Question

#include <vector>

class A {
private:
    std::vector<int> v_;
public:
    A(int size = 100, int init_val = 100){
        for(int i=0; i<size; i++)
            v_.push_back(init_val);
    }
};

In the main, if I do:

A a(1000, 100);

What really happens? It is the first time I’ve seen hardcoded parameters in a constructor!

Answer 1

The passed values will simply replace default values of parameters with the passed ones.

• A definition A a; will result in call to A::A(100, 100)
• A definition A a(5); will result in call to A::A(5, 100)
• A definition A a(5, 6); will result in call to A::A(5, 6)