//----------------------------------------------------------------
//
// point6.cpp
//
// written by: Simon Parsons
// modified  : 17th October 2007
//
// Illustrating the use of assert.
//
//----------------------------------------------------------------

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

//----------------------------------------------------------------
//
// Class definition

// Class point represents a location in a set of cartesian coordinates.
//
// It has two data members, an x and a y value, and three constructors.
// The constructors initialise the data members.
 
class point {

public:

  point() : x(0), y(0) { }	     // Default constructor
  point( double u ) : x(u), y(0) { } // Convert double to point
  point( double u, double v )        // Initialise both x and y if we are
    : x(u), y(v) { }                 // given values for them.

  void print() const;
  void set( double u, double v );

private:
  double x, y;
}; 

// Member functions of point. Print the values and set the values.

void point::print() const {
  cout << "(" << x << "," << y << ")\n";
} // end of print()
 
void point::set( double u, double v ) {
  assert(u > 0);                     // Here is where we use assert
  assert(v > 0);                     // to check for errors.
  x = u;
  y = v;
} // end of set()

//----------------------------------------------------------------
//
// The main program

// This creates three instances of point, creating them in different ways, and
// then printing out their contents.

int main() {
  point a;
  double p;
  double q;

  cout << "Enter an x-coordinate ";
  cin  >> p;
  cout << "Enter a y-coordinate ";
  cin  >> q;
  
  a.set( p, q );
  cout << "point a = ";
  a.print();

} // end of main()