2009/10/8 Cristiano Paris <fr...@theshire.org>: > On Thu, Oct 8, 2009 at 12:48 PM, Lennart Augustsson > <lenn...@augustsson.net> wrote: >> The reason a gets a single type is the monomorphism restriction (read >> the report). >> Using NoMonomorphismRestriction your example with a works fine. > > Could you explain why, under NoMonomorphismRestriction, this typechecks: > > let a = 1 in (a + (1 :: Int),a + (1 :: Float)) > > while this not: > > foo :: Num a => a -> (Int,Float) > foo k = (k + (1 :: Int), k + (1.0 :: Float))
I think it is the same thing that my (\f -> f f True) question, i.e. the polymorphism of k is fixed inside foo (you don't want that). So I guess using the rank-2 types and the corresponding type annotation to keep k polymorph should work. In other words, foo is polymorph on k but k is not polymorph when given to foo in a specific application. Thu _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
