lst-0038-book.cpp
// https://godbolt.org/z/dMvqG85fr
double add(double a, double b) { return a + b; }
double add(int, int) = delete; // prohibit add(3,4)
// https://godbolt.org/z/dMvqG85fr
double add(double a, double b) { return a + b; }
double add(int, int) = delete; // prohibit add(3,4)