From fab20f52753ebb688a5fefb2b1d92f45bec93fb7 Mon Sep 17 00:00:00 2001
From: Mart Lubbers <mart@martlubbers.net>
Date: Fri, 8 Mar 2019 13:48:35 +0100
Subject: [PATCH] letrec

---
 ast.icl            |  2 +-
 check.icl          | 13 +++++++------
 tests/preamble.mfp |  2 +-
 3 files changed, 9 insertions(+), 8 deletions(-)

diff --git a/ast.icl b/ast.icl
index 9280dd3..1a4d7c1 100644
--- a/ast.icl
+++ b/ast.icl
@@ -16,7 +16,7 @@ instance toString Expression where
 	toString (Let ns r) = concat
 		[ "let\n"
 		, concat [concat ["\t", toString n, " = ", toString v, "\n"]\\(n, v)<-ns]
-		, " in\n", toString r]
+		, "in\n", toString r]
 	toString _ = abort "toString Expression not implemented"
 
 instance toString Value where
diff --git a/check.icl b/check.icl
index b0e078d..abff97a 100644
--- a/check.icl
+++ b/check.icl
@@ -40,12 +40,12 @@ preamble :: TypeEnv
 preamble = fromList
 	[(['_if'],  Forall [['_ift']]
 		$ TBool --> TVar ['_ift'] --> TVar ['_ift'] --> TVar ['_ift'])
-	,(['_eq'],  Forall [['_eq']] $ TInt --> TInt --> TBool)
+	,(['_eq'],  Forall [['_eq']]  $ TInt --> TInt --> TBool)
 	,(['_mul'], Forall [['_mul']] $ TInt --> TInt --> TInt)
 	,(['_add'], Forall [['_add']] $ TInt --> TInt --> TInt)
 	,(['_sub'], Forall [['_sub']] $ TInt --> TInt --> TInt)
 	]
-:: Subst   :== Map [Char] Type
+:: Subst :== Map [Char] Type
 
 :: Infer a :== StateT [Int] (Either [String]) a
 runInfer :: (Infer (Subst, Type)) -> Either [String] Scheme
@@ -55,7 +55,7 @@ runInfer i = uncurry ((o) (generalize newMap) o apply)
 fresh :: Infer Type
 fresh = getState >>= \[s:ss]->put ss >>| pure (TVar (['v':[c\\c<-:toString s]]))
 
-(oo) infixr 9 :: Subst Subst -> Subst
+(oo) infixl 9 :: Subst Subst -> Subst
 (oo) s1 s2 = 'Data.Map'.union (apply s1 <$> s2) s1
 
 class Substitutable a where
@@ -125,12 +125,13 @@ infer env (Lambda x b)
 	=              fresh
 	>>= \tv->      infer ('Data.Map'.put x (Forall [] tv) env) b
 	>>= \(s1, t1)->pure (s1, apply s1 tv --> t1)
-//infer env (Let x e1 e2)
+//infer env (Let [(x, e1)] e2)
 //	=              infer env e1
 //	>>= \(s1, t1)->infer ('Data.Map'.put x (generalize (apply s1 env) t1) env) e2
 //	>>= \(s2, t2)->pure (s1 oo s2, t2)
 infer env (Let [(x, e1)] e2)
 	=              fresh
-	>>= \tv->      infer ('Data.Map'.put x (Forall [] tv) env) e1
-	>>= \(s1, t1)->infer ('Data.Map'.put x (generalize (apply s1 env) t1) env) e2
+	>>= \tv->      let env` = 'Data.Map'.put x (Forall [] tv) env
+	               in infer env` e1
+	>>= \(s1,t1)-> infer ('Data.Map'.put x (generalize (apply s1 env`) t1) env`) e2
 	>>= \(s2, t2)->pure (s1 oo s2, t2)
diff --git a/tests/preamble.mfp b/tests/preamble.mfp
index 617b195..8c01e96 100644
--- a/tests/preamble.mfp
+++ b/tests/preamble.mfp
@@ -6,4 +6,4 @@ $ ifxr 0 x y = x y;
 + ifxl 6 = code add;
 if = code if;
 fac i = if (i == 0) 1 (i * fac (i - 1));
-start = fac 15;
+start = fac;
-- 
2.20.1