Stjepan Rajko wrote:
[comes to a screeching halt from changing code]
Yep. :-)
I'm still not entirely on very sure footing when it comes to rvalues and lvalues, so can I bother you with a practical clarification?
So, if I have, say, a function object with operator()(int &), I should specify result<F(int &)>, (but maybe if I have operator()(const int &), or operator()(int), I can specify result<F(int)>?)
If you have operator()( int& ), you need result<F(int&)>. If you have operator()( int ), you need both result<F(int)> and result<F(int&)> because your operator() can take either an lvalue or an rvalue. In this simple case you can just provide result_type, of course. You are allowed to provide result<F(int)> in addition to result<F(int&)> even in the first case; failing invalid queries is not required. What this means in practice is that in 99% of the cases you just need to strip the reference from the argument types when providing result or a result_of specialization. Only odd function objects such as struct F { int operator()( int& ); void operator()( long ); }; need special handling.