add max rec depth (#2)

* add RecursionError: maximum recursion depth 1500 for while loop

* One does not simply merge into master

Author: felixbd

src/WhileEvaluation.hs

@@ -13,6 +13,7 @@ module WhileEvaluation
   ,VarStateWorld
   ) where
 
+import Data.List (nub)
 
 import WhileParser
   (WhileAST(..)
@@ -64,12 +65,9 @@ evalExpression :: Expression -> VarStateWorld -> Int
 evalExpression expr state = case expr of
                              (Constant c)         -> c
                              (Variable varName)   -> lookUpVarState varName state
-                             (Add exp1 exp2)      -> helper (+) [exp1, exp2]
+                             (Add exp1 exp2)      -> foldl (\acc x -> acc + evalExpression x state) 0 [exp1, exp2]
                              (Subtract exp1 exp2) -> max 0 $ evalExpression exp1 state - evalExpression exp2 state
-                             (Neq exp1 exp2)      -> fromEnum $ evalExpression exp1 state /= evalExpression exp2 state
-  where
-    -- helper :: (Int -> Int -> Int) -> [Expression] -> Int
-    helper f = foldl (\acc x -> f acc (evalExpression x state)) 0
+                             (Neq exp1 exp2)      -> fromEnum $ length (nub $ map (`evalExpression` state) [exp1, exp2]) == 2
 
 --------------------------------------------------------------------------------
 
@@ -78,17 +76,22 @@ evalAssignment (Assignment name expr) state = updateVarState name (evalExpressio
 evalAssignment _ _ = undefined
 
 evalWhileExp :: WhileAST -> VarStateWorld -> VarStateWorld
-evalWhileExp (While expr whileAST) state = helperWhile expr whileAST state
+evalWhileExp (While expr whileAST) state = helperWhile expr whileAST state 0
 evalWhileExp _ _ = undefined
 
--- NOTE maybe check if `evalExpression p state` returns either 0 or 1 ...
-helperWhile :: Expression -> WhileAST -> VarStateWorld -> VarStateWorld
-helperWhile p ast state = if evalExpression p state == 1
-                          then helperWhile p ast (eval ast state)
-                          else state
+helperWhile :: Expression -> WhileAST -> VarStateWorld -> Int -> VarStateWorld
+helperWhile p ast state maxRec
+  | maxRec >= getRecursionLimit = error "\n\ESC[91m[RecursionError]\ESC[0m: maximum recursion depth exceeded!"
+  | evalExpression p state == 1 = helperWhile p ast (eval ast state) (maxRec + 1)
+  | otherwise = state
+  where
+    -- getRecursionLimit :: Int
+    getRecursionLimit = 1500
+
 
 evalLoopExp :: WhileAST -> VarStateWorld -> VarStateWorld
 -- evalLoopExp (Loop exp whileAST) state = (foldr (.) id (replicate (evalExpression exp state) eval))
+-- foldr (\_ accState -> evalLoopExp whileAST (eval expr accState)) state [1..evalExpression expr state]
 evalLoopExp (Loop expr whileAST) state = helperLoop whileAST state (evalExpression expr state)
 evalLoopExp _ _ = undefined