Should the functor instances be allowed to be passed to register_function?

[bananu7]

Example functor:

template<typename A>
struct void_unary {
    void operator()(A a) { }
};

This is probably a low priority issue, but I've been wondering if we will ever want to support those. Right now the workaround is obviously to use a lambda wrapper.

[ghost]

I assumed if lambdas worked, then regular (not templates) functors would too. As for templates, I think we should ask the caller so supply a list of types to instianciate the functor with, and dispatch the overloads afterwards? Would your type generator work in that kind of case?