Working Monad transformer except for Clean not finding an existing instance

diff --git a/sem.icl b/sem.icl
index 6c78854..a973a02 100644 (file)
--- a/sem.icl
+++ b/sem.icl
@@ -9,6 +9,7 @@ import Control.Applicative
 import Control.Monad
 import Control.Monad.State
 import Control.Monad.Identity
+import Control.Monad.Trans
 import StdMisc
 from StdFunc import id, const
 import StdString
@@ -20,27 +21,9 @@ import AST
 from parse import :: ParserOutput, :: Error
 
 :: Gamma :== 'Map'.Map String Type
-:: Env a = Env (State Gamma (Either SemError a))
+:: Env a :== StateT Gamma (Either SemError) a
 
-instance Functor Env where
-    fmap f m = liftM f m
-
-instance Applicative Env where
-    (<*>) f g   = ap f g
-    pure  a     = Env $ pure $ Right a
-
-//instance Alternative Env where
-//    empty       = Env $ pure $ Left (Error "Undefined error")
-//    (<|>) f g   = f >>= \ef -> g >>= \eg -> Env $ pure $ case ef of 
-//        Left e  = eg
-//        Right r = Right r
-
-instance Monad Env where
-    bind e f    = e >>= \ee -> Env $ pure $ case ee of
-        (Left e) = Left e
-        (Right r) = f r
-
-get = state $ \s -> (s,s)
+get = gets id
 
 instance toString SemError where
     toString (ParseError p e) = concat [
@@ -52,25 +35,23 @@ instance toString SemError where
         "SemError: Cannot unify types. Expected: ",
         toString t1, ". Given: ", toString t2]
 
-sem :: AST -> SemOutput
-sem x = undef
-/*
 putIdent :: String Type -> Env Void
-putIdent i t = gets ('Map'.get i) >>= \mt -> case mt of
+putIdent i t = undef
+/*putIdent i t = gets ('Map'.get i) >>= \mt -> case mt of
     Nothing = pure <$> modify ('Map'.put i t)
     Just t2 = unify t t2 >>= \r -> case r of
         Left e  = pure $ Left e
-        Right t3 = pure <$> modify ('Map'.put i t3)
+        Right t3 = pure <$> modify ('Map'.put i t3)*/
 
 sem :: AST -> SemOutput
-sem (AST vd fd)
-# (eithervds, gamma) = runState (mapM semVarDecl vd) 'Map'.newMap
-# (eitherfds, gamma) = runState (mapM semFunDecl fd) gamma
-= case splitEithers eithervds of
-       (Left errs) = Left $ errs ++ [x\\(Left x)<-eitherfds]
-       (Right vds) = case splitEithers eitherfds of
-               (Left errs) = Left errs
-               (Right fds) = Right $ AST vds fds
+sem (AST vd fd) = case evalStateT m 'Map'.newMap of
+    Left e = Left [e]
+    Right (vds, fds) = Right (AST vds fds)
+where 
+    m :: Env (([VarDecl], [FunDecl]))
+    m = (mapM semVarDecl vd) >>= \vds -> 
+        mapM semFunDecl fd >>= \fds -> 
+        pure (vds, fds)
 
 splitEithers :: [Either a b] -> Either [a] [b]
 splitEithers [] = Right []
@@ -78,23 +59,20 @@ splitEithers [Right x:xs] = splitEithers xs >>= \rest->Right [x:rest]
 splitEithers xs = Left $ [x\\(Left x)<-xs]
 
 semFunDecl :: FunDecl -> Env FunDecl
-semFunDecl f = pure $ Right f
+semFunDecl f = pure f
 
 semVarDecl :: VarDecl -> Env VarDecl
-semVarDecl vd=:(VarDecl pos type ident ex) = unify type ex
-       >>= \et->case et of
-               Left err = pure $ Left err
-               Right t = putIdent ident t >>| pure (Right $ VarDecl pos t ident ex)
+semVarDecl (VarDecl pos type ident ex) = unify type ex
+    >>= \t-> putIdent ident t >>| (pure $ VarDecl pos t ident ex)
 
