Here's a tip: leave off the type signature, and ask ghci what it is. $ ghci Prelude> let contain x [] = False ; contain x (y:ys) = if x == y then True else contain x ys Prelude> :t contain contain :: (Eq a) => a -> [a] -> Bool
-- ryan 2008/12/22 Raeck Zhao <[email protected]>: > I am trying to define a containing function to see if a value is one of the > elements within a list which is polymorphic, but failed with the following > codes: >> contain :: a -> [a] -> Bool >> contain x [] = False >> contain x (y:ys) = if x == y then True else contain x ys it seems that the >> problem is the 'operator' == does not support a polymorphic check? > Any way can solve the problem? or any alternative solution to achieve the > purpose? > Thanks! > Raeck > > ________________________________ > It's the same Hotmail(R). If by "same" you mean up to 70% faster. Get your > account now. > _______________________________________________ > Haskell-Cafe mailing list > [email protected] > http://www.haskell.org/mailman/listinfo/haskell-cafe > > _______________________________________________ Haskell-Cafe mailing list [email protected] http://www.haskell.org/mailman/listinfo/haskell-cafe
