David Abrahams wrote:
Hi,
I know we've discussed this in the past, but did we ever settle on an interface for deducing the return and parameter types of function (object)s? Doug G.'s result_of<F(a,b)> template works for return types, but it's not very portable and is not even in Boost proper AFAIK. Many function objects and all function pointers have specific (non-templated) parameter types, and it would be extremely valuable to be able to deduce those as well.
It's hard to believe that with all the functional programming libraries we have, there's no standardized facility for this sort of deduction.
I'm joining this thread slightly late but nonetheless, this is on my wish-list too and I've got code right now that would greatly benefit from standardized return type deduction. What I want to add to the discussion is that I believe we need _two_ versions of return_type (or whatever we choose to call it). Even though I like the power and syntax of the result_of<F(a,b)>, I'd say it's not unreasonable to be in a situation where the argument types (if any) simply aren't know. In such cases a plain return_type<F> that would atleast make an "educated guess" would be better than nothing. Just my 2c // Fredrik Blomqvist