Re: [Haskell-beginners] case in monadic function

Kovacs David wrote:

Hello!

I have a function like this: http://rafb.net/p/8E66FI29.html, starting with evalState. The problem is with checkPredName cause it's return type is SemanticError what's not a monadic value but case waiting for m a (as the error message sais), but if I use return to checkPredName then ofc the pattern match will fail. How can I fix this?

Regards, David

You can use liftM/fmap to lift a function into a monad: case (checkPredName pn . snd) `fmap` get of ...