[Haskell] Views in Haskell

[Simon Peyton-Jones]

Dear Haskellers

Provoked by a discussion with Don Syme, and after some helpful conversations at POPL, I have finally written up a proposal for adding "view patterns" to Haskell.  We've wanted views for a long time, but they have never made it, into GHC at any rate.  This proposal is a very lightweight (and hence, I hope, cost-effective) proposal for a view-like mechanism.

        http://hackage.haskell.org/trac/haskell-prime/wiki/ViewPatterns

I'm thinking of implementing it in GHC, so I'd be interested in feedback of the form
        - how desirable is it to have a feature of this general form?
        - can this particular proposal be improved?

I've made it into a Wiki page on the Haskell Prime site.  It's probably premature to treat it as a serious contender for Haskell Prime (unless there is wild enthusiasm), because it hasn't been tried in practice yet, but that seems like the right forum to discuss it.

Discussion would best be directed via the open Haskell-Prime mailing list haskell-prime at haskell.org.
        http://haskell.org/mailman/listinfo/haskell-prime

Thanks

Simon