Re: [boost] boost::result_of and C++03

7 Apr 2008


      Anthony Williams:
...
"Peter Dimov" <pdimov@pdimov.com> writes:
...
Anthony Williams:
...
"Peter Dimov" <pdimov@pdimov.com> writes:
...
Eric Niebler:
...
Can you write what the identity function object would look like in
C++0x?
struct identity
{
    template<class A> A operator()( A && a ) const
    {
        return std::forward<A>( a );
    }
};
I guess.
No. That will convert lvalues to rvalues.
Try it.
I have, and it doesn't work.
With what compiler does it not work? Can you post the example program?
...
Besides, you can see in the signature: it returns "A" by value.
There's a special deduction rule for A&&, where A is a template parameter: 
when passed an lvalue of type T, A is deduced as T& and not as T. So in this 
case operator() returns a T& "by value".