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
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
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: purpose? Thanks! Raeck
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