Re: [Boost-users] Re: Re: Re: result_of tutorial

Ian McCulloch wrote:

Peter Dimov wrote:

...

Ian McCulloch wrote:

...

Yes, if you want to forward to a function but you don't know if it takes arguments by value or const reference.

It doesn't matter. When you forward, you pass to result_of the exact types of the arguments you are supplying in the function (object) call, with a reference when the argument is an lvalue.

int x; long y; int const z; int g(); int & h();

f(x, y); // result_of f(1, x); // result_of f(z, 4); // result_of f( g(), h() ); // result_of

What is 'f' and how it takes its arguments in the cases above does not affect how result_of is used.

But what happens if F doesn't have an operator() overload that takes F(int const&, int) but only has F(int, int) ? It seems you need to know this in advance.

No, you don't have to know this in advance. It is up to the implementation or specialization of result_of to handle these cases and return the correct result.