Re: [Haskell-beginners] [Haskell-cafe] parser error in pattern

17 Oct 2011


      actual error message is

homework2.lhs:137:20: parse error on input `where'

data Term = Tru
          | Fls
          | If Term Term Term
          | Zero
          | Succ Term
          | Pred Term
          | IsZero Term
          deriving Eq


On Mon, Oct 17, 2011 at 4:03 PM, Ivan Lazar Miljenovic <
ivan.miljenovic@gmail.com> wrote:
...
On 18 October 2011 08:56, kolli kolli  wrote:
...
after parsing a string i am evaluating it...
string if t1 then t2 else t3
my code is
eval1 :: Term ->  Maybe Term
eval1(If Tru t2 t3) = Just t2
eval1(If Fls t2 t3) = Just t3
eval1(If t1 t2 t3) =  case eval t1
                    where eval1(If t1 t2 t3) =  Just t1
eval :: Term -> Term
eval (IsZero Zero) = Tru
eval (Zero) = Zero
eval(Pred Zero) = Pred Zero
Your case statement is incomplete for starters...
Can you please provide the actual error message as well?  Your
definition of Term would also be useful.
...
On Mon, Oct 17, 2011 at 3:46 PM, Ivan Lazar Miljenovic
 wrote:
...
On 18 October 2011 08:43, kolli kolli  wrote:
...
hey can anyone tell me what is parser error in parser??Plz help me out
It's when the parser can't parse what it's provided.... providing the
code that caused the problem and the actual error message is required
for a more detailed explanation.
--
Ivan Lazar Miljenovic
Ivan.Miljenovic@gmail.com
IvanMiljenovic.wordpress.com
--
Ivan Lazar Miljenovic
Ivan.Miljenovic@gmail.com
IvanMiljenovic.wordpress.com