On 8 April 2013 21:11, Jan Stolarek <jan.stola...@p.lodz.pl> wrote: > 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.
My initial take on this is that such capabilities would be too easy to mis-use accidentally; e.g. refactoring and changing variable names, thus causing patterns to match when you don't mean them to. > > Janek > > _______________________________________________ > Haskell-Cafe mailing list > Haskell-Cafe@haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe -- Ivan Lazar Miljenovic ivan.miljeno...@gmail.com http://IvanMiljenovic.wordpress.com _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
