Tehee

3/Assignment.hs

@@ -2,14 +2,10 @@
 module Assignment where
 
 import Chi
-import Control.Monad
-import Control.Monad.Identity
-import Debug.Trace (trace)
-import Data.HashMap.Strict (HashMap)
-import qualified Data.HashMap.Strict as HM
 import Data.Functor ( (<&>) )
 import Control.Monad.Identity (Identity(runIdentity))
 
+-- Task 3
 subst :: Variable -> Exp -> Exp -> Exp
 subst var e = \case
   Apply e1 e2 -> Apply (subst var e e1) (subst var e e2)
@@ -22,27 +18,32 @@ subst var e = \case
       substBr :: Br -> Br
       substBr (Branch c vs e') = Branch c vs $ if var `notElem` vs then subst var e e' else e'
 
-lookupBranch :: Constructor -> [Br] -> Identity ([Variable], Exp)
-lookupBranch c [] = error "No matching branch"
-lookupBranch c ((Branch c' bs e):brs) = if c == c' then pure (bs,e) else lookupBranch c brs
-
-eval' :: Exp -> Identity Exp
-eval' = \case
-  e@(Apply e1 e2) -> eval' e1 >>= \case
-    Lambda x e' -> eval' e2 >>= eval' . flip (subst x) e'
-    _ -> error $ "Function was not function in evaluation: " <> show e
-  Const c es -> mapM eval' es <&> Const c
-  Rec x e -> eval' $ subst x (Rec x e) e
-  Case e bs -> eval' e >>= \case
-    Const c vs -> lookupBranch c bs >>= \case
-      (xs,e') ->
-        if length vs /= length xs then error "Not the same amount of arguments in case" else
-        eval' $ foldr (uncurry subst) e' (zip xs vs)
-    e -> error $ "Non const in case: " <> show e
-  x -> pure x
-
+-- Task 5
 eval :: Exp -> Exp
 eval = runIdentity . eval'
+  where
+    eval' :: Exp -> Identity Exp
+    eval' = \case
+      e@(Apply e1 e2) -> eval' e1 >>= \case
+        Lambda x e' -> eval' e2 >>= eval' . flip (subst x) e'
+        _ -> error $ "Function was not function in evaluation: " <> show e
+      Const c es -> mapM eval' es <&> Const c
+      Rec x e -> eval' $ subst x (Rec x e) e
+      Case e bs -> eval' e >>= \case
+        Const c vs -> lookupBranch c bs >>= \case
+          (xs,e') ->
+            if length vs /= length xs then error "Not the same amount of arguments in case" else
+            eval' $ foldr (uncurry subst) e' (zip xs vs)
+        e -> error $ "Non const in case: " <> show e
+      x -> pure x
+    
+    lookupBranch :: Constructor -> [Br] -> Identity ([Variable], Exp)
+    lookupBranch c [] = error "No matching branch"
+    lookupBranch c ((Branch c' bs e):brs) =
+      if c == c'
+      then pure (bs,e)
+      else lookupBranch c brs
+
 
 main :: IO ()
 main = getLine >>= print . eval . parse