Awesome, thank you. :-) One more question out of pure curiosity, if you have the time: What is allowing you to keep them in? I thought that the problem was that they made a mess that touched every party of the type checker rather than being centralized in one place. Was there a trick you discovered that now allows you to support them without creating such a mess? Cheers, Greg On 11/19/10 11:45 AM, Simon Peyton-Jones wrote:
Yes, impredicative types are still in, but in a simpler form than before, along the lines of QML http://research.microsoft.com/en-us/um/people/crusso/qml/
I have been too busy with getting the new type checker working to describe or document it. Notably, I have not yet added syntax for QML's rigid type annotations, which leads to a loss of expressive power.
too much to do!
Bottom line: if you are interested in impredicative polymorphism, let me know. A good way to do so would be to register your interest on http://hackage.haskell.org/trac/ghc/ticket/4295 Just add your email address to the cc list, *and* write a comment giving an example of how you are using impredicative poly, and pointing to any further info. That'll help motivate me to do the remaining work!
Thanks
Simon
| -----Original Message----- | From: haskell-cafe-bounces@haskell.org [mailto:haskell-cafe-bounces@haskell.org] | On Behalf Of Gregory Crosswhite | Sent: 19 November 2010 19:23 | To: Haskell Cafe | Subject: [Haskell-cafe] Impredicative Types | | Hey everyone! I haven't had a chance to try out GHC 7 myself, but I saw | in the documentation that Impredicative Types are still supported. Is | this true? I thought that they were on their way out because they | overcomplicated type checking; has this plan been changed? | | Cheers, | Greg | _______________________________________________ | Haskell-Cafe mailing list | Haskell-Cafe@haskell.org | http://www.haskell.org/mailman/listinfo/haskell-cafe