lst-0015-book.cpp
// https://godbolt.org/z/q4ov41cnv
#include <iostream>
double twice(double num) { // value parameter and return value
return num * 2.0;
}
int main() {
double num = 7.25;
num = twice(num); // change expressed by return value
std::cout << num << "\n"; // also 14.5
}