std::enable_if minimal example

Also seeĀ std::enable_if and std::is_floating_point minimal example andĀ std::enable_if and std::is_same minimal example

Let’s say you have a template function:

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

Now you want to enable this function only if T is a floating point number (i.e. no integer!). Use std::enable_if like this:

template<typename T, typename std::enable_if<std::is_floating_point<T>::value>::type* = nullptr> 
T mySineFloatingPointOnly(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_floating_point<T>::value>::type* = nullptr> 
T mySineFloatingPointOnly(T arg) {
    return sin(arg);
}

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