On 3 February 2011 21:09, Patrick Browne
Hi, I am studying type classes using examples from the literature [1]. The attached code is a formalization of basic object oriented ideas. The particular approach seems to be built on the concepts of: thing, object, and identifier. I have no intension to implement anything or significantly change the code below. Rather, I am trying to understand the code as it stands. I include a number of test runs which seem OK, but I cannot get the *obj* function to work.
obj :: t -> i -> o t i obj t i = Obj t i
The type signature says "Given any `t' and any `i', this will return any `o t i' (for some unspecified type `o')". However, your actual implementation uses a specific data-type, namely Object for `o'. Change the type signature to be "obj :: t -> i -> Object t i". -- Ivan Lazar Miljenovic Ivan.Miljenovic@gmail.com IvanMiljenovic.wordpress.com