[Haskell-cafe] Maybe a, The Rationale
dons at galois.com
Sun May 11 22:42:47 EDT 2008
> > Maybe types force you to deal with it, while simultaneously
> >providing convenience functions to help you deal with it.
> I readily grant that Maybe is a wonderful wonderful thing and I use it
> freely and
> voluntarily. BUT it should not dominate the code.
> Consider Haskell's getChar and hGetChar. They DON'T return Maybe
> Char; they
> raise an exception at end of file. You have to keep testing isEOF/
> hIsEOF before
> each character read, as if we had learned nothing since Pascal.
> Arguably, maybeGetChar :: IO (Maybe Char) and hMaybeGetChar :: Handle -
> > IO (Maybe Char)
> would be a good idea, at least then one could easily set up some
> combinators to
> deal with this nuisance.
Thankfully its easy to lift IO-throwing things into a safer world.
import Prelude hiding (getChar)
import qualified Prelude as P
getChar :: IO (Maybe Char)
getChar = handle (const (return Nothing)) (Just `fmap` P.getChar)
More information about the Haskell-Cafe