
+⊓-MonStr : (ℓ : Level) -> MonStruct {n = ℓ-suc ℓ}
+car (⊓-MonStr ℓ) = hProp ℓ
+alg (⊓-MonStr ℓ) (`e , i) = L.⊤
+alg (⊓-MonStr ℓ) (`⊕ , i) = i fzero ⊓ i fone
+
+⊓-MonStr-MonSEq : (ℓ : Level) -> ⊓-MonStr ℓ ⊨ MonSEq
+⊓-MonStr-MonSEq ℓ `unitl ρ = ⊓-identityˡ (ρ fzero)
+⊓-MonStr-MonSEq ℓ `unitr ρ = ⊓-identityʳ (ρ fzero)
+⊓-MonStr-MonSEq ℓ `assocr ρ = sym (⊓-assoc (ρ fzero) (ρ fone) (ρ ftwo))
\ No newline at end of file
diff --git a/Cubical/Structures/Set/Mon/Free.agda b/Cubical/Structures/Set/Mon/Free.agda
new file mode 100644
index 0000000..08924b4
--- /dev/null
+++ b/Cubical/Structures/Set/Mon/Free.agda
@@ -0,0 +1,144 @@
+{-# OPTIONS --cubical --safe --exact-split #-}
+
+module Cubical.Structures.Set.Mon.Free where
+
+open import Cubical.Foundations.Everything
+open import Cubical.Data.Sigma
+open import Cubical.Data.List
+open import Cubical.Data.Nat
+open import Cubical.Data.Nat.Order
+import Cubical.Data.Empty as ⊥
+
+import Cubical.Structures.Set.Mon.Desc as M
+import Cubical.Structures.Free as F
+open import Cubical.Structures.Sig
+open import Cubical.Structures.Str public
+open import Cubical.Structures.Tree
+open import Cubical.Structures.Eq
+open import Cubical.Structures.Arity
+
+data FreeMon {ℓ : Level} (A : Type ℓ) : Type ℓ where
+  η : (a : A) -> FreeMon A
+  e : FreeMon A
+  _⊕_ : FreeMon A -> FreeMon A -> FreeMon A
+  unitl : ∀ m -> e ⊕ m ≡ m
+  unitr : ∀ m -> m ⊕ e ≡ m
+  assocr : ∀ m n o -> (m ⊕ n) ⊕ o ≡ m ⊕ (n ⊕ o)
+  trunc : isSet (FreeMon A)
+
+module elimFreeMonSet {p n : Level} {A : Type n} (P : FreeMon A -> Type p)
+                    (η* : (a : A) -> P (η a))
+                    (e* : P e)
+                    (_⊕*_ : {m n : FreeMon A} -> P m -> P n -> P (m ⊕ n))
+                    (unitl* : {m : FreeMon A} (m* : P m) -> PathP (λ i → P (unitl m i)) (e* ⊕* m*) m*)
+                    (unitr* : {m : FreeMon A} (m* : P m) -> PathP (λ i → P (unitr m i)) (m* ⊕* e*) m*)
+                    (assocr* : {m n o : FreeMon A}
+                               (m* : P m) ->
+                               (n* : P n) ->
+                               (o* : P o) -> PathP (λ i → P (assocr m n o i)) ((m* ⊕* n*) ⊕* o*) (m* ⊕* (n* ⊕* o*)))
+                    (trunc* : {xs : FreeMon A} -> isSet (P xs))
+                    where
+  f : (x : FreeMon A) -> P x
+  f (η a) = η* a
+  f e = e*
+  f (x ⊕ y) = f x ⊕* f y
+  f (unitl x i) = unitl* (f x) i
+  f (unitr x i) = unitr* (f x) i
+  f (assocr x y z i) = assocr* (f x) (f y) (f z) i
+  f (trunc xs ys p q i j) =
+     isOfHLevel→isOfHLevelDep 2 (\xs -> trunc* {xs = xs}) (f xs) (f ys) (cong f p) (cong f q) (trunc xs ys p q) i j
+
+module recFreeMonSet {p n : Level} {A : Type n} (P : Type p)
+                    (η* : (a : A) -> P)
+                    (e* : P)
+                    (_⊕*_ : P -> P -> P)
+                    (unitl* : (m* : P) -> PathP (λ i → P) (e* ⊕* m*) m*)
+                    (unitr* : (m* : P) -> PathP (λ i → P) (m* ⊕* e*) m*)
+                    (assocr* : (m* : P) ->
+                               (n* : P) ->
+                               (o* : P) -> PathP (λ i → P) ((m* ⊕* n*) ⊕* o*) (m* ⊕* (n* ⊕* o*)))
+                    (trunc* : isSet P)
+                    where
+  f : (x : FreeMon A) -> P
+  f = elimFreeMonSet.f (\_ -> P) η* e* _⊕*_ unitl* unitr* assocr* trunc*
+
+module elimFreeMonProp {p n : Level} {A : Type n} (P : FreeMon A -> Type p)
+                    (η* : (a : A) -> P (η a))
+                    (e* : P e)
+                    (_⊕*_ : {m n : FreeMon A} -> P m -> P n -> P (m ⊕ n))
+                    (trunc* : {xs : FreeMon A} -> isProp (P xs))
+                    where
+  f : (x : FreeMon A) -> P x
+  f = elimFreeMonSet.f P η* e* _⊕*_ unitl* unitr* assocr* (isProp→isSet trunc*)
+    where
+      abstract
+        unitl* : {m : FreeMon A} (m* : P m) -> PathP (λ i → P (unitl m i)) (e* ⊕* m*) m*
+        unitl* {m} m* = toPathP (trunc* (transp (λ i -> P (unitl m i)) i0 (e* ⊕* m*)) m*)
+        unitr* : {m : FreeMon A} (m* : P m) -> PathP (λ i → P (unitr m i)) (m* ⊕* e*) m*
+        unitr* {m} m* = toPathP (trunc* (transp (λ i -> P (unitr m i)) i0 (m* ⊕* e*)) m*)
+        assocr* : {m n o : FreeMon A}
+                  (m* : P m) ->
+                  (n* : P n) ->
+                  (o* : P o) -> PathP (λ i → P (assocr m n o i)) ((m* ⊕* n*) ⊕* o*) (m* ⊕* (n* ⊕* o*))
+        assocr* {m} {n} {o} m* n* o* =
+          toPathP (trunc* (transp (λ i -> P (assocr m n o i)) i0 ((m* ⊕* n*) ⊕* o*)) (m* ⊕* (n* ⊕* o*)))
+
+freeMon-α : ∀ {n : Level} {X : Type n} -> sig M.MonSig (FreeMon X) -> FreeMon X
+freeMon-α (M.`e , i) = e
+freeMon-α (M.`⊕ , i) = i fzero ⊕ i fone
+
+module Free {x y : Level} {A : Type x} {𝔜 : struct y M.MonSig} (isSet𝔜 : isSet (𝔜 .car)) (𝔜-monoid : 𝔜 ⊨ M.MonSEq) where
+  module 𝔜 = M.MonSEq 𝔜 𝔜-monoid
+
+  𝔉 : struct x M.MonSig
+  𝔉 = < FreeMon A , freeMon-α >
+
+  module _ (f : A -> 𝔜 .car) where
+    _♯ : FreeMon A -> 𝔜 .car
+    (η a) ♯ = f a
+    e ♯ = 𝔜.e
+    (m ⊕ n) ♯ = (m ♯) 𝔜.⊕ (n ♯)
+    (unitl m i) ♯ = 𝔜.unitl (m ♯) i
+    (unitr m i) ♯ = 𝔜.unitr (m ♯) i
+    (assocr m n o i) ♯ = 𝔜.assocr (m ♯) (n ♯) (o ♯) i
+    (trunc m n p q i j) ♯ = isSet𝔜 (m ♯) (n ♯) (cong _♯ p) (cong _♯ q) i j
+
+    ♯-isMonHom : structHom 𝔉 𝔜
+    fst ♯-isMonHom = _♯
+    snd ♯-isMonHom M.`e i = 𝔜.e-eta
+    snd ♯-isMonHom M.`⊕ i = 𝔜.⊕-eta i _♯
+
+  private
+    freeMonEquivLemma : (g : structHom 𝔉 𝔜) -> (x : FreeMon A) -> g .fst x ≡ ((g .fst ∘ η) ♯) x
