template_specialization_location_matters.cpp

// The place of definition of template explicit specialization matters!
// The Dimov/Abrahams Example
// http://www.gotw.ca/publications/mill17.htm

#include <iostream>

template <class T> // (a) a base template
void f(T) {
    std::cout << "void f(T)\n";
}

template <class T> // (b) a second base template, overloads (a)
void f(T*)         //     (function templates can't be partially
                   //     specialized; they overload instead)
{
    std::cout << "void f(T*)\n";
}

template <> // (c) explicit specialization of (b)
void f<>(int*) {
    std::cout << "void f<>(int*)\n";
}

int main() {
    int* p = nullptr;
    f(p); // calls (c);
          // Note: switching the order of (b) with (c) will result in calling
    // f(T*), since f<>(int*) will be seen as an explicit specialization of (a)
}