An Dispair Phenomenon-Compliers Fail to Implement "Separation Moedl of Function Template"

 Most complier fail to implement the compliing mechnisam of function template-separation model, include g++,v s2008. Follow is my test code.

in "separation_model.h"

#if !defined(SEPARATION_MODEL)
#define SEPARATION_MODEL

template <class T>
T _max(T pf,T ps); 
#endif

in "separation_model.cpp"

#include "separation_model"

export template <class T>
T _max(T pf, T ps) ...{
    if (pf > ps) return pf;
    else return ps;
}

in test code "separetion_test.cpp"

#include "separation_model.h"

#include <iostream>

using namespace std;

int main(int argc, char *argv[])
...{
    cout << _max(10, 20) << endl;
    
    system("pause");
    return 0;
}