Re: [Haskell-cafe] principle types

Vikrant wrote:

(map map)::[a -> b] -> [[a] -> [b]]

I am able to interpret the expressions "[a -> b] -> [[a] -> [b]]" vaguely...

does this mean that 'map map' takes list of functions of type (a->b) and returns list of functions of type ([a]->[b]) if yes ..how do I derive it from basic type declaration of map?

Think substitution. It helps if you distinguish the letters. Start by saying that one of the maps has type (c -> d) -> [c] -> [d]. Then substitute a =(c->d), b=[c] (I think it would be). Paul.