[Haskell-cafe] Simple "Maybe" question
mark at chaos.x-philes.com
Tue Jan 27 08:15:57 EST 2004
On Tue, 27 Jan 2004, Jim Lewis wrote:
> I'm new to Haskell and can't find an example to solve a trivial problem.
> I have code like this:
> findBlank ::  -> Int
> findBlank str = findIndex (==' ') str
> But interpreter complains elsewhere of mismatch of Int with Maybe Int. I want to handle the maybe only here and nowhere else.
This may somehow help,
findBlank' :: [Char] -> Int
findBlank' str = fromJust (findIndex (==' ') str)
findBlank'' :: [Char] -> Int
findBlank'' str = let Just index = findIndex (==' ') str in index
findBlank''' :: [Char] -> Int
findBlank''' str = maybe (error "Pigs flew") id (findIndex (==' ') str)
You may have to import Maybe to get some of those to work.
Matthew Walton's comments also look good.
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