// CS 1621 Fall 2005
// Examples of conditional loops in C++ -- using pretest and posttest
// loops to emulate the other.

#include <iostream>
using namespace std;
int main()
{
     int value;  bool done = false;

     // Classic example where a posttest loop applies -- error checking
     // user input
     do
     {
          cout << "Enter a positive integer: " << endl;
          cin >> value;
          if (value > 0) done = true;
     } while (!done);
     cout << "Thanks for your input of " << value << endl;

     // Pretest loop to simulate posttest loop.  Note that we "rig" the
     // condition initially so that it will definitely be true. Once the
     // first iteration has occurred, the condition can be true or false.
     // This example could also be done without the bool variable.
     done = false;
     while (!done)
     {
          cout << "Enter a positive integer: " << endl;
          cin >> value;
          if (value > 0) done = true;
     }
     cout << "Thanks for your input of " << value << endl;

     // Classic example of a pretest loop -- user enters a sequence of data,
     // any of which (including the first) could be a sentinel value,
     // terminating the loop.
     cout << "Please enter a sequence of positive integers (<= 0 to quit)" << endl;
     cin >> value;
     while (value > 0)
     {
          cout << "The current value is " << value << endl;
          cout << "Please enter the next value (<= 0 to quit)" << endl;
          cin >> value;
     }
     cout << "Your sequence is finished" << endl;
     
     // Posttest loop to simulate pretest loop.  Now we have to test the
     // condition before entering the loop, using an if statement.  This
     // allows for the possibility of 0 iterations.
     cout << "Please enter a sequence of positive integers (<= 0 to quit)" << endl;
     cin >> value;
     if (value > 0)
     {
          do
          {
               cout << "The current value is " << value << endl;
               cout << "Please enter the next value (<= 0 to quit)" << endl;
               cin >> value;
          } while (value > 0);
     }
     cout << "Your sequence is finished" << endl;
}