Re: plus( 2, 3 )

From:

ram@zedat.fu-berlin.de (Stefan Ram)

Newsgroups:

comp.lang.c++

Date:

30 Mar 2014 22:24:05 GMT

Message-ID:

<plus-20140331002122@ram.dialup.fu-berlin.de>

Ian Collins <ian-news@hotmail.com> writes:

The use the superfluous form "::std"?

  The following program prints ?example?.

#include <iostream>
#include <ostream>

namespace alpha
{ namespace std {} void example() { ::std::cout << "example\n"; }}

int main(){ ::alpha::example(); }

  I believe it will not do so anymore when ?::std? is replaced
  by ?std?. This is because

      ?std? means ?any nearby namespace "std"?, while
      ?::std? means ?the famous standard namespace "std"?.

  Since I wanted to refer to the standard namespace in this
  case, I chose ?::std?.

I don't think std::plus is intended to be used in the way you want, it
is designed for use in algorithms. Anyway, how about:
template <typename T> T
plus( const T& x, const T& y ) {return std::plus<T>()( x, y ); }
int main(){ std::cout << plus( 2, 3 )<< '\n'; }

  Thanks! That helped me to find what I was looking for:

#include <iostream>
#include <ostream>
#include <functional>

int main(){ std::cout << ::std::plus< int >()( 2, 3 )<< '\n'; }

  . I thought that I had tried this one before I send my post,
  but I must have gotten some detail wrong.