From 224ec0bc9841a342c9f7aa5a295acf9e0bf5ebf6 Mon Sep 17 00:00:00 2001
From: Emi Simpson <emi@alchemi.dev>
Date: Wed, 8 Mar 2023 11:50:03 -0500
Subject: [PATCH] Add a repl

---
 genir.py       |  5 ++---
 ir.py          | 10 ++++++----
 main.py        | 12 ++++++++++--
 silly_thing.py | 28 +++++++++++++++++++++++++++-
 4 files changed, 45 insertions(+), 10 deletions(-)

diff --git a/genir.py b/genir.py
index d0891d1..1698029 100644
--- a/genir.py
+++ b/genir.py
@@ -1,9 +1,8 @@
 from emis_funky_funktions import *
 from typing import *
 
-from silly_thing import *
 from pattern import lex_and_parse_pattern
-from ir import Function, Application, Int, Variable, LetBinding, Unit
+from ir import Expression, Function, Application, Int, Variable, LetBinding, ReplHole
 
 import json
 
@@ -23,7 +22,7 @@ def json_to_ir(j: JsonType) -> Expression:
 			case [first, *rest]:
 				return Application(json_to_ir(first), [json_to_ir(a) for a in rest])
 			case []:
-				return Unit()
+				return ReplHole()
 		raise Exception('Unreachable')
 	else:
 		return Int(j)
\ No newline at end of file
diff --git a/ir.py b/ir.py
index b2ed306..086c43d 100644
--- a/ir.py
+++ b/ir.py
@@ -3,7 +3,7 @@ from emis_funky_funktions import *
 from typing import Mapping, Sequence, Tuple, TypeAlias
 
 
-Expression: TypeAlias = 'Function | Application | Int | Variable | Builtin | LetBinding | Unit'
+Expression: TypeAlias = 'Function | Application | Int | Variable | Builtin | LetBinding | ReplHole'
 Pattern: TypeAlias = 'NamePattern | IntPattern | SPattern | IgnorePattern'
 
 @dataclass(frozen=True)
@@ -119,9 +119,11 @@ class SPattern:
 		return 'S ' + repr(self.pred)
 
 @dataclass(frozen=True)
-class Unit:
+class ReplHole:
+	bindings: Sequence[Tuple[str, Expression]] = tuple()
+
 	def subst(self, expression: Expression, variable: str) -> Expression:
-		return self
+		return ReplHole((*self.bindings, (variable, expression)))
 
 	def is_value(self) -> bool:
 		return True
@@ -280,7 +282,7 @@ class Application:
 									body = rest
 									match body:
 										case []:
-											return Some(Unit())
+											return Some(ReplHole())
 										case [body_first, *body_rest]:
 											return Some(LetBinding(lhs, rhs, Application(body_first, body_rest)))
 								else:
diff --git a/main.py b/main.py
index 29c011f..c8e555e 100644
--- a/main.py
+++ b/main.py
@@ -1,8 +1,16 @@
 from emis_funky_funktions import *
 
 from genir import json_to_ir
-from silly_thing import evaluate
+from silly_thing import repl, repl_expr
 
 import json, sys
 
-print(evaluate(json_to_ir(json.loads(open(sys.argv[1]).read()))))
\ No newline at end of file
+def main():
+	match sys.argv:
+		case [_, file]:
+			repl_expr(json_to_ir(json.loads(open(sys.argv[1]).read())))
+		case _:
+			repl()
+
+if __name__ == '__main__':
+	main()
\ No newline at end of file
diff --git a/silly_thing.py b/silly_thing.py
index fa104aa..84c533b 100644
--- a/silly_thing.py
+++ b/silly_thing.py
@@ -1,8 +1,10 @@
 from emis_funky_funktions import *
 from typing import Collection, Sequence, TypeAlias
 
-from ir import Expression
+from ir import Expression, ReplHole, subst_all
+from genir import json_to_ir
 
+import json
 from dataclasses import dataclass
 from operator import add
 
@@ -35,6 +37,30 @@ def evaluate(expr: Expression) -> Expression:
 				raise AssertionError('Evaluate called on a value which cannot step:', expr)
 	raise Exception('Unreachable')
 
+def repl_expr(expr: Expression, bindings: Sequence[Tuple[str, Expression]] = tuple()):
+	expr_subst = subst_all(bindings, expr)
+	result = evaluate(expr_subst)
+	if isinstance(result, ReplHole):
+		print('Environment updated\n')
+		repl(result.bindings)
+	else:
+		print(result, end='\n\n')
+		repl(bindings)
+
+def repl(bindings: Sequence[Tuple[str, Expression]] = tuple()):
+	print('Enter a JSON expression:')
+	try:
+		expr = input('-> ')
+	except EOFError:
+		print('<exit>')
+		return
+	try:
+		ast = json.loads(expr)
+	except json.decoder.JSONDecodeError as e:
+		print(f'Bad json: ', e.args[0], end='\n\n')
+		return repl(bindings)
+	repl_expr(json_to_ir(ast), bindings)
+
 if __name__ == '__main__':
 	import doctest
 	doctest.testmod()
\ No newline at end of file