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#view-patterns
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
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