fix division by zero

src/Computing/ComputeAST.hs

@@ -94,7 +94,6 @@ computeFunctionBody env (Function _ fnParams (x:_)) args =
     case replaceFunctionParams env fnParams x args of
         (newEnv, Nothing) -> (newEnv, Right (undefined))
         (newEnv, Just replaced) -> computeAST newEnv replaced
-
 computeFunction :: Env -> Function -> [Tree] -> (Env, Result)
 computeFunction env (Function fnName fnParams (x:xs:rest)) args =
     case computeFunctionBody env (Function fnName fnParams [x]) args of

src/Computing/Operators/Calculate.hs

@@ -7,11 +7,11 @@
 
 module Computing.Operators.Calculate
     (
-      addition,
-      subtraction,
-      multiplication,
-      division,
-      modulo,
+        addition,
+        subtraction,
+        multiplication,
+        division,
+        modulo,
     ) where
 
 import Types
@@ -30,20 +30,24 @@ calculate a b "mod" = Number (a `mod` b)
 calculate _ _ _ = Number 0
 
 maybeCalculate :: Maybe Tree -> Maybe Tree -> Symbol -> Env -> (Env, Result)
+maybeCalculate _ (Just (Number 0)) "div" env
+    = (registerError env "Division by 0", Right (undefined))
 maybeCalculate (Just (Number a)) (Just (Number b)) operator env =
     (env, Left (Just (calculate a b operator)))
 maybeCalculate _ _ _ env =
     (registerError env "Symbol not found", Right (undefined))
 
 calculateOperator :: Env -> [Tree] -> Symbol -> (Env, Result)
+calculateOperator env [_, Number 0] "div" =
+    (registerError env "Division by 0", Right (undefined))
 calculateOperator env [Number a, Number b] operator =
-  (env, Left (Just (calculate a b operator)))
+    (env, Left (Just (calculate a b operator)))
 calculateOperator env [Number a, Symbol b] operator =
-  maybeCalculate (Just (Number a)) (evaluateSymbol env b) operator env
+    maybeCalculate (Just (Number a)) (evaluateSymbol env b) operator env
 calculateOperator env [Symbol a, Number b] operator =
-  maybeCalculate (evaluateSymbol env a) (Just (Number b)) operator env
+    maybeCalculate (evaluateSymbol env a) (Just (Number b)) operator env
 calculateOperator env [Symbol a, Symbol b] operator =
-  maybeCalculate (evaluateSymbol env a) (evaluateSymbol env b) operator env
+    maybeCalculate (evaluateSymbol env a) (evaluateSymbol env b) operator env
 calculateOperator env list _
     | length list /= 2 =
         (registerError env "Addition need 2 params", Right (undefined))

test/Spec.hs

@@ -208,6 +208,10 @@ unitTestsComputeBasics = testGroup "Tests compute basics"
         assertEqual "2 + 3 * (8 + (5* ( 2 + 3))) = 107"
           (defaultEnv, [Left (Just (Number 101))])
           (computeAllAST (defaultEnv) [(List [Symbol "+", Number 2, (List [Symbol "*", Number 3, (List [Symbol "+", Number 8, (List [Symbol "*", Number 5, (List [Symbol "+", Number 2, Number 3])])])])])])
+    , testCase "div 42 0" $
+        assertEqual "div 42 0"
+          (Env {defines = [], errors = ["Division by 0"], functions = []}, Right (undefined))
+          (computeAST (defaultEnv) (List [Symbol "div", Number 42, Number 0]))
   ]
 
 unitTestsComputeFunctions :: TestTree