+    freeMonEquivLemma (g , homMonWit) = elimFreeMonProp.f (λ x -> g x ≡ ((g ∘ η) ♯) x)
+      (λ _ -> refl)
+      (sym (homMonWit M.`e (lookup [])) ∙ 𝔜.e-eta)
+      (λ {m} {n} p q ->
+        g (m ⊕ n) ≡⟨ sym (homMonWit M.`⊕ (lookup (m ∷ n ∷ []))) ⟩
+        𝔜 .alg (M.`⊕ , (λ w -> g (lookup (m ∷ n ∷ []) w))) ≡⟨ 𝔜.⊕-eta (lookup (m ∷ n ∷ [])) g ⟩
+        g m 𝔜.⊕ g n ≡⟨ cong₂ 𝔜._⊕_ p q ⟩
+        _ ∎
+      )
+      (isSet𝔜 _ _)
+
+    freeMonEquivLemma-β : (g : structHom 𝔉 𝔜) -> g ≡ ♯-isMonHom (g .fst ∘ η)
+    freeMonEquivLemma-β g = structHom≡ 𝔉 𝔜 g (♯-isMonHom (g .fst ∘ η)) isSet𝔜 (funExt (freeMonEquivLemma g))
+
+  freeMonEquiv : structHom 𝔉 𝔜 ≃ (A -> 𝔜 .car)
+  freeMonEquiv =
+    isoToEquiv (iso (λ g -> g .fst ∘ η) ♯-isMonHom (λ _ -> refl) (sym ∘ freeMonEquivLemma-β))
+      
+module FreeMonDef = F.Definition M.MonSig M.MonEqSig M.MonSEq
+
+freeMon-sat : ∀ {n} {X : Type n} -> < FreeMon X , freeMon-α > ⊨ M.MonSEq
+freeMon-sat M.`unitl ρ = unitl (ρ fzero)
+freeMon-sat M.`unitr ρ = unitr (ρ fzero)
+freeMon-sat M.`assocr ρ = assocr (ρ fzero) (ρ fone) (ρ ftwo)
+
+freeMonDef : ∀ {ℓ ℓ'} -> FreeMonDef.Free ℓ ℓ' 2
+F.Definition.Free.F freeMonDef = FreeMon
+F.Definition.Free.η freeMonDef = η
+F.Definition.Free.α freeMonDef = freeMon-α
+F.Definition.Free.sat freeMonDef = freeMon-sat
+F.Definition.Free.isFree freeMonDef isSet𝔜 satMon = (Free.freeMonEquiv isSet𝔜 satMon) .snd
+ 
\ No newline at end of file
diff --git a/Cubical/Structures/Set/Mon/List.agda b/Cubical/Structures/Set/Mon/List.agda
new file mode 100644
index 0000000..426a8f4
--- /dev/null
+++ b/Cubical/Structures/Set/Mon/List.agda
@@ -0,0 +1,120 @@
+{-# OPTIONS --cubical --safe --exact-split #-}
+
+module Cubical.Structures.Set.Mon.List where
+
+open import Cubical.Foundations.Everything
+open import Cubical.Data.Sigma
+open import Cubical.Data.List
+open import Cubical.Data.Nat
+open import Cubical.Data.Nat.Order
+open import Cubical.Data.Unit
+import Cubical.Data.Empty as ⊥
+open import Cubical.Functions.Logic as L
+
+import Cubical.Structures.Set.Mon.Desc as M
+import Cubical.Structures.Free as F
+open import Cubical.Structures.Sig
+open import Cubical.Structures.Str public
+open import Cubical.Structures.Tree
+open import Cubical.Structures.Eq
+open import Cubical.Structures.Arity
+open import Cubical.HITs.PropositionalTruncation as P
+open import Cubical.Data.Sum as ⊎
+
+private
+  variable
+    ℓ : Level
+    A B : Type ℓ
+
+list-α : sig M.MonSig (List A) -> List A
+list-α (M.`e , i) = []
+list-α (M.`⊕ , i) = i fzero ++ i fone
+
+module Free {x y : Level} {A : Type x} {𝔜 : struct y M.MonSig} (isSet𝔜 : isSet (𝔜 .car)) (𝔜-monoid : 𝔜 ⊨ M.MonSEq) where  
+  module 𝔜 = M.MonSEq 𝔜 𝔜-monoid
+
+  𝔏 : M.MonStruct
+  𝔏 = < List A , list-α >
+
+  module _ (f : A -> 𝔜 .car) where
+    _♯ : List A -> 𝔜 .car
+    [] ♯ = 𝔜.e
+    (x ∷ xs) ♯ = f x 𝔜.⊕ (xs ♯)
+
+    private
+      ♯-++ : ∀ xs ys -> (xs ++ ys) ♯ ≡ (xs ♯) 𝔜.⊕ (ys ♯)
+      ♯-++ [] ys = sym (𝔜.unitl (ys ♯))
+      ♯-++ (x ∷ xs) ys = cong (f x 𝔜.⊕_) (♯-++ xs ys) ∙ sym (𝔜.assocr (f x) (xs ♯) (ys ♯)) 
+
+    ♯-isMonHom : structHom 𝔏 𝔜
+    fst ♯-isMonHom = _♯
+    snd ♯-isMonHom M.`e i = 𝔜.e-eta
+    snd ♯-isMonHom M.`⊕ i = 𝔜.⊕-eta i _♯ ∙ sym (♯-++ (i fzero) (i fone))
+
+  private
+    listEquivLemma : (g : structHom 𝔏 𝔜) -> (x : List A) -> g .fst x ≡ ((g .fst ∘ [_]) ♯) x
+    listEquivLemma (g , homMonWit) [] = sym (homMonWit M.`e (lookup [])) ∙ 𝔜.e-eta
+    listEquivLemma (g , homMonWit) (x ∷ xs) =
+      g (x ∷ xs) ≡⟨ sym (homMonWit M.`⊕ (lookup ([ x ] ∷ xs ∷ []))) ⟩
+      𝔜 .alg (M.`⊕ , (λ w -> g (lookup ((x ∷ []) ∷ xs ∷ []) w))) ≡⟨ 𝔜.⊕-eta (lookup ([ x ] ∷ xs ∷ [])) g ⟩
+      g [ x ] 𝔜.⊕ g xs ≡⟨ cong (g [ x ] 𝔜.⊕_) (listEquivLemma (g , homMonWit) xs) ⟩ 
+      _ ∎
+
+    listEquivLemma-β : (g : structHom 𝔏 𝔜) -> g ≡ ♯-isMonHom (g .fst ∘ [_])
+    listEquivLemma-β g = structHom≡ 𝔏 𝔜 g (♯-isMonHom (g .fst ∘ [_])) isSet𝔜 (funExt (listEquivLemma g))
+
+  listEquiv : structHom 𝔏 𝔜 ≃ (A -> 𝔜 .car)
+  listEquiv =
+    isoToEquiv (iso (λ g -> g .fst ∘ [_]) ♯-isMonHom (λ g -> funExt (𝔜.unitr ∘ g)) (sym ∘ listEquivLemma-β))
+
+module ListDef = F.Definition M.MonSig M.MonEqSig M.MonSEq
+
+list-sat : ∀ {n} {X : Type n} -> < List X , list-α > ⊨ M.MonSEq
+list-sat M.`unitl ρ = refl
+list-sat M.`unitr ρ = ++-unit-r (ρ fzero)
+list-sat M.`assocr ρ = ++-assoc (ρ fzero) (ρ fone) (ρ ftwo)
+
+listDef : ∀ {ℓ ℓ'} -> ListDef.Free ℓ ℓ' 2
+F.Definition.Free.F listDef = List
+F.Definition.Free.η listDef = [_]
+F.Definition.Free.α listDef = list-α
+F.Definition.Free.sat listDef = list-sat
+F.Definition.Free.isFree listDef isSet𝔜 satMon = (Free.listEquiv isSet𝔜 satMon) .snd
+
+list-⊥ : (List ⊥.⊥) ≃ Unit
+list-⊥ = isoToEquiv (iso (λ _ -> tt) (λ _ -> []) (λ _ -> isPropUnit _ _) lemma)
+  where
+  lemma : ∀ xs -> [] ≡ xs
+  lemma [] = refl
+  lemma (x ∷ xs) = ⊥.rec x
+
+module Membership {ℓ} {A : Type ℓ} (isSetA : isSet A) where
+  open Free {A = A} isSetHProp (M.⊔-MonStr-MonSEq ℓ)
+
+  ∈Prop : A -> List A -> hProp ℓ 
+  ∈Prop x = (λ y -> (x ≡ y) , isSetA x y) ♯
+
+  _∈_ : A -> List A -> Type ℓ
+  x ∈ xs = ∈Prop x xs .fst
+
+  isProp-∈ : (x : A) -> (xs : List A) -> isProp (x ∈ xs)
+  isProp-∈ x xs = (∈Prop x xs) .snd
+  
+  x∈xs : ∀ x xs -> x ∈ (x ∷ xs)
+  x∈xs x xs = L.inl refl
+
+  x∈[x] : ∀ x -> x ∈ [ x ]
+  x∈[x] x = x∈xs x []
+
+  ∈-∷ : ∀ x y xs -> x ∈ xs -> x ∈ (y ∷ xs)
+  ∈-∷ x y xs p = L.inr p
