#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!
The passed values will simply replace default values of parameters with the passed ones.
A a; will result in call to A::A(100, 100)A a(5); will result in call to A::A(5, 100)A a(5, 6); will result in call to A::A(5, 6)Those aren't "hardcoded", just default parameters. If you don't supply the parameters, then size defaults to 100, and init_val to 100. Parameters that you do supply override the defaults. Hence:
A a1(); // size = 100, init_val = 100
A a2(1000); // size = 1000, init_val = 100
A a3(1000, 1000); // size = 1000, init_val = 1000
The declaration
A(int size = 100, int init_val = 100)
does not define "hardcoded parameters", but rather default values. If you call A::A() leaving the parameters away, the compiler will use the default values. That's all there is to it.
Default values of constructor parameters(and content accordingly).