💀 renamed A1 pdf and messed around with state

a2/a2-handout/src/APL/AST.hs

@@ -21,4 +21,5 @@ data Exp
   | Lambda VName Exp
   | Apply Exp Exp
   | TryCatch Exp Exp
+  --  | Print String Exp
   deriving (Eq, Show)

a2/a2-handout/src/APL/Eval.hs

@@ -17,9 +17,14 @@ data Val
 
 type Env = [(VName, Val)]
 
+type State = [String]
+
 envEmpty :: Env
 envEmpty = []
 
+stateEmpty :: State
+stateEmpty = []
+
 envExtend :: VName -> Val -> Env -> Env
 envExtend v val env = (v, val) : env
 
@@ -28,40 +33,43 @@ envLookup v env = lookup v env
 
 type Error = String
 
-newtype EvalM a = EvalM (Env -> Either Error a)
+newtype EvalM a = EvalM (Env -> State -> (State, Either Error a))
 
 instance Functor EvalM where
   fmap = liftM
 
 instance Applicative EvalM where
-  pure x = EvalM $ \_env -> Right x
+  pure x = EvalM $ \_env state -> (state, Right x)
   (<*>) = ap
 
 instance Monad EvalM where
-  EvalM x >>= f = EvalM $ \env ->
-    case x env of
-      Left err -> Left err
-      Right x' ->
+  EvalM x >>= f = EvalM $ \env state ->
+    case x env state of
+      (state', Left err) -> (state', Left err)
+      (state', Right x') ->
         let EvalM y = f x'
-         in y env
+         in y env state'
 
 askEnv :: EvalM Env
-askEnv = EvalM $ \env -> Right env
+askEnv = EvalM $ \env state -> (state, Right env)
 
 localEnv :: (Env -> Env) -> EvalM a -> EvalM a
 localEnv f (EvalM m) = EvalM $ \env -> m (f env)
 
 failure :: String -> EvalM a
-failure s = EvalM $ \_env -> Left s
+failure s = EvalM $ \_env state -> (state, Left s)
 
 catch :: EvalM a -> EvalM a -> EvalM a
-catch (EvalM m1) (EvalM m2) = EvalM $ \env ->
-  case m1 env of
-    Left _ -> m2 env
-    Right x -> Right x
+catch (EvalM m1) (EvalM m2) = EvalM $ \env state ->
+  case m1 env state of
+    (state', Left _) -> m2 env state'
+    (state', Right x) -> (state', Right x)
 
-runEval :: EvalM a -> Either Error a
-runEval (EvalM m) = m envEmpty
+evalPrint :: String -> EvalM ()
+evalPrint a = undefined
+
+runEval :: EvalM a -> (State, Either Error a)
+runEval (EvalM m) = m envEmpty stateEmpty
 
 evalIntBinOp :: (Integer -> Integer -> EvalM Integer) -> Exp -> Exp -> EvalM Val
 evalIntBinOp f e1 e2 = do

a2/a2-handout/src/APL/Eval_Tests.hs

@@ -5,7 +5,7 @@ import APL.Eval (Error, Val (..), eval, runEval)
 import Test.Tasty (TestTree, testGroup)
 import Test.Tasty.HUnit (testCase, (@?=))
 
-eval' :: Exp -> Either Error Val
+eval' :: Exp -> ([String], Either Error Val)
 eval' = runEval . eval
 
 evalTests :: TestTree