Vector clear vs. resize

Question

I read on the Internet that if you are clearing a std::vector repetitively (in a tight loop), it might be better to use resize(0) instead of

Answer 1

There appears to be a difference between clear and resize(0) when the vector contains objects of a class that does not have a default constructor. For example, the following code will compile:

#include 

class A {
private:
    int x,y;
public:
    A(int x,int y) :x(x), y(y) {}
};

int main() {
  std::vector  aa;

  aa.clear();
}

But if you substitute the aa.clear() by aa.resize(0), you get compilation error:

error: no matching function for call to 'A::A()'