Re: Major type-class overhaul

16 Nov 2006

      Simon Peyton-Jones wrote:
...
3. Dictionaries are packaged in data constructors
...
This feature has been often requested, becuase it allows you to
package a dictionary into an ordinary (non-existential) data type, and
be able to use it.
Indeed, one can now simply reify class instances:

   data NumInst a where
     MkNumInst :: Num a => NumInst a

   intInst :: NumInst Int
   intInst = MkNumInst

   plus :: NumInst a -> a -> a -> a
   plus MkNumInst p q = p + q

Expect a whole new batch of type shenanigans from Oleg.

-- 
Ashley Yakeley
Seattle, WA