[Haskell] IO, exceptions and error handling

[John Meacham]

On Mon, Jun 14, 2004 at 05:41:03PM +0100, Keith Wansbrough wrote:
> > Philippa Cowderoy wrote:
> > 
> > > The ability to fail doesn't need the do notation, just use of 
> > > return for success - similar for propagating failure.
> > 
> > I'm not sure I understand. Do you mean writing functions
> > like:
> > 
> >     sqr x | x < 0     = fail "less than zero"
> >           | otherwise = return (sqrt x)
> 
> s/fail/error/
> s/return//

better yet, 
import Control.Monad.Identity

sqr' x = runIdentity (sqr x)

now sqr' behaves exactly as if you used 'error' and direct code, but the
monadic version is still available for those that care about it.
        John


-- 
John Meacham - ⑆repetae.net⑆john⑈