Reverse output order for rendering ReplHole code generation

README.md

@@ -135,14 +135,6 @@ aka a let binding without an "in" clause
 ["addTwo", {"x": ["S", ["S", "x"]]}]
 ```
 
-### Execute REPL within context
-
-(this is still a bit buggy, and may create an invalid REPL)
-
-```json
-[{"x": []}, 12]
-```
-
 ### Multi-argument functions
 
 ```json

fibb.json

@@ -1,5 +1,12 @@
 [
-	"fibb",
+	"slow_fibb",
+	{
+		"0": 0,
+		"1": 1,
+		"n": ["+", ["slow_fibb", ["+", "n", -2]], ["slow_fibb", ["+", "n", -1]]]
+	},
+
+	"fast_fibb",
 	[
 		"fibb_helper",
 		{

ir.py

@@ -11,6 +11,12 @@ import types_
 Expression: TypeAlias = 'MonoFunc | Application | Int | Variable | Builtin | LetBinding | ReplHole | Switch'
 Value: TypeAlias = 'MonoFunc | Int | Builtin | ReplHole'
 
+dollar_count: int = 0
+def mk_dollar() -> str:
+	global dollar_count
+	dollar_count += 1
+	return f'${dollar_count-1}'
+
 @dataclass(frozen=True)
 class ReplHole:
 	typ_bindings: types_.Context
@@ -34,7 +40,7 @@ class ReplHole:
 	def render(self) -> str:
 		return '\n'.join(
 			f'const {var_name} = ({var_expr.codegen()});'
-			for (var_name, var_expr) in self.val_bindings
+			for (var_name, var_expr) in self.val_bindings[::-1]
 			if var_name not in types_.BUILTINS_CONTEXT
 		)
 
@@ -120,18 +126,20 @@ class MonoFunc:
 					case [(var, [])]: # Binds a single variable to the entire input
 						return Ok(MonoFunc(var, body))
 
+		local_variable = mk_dollar()
+
 		# If those special cases fail, we eliminate the pattern matching to produce a
 		# single body:
 		match_trees = tuple( # Construct a match tree for each possible branch
 			pattern.match_tree(
 				EMPTY_STRUCT_PATH,
-				LeafNode.from_value(bindings_to_lets(pattern.bindings(), Variable('$'), body))
+				LeafNode.from_value(bindings_to_lets(pattern.bindings(), Variable(local_variable), body))
 			)
 			for (pattern, body) in forms
 		)
 		unified_match_tree = merge_all_trees(match_trees) # Unify all the trees
-		compiled_tree = compile_tree(unified_match_tree, Variable('$')) # Turn each tree into IR
-		return compiled_tree <= p(MonoFunc, '$')
+		compiled_tree = compile_tree(unified_match_tree, Variable(local_variable)) # Turn each tree into IR
+		return compiled_tree <= p(MonoFunc, local_variable)
 
 	def try_apply(self, v: Expression) -> Option[Expression]:
 		return Some(self.body.subst(v, self.arg))
@@ -222,7 +230,7 @@ class Application:
 			return unwrap_opt(self.first.try_apply(self.arg)).codegen()
 		else:
 			match self.first:
-				case Application(Builtin(Builtin.BB_PLUS), addend1):
+				case Application(Builtin(Builtin.BB_PLUS()), addend1):
 					return f'({addend1.codegen()} + {self.arg.codegen()})'
 				case Builtin(Builtin.BB_PLUS_CONST(n)):
 					return f'({self.arg.codegen()}{n:+})'

opt.py

@@ -10,8 +10,9 @@ Optimization: TypeAlias = Callable[[Expression], Option[Expression]]
 def eliminate_single_let(expr: Expression) -> Option[Expression]:
 	match expr:
 		case LetBinding(lhs, rhs, body):
-			if count_uses(lhs, body) <= 1:
-				# RHS is used at most once i nthe body
+			rhs_is_simple = isinstance(rhs, Int | Variable | Builtin)
+			if count_uses(lhs, body) <= 1 or rhs_is_simple:
+				# RHS is used at most once i nthe body or replication wouldnt be costly
 				if count_uses(lhs, rhs) > 0:
 					# RHS is recursive
 					if not isinstance(body, Variable):