How can I make a variable always equal to the result of some calculations?

Question

In math, if z = x + y / 2, then z will always change whenever we replace the value of x and y. Can we do that in programming

Answer 1

The closest you probably can get is to create a functor:

#include 

int main() {
    int x;
    int y;

    auto z = [&x, &y] { return x + y; }; // a lambda capturing x and y

    while(true) {
        std::cin >> x;
        std::cin >> y;
        std::cout << z() << "\n";
    }
}