Hello Johannes, Tuesday, January 31, 2006, 5:34:44 PM, you wrote: JW> Bulat Ziganshin wrote:
instead of writing foo :: (Num a, Monad m) => a -> m () allow to write foo :: Num -> Monad ()
JW> as has been noted, that would be special treatment JW> for unary type classes with argument of kind *. not sure. multi-parameter type classes will be equivalent to parametric types: class (Monad m) => Stream m h ... foo :: Stream m h -> m () equals to foo :: (Stream m h) => h -> m () JW> Also, *if* we want such a shorthand, it is not clear whether we want JW> existential or forall typing per default. Referring to your example, JW> the "foo" function must be able to return a value in *each* monad JW> that the caller specifies at the call site, while we were discussing JW> functions that make their own choice of returning *some* monad instance. *i* mean just syntax sugar, short-hand for existing forall declarations, which i'm using a lot just now btw, on the http://haskell.galois.com/trac/haskell-prime/wiki/PartialTypeSigs author mean using underscore for "(exists a . a)" types -- Best regards, Bulat mailto:bulatz@HotPOP.com