+
+  ∈-++ : ∀ x xs ys -> x ∈ ys -> x ∈ (xs ++ ys)
+  ∈-++ x [] ys p = p
+  ∈-++ x (a ∷ as) ys p = ∈-∷ x a (as ++ ys) (∈-++ x as ys p)
+
+  ¬∈[] : ∀ x -> (x ∈ []) -> ⊥.⊥
+  ¬∈[] x = ⊥.rec*
+
+  x∈[y]→x≡y : ∀ x y -> x ∈ [ y ] -> x ≡ y
+  x∈[y]→x≡y x y = P.rec (isSetA x y) $ ⊎.rec (idfun _) ⊥.rec*
diff --git a/Cubical/Structures/Sig.agda b/Cubical/Structures/Sig.agda
new file mode 100644
index 0000000..5ad9f06
--- /dev/null
+++ b/Cubical/Structures/Sig.agda
@@ -0,0 +1,61 @@
+{-# OPTIONS --cubical --safe --exact-split #-}
+
+module Cubical.Structures.Sig where
+
+open import Cubical.Foundations.Everything
+open import Cubical.Foundations.Equiv
+open import Cubical.Functions.Image
+open import Cubical.HITs.PropositionalTruncation as P
+open import Cubical.Data.Nat
+open import Cubical.Data.Fin
+open import Cubical.Data.List as L
+open import Cubical.Data.Sigma
+open import Cubical.Data.Empty as ⊥
+open import Cubical.Data.Sum as ⊎
+open import Cubical.Reflection.RecordEquiv
+open import Cubical.HITs.SetQuotients as Q
+open import Agda.Primitive
+
+record Sig (f a : Level) : Type ((ℓ-suc f) ⊔ (ℓ-suc a)) where
+  field
+    symbol : Type f
+    arity : symbol -> Type a
+open Sig public
+
+FinSig : (f : Level) -> Type (ℓ-suc f)
+FinSig f = Σ (Type f) \sym -> sym -> ℕ
+
+finSig : {f : Level} -> FinSig f -> Sig f ℓ-zero
+symbol (finSig σ) = σ .fst
+arity (finSig σ) = Fin ∘ σ .snd
+
+emptySig : Sig ℓ-zero ℓ-zero
+symbol emptySig = ⊥.⊥
+arity emptySig = ⊥.rec
+
+sumSig : {f a g b : Level} -> Sig f a -> Sig g b -> Sig (ℓ-max f g) (ℓ-max a b)
+symbol (sumSig σ τ) = symbol σ ⊎ symbol τ
+arity (sumSig {b = b} σ τ) (inl x) = Lift {j = b} ((arity σ) x)
+arity (sumSig {a = a} σ τ) (inr x) = Lift {j = a} ((arity τ) x)
+
+signature functor
+module _ {f a n : Level} (σ : Sig f a) where
+  sig : Type n -> Type (ℓ-max f (ℓ-max a n))
+  sig X = Σ (σ .symbol) \f -> σ .arity f -> X
+
+  sig≡ : {X : Type n} (f : σ .symbol) {i j : σ .arity f -> X}
+      -> ((a : σ .arity f) -> i a ≡ j a)
+      -> Path (sig X) (f , i) (f , j)
+  sig≡ f H = ΣPathP (refl , funExt H)
+
+  sigF : {X Y : Type n} -> (X -> Y) -> sig X -> sig Y
+  sigF h (f , i) = f , h ∘ i
+
+module _ {f n : Level} (σ : FinSig f) where
+  sigFin : (X : Type n) -> Type (ℓ-max f n)
+  sigFin X = sig (finSig σ) X
+
+  sigFin≡ : {X : Type n} (f : σ .fst) {i j : finSig σ .arity f -> X}
+         -> ((a : finSig σ .arity f) -> i a ≡ j a)
+         -> Path (sigFin X) (f , i) (f , j)
+  sigFin≡ = sig≡ (finSig σ)
diff --git a/Cubical/Structures/Str.agda b/Cubical/Structures/Str.agda
new file mode 100644
index 0000000..895bb43
--- /dev/null
+++ b/Cubical/Structures/Str.agda
@@ -0,0 +1,49 @@
+{-# OPTIONS --cubical --safe --exact-split #-}
+
+module Cubical.Structures.Str where
+
+open import Cubical.Foundations.Everything
+open import Cubical.Foundations.Equiv
+open import Cubical.Functions.Image
+open import Cubical.HITs.PropositionalTruncation as P
+open import Cubical.Data.Nat
+open import Cubical.Data.List as L
+open import Cubical.Data.Sigma
+open import Cubical.Reflection.RecordEquiv
+open import Cubical.HITs.SetQuotients as Q
+open import Agda.Primitive
+
+open import Cubical.Structures.Sig
+
+record struct {f a : Level} (n : Level) (σ : Sig f a) : Type (ℓ-max f (ℓ-max a (ℓ-suc n))) where
+  constructor <_,_>
+  field
+    car : Type n
+    alg : sig σ car -> car
+open struct public
+
+module _ {f a x y : Level} {σ : Sig f a} (𝔛 : struct x σ) (𝔜 : struct y σ) where
+  structIsHom : (h : 𝔛 .car -> 𝔜 .car) -> Type (ℓ-max f (ℓ-max a (ℓ-max x y)))
+  structIsHom h =
+    ((f : σ .symbol) -> (i : σ .arity f -> 𝔛 .car) -> 𝔜 .alg (f , h ∘ i) ≡ h (𝔛 .alg (f , i)))
+
+  structHom : Type (ℓ-max f (ℓ-max a (ℓ-max x y)))
+  structHom = Σ[ h ∈ (𝔛 .car -> 𝔜 .car) ] structIsHom h
+
+  structHom≡ : (g h : structHom) -> isSet (𝔜 .car) -> g .fst ≡ h .fst -> g ≡ h
+  structHom≡ (g-f , g-hom) (h-f , h-hom) isSetY =
+    Σ≡Prop (\fun -> isPropΠ \f -> isPropΠ \o -> isSetY (𝔜 .alg (f , fun ∘ o)) (fun (𝔛 .alg (f , o))))
+
+module _  {f a x : Level} {σ : Sig f a} (𝔛 : struct x σ) where
+  idHom : structHom 𝔛 𝔛
+  idHom = idfun _ , \f i -> refl
+
+module _  {f a x y z : Level} {σ : Sig f a} (𝔛 : struct x σ) (𝔜 : struct y σ) (ℨ : struct z σ) where
+  structHom∘ : (g : structHom 𝔜 ℨ) -> (h : structHom 𝔛 𝔜) -> structHom 𝔛 ℨ
+  structHom∘ (g-f , g-hom) (h-f , h-hom) = g-f ∘ h-f , lemma-α
+    where
+    lemma-α : structIsHom 𝔛 ℨ (g-f ∘ h-f)
+    lemma-α eqn i =
+      ℨ .alg (eqn , g-f ∘ h-f ∘ i) ≡⟨ g-hom eqn (h-f ∘ i) ⟩
+      g-f (𝔜 .alg (eqn , h-f ∘ i)) ≡⟨ cong g-f (h-hom eqn i) ⟩
+      _ ∎
diff --git a/Cubical/Structures/Tree.agda b/Cubical/Structures/Tree.agda
new file mode 100644
index 0000000..a38a746
--- /dev/null
+++ b/Cubical/Structures/Tree.agda
@@ -0,0 +1,134 @@
+{-# OPTIONS --cubical --safe --exact-split #-}
+
+module Cubical.Structures.Tree where
+
+open import Cubical.Foundations.Everything
+open import Cubical.Foundations.Equiv
+open import Cubical.Functions.Image
+open import Cubical.HITs.PropositionalTruncation as P
+open import Cubical.Data.Nat
+open import Cubical.Data.Fin
+open import Cubical.Structures.Sig
+open import Cubical.Structures.Str
+open import Cubical.Data.Nat.Order
+open import Cubical.Data.Empty as ⊥
+open import Cubical.Data.Sum as S
+open import Cubical.Foundations.Isomorphism renaming (Iso to _≅_)
+
+module _ {f a n : Level} (σ : Sig f a) where
