To my letter on Haskell-2 with >>Remark and question on the ambiguity problem >>M.Jones & S.P.Jones paper "...Exploration of Design Space." Dominic Duggan <[EMAIL PROTECTED]> writes >E. Meijer is also an author of this paper. I am sorry. >Matrix multiplication: * :: Matrix a -> Matrix b -> Matrix c > >does not satisfy the single-argument restriction, or even >its generalization to an n-argument restriction. >What happens if M1 :: Matrix Int and I type: M2 = M1 * M1 * M1 > >I get: Mult (Matrix Int) (Matrix Int) a, Mult a (Matrix Int) b => b > >and type-checking fails due to ambiguity. You have to say: > >M2 = ((((M1 * M1) :: (Matrix Int)) * M1) :: (Matrix Int)) > >[...] Could you explain all this? Are you considering the program class Mult a b c where (*) :: a -> b -> c instance ...=> Mult (Matrix a) (Matrix b) (Matrix c) where (*) = ... f = let m1 =...:: Matrix Int in (m1*m1)*m1 ? Or maybe, `*' is a type constructor? In Haskell `M1',`M2' cannot denote a value. `m1',`m2' can. And the question was of the ambiguity of a class operation definition. ------------------ Sergey Mechveliani [EMAIL PROTECTED]
