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/
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