Bulat Ziganshin wrote:
Hello Brian,
Tuesday, August 22, 2006, 9:35:21 PM, you wrote:
I feel "if it ain't broken don't fix it", and not only is the existing syntax not broken, it's already (imho) absolutely perfect in it's clarity and consistency
it's because you not programmed a lot with type classes. if you start, you will soon realize that type signatures with classes are just unreadable. just look at sources of my streams library
copyStream :: (BlockStream h1, BlockStream h2, Integral size) => h1 -> h2 -> size -> IO () Here is another possible syntax, which wouldn't conflict with the existing syntax but could be used as a sugar: copyStream :: {BlockStream} h1 -> {BlockStream} h2 -> {Integral} size -> IO () The type variables could be optional if they are distinct (or not needed in the body) so you could write: copyStream :: {BlockStream} -> {BlockStream} -> {Integral} -> IO () The {} is needed to distinguish the use of classes from that of types, and also allows more than one constraint eg: foo :: (Num a, Bar a) => a -> a === foo :: {Num, Bar} a -> a (the constraint(s) just get written before the first occurrence of a given type variable), and it's even possible to represent constraints between type variables eg: foo :: Collection c a => a -> c === foo :: {Collection c} a -> c It's slightly more difficult to know how to represent the following: foo :: Collection c a => c -> c perhaps: foo :: {Collection * a} c -> c where the * represents the location of the variable in the constraint. Even a rank 2 type like: forall a. Num a => (forall b. (Coll b a, Ord b) => b a -> ()) -> () (forall b. {Coll * a, Ord}b {Num}a -> ()) -> () ie forall a. (forall b. ({Coll * a, Ord} b) ({Num} a) -> ()) -> () (It doesn't matter how nested the location of the constraints are since we'd just gather them up and use them to restrict the quantification for that variable) Anyway that's as far as I've got trying to think up alternative representations - the above may have some bug or problem with it but I'm half thinking of adding the above sugar to my editor (when I eventally get past all the low-level gui stuff I'm doing at the moment). Best regards, Brian. -- Logic empowers us and Love gives us purpose. Yet still phantoms restless for eras long past, congealed in the present in unthought forms, strive mightily unseen to destroy us. http://www.metamilk.com