[Haskell-cafe] parser error in pattern

[Ivan Lazar Miljenovic]

On 18 October 2011 09:08, kolli kolli <nammukolli04 at gmail.com> wrote:
> 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
>

As I said, the error is from your incorrect usage of the case
statement; it _should_ look something like:

case foo of
    bar -> baz
    bar' -> baz'

>
>
>
>
> On Mon, Oct 17, 2011 at 4:03 PM, Ivan Lazar Miljenovic
> <ivan.miljenovic at gmail.com> wrote:
>>
>> On 18 October 2011 08:56, kolli kolli <nammukolli04 at gmail.com> 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
>> > <ivan.miljenovic at gmail.com> wrote:
>> >>
>> >> On 18 October 2011 08:43, kolli kolli <nammukolli04 at gmail.com> 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 at gmail.com
>> >> IvanMiljenovic.wordpress.com
>> >
>> >
>>
>>
>>
>> --
>> Ivan Lazar Miljenovic
>> Ivan.Miljenovic at gmail.com
>> IvanMiljenovic.wordpress.com
>
>



-- 
Ivan Lazar Miljenovic
Ivan.Miljenovic at gmail.com
IvanMiljenovic.wordpress.com