On 18 October 2011 09:14, kolli kolli <[email protected]> wrote: > I didnt understand properly but made changes according to what I > understood..Its still giving me the same error > > eval1(If t1 t2 t3) = case (If t1 t2 t3) of > eval1(If t1 t2 t3) -> Just t1
You can't do that.... if you want the result to be "Just t1", why not just have "eval1 (If t1 t2 t3) = Just t1", with no case or where statement? > > > On Mon, Oct 17, 2011 at 4:10 PM, Ivan Lazar Miljenovic > <[email protected]> wrote: >> >> On 18 October 2011 09:08, kolli kolli <[email protected]> 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 >> > <[email protected]> wrote: >> >> >> >> On 18 October 2011 08:56, kolli kolli <[email protected]> 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 >> >> > <[email protected]> wrote: >> >> >> >> >> >> On 18 October 2011 08:43, kolli kolli <[email protected]> >> >> >> 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 >> >> >> [email protected] >> >> >> IvanMiljenovic.wordpress.com >> >> > >> >> > >> >> >> >> >> >> >> >> -- >> >> Ivan Lazar Miljenovic >> >> [email protected] >> >> IvanMiljenovic.wordpress.com >> > >> > >> >> >> >> -- >> Ivan Lazar Miljenovic >> [email protected] >> IvanMiljenovic.wordpress.com > > -- Ivan Lazar Miljenovic [email protected] IvanMiljenovic.wordpress.com _______________________________________________ Haskell-Cafe mailing list [email protected] http://www.haskell.org/mailman/listinfo/haskell-cafe
