I've looked at this page and some other documents since I wanted to implement type classes in Juniper (a FRP language for the Arduino). It turns out that the dictionary passing is only necessary if you want to support polymorphic recursion. In all other cases, the call to a function that is part of a type class can be monomorphized.
Hindley-Milner has problems with inferring types in the presence of polymorphic recursion, and a user provided type annotation is usually necessary. Polymorphic recursion does allow some cool things such as arbitrarily nested lists. This is a feature that users from a dynamically typed language might miss.
Hindley-Milner has problems with inferring types in the presence of polymorphic recursion, and a user provided type annotation is usually necessary. Polymorphic recursion does allow some cool things such as arbitrarily nested lists. This is a feature that users from a dynamically typed language might miss.