[Haskell-cafe] Newbie Question on type constructors

[David Menendez]

Benjamin Franksen writes:

> On Monday 01 November 2004 23:40, Jon Fairbairn wrote:
> > Apart from matching up with the names there's not much to
> > choose between one destructor and many, except possibly when
> > one considers something like:
> > 
> >    case e of
> >      Square s -> ...
> >      _ -> ...
> > 
> > particularly if the type has more than two constructors.
> 
> True. Anyway, we don't really want to abandon pattern matching
> syntax, do we?

Explicit destructor functions are nice when working in a point-free
fashion. Consider these:

    c1 = someComputation >>= maybe mzero return

    c2 = do
        x <- someComputation
        case x of
            Just x' -> return x'
            Nothing -> mzero


On the other hand, this function (which I actually have in my code) may
be over-doing it:

    swap = maybe (Right Nothing) (either Left (Right . Just))
-- 
David Menendez <zednenem at psualum.com> <http://www.eyrie.org/~zednenem/>