C++ : &(std::cout) as template argument

Question

Why isn\'t it possible to pass std::cout\'s address as template argument? Or if it is possible then how?

Here is what I tried:

#include          


        

Answer 1

Before C++17 removed this restriction, the syntactic form of a template argument for a pointer or reference template parameter was restricted. N4140 [temp.arg.nontype]/1.3 says that it must be

expressed (ignoring parentheses) as & id-expression, where the id-expression is the name of an object or function, except that the & may be omitted if the name refers to a function or array and shall be omitted if the corresponding template-parameter is a reference

(std::cout) isn't an id-expression. It's a primary-expression.

The "(ignoring parentheses)" part was added by Core issue 773, and is apparently meant to permit (&i), not &(i).