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 just makes matters worse: findBlank str = Just findIndex (==' ') str
Thanks.
The result type of findIndex (==' ') str is Maybe Int, therefore you need to be prepared to handle both sides of a Maybe result, which could be Just n (where n is some Int), or Nothing. The simplest solution is to use 'case' to handle when findIndex returns Just n, and when findIndex returns Nothing, although you'll need to find a suitable Int for findBlank to return when findIndex returns Nothing. Although were I writing the code, I'd be tempted to make findBlank return a Maybe Int as well, and let the code which calls that deal with Nothing as an error condition.