+  data Tree (V : Type n) : Type (ℓ-max (ℓ-max f a) n) where
+    leaf : V -> Tree V
+    node : sig σ (Tree V) -> Tree V
+  open Tree
+
+
+module _  {f a n y : Level} (σ : Sig f a) {V : Type n} where
+  open import Cubical.Data.W.Indexed
+
+  S : Type n -> Type (ℓ-max f n)
+  S _ = V ⊎ (σ .symbol)
+
+  P : (V : Type n) -> S V -> Type a
+  P V (inl v) = ⊥*
+  P V (inr f) = σ .arity f
+
+  inX : ∀ V (s : S V) -> P V s -> Type n
+  inX V s p = V
+
+  RepTree : Type (ℓ-max f (ℓ-max a (ℓ-suc n)))
+  RepTree = IW S P inX V
+
+  Tree→RepTree : Tree σ V -> RepTree
+  Tree→RepTree (leaf v) = node (inl v) ⊥.rec*
+  Tree→RepTree (node (f , i)) = node (inr f) (Tree→RepTree ∘ i)
+
+  RepTree→Tree : RepTree -> Tree σ V
+  RepTree→Tree (node (inl v) subtree) = leaf v
+  RepTree→Tree (node (inr f) subtree) = node (f , RepTree→Tree ∘ subtree)
+
+  Tree→RepTree→Tree : ∀ t -> RepTree→Tree (Tree→RepTree t) ≡ t
+  Tree→RepTree→Tree (leaf v) = refl
+  Tree→RepTree→Tree (node (f , i)) j = node (f , \a -> Tree→RepTree→Tree (i a) j)
+
+  RepTree→Tree→RepTree : ∀ r -> Tree→RepTree (RepTree→Tree r) ≡ r
+  RepTree→Tree→RepTree (node (inl v) subtree) = congS (node (inl v)) (funExt (⊥.rec ∘ lower))
+  RepTree→Tree→RepTree (node (inr f) subtree) = congS (node (inr f)) (funExt (RepTree→Tree→RepTree ∘ subtree))
+
+  isoRepTree : Tree σ V ≅ RepTree
+  Iso.fun isoRepTree = Tree→RepTree
+  Iso.inv isoRepTree = RepTree→Tree
+  Iso.rightInv isoRepTree = RepTree→Tree→RepTree
+  Iso.leftInv isoRepTree = Tree→RepTree→Tree
+
+  isOfHLevelMax : ∀ {ℓ} {n m : HLevel} {A : Type ℓ}
+    -> isOfHLevel n A
+    -> isOfHLevel (max n m) A
+  isOfHLevelMax {n = n} {m = m} {A = A} p =
+    let
+      (k , o) = left-≤-max {m = n} {n = m}
+    in
+      subst (λ l -> isOfHLevel l A) o (isOfHLevelPlus k p)
+
+  isOfHLevelS : (h h' : HLevel)
+    (p : isOfHLevel (2 + h) V) (q : isOfHLevel (2 + h') (σ .symbol))
+    -> isOfHLevel (max (2 + h) (2 + h')) (S V)
+  isOfHLevelS h h' p q =
+    isOfHLevel⊎ _
+      (isOfHLevelMax {n = 2 + h} {m = 2 + h'} p)
+      (subst (λ h'' -> isOfHLevel h'' (σ .symbol)) (maxComm (2 + h') (2 + h)) (isOfHLevelMax {n = 2 + h'} {m = 2 + h} q))
+
+  isOfHLevelRepTree : ∀ {h h' : HLevel}
+    -> isOfHLevel (2 + h) V
+    -> isOfHLevel (2 + h') (σ .symbol)
+    -> isOfHLevel (max (2 + h) (2 + h')) RepTree
+  isOfHLevelRepTree {h} {h'} p q =
+    isOfHLevelSuc-IW (max (suc h) (suc h')) (λ _ -> isOfHLevelPath' _ (isOfHLevelS _ _ p q)) V
+
+  isOfHLevelTree : ∀ {h h' : HLevel}
+    -> isOfHLevel (2 + h) V
+    -> isOfHLevel (2 + h') (σ .symbol)
+    -> isOfHLevel (max (2 + h) (2 + h')) (Tree σ V)
+  isOfHLevelTree {h} {h'} p q =
+    isOfHLevelRetract (max (2 + h) (2 + h'))
+      Tree→RepTree
+      RepTree→Tree
+      Tree→RepTree→Tree
+      (isOfHLevelRepTree p q)
+
+module _ {f : Level} (σ : FinSig f) where
+  FinTree : (k : ℕ) -> Type f
+  FinTree k = Tree (finSig σ) (Fin k)
+
+module _ {f a : Level} (σ : Sig f a) where
+  algTr : ∀ {x} (X : Type x) -> struct (ℓ-max f (ℓ-max a x)) σ
+  car (algTr X) = Tree σ X
+  alg (algTr X) = node
+
+module _  {f a : Level} (σ : Sig f a) {x y} {X : Type x} (𝔜 : struct y σ) where
+  private
+    𝔛 : struct (ℓ-max f (ℓ-max a x)) σ
+    𝔛 = algTr σ X
+
+  sharp : (X -> 𝔜 .car) -> Tree σ X -> 𝔜 .car
+  sharp ρ (leaf v) = ρ v
+  sharp ρ (node (f , o)) = 𝔜 .alg (f , sharp ρ ∘ o)
+
+  eval : (X -> 𝔜 .car) -> structHom 𝔛 𝔜
+  eval h = sharp h , λ _ _ -> refl
+
+  sharp-eta : (g : structHom 𝔛 𝔜) -> (tr : Tree σ X) -> g .fst tr ≡ sharp (g .fst ∘ leaf) tr
+  sharp-eta g (leaf x) = refl
+  sharp-eta (g-f , g-hom) (node x) =
+    g-f (node x) ≡⟨ sym (g-hom (x .fst) (x .snd)) ⟩
+    𝔜 .alg (x .fst , (λ y → g-f (x .snd y))) ≡⟨ cong (λ z → 𝔜 .alg (x .fst , z)) (funExt λ y -> sharp-eta ((g-f , g-hom)) (x .snd y)) ⟩
+    𝔜 .alg (x .fst , (λ y → sharp (g-f ∘ leaf) (x .snd y)))
+    ∎
+
+  sharp-hom-eta : isSet (𝔜 .car) -> (g : structHom 𝔛 𝔜) -> g ≡ eval (g .fst ∘ leaf)
+  sharp-hom-eta p g = structHom≡ 𝔛 𝔜 g (eval (g .fst ∘ leaf)) p (funExt (sharp-eta g))
+
+  trEquiv : isSet (𝔜 .car) -> structHom 𝔛 𝔜 ≃ (X -> 𝔜 .car)
+  trEquiv isSetY = isoToEquiv (iso (\g -> g .fst ∘ leaf) eval (\_ -> refl) (sym ∘ sharp-hom-eta isSetY))
+
+  trIsEquiv : isSet (𝔜 .car) -> isEquiv (\g -> g .fst ∘ leaf)
+  trIsEquiv = snd ∘ trEquiv
diff --git a/Everything.agda b/Everything.agda
new file mode 100644
index 0000000..2a10c8a
--- /dev/null
+++ b/Everything.agda
@@ -0,0 +1,3 @@
+{-# OPTIONS --cubical --safe --exact-split #-}
+
+module Everything where
diff --git a/Experiments/Fin.agda b/Experiments/Fin.agda
new file mode 100644
index 0000000..4a4af8e
--- /dev/null
+++ b/Experiments/Fin.agda
@@ -0,0 +1,50 @@
+{-# OPTIONS --cubical --allow-unsolved-metas #-}
+
+module Experiments.Fin where
+
+open import Cubical.Foundations.Everything
+open import Cubical.Data.Sigma
+open import Cubical.Data.Fin
+open import Cubical.Data.Nat
+open import Cubical.Data.Nat.Order
+open import Cubical.Data.Sum as ⊎
+import Cubical.Data.Empty as ⊥
+
+open import Cubical.Structures.Set.Mon.Array
+import Cubical.Structures.Set.Mon.Desc as M
+import Cubical.Structures.Free as F
+open import Cubical.Structures.Sig
+open import Cubical.Structures.Str public
+open import Cubical.Structures.Tree
+open import Cubical.Structures.Eq
+open import Cubical.Structures.Arity
+import Cubical.Structures.Set.Mon.List as LM
+
+open Iso
+
+open import Agda.Builtin.Reflection hiding (Type)
+open import Agda.Builtin.String
