On Wed, 7 Nov 2007, Tim Newsham wrote: > Data.Maybe has functions for processing Maybe's but nothing useful > for creating maybe. I think the following would be a very useful > addition, a guarded function: > > guarded :: (a -> Bool) -> (a -> b) -> a -> Maybe b > guarded p f x | p x = Just (f x) > | otherwise = Nothing > > such a function in the std libs would make functions like "unfoldr" > more attractive -- uses of foldr nearly always encapsulate this > notion.
This would be guarded p f x = toMaybe (p x) (f x) in terms of my beloved but already rejected 'toMaybe': http://www.haskell.org/pipermail/libraries/2004-July/002326.html _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe