Demonstrating STL vector constructors with a user-defined type and showing copying explicitly

   
 

#include <iostream>
#include <cassert>
#include <vector>
using namespace std;

class MyClass {
public:
  unsigned long id;
  unsigned long generation;
  static unsigned long total_copies;

  MyClass() : id(0), generation(0) { }

  MyClass(unsigned long n) : id(n), generation(0) { }

  MyClass(const MyClass& z) : id(z.id), generation(z.generation + 1) {
    ++total_copies;
  }
};

bool operator==(const MyClass& x, const MyClass& y)
{
  return x.id == y.id;
}

bool operator!=(const MyClass& x, const MyClass& y)
{
  return x.id != y.id;
}

unsigned long MyClass::total_copies = 0;

int main()
{
  vector<MyClass> vector1, vector2(3);

  assert (vector1.size() == 0);
  assert (vector2.size() == 3);

  assert (vector2[0] == MyClass() && vector2[1] == MyClass() &&
          vector2[2] == MyClass());

  for (int i = 0; i != 3; ++i)
    cout << "vector2[" << i << "].generation: " << vector2[i].generation << endl;

  cout << "Total copies: " << MyClass::total_copies << endl;
  return 0;
}

/* 
vector2[0].generation: 1
vector2[1].generation: 1
vector2[2].generation: 1
Total copies: 3

 */

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Demonstrating STL vector constructors with a user-defined type and showing copying explicitly : vector « Vector « C++

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