+open import Cubical.Reflection.Base
+open import Cubical.Tactics.FunctorSolver.Solver
+open import Cubical.Tactics.Reflection
+
+private
+  variable
+    ℓ : Level
+    A : Type ℓ
+
+
+infixr 5 _∷_
+
+data FMSet (A : Type ℓ) : Type ℓ where
+  []    : FMSet A
+  _∷_   : (x : A) → (xs : FMSet A) → FMSet A
+  comm  : ∀ x y xs → x ∷ y ∷ xs ≡ y ∷ x ∷ xs
+  trunc : isSet (FMSet A)
+
+_++_ : ∀ (xs ys : FMSet A) → FMSet A
+[] ++ ys = ys
+(x ∷ xs) ++ ys = x ∷ xs ++ ys
+comm x y xs i ++ ys = comm x y (xs ++ ys) i
+trunc xs zs p q i j ++ ys = {! trunc (xs ++ ys) (zs ++ ys) (cong (_++ ys) p) (cong (_++ ys) q) !}
+  trunc (xs ++ ys) (zs ++ ys) (cong (_++ ys) p) (cong (_++ ys) q) i j
diff --git a/Experiments/FreeStr.agda b/Experiments/FreeStr.agda
new file mode 100644
index 0000000..9dc2dde
--- /dev/null
+++ b/Experiments/FreeStr.agda
@@ -0,0 +1,141 @@
+{-# OPTIONS --cubical #-}
+
+module Experiments.FreeStr where
+
+open import Cubical.Foundations.Everything
+open import Cubical.Foundations.Equiv
+open import Cubical.Functions.Image
+open import Cubical.HITs.PropositionalTruncation as P
+open import Cubical.Data.Nat
+open import Cubical.Data.FinData as F
+open import Cubical.Data.List as L
+open import Cubical.Data.List.FinData as F
+open import Cubical.Data.Sigma
+open import Cubical.Reflection.RecordEquiv
+open import Cubical.HITs.SetQuotients as Q
+open import Agda.Primitive
+
+module _ {f a e n : Level} (σ : Sig f a) (τ : EqSig e n) (ε : seq σ τ) where
+  srel : (X : Type n) -> Tree σ X -> Tree σ X -> Type {!!}
+  srel X l r = sat σ τ ε {!!}
+
+  Fr : (X : Type n) -> walg σ
+  Fr X = (Tree σ X / {!!}) , {!!}
+
+module _ {f a e n : Level} (σ : Sig f a) (τ : EqSig e n) where
+
+  evalEq : {X : Type n} -> (n : τ .name) -> (ρ : X -> τ .free n) -> Tree σ X -> Tree σ (τ .free n)
+  evalEq {X = X} n ρ = _♯ σ {X = X} {Y = TreeStr σ (τ .free n)} (leaf ∘ ρ)
+
+  eqs : {X : Type n} -> Tree σ X -> Tree σ X -> Type (ℓ-max (ℓ-max f a) (ℓ-max e n))
+  eqs {X = X} lhs rhs = (n : τ .name) (ρ : X -> τ .free n) -> evalEq n ρ lhs ≡ evalEq n ρ rhs
+
+  Free : Type n -> Type (ℓ-max (ℓ-max f a) (ℓ-max e n))
+  Free X = Tree σ X / eqs
+
+module _ {f a e n : Level} (σ : Sig f a) (τ : EqSig e n) where
+
+  t2f : {X : Type n} -> Tree σ X -> Free σ τ X
+  t2f = Q.[_]
+
+  f2t : {X : Type n} -> Free σ τ X -> ∥ Tree σ X ∥₁
+  f2t F = let p = ([]surjective F) in P.map fst p
+
+  FreeStr : (X : Type n) -> Str (ℓ-max (ℓ-max (ℓ-max f a) e) n) σ
+  car (FreeStr X) = Free σ τ X
+  ops (FreeStr X) f o = {!!}
+  isSetStr (FreeStr X) = {!!}
+
+ℕ-MonStrEq : Eqs ℓ-zero MonSig ℕ-MonStr
+Eqs.name ℕ-MonStrEq = MonEq
+Eqs.free ℕ-MonStrEq = MonEqFree
+Eqs.lhs ℕ-MonStrEq = MonEqLhs
+Eqs.rhs ℕ-MonStrEq = MonEqRhs
+Eqs.equ ℕ-MonStrEq unitl = refl
+Eqs.equ ℕ-MonStrEq unitr = funExt \v -> +-zero (v zero)
+Eqs.equ ℕ-MonStrEq assocr = funExt \v -> sym (+-assoc (v zero) (v one) (v two))
+
+Free-MonStr : (X : Type) -> Str ℓ-zero MonSig
+Str.car (Free-MonStr X) = Free MonSig X
+Str.ops (Free-MonStr X) e f = op e f
+Str.ops (Free-MonStr X) ⊕ f = op ⊕ f
+Str.isSetStr (Free-MonStr X) = isSetStr
+
+
+Sig : (f a : Level) -> Type (ℓ-max (ℓ-suc f) (ℓ-suc a))
+Sig f a = Σ[ F ∈ Type f ] (F -> Type a)
+
+Op : {a x : Level} -> Type a -> Type x -> Type (ℓ-max a x)
+Op A X = (A -> X) -> X
+
+Str : {f a : Level} (x : Level) -> Sig f a -> Type (ℓ-max (ℓ-max f a) (ℓ-suc x))
+Str {f} {a} x (F , ar) = Σ[ X ∈ Type x ] ((f : F) -> Op (ar f) X)
+
+MonSig : Sig ℓ-zero ℓ-zero
+MonSig = MonDesc , MonAr
+
+MonStr = Str ℓ-zero MonSig
+
+ℕ-MonStr : MonStr
+ℕ-MonStr = ℕ , \{ e f -> 0
+                ; ⊕ f -> f zero + f (suc zero) }
+--
+
+module FreeStr {f a : Level} (σ @ (F , ar) : Sig f a) where
+
+  data Free {x} (X : Type x) : Type {!!} where
+    η : X -> Free X
+    op : (f : F) -> Op (ar f) (Free X) -> Free X
+    isSetStr : isSet (Free X)
+
+Op : (a : Level) -> ℕ -> Type a -> Type a
+Op a n A = (Fin n -> A) -> A
+
+Str : {f : Level} (a : Level) -> Sig f -> Type {!!}
+Str {f} a (F , ar) = Σ[ A ∈ Type a ] ((f : F) -> Op a (ar f) A)
+
+MonSig : Sig ℓ-zero
+MonSig = Fin 2 , lookup (0 ∷ 2 ∷ [])
+
+ℕ-MonStr : Str ℓ-zero MonSig
+ℕ-MonStr = ℕ , F.elim {!!} (\_ -> 0) {!!}
+
+F.elim (\{k} f -> Op ℓ-zero {!!} ℕ) {!!} {!!}
+(f : Fin 2) → (Fin (lookup (0 ∷ 2 ∷ []) f) → ℕ) → ℕ
+(f : fst MonSig) → Op ℓ-zero (snd MonSig f) ℕ
+
+F.elim (\f -> Op ℓ-zero (rec 0 2 f) ℕ) (\_ -> 0) (\_ -> {!!})
+
+record FreeS (ℓ : Level) (S : Type ℓ → Type ℓ') : Type (ℓ-max (ℓ-suc ℓ) ℓ') where
+  field
+    F : Type ℓ -> Type ℓ
+    F-S : (A : Type ℓ) -> S (F A)
+    η : (A : Type ℓ) -> A -> F A
+
+freeS : (S : Type ℓ -> Type ℓ') -> FreeS ℓ S
+monad T, T-alg
+
+monads on hSet
+
+record Monad {ℓ : Level} : Type (ℓ-suc ℓ) where
+  field
+    T : Type ℓ -> Type ℓ
+    map : ∀ {A B} -> (A -> B) -> T A -> T B
+    η : ∀ {A} -> A -> T A
+    μ : ∀ {A} -> T (T A) -> T A
+
+record T-Alg {ℓ} (T : Monad {ℓ}) : Type (ℓ-suc ℓ) where
+  module T = Monad T
+  field
+    el : Type ℓ
+    alg : T.T el -> el
+    unit : alg ∘ T.η ≡ idfun _
+    action : alg ∘ T.map alg ≡ alg ∘ T.μ
+
+record T-AlgHom {ℓ} {T : Monad {ℓ}} (α β : T-Alg T) : Type (ℓ-suc ℓ) where
+  module T = Monad T
+  module α = T-Alg α
+  module β = T-Alg β
+  field
+    f : α.el -> β.el
+    f-coh : β.alg ∘ T.map f ≡ f ∘ α.alg
diff --git a/Experiments/FreeStrFin.agda b/Experiments/FreeStrFin.agda
new file mode 100644
index 0000000..19e3f49
--- /dev/null
