Re: static or not?
* kwikius:
On Jan 29, 12:14 pm, "Alf P. Steinbach" <al...@start.no> wrote:
kwikius wrote :
<...>
Could add that its an unnecessary requirement AFAICS. (Perhaps the
return type was changed from value to const reference at some point.)
#include <algorithm>
#include <iostream>
struct my{
explicit my (double v_in) : v (v_in){};
double v;
private :
my ( my const &);
};
inline bool operator <
(my const & lhs, my const & rhs)
{
return lhs.v < rhs.v;
}
int main()
{
my x(1),y(2);
my const & r = std::min(x,y);
Consider instead
my const& r = std::min( x, my(2) );
Ouch. hang about. But what difference does it make whether the
arguments are copy constructible or not?
A class type rvalue passed as actual argument to T const& formal
argument must have an accessible copy constructor (formally), per the
current standard, because the implementation is free to create a new
temporary, or any number of temporaries, and pass reference to that.
Or is the result r referencing a temporary copied from one of the
inputs or what?
Would depend on the implementation, if it accepted the code.
With some copyable type the above example (with arguments transposed to
yield reference to temporary as std::min result) would just be UB.
Cheers,
- Alf
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