Use assert to check : assert « Development « C++ Tutorial

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3. assert

#include <iostream>
#include <cassert>
#include <deque>
#include <algorithm>  // For find
using namespace std;


int main()
{
  char x[5] = {'a', 'r', 'e', 'q', 't'};

  deque<char> deque1(&x[0], &x[5]);

  // Search for the first occurrence of the letter e:
  deque<char>::iterator where = find(deque1.begin(), deque1.end(), 'e');

  assert (*where == 'e' );
  cout << "Ok." << endl;
  return 0;
}

Ok.