[Haskell] View patterns in GHC: Request for feedback

[ajb at spamcop.net]

G'day all.

On Mon, Jul 23, 2007 at 05:09:01AM -0400, Dan Licata wrote:

> Simon PJ and I are implementing view patterns, a way of pattern matching
> against abstract datatypes, in GHC.  Our design is described here:
>
> http://hackage.haskell.org/trac/ghc/wiki/ViewPatterns

I have to agree.  Great work here, though I'm extremely dubious about
the utility of the "Maybe" patterns.

One important issue.

    "We should be able to give clear rules for when the avoidance
    of repeat computation is guaranteed."

This, for me, is a show stopper.  I really want to see these "clear rules".

Cheers,
Andrew Bromage