 typeExpr :: Expr -> Env Type
-typeExpr (IntExpr _ _) = pure $ Right IntType
-typeExpr (CharExpr _ _) = pure $ Right CharType
-typeExpr (BoolExpr _ _) = pure $ Right BoolType
+typeExpr (IntExpr _ _) = pure IntType
+typeExpr (CharExpr _ _) = pure CharType
+typeExpr (BoolExpr _ _) = pure BoolType
 typeExpr (Op1Expr p UnNegation expr) = unify BoolType expr
 typeExpr (Op1Expr p UnMinus expr) = unify IntType expr
 typeExpr (TupleExpr p (e1, e2)) = typeExpr e1 
-       >>= \ete1->typeExpr e2 >>= \ete2->pure (
-               ete1 >>= \te1->ete2 >>= \te2->Right $ TupleType (te1, te2))
+    >>= \t1-> typeExpr e2 >>= \t2-> pure $ TupleType (t1, t2)
 //Int
 typeExpr (Op2Expr p e1 BiPlus e2) = unify IntType e1 >>| unify IntType e2
 typeExpr (Op2Expr p e1 BiMinus e2) = unify IntType e1 >>| unify IntType e2
@@ -122,25 +100,24 @@ typeExpr (Op2Expr p e1 BiCons e2) = undef
 class unify a :: Type a -> Env Type
 
 instance unify Expr where
-       unify (_ ->> _) e = pure $ Left $ ParseError (extrPos e)
+       unify (_ ->> _) e = liftT $ Left $ ParseError (extrPos e)
                        "Expression cannot be a higher order function. Yet..."
-       unify VoidType e = pure $ Left $ ParseError (extrPos e)
+       unify VoidType e = liftT $ Left $ ParseError (extrPos e)
                        "Expression cannot be a Void type."
-       unify (IdType _) e = pure $ Left $ ParseError (extrPos e)
+       unify (IdType _) e = liftT $ Left $ ParseError (extrPos e)
                        "Expression cannot be an polymorf type."
     unify VarType e = typeExpr e
-       unify t e = typeExpr e
-               >>= \eithertype->case eithertype of
-                       Left e = pure $ Left e
-                       Right tex = unify t tex >>= \eitherun->case eitherun of
-                               Left err = pure $ Left $ decErr e err
-                               Right t = pure $ Right t
+    //we have to cheat to decorate the error, can be done nicer?
+    unify t e = StateT $ \s0 -> let res = runStateT m s0 in case res of
+        Left err = Left $ decErr e err
+        Right t = Right t //note, t :: (Type, Gamma) 
+    where m = typeExpr e >>= \tex-> unify t tex 
 
 instance unify Type where
-       unify IntType IntType = pure $ Right IntType
-       unify BoolType BoolType = pure $ Right BoolType
-       unify CharType CharType = pure $ Right CharType
-       unify t1 t2 = pure $ Left $ UnifyError zero t1 t2
+       unify IntType IntType = pure IntType
+       unify BoolType BoolType = pure BoolType
+       unify CharType CharType = pure CharType
+       unify t1 t2 = liftT $ Left $ UnifyError zero t1 t2
 
 instance zero Pos where
        zero = {line=0,col=0}
@@ -150,6 +127,10 @@ decErr e (UnifyError _ t1 t2) = UnifyError (extrPos e) t1 t2
 decErr e (ParseError _ s) = ParseError (extrPos e) s
 decErr e err = err
 
+dc2 :: Expr (Either SemError a) -> Either SemError a
+dc2 e (Right t) = Right t
+dc2 e (Left err) = Left err
+
 extrPos :: Expr -> Pos
 extrPos (VarExpr p _) = p
 extrPos (Op2Expr p _ _ _) = p
@@ -159,5 +140,4 @@ extrPos (CharExpr p _) = p
 extrPos (BoolExpr p _) = p
 extrPos (FunExpr p _) = p
 extrPos (EmptyListExpr p) = p
-extrPos (TupleExpr p _) = p
-*/
\ No newline at end of file
+extrPos (TupleExpr p _) = p
\ No newline at end of file