Int template member function within a template class

Question

Duplicate question of this.

I have a class like this:

template <class T>
class foo {
public:        

    foo(){}

    template <int S>
    void bar (){}

}

If this class is called with:

int main(){
    foo<float> m;
    m.bar<1>();
}

It gives the error:

error: expected primary-expression before ')' token

deprecated again:

My code is:

#define BOOST_TEST_DYN_LINK
#define BOOST_TEST_MAIN

#include <boost/mpl/list.hpp>
#include <boost/test/unit_test.hpp>
#include <boost/test/test_case_template.hpp>
using namespace boost::unit_test;

#include "foo.hpp"

BOOST_AUTO_TEST_SUITE();

typedef boost::mpl::list<char, int> test_types;

BOOST_AUTO_TEST_CASE_TEMPLATE(test_Mat_constructor_hwd, T, test_types){

    foo<T> m;
    m.bar<1>();
}

BOOST_AUTO_TEST_SUITE_END()

This however does not compile as the BOOST_AUTO_TEST_CASE_TEMPLATE is doing something weird...

Following text is deprecated:

However, when I call the function with:

foo f;
f.bar<1>();

I am getting the error:

A bound member function may only be called

If I however wrap the bar function into something like void bar1(){return bar<1>();}, it would work. I know if T is not known during compile time, it will not compile. But I don't know why the compiler is not smart enough to figure out the 1 in f.bar<1> is static?

thanks!

Answer 1

Because the T argument is unknown when parsing the test function, the compiler is unable to determine what the m.bar expression is, and therefore assumes it is a non-template variable. m.bar<1>() is therfore parsed as (m.bar<1)>(), the last bit being illegal. The fix is to explictly state that bar is a template:

foo<T> m;
m.template bar<1>();

Answer 2

you need to make the member functions public if you wish to call them externally, this works fine on my compiler

class foo {
public:
    foo(){}

    template <int T>
    void bar (){}
 };

int main(){
    foo f;
    f.bar<1>();
}