+++ b/Experiments/FreeStrFin.agda
@@ -0,0 +1,113 @@
+{-# OPTIONS --cubical --type-in-type #-}
+
+module _ where
+
+open import Cubical.Foundations.Everything
+open import Cubical.Foundations.Equiv
+open import Cubical.Functions.Image
+open import Cubical.HITs.PropositionalTruncation as P
+open import Cubical.Data.Nat
+open import Cubical.Data.FinData as F
+open import Cubical.Data.List as L
+open import Cubical.Data.List.FinData as F
+open import Cubical.Data.Sigma
+open import Cubical.Reflection.RecordEquiv
+open import Cubical.HITs.SetQuotients as Q
+open import Agda.Primitive
+
+record Sig : Type₁ where
+  field
+    symbol : Type
+    arity : symbol -> ℕ
+open Sig public
+
+module _ (σ : Sig) where
+  sig : Type -> Type
+  sig X = Σ (σ .symbol) \f -> Fin (σ .arity f) -> X
+
+  sigF : {X Y : Type} -> (X -> Y) -> sig X -> sig Y
+  sigF h (f , i) = f , h ∘ i
+
+module _ (σ : Sig) where
+  struct : Type₁
+  struct = Σ Type (\X -> sig σ X -> X)
+
+  structIsHom : (𝔛 𝔜 : struct) (h : 𝔛 .fst -> 𝔜 .fst) -> Type
+  structIsHom (X , α) (Y , β) h =
+    ((f , i) : sig σ X) -> β (f , h ∘ i) ≡ h (α (f , i))
+
+  structHom : struct -> struct -> Type
+  structHom 𝔛 𝔜 = Σ[ h ∈ (𝔛 .fst -> 𝔜 .fst) ] structIsHom 𝔛 𝔜 h
+
+record EqSig : Type₁ where
+  field
+    name : Type
+    free : name -> Type
+open EqSig public
+
+data Tree (σ : Sig) (V : Type) : Type where
+  leaf : V -> Tree σ V
+  node : sig σ (Tree σ V) -> Tree σ V
+
+module _ {σ : Sig} (𝔛 : struct σ) where
+  ext : {V : Type} -> (V -> 𝔛 .fst) -> Tree σ V -> 𝔛 .fst
+  ext h (leaf v) = h v
+  ext h (node (f , i)) = 𝔛 .snd (f , (ext h ∘ i))
+
+  extHom : {V : Type} -> (V -> 𝔛 .fst) -> structHom σ (Tree σ V , node) 𝔛
+  extHom h = ext h , \_ → refl
+
+module _ (σ : Sig) (τ : EqSig) where
+  eqs : Type
+  eqs = (e : τ .name) -> Tree σ (τ .free e) × Tree σ (τ .free e)
+
+module _ {σ : Sig} {τ : EqSig} where
+  infix 30 _⊨_
+  _⊨_ : struct σ -> eqs σ τ -> Type
+  𝔛 ⊨ ε = (e : τ .name) (ρ : τ .free e -> 𝔛 .fst)
+       -> ext 𝔛 ρ (ε e .fst) ≡ ext 𝔛 ρ (ε e .snd)
+
+module Free1 (σ : Sig) (τ : EqSig) (ε : eqs σ τ) where
+
+  congruence relation generated by equations
+  data _≈_ {X : Type} : Tree σ X -> Tree σ X -> Type₁ where
+    ≈-refl : ∀ t -> t ≈ t
+    ≈-sym : ∀ t s -> t ≈ s -> s ≈ t
+    ≈-trans : ∀ t s r -> t ≈ s -> s ≈ r -> t ≈ r
+    ≈-cong : (f : σ .symbol) -> {t s : Fin (σ .arity f) -> Tree σ X}
+          -> ((a : Fin (σ .arity f)) -> t a ≈ s a)
+          -> node (f , t) ≈ node (f , s)
+    ≈-eqs : (𝔜 : struct σ) (ϕ : 𝔜 ⊨ ε)
+         -> (e : τ .name) (ρ : X -> 𝔜 .fst)
+         -> ∀ t s -> ext 𝔜 ρ t ≡ ext 𝔜 ρ t
+         -> t ≈ s
+
+  Free : Type -> Type₁
+  Free X = Tree σ X / _≈_
+
+  test1 : {X : Type} (n : ℕ) -> (Fin n -> Free X) -> (Fin n -> Tree σ X)
+  test1 zero i ()
+  test1 (suc n) i zero = {!!} ??
+  test1 (suc n) i (suc k) = test1 n (i ∘ weakenFin) k
+
+  freeAlg : (X : Type) -> sig σ (Free X) -> Free X
+  freeAlg X (f , i) = Q.[ node (f , {!!}) ] needs choice?
+
+  freeStruct : (X : Type) -> struct σ
+  freeStruct X = Free X , freeAlg X
+
+module Free2 (σ : Sig) (τ : EqSig) (ε : eqs σ τ) where
+
+  mutual
+    data Free (X : Type) : Type where
+      η : X -> Free X
+      α : sig σ (Free X) -> Free X
+      sat : (Free X , α) ⊨ ε
+
+    ext 𝔜 (sharp ϕ h ∘ ρ) (ε₁ e .snd) !=
+    sharp ϕ h (ext (Free X , α) ρ (ε₁ e .snd))
+
+    sharp : {X : Type} {𝔜 : struct σ} (ϕ : 𝔜 ⊨ ε) (h : X -> 𝔜 .fst) -> Free X -> 𝔜 .fst
+    sharp ϕ h (η x) = h x
+    sharp {𝔜 = 𝔜} ϕ h (α (f , o)) = 𝔜 .snd (f , (sharp ϕ h ∘ o))
+    sharp ϕ h (sat e ρ i) = ϕ e (sharp ϕ h ∘ ρ) {!i!}
diff --git a/Experiments/ListArray.agda b/Experiments/ListArray.agda
new file mode 100644
index 0000000..6133367
--- /dev/null
+++ b/Experiments/ListArray.agda
@@ -0,0 +1,63 @@
+{-# OPTIONS --cubical #-}
+
+module Experiments.ListArray where
+
+open import Cubical.Foundations.Everything
+open import Cubical.Data.Sigma
+open import Cubical.Data.List renaming (_∷_ to _∷ₗ_)
+open import Cubical.Data.Fin
+open import Cubical.Data.Nat
+open import Cubical.Data.Nat.Order
+open import Cubical.Data.Sum as ⊎
+open import Cubical.Induction.WellFounded
+import Cubical.Data.Empty as ⊥
+
+import Cubical.Structures.Set.Mon.Desc as M
+import Cubical.Structures.Free as F
+open import Cubical.Structures.Sig
+open import Cubical.Structures.Str public
+open import Cubical.Structures.Tree
+open import Cubical.Structures.Eq
+open import Cubical.Structures.Arity
+
+open import Cubical.Structures.Set.Mon.Array
+open import Cubical.Structures.Set.Mon.List
+
+open Iso
+
+private
+  variable
+    ℓ : Level
+    A : Type ℓ
+
+an-array : Array ℕ
+an-array = 3 , lemma
+  where
+  lemma : Fin 3 -> ℕ
+  lemma (0 , p) = 5
+  lemma (1 , p) = 9
+  lemma (2 , p) = 2
+  lemma (suc (suc (suc n)) , p) = ⊥.rec (¬-<-zero (<-k+-cancel p))
+
+module MonDef = F.Definition M.MonSig M.MonEqSig M.MonSEq
+
+want : List ℕ
+want = 5 ∷ₗ 9 ∷ₗ 2 ∷ₗ []
+
+to-list : structHom < Array ℕ , array-α > < List ℕ , list-α >
+to-list = MonDef.Free.ext arrayDef (isOfHLevelList 0 isSetℕ) list-sat [_]
+
+_ : to-list .fst an-array ≡ want
+_ = refl
+
+to-list' : structHom < Array ℕ , MonDef.Free.α (arrayDef' {ℓ' = ℓ-zero}) > < List ℕ , list-α >
+to-list' = MonDef.Free.ext arrayDef' (isOfHLevelList 0 isSetℕ) list-sat [_]
+
+_ : to-list' .fst an-array ≡ want
+_ = refl
+
+to-list'' : Array ℕ -> List ℕ
+to-list'' = MonDef.freeIso arrayDef listDef (isSetArray isSetℕ) (isOfHLevelList 0 isSetℕ) .fun
