Hi all,
consider this simple reimplementation of 'elem' function:
member :: Eq a => a -> [a] -> Bool
member _ [] = False
member y (x:xs) | x == y = True
| otherwise = member y xs
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". Many times I have found myself instinctively writing
patterns in this way,
only to get a compilation error. I was thinking about implementing language
extension for GHC
that would allow to write Prolog-style patterns. Would there be an interest in
such an extension?
Also, if I missed something obvious please let me know.
Janek
_______________________________________________
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
