[jerf]

You have to specify the language; there's no (useful) definition of type classes and interfaces outside of the context of a specific language that is specific enough to make reliable comparisons.

If you mean "Are Haskell type classes equivalent to Go interfaces?", the answer is no, Haskell type classes are substantially more powerful, even before you start turning on extensions. For instance, "Go" can not express the Monad typeclass at all.

[bunderbunder]

I was more thinking Haskell type classes vs. C# or Java interfaces. They're a bit more powerful than Go interfaces because they can be used in combination with generics.

[jerf]

The Monad type class is a pretty good test. Last I knew it wasn't properly expressible in C# or Java either in the fully general sense, though you can get closer than Go, certainly. Whether it gets close enough that you can call it "done" is a bit of a judgment call; in the end, the semantics are never quite identical even in the best of cases.