On Thu, Jun 17, 2004 at 06:03:31PM -0400, David Menendez wrote:
Stefan Holdermans writes:
Well, you've just identified the well-known trade-off between abstraction and induction. A language extension involving 'views' [4, 1, 3] has been proposed [2] to deal with this issue.
That proposal for views is eight years old. Has there been any movement towards implementing it? Did some technical obsticle arise, or have people simply been busy elsewhere?
I think it was a couple things, Pattern guards were introduced which were conceptually a whole lot simpler and provided a way to do many of the things views did. http://research.microsoft.com/~simonpj/Haskell/guards.html The other thing is that it is unclear whether they are a good idea, I mean, they would probably be useful to some, but as extensions go, they would be a pretty radical change to the language. Many consider the simplicity and consistancy of pattern matching a virtue. Also, the views proposal is 8 years old, I don't know if anyone has thought much about how they would interact with all the other generally accepted language extensions that have happened in the meantime. I think the moral is, don't hold your breath. and learn pattern guards, they are a really really useful and universal extension to the language. John -- John Meacham - ⑆repetae.net⑆john⑈