+
+_ : to-list'' an-array ≡ want
+_ = refl
diff --git a/Experiments/ListMon.agda b/Experiments/ListMon.agda
new file mode 100644
index 0000000..1711710
--- /dev/null
+++ b/Experiments/ListMon.agda
@@ -0,0 +1,112 @@
+{-# OPTIONS --cubical #-}
+
+module Experiments.ListMon where
+
+open import Cubical.Foundations.Everything
+open import Cubical.Data.Sigma
+import Mon as M
+
+data List (A : Type) : Type where
+  [] : List A
+  _∷_ : (a : A) -> List A -> List A
+  trunc : isSet (List A)
+
+module elimListSet {p : Level} {A : Type} (P : List A -> Type p)
+                   ([]* : P [])
+                   (_∷*_ : (x : A) {xs : List A} -> P xs -> P (x ∷ xs))
+                   (trunc* : {xs : List A} -> isSet (P xs))
+                   where
+  f : (xs : List A) -> P xs
+  f [] = []*
+  f (x ∷ xs) = x ∷* f xs
+  f (trunc xs ys p q i j) =
+    isOfHLevel→isOfHLevelDep 2 (\xs -> trunc* {xs = xs}) (f xs) (f ys) (cong f p) (cong f q) (trunc xs ys p q) i j
+
+module elimListProp {p : Level} {A : Type} (P : List A -> Type p)
+                   ([]* : P [])
+                   (_∷*_ : (x : A) {xs : List A} -> P xs -> P (x ∷ xs))
+                   (trunc* : {xs : List A} -> isProp (P xs))
+                   where
+  f : (xs : List A) -> P xs
+  f = elimListSet.f P []* _∷*_ (isProp→isSet trunc*)
+
+[_] : {A : Type} -> A -> List A
+[ a ] = a ∷ []
+
+_⊕_ : {A : Type} -> List A -> List A -> List A
+[] ⊕ ys = ys
+(x ∷ xs) ⊕ ys = x ∷ (xs ⊕ ys)
+trunc xs ys p q i j ⊕ zs = trunc (xs ⊕ zs) (ys ⊕ zs) (cong (_⊕ zs) p) (cong (_⊕ zs) q) i j
+
+unitl : {A : Type} -> ∀ (m : List A) -> [] ⊕ m ≡ m
+unitl _ = refl
+
+unitr : {A : Type} -> ∀ (m : List A) -> m ⊕ [] ≡ m
+unitr =
+  elimListProp.f _
+    refl
+    (\x p -> cong (x ∷_) p) 
+    (trunc _ _)
+
+assocr : {A : Type} -> ∀ (m n o : List A) -> (m ⊕ n) ⊕ o ≡ m ⊕ (n ⊕ o)
+assocr =
+  elimListProp.f _
+    (λ _ _ -> refl)
+    (λ x p n o -> cong (x ∷_) (p n o))
+    (isPropΠ λ _ -> isPropΠ λ _ -> trunc _ _)
+
+listMon : (A : Type) -> M.MonStruct (List A)
+M.MonStruct.e (listMon _) = []
+M.MonStruct._⊕_ (listMon _) = _⊕_
+M.MonStruct.unitl (listMon _) = unitl
+M.MonStruct.unitr (listMon _) = unitr
+M.MonStruct.assocr (listMon _) = assocr
+M.MonStruct.trunc (listMon _) = trunc
+
+module _ {A B : Type} (M : M.MonStruct B) where
+  module B = M.MonStruct M
+  module _ (f : A -> B) where
+
+    _♯ : List A -> B
+    (_♯) [] = B.e
+    (_♯) (x ∷ xs) = f x B.⊕ (_♯) xs
+    (_♯) (trunc m n p q i j) = B.trunc ((_♯) m) ((_♯) n) (cong (_♯) p) (cong (_♯) q) i j
+
+    _♯-isMonHom : M.isMonHom (listMon A) M _♯
+    M.isMonHom.f-e _♯-isMonHom = refl
+    M.isMonHom.f-⊕ _♯-isMonHom =
+      elimListProp.f _
+        (λ b -> sym (B.unitl (b ♯)))
+        (λ x {xs} p b ->
+          f x B.⊕ ((xs ⊕ b) ♯) ≡⟨ cong (f x B.⊕_) (p b) ⟩
+          f x B.⊕ ((xs ♯) B.⊕ (b ♯)) ≡⟨ sym (B.assocr (f x) _ _) ⟩
+          (f x B.⊕ (xs ♯)) B.⊕ (b ♯)
+          ∎
+        )
+        (isPropΠ λ _ -> B.trunc _ _)
+       
+  private
+    listMonEquivLemma : (f : List A -> B) -> M.isMonHom (listMon A) M f -> (x : List A) -> f x ≡ ((f ∘ [_]) ♯) x
+    listMonEquivLemma f homMonWit = elimListProp.f _
+      (M.isMonHom.f-e homMonWit)
+      (λ x {xs} p ->
+        f ([ x ] ⊕ xs) ≡⟨ M.isMonHom.f-⊕ homMonWit [ x ] xs ⟩
+        f [ x ] B.⊕ f xs ≡⟨ cong (f [ x ] B.⊕_) p ⟩
+        (f ∘ [_]) x B.⊕ ((f ∘ [_]) ♯) xs
+        ∎)
+      (B.trunc _ _)
+    
+    listMonEquivLemma-β : (f : List A -> B) -> M.isMonHom (listMon A) M f -> ((f ∘ [_]) ♯) ≡ f
+    listMonEquivLemma-β f homMonWit i x = listMonEquivLemma f homMonWit x (~ i)
+
+  listMonEquiv : M.MonHom (listMon A) M ≃ (A -> B)
+  listMonEquiv = isoToEquiv
+    ( iso
+      (λ (f , ϕ) -> f ∘ [_])
+      (λ f -> (f ♯) , (f ♯-isMonHom))
+      (λ f i x -> B.unitr (f x) i)
+      (λ (f , homMonWit) -> Σ≡Prop M.isMonHom-isProp (listMonEquivLemma-β f homMonWit))
+    )
+
+  listMonIsEquiv : isEquiv {A = M.MonHom (listMon A) M} (\(f , ϕ) -> f ∘ [_])
+  listMonIsEquiv = listMonEquiv .snd
diff --git a/Experiments/Mon.agda b/Experiments/Mon.agda
new file mode 100644
index 0000000..295e512
--- /dev/null
+++ b/Experiments/Mon.agda
@@ -0,0 +1,44 @@
+{-# OPTIONS --cubical #-}
+
+module Experiments.Mon where
+
+open import Cubical.Foundations.Everything
+open import Cubical.Data.Sigma
+open import Cubical.Functions.FunExtEquiv 
+open import Agda.Primitive
+
+record MonStruct (A : Type) : Type where
+  field
+    e : A
+    _⊕_ : A -> A -> A
+    unitl : ∀ m -> e ⊕ m ≡ m
+    unitr : ∀ m -> m ⊕ e ≡ m
+    assocr : ∀ m n o -> (m ⊕ n) ⊕ o ≡ m ⊕ (n ⊕ o)
+    trunc : isSet A
+
+record isMonHom {A B : Type} (M : MonStruct A) (N : MonStruct B) (f : A -> B) : Type where
+  pattern
+  inductive
+  constructor monHom
+
+  module M = MonStruct M
+  module N = MonStruct N
+
+  field
+    f-e : f (M.`e) ≡ N.e
+    f-⊕ : ∀ a b -> f (a M.`⊕ b) ≡ f a N.⊕ f b
+
+  f-unitl : ∀ a -> cong f (M.unitl a) ≡ f-⊕ M.`e a ∙ cong (N._⊕ f a) f-e ∙ N.unitl (f a)
+  f-unitl a = N.trunc _ _ _ _
+
+module _ {A B : Type} {M : MonStruct A} {N : MonStruct B} (f : A -> B) where
+  module M = MonStruct M
+  module N = MonStruct N
+
+  isMonHom-isProp : isProp (isMonHom M N f)
+  isMonHom-isProp (monHom x-e x-⊕) (monHom y-e y-⊕) =
+    cong₂ monHom (N.trunc _ _ x-e y-e) ((isPropΠ λ _ → isPropΠ (λ _ → N.trunc _ _)) x-⊕ y-⊕)
+
+MonHom : {A B : Type} (M : MonStruct A) (N : MonStruct B) -> Type
