Fixed parsing and display of parentheses

src/Parser/PNET.hs

@@ -137,9 +137,10 @@ termOperatorTable =
         ]
 
 termAtom :: Parser Term
-termAtom =  parens term
+termAtom =  (Var <$> ident)
         <|> (Const <$> integer)
-        <|> (Var <$> ident)
+        <|> parens term
+        <?> "basic term"
 
 term :: Parser Term
 term = buildExpressionParser termOperatorTable termAtom <?> "term"
@@ -167,10 +168,11 @@ formOperatorTable =
         ]
 
 formAtom :: Parser Formula
-formAtom =  parens formula
+formAtom =  try linIneq
         <|> (reserved "true" *> return FTrue)
         <|> (reserved "false" *> return FFalse)
-        <|> linIneq
+        <|> parens formula
+        <?> "basic formula"
 
 formula :: Parser Formula
 formula = buildExpressionParser formOperatorTable formAtom <?> "formula"

src/Property.hs

@@ -20,10 +20,10 @@ data Term = Var String
 instance Show Term where
         show (Var x) = x
         show (Const c) = show c
-        show (Minus t) = "-(" ++ show t ++ ")"
-        show (t :+: u) = show t ++ " + " ++ show u
-        show (t :-: u) = show t ++ " - " ++ show u
-        show (t :*: u) = "(" ++ show t ++ ") * (" ++ show u ++ ")"
+        show (Minus t) = "-" ++ show t
+        show (t :+: u) = "(" ++ show t ++ " + " ++ show u ++ ")"
+        show (t :-: u) = "(" ++ show t ++ " - " ++ show u ++ ")"
+        show (t :*: u) = show t ++ " * " ++ show u
 
 data Op = Gt | Ge | Eq | Ne | Le | Lt