std::enable_if and std::is_same minimal example

Also see std::enable_if minimal example and std::enable_if and std::is_floating_point minimal example

Example for a template function that is only enabled if the template argument T is a double using std::enable_if and std::is_same:

template<typename T, typename std::enable_if<std::is_same<T, double>::value>::type* = nullptr> 
T mySineDoubleOnly(T arg) {
    return sin(arg);
}

Full example:

#include <iostream>
#include <type_traits>
#include <cmath>

using std::cout;
using std::endl;

template<typename T>
T mySine(T arg) {
    return sin(arg);
}

template<typename T, typename std::enable_if<std::is_same<T, double>::value>::type* = nullptr> 
T mySineDoubleOnly(T arg) {
    return sin(arg);
}

int main() {
    cout << mySine(1.5) << endl;
    // mySine(1) will work
    // mySineDoubleOnly(1) will fail to compile
    cout << mySineDoubleOnly(1.5) << endl;
}