Officially, what is typename for?

Question

On occasion I\'ve seen some really indecipherable error messages spit out by gcc when using templates... Specifically, I\'ve had problems where seemingly correc

Answer 1

#include 

class A {
public:
    typedef int my_t;
};

template 
class B {
public:
    // T::my_t *ptr; // It will produce compilation error
    typename T::my_t *ptr; // It will output 5
};

int main() {
    B b;
    int my_int = 5;
    b.ptr = &my_int;
    std::cout << *b.ptr;
    std::cin.ignore();
    return 0;
}