[Haskell-cafe] generating Maybe

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. Tim Newsham http://www.thenewsh.com/~newsham/