template关键字的一个特殊用法

#include <iostream>

struct T1
{
T1() : value(0) { }
const int value;
};

struct T2
{
template <int N>
int value(int n) const
{
return(N + n);
}
};

template <typename T>
int func1(const T & t)
{
/* same as: return((t.value < 3) > 5); */
return(t.value<3>(5));
}

template <typename T>
int func2(const T & t)
{
/* call member template function of T */
return(t. template value<3>(5));
}

int main(int argc, char * argv[])
{
T1 t1;
T2 t2;

std::cout << (t1.value<3>(5)) << std::endl;
std::cout << (t2.value<3>(5)) << std::endl;

std::cout << func1(t1) << std::endl;
//  std::cout << func1(t2) << std::endl; // error

//  std::cout << func2(t1) << std::endl; // error
std::cout << func2(t2) << std::endl;

return(0);
}

obj.template mem_template_func<arg_type>(args);