Hi Sebastiaan, I like your extensions of generalized booleans to other common Haskell types!
I also prefer using type families to fundeps. In this case I didn't because of some awkwardness with vector operations, but I'm going to try again. I'm confused about your particular fundep choice. For instance, class Bool f r | f -> r where bool :: r -> r -> f -> r false :: f true :: f Do you *really* mean that the boolean type f determines the value type r? Regards, - Conal On Tue, Jun 30, 2009 at 1:34 AM, Sebastiaan Visser <sfvis...@cs.uu.nl>wrote: > > On Jun 30, 2009, at 2:44 AM, Conal Elliott wrote: > >> I just uploaded a new package [1] for generalized booleans, which provides >> type classes with generalizations of boolean values & operations, >> if-then-else, Eq and Ord. These values & types come up for me with every >> new deep DSEL, and I think they do for others as well. The design space has >> some tricky trade-offs, and I'm not positive I've found the optimum yet. >> Users & comments are very welcome. Please direct discussion to the >> haskell-cafe list (rather than haskell list). >> > > Conal, > > Good work! > > Together with Tom Lokhorst I've been working on something very similar. > We've been using a rather consistent way of eliminating data structures that > scales well to other data types. Although we are also using functional > dependencies I think we might want to change them to type families. > > Examples: > >> class Bool f r | f -> r where >> bool :: r -> r -> f -> r >> false :: f >> true :: f >> >> class Maybe f a r | f -> a, f -> r where >> maybe :: r -> (a -> r) -> f a -> r >> nothing :: f a >> just :: a -> f a >> >> class Either f a b r | f -> a, f -> b, f -> r where >> either :: (a -> r) -> (b -> r) -> f a b -> r >> left :: a -> f a b >> right :: b -> f a b >> > Currently we have a very limited and somewhat messy code base on github[1] > which shows how to instantiate these types to get back the original Haskell > functionality and how to produce JavaScript code that runs in a browser. The > the JavaScript instance is very much the same as I used in my FRP to JS > EDSL[4]. Next target will, off course, be Objective C. :-) > Our code is not yet release worthy and probably never will be in this form. > But is would be very nice to see some kind of generalized prelude evolving. > > > [1]: http://hackage.haskell.org/cgi-bin/hackage-scripts/package/Boolean >> >> - Conal >> > > -- > Sebastiaan Visser > > [1] http://github.com/tomlokhorst/AwesomePrelude/tree/master > [2] http://github.com/sebastiaanvisser/frp-js > >
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