+MonHom {A} {B} M N = Σ[ f ∈ (A -> B) ] isMonHom M N f
+  
\ No newline at end of file
diff --git a/Experiments/Norm.agda b/Experiments/Norm.agda
new file mode 100644
index 0000000..a8e50d3
--- /dev/null
+++ b/Experiments/Norm.agda
@@ -0,0 +1,67 @@
+{-# OPTIONS --cubical --safe --exact-split #-}
+
+open import Agda.Primitive
+
+TODO: Fix levels in Free so this isn't necessary
+module Experiments.Norm {ℓ : Level} {A : Set ℓ} where
+
+open import Cubical.Foundations.Everything
+open import Cubical.Functions.Embedding
+open import Cubical.Data.Sigma
+open import Cubical.Data.Fin
+open import Cubical.Data.Nat
+open import Cubical.Data.Nat.Order
+open import Cubical.Data.Sum as ⊎
+open import Cubical.Induction.WellFounded
+import Cubical.Data.Empty as ⊥
+open import Cubical.HITs.SetQuotients as Q
+
+import Cubical.Structures.Set.CMon.Desc as M
+import Cubical.Structures.Free as F
+
+open import Cubical.Structures.Set.CMon.Free as F
+open import Cubical.Structures.Set.CMon.QFreeMon
+open import Cubical.Structures.Set.CMon.Bag
+open import Cubical.Structures.Set.CMon.SList as S
+
+module CMonDef = F.Definition M.CMonSig M.CMonEqSig M.CMonSEq
+
+module FCM = CMonDef.Free
+
+ηᵇ : A -> Bag A
+ηᵇ = FCM.η bagFreeDef
+
+ηˢ : A -> SList A
+ηˢ = FCM.η {ℓ' = ℓ} slistDef
+
+ηˢ♯ : structHom < Bag A , FCM.α bagFreeDef > < SList A , FCM.α {ℓ' = ℓ} slistDef >
+ηˢ♯ = FCM.ext bagFreeDef S.trunc (FCM.sat {ℓ' = ℓ} S.slistDef) ηˢ
+
+ηᵇ♯ : structHom < SList A , FCM.α {ℓ' = ℓ} slistDef > < Bag A , FCM.α bagFreeDef >
+ηᵇ♯ = FCM.ext slistDef Q.squash/ (FCM.sat bagFreeDef) (FCM.η bagFreeDef)
+
+ηᵇ♯∘ηˢ♯ : structHom < Bag A , FCM.α bagFreeDef > < Bag A , FCM.α bagFreeDef >
+ηᵇ♯∘ηˢ♯ = structHom∘ < Bag _ , FCM.α bagFreeDef > < SList _ , FCM.α {ℓ' = ℓ} slistDef > < Bag _ , FCM.α bagFreeDef > ηᵇ♯ ηˢ♯
+
+ηᵇ♯∘ηˢ♯-β : ηᵇ♯∘ηˢ♯ .fst ∘ ηᵇ ≡ ηᵇ
+ηᵇ♯∘ηˢ♯-β =
+    ηᵇ♯ .fst ∘ ηˢ♯ .fst ∘ ηᵇ
+  ≡⟨ cong (ηᵇ♯ .fst ∘_) (FCM.ext-η bagFreeDef S.trunc (FCM.sat {ℓ' = ℓ} slistDef) ηˢ) ⟩
+    ηᵇ♯ .fst ∘ ηˢ
+  ≡⟨ FCM.ext-η slistDef Q.squash/ (FCM.sat bagFreeDef) ηᵇ ⟩
+    ηᵇ
+  ∎
+
+ηᵇ♯∘ηˢ♯-η : ηᵇ♯∘ηˢ♯ ≡ idHom < Bag A , FCM.α bagFreeDef >
+ηᵇ♯∘ηˢ♯-η = FCM.hom≡ bagFreeDef Q.squash/ (FCM.sat bagFreeDef) ηᵇ♯∘ηˢ♯ (idHom _) ηᵇ♯∘ηˢ♯-β
+
+𝔫𝔣 : Bag A -> SList A
+𝔫𝔣 = ηˢ♯ .fst
+
+𝔫𝔣-inj : {as bs : Bag A} -> 𝔫𝔣 as ≡ 𝔫𝔣 bs -> as ≡ bs
+𝔫𝔣-inj {as} {bs} p = sym (funExt⁻ (cong fst ηᵇ♯∘ηˢ♯-η) as) ∙ cong (ηᵇ♯ .fst) p ∙ funExt⁻ (cong fst ηᵇ♯∘ηˢ♯-η) bs
+
+norm : isEmbedding 𝔫𝔣
+norm = injEmbedding trunc 𝔫𝔣-inj
+
+also equivalence
diff --git a/Experiments/TList.agda b/Experiments/TList.agda
new file mode 100644
index 0000000..ada4120
--- /dev/null
+++ b/Experiments/TList.agda
@@ -0,0 +1,58 @@
+{-# OPTIONS --cubical #-}
+
+module Experiments.TList where
+
+open import Cubical.Foundations.Everything
+open import Cubical.Data.List
+open import Cubical.HITs.SetTruncation as S
+
+MList : ∀ {ℓ} -> Type ℓ -> Type ℓ
+MList A = ∥ List A ∥₂
+
+variable
+  ℓ : Level
+  A B C : Type ℓ
+
+inc : (A -> List B) -> (A -> MList B)
+inc = ∣_∣₂ ∘_
+
+eta : A -> MList A
+eta = inc [_]
+
+map₂ : (A -> B -> C) -> ∥ A ∥₂ -> ∥ B ∥₂ -> ∥ C ∥₂
+map₂ f ∣ a ∣₂ = S.map (f a)
+map₂ f (squash₂ a a' p q i j) = {!!}
+
+fmap : (A -> B) -> ∥ A ∥₂ -> ∥ B ∥₂
+fmap f ∣ a ∣₂ = ∣ f a ∣₂
+fmap f (squash₂ a b p q i j) =
+  squash₂ (fmap f a) (fmap f b) (cong (fmap f) p) (cong (fmap f) q) i j
+
+module _ (P : List A -> Type ℓ)
+         (h : (xs : List A) -> P xs)
+         (trunc : {xs : List A} -> isSet (P xs))
+         where
+  f : (xs : MList A) -> P {!!}
+  f = {!!}
+
+e : MList A
+e = ∣ [] ∣₂
+
+_⊕_ : MList A -> MList A -> MList A
+_⊕_ = map₂ _++_
+
+map-inc : ∀ {f : A -> B} {a} -> S.map f (∣ a ∣₂) ≡ ∣ f a ∣₂
+map-inc = refl
+
+map₂-inc : ∀ {f : A -> B -> C} {a b} -> map₂ f a ∣ b ∣₂ ≡ S.map (\a -> f a b) a
+map₂-inc {a = a} = {!!}
+
+congmap : ((a b : A) -> f a ≡ g b)
+        -> (a' b' : ∥ A ∥₂) -> map f a' ≡ map g b'
+
+unitr : (xs : MList A) -> xs ⊕ e ≡ xs
+unitr xs =
+  map₂ _++_ xs e ≡⟨ {!!} ⟩
+  S.map (\xs -> xs ⊕ e) e  ≡⟨ {!!} ⟩
+  idfun _ xs
+  ∎
diff --git a/index.agda b/index.agda
new file mode 100644
index 0000000..8fc3dca
--- /dev/null
+++ b/index.agda
@@ -0,0 +1,49 @@
+{-# OPTIONS --cubical --safe --exact-split #-}
+
+module index where
+
+an organised list of modules:
+--
+universal algebra
+algebraic theories and 2-theories
+import Cubical.Structures.Sig
+import Cubical.Structures.Str
+import Cubical.Structures.Eq
+import Cubical.Structures.Coh
+
+free algebras
+import Cubical.Structures.Free
+
+free monoids on sets
+import Cubical.Structures.Set.Mon.Free
+import Cubical.Structures.Set.Mon.List
+import Cubical.Structures.Set.Mon.Array
+
+free commutative monoids on sets
+import Cubical.Structures.Set.CMon.Free
+import Cubical.Structures.Set.CMon.SList
+import Cubical.Structures.Set.CMon.CList
+import Cubical.Structures.Set.CMon.PList
+import Cubical.Structures.Set.CMon.QFreeMon
+import Cubical.Structures.Set.CMon.Bag
+
+free monoidal groupoids on groupoids
+import Cubical.Structures.Gpd.Mon.Free
+import Cubical.Structures.Gpd.Mon.List
+
+free symmetric monoidal groupoids on groupoids
+import Cubical.Structures.Gpd.SMon.Free
+import Cubical.Structures.Gpd.SMon.SList
+
+sorting and order equivalence
+import Cubical.Structures.Set.CMon.SList.Sort
+
+combinatorics properties
+import Cubical.Structures.Set.CMon.SList.Seely
+
+useful experiments
+import Experiments.Norm
+
+an exhaustive list of all modules:
+--
+import Everything