Ambiguos Types

Hi, I have 2 questions: 1- When I load the following module: module Foo() where default (Float) into ghci. 2+3 gives (5::Integer). Should it not give (5.0::Float). Hugs does. 2. class Op a where (%+) :: a -> a -> a instance Op Integer where (%+) = (+) with the above code: (2 %+ 3) should be resolved to Integer type. Could anybody explain why it should not. Thanks, S