Pass class with templated method as template parameter with GCC

Question

Is it possible to pass object of a class with templated method as a template parameter under GCC? All search I conducted pointed me to questions regarding templated class, which is not applicable in my case.

Sample code:

#include <iostream>

class Foo
{
public:
    template<typename T>
    void print(const T& arg) const
    {
        std::cout << arg << std::endl;
    }
};

template<typename A>
void print(const A& printer)
{
    printer.print<int>(1);
}

int main()
{
    Foo foo;
    print<Foo>(foo);
    return 0;
}

Compiling under MinGW.org GCC-6.3.0-1 I get the following results:

tmpl.cpp: In function 'void print(const A&)':
tmpl.cpp:16:19: error: expected primary-expression before 'int'
     printer.print<int>(1);
                   ^~~
tmpl.cpp:16:19: error: expected ';' before 'int'

VisualStudio compiles the same code cleanly, application works as expected. If I make print function not templated, so that is explicitly takes object of Foo it works as expected both compilers.

Answer 1

You need to use template keyword to tell that print is a template.

Inside a template definition, template can be used to declare that a dependent name is a template.

e.g.

template<typename A>
void print(const A& printer)
{
    printer.template print<int>(1);
    //      ~~~~~~~~
}

print is a dependent name, it depends on the template parameter A. Before the template gets instantiated the compiler knows nothing about A; so you need to add the template keyword to tell the compiler that print is a template, then the < after the name print is valid; otherwise < will be treated as the operator< then cause the error.

Answer 2

You need the template keyword in order to specify that print() is a template, like this:

printer.template print<int>(1);