David Tolpin wrote:
could you please point me to a reference (paper/note/something else) that explains that class constraint in a class definition is a guarantee with regard to a type declaration but a requirement with regard to an instance declaration?
Sebastian Sylvan wrote:
Well, I guess the H98 report would be a good start.
I'm not sure that is a good place to start. True, it is likely possible to deduce both of those facts from the Report. But the Report is a language spec. It assumes that you already know about the type system, and it is difficult to read if you don't.
...there are multiple tutorials on type classes that will cover this, most of which are available from haskell.org
That sounds like a much better idea. Any particular suggestions? Thanks, Yitz