Hi, Jan Stolarek wrote:
If Haskell allowed to write pattern matching similar to Prolog then we could write this function like this:
member :: Eq a => a -> [a] -> Bool member _ [] = False member x (x:_) = True member x (_:xs) = member x xs
The meaning of pattern in the second equation is "match this equation if the first argument equals to head of the list".
You can achieve something similar with the ViewPatterns language extension. See http://www.haskell.org/ghc/docs/latest/html/users_guide/syntax-extns.html#vi... and http://hackage.haskell.org/trac/ghc/wiki/ViewPatterns. member _ [] = False member x (((x ==) -> True) : _) = True member x (_ : xs) = member x xs or member _ [] = False member x ((compare x -> EQ) : _) = True member x (_ : xs) = member x xs Tillmann