code snippets

test

// t.h
#include <iostream>

using namespace std;

template <typename T1, typename T2> 
class A { 
  public:
  void foo();
};

// t2.cpp
#include "t.h"

template<typename T1> 
class A<T1, int> {
  public:
  void foo() {
    cout << "T1, int" << endl;
  }
};

template<>
class A<int, int> {
  public:
  void foo() {
    cout << "int, int" << endl;
  }
};

template class A<float, int>;
template class A<int, int>;

// t.cpp
#include "t.h"

int main() {
  A<float, int> a;
  a.foo();  // no error
  A<int, int> a1; 
  a1.foo(); // undefined reference, why?
  return 0;
}