Question

If I enable double and integer only, then it is 4 functions. But I want to enable all data types (int long float double unsigned numbers etc.) How is it possible?

#include <iostream>

using namespace std;

double diff(int num1, int num2) {
    return double(num1-num2);
}

double diff(int num1, double num2) {
    return double(num1)-num2;
}

double diff(double num1, int num2) {
    return num1-double(num2);
}

double diff(double num1, double num2) {
    return num1-num2;
}

int main() {
    int a = 10;
    double b = 4.4;
    cout << diff(a, b) << endl;
    return 0;
}

Answer 1

template <typename T, typename U>
double diff(T a, U b) {
    return a - b;
}

You don’t need the cast to double — this is done for you if either argument is a double, and during return when both are integers. However,

double diff(double a, double b);

can be called with int arguments as well.