Add parenthesis to parsing

diff --git a/AST.hs b/AST.hs
index 720413652e4343740ad6268e0a866b0576e4c4aa..73523d6d4c8a37cef977d5614d355aaac13756af 100644 (file)
--- a/AST.hs
+++ b/AST.hs
@@ -39,7 +39,8 @@ instance Read AST where
             return (Function name params body)
 
 instance Read Expr where
-  readPrec = choice [ parseNum
+  readPrec = choice [ parseParens
+                    , parseNum
                     , parseVar
                     , parseCall
                     , parseIf
@@ -50,7 +51,9 @@ instance Read Expr where
                     , parseBinOp "<" (Cmp LT)
                     , parseBinOp "==" (Cmp EQ)
                     ]
-    where parseNum = Num <$> readPrec
+    where parseParens = step $ lift $
+            between (char '(') (char ')') (readS_to_P reads)
+          parseNum = Num <$> readPrec
           parseVar = Var <$> lift (munch1 isAlpha)
           parseCall = do
             func <- lift (munch1 isAlpha)