//----------------------------------------------------------------
//
// exception.cpp
//
// Illustrating the use of assert, try, catch and throw. We use our
// old familar point class.
//
// written by: Simon Parsons
// modified  : March 1st 2009
//
//----------------------------------------------------------------

#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);                // We overload the function set.
  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()
 

// Here's a version of set, with one argument, which uses assert.

void point::set(double u) {
  assert(u > 0);                     
  x = u;
  y = 0;
} // end of set()

// Here's a version of set, with two arguments, that uses an try, throw
// catch exception handler.

void point::set(double u, double v) {
  string str = "Everything is cool!";
  try{                             
    if(!(u > 0)){                   // Test for the exception. If 
      throw u;                      // there is a problem, correct it
    }                           
    else{
      x = u;                        // Else use the exception handling
      throw str;                    // mechanism to say everything is ok.
    }
  }

  catch(double u){                  // A catch to handle a double
    cout << "That value of x is no good" << endl;
    cout << "I'm setting x to zero" << endl;
    x = 0;
  }

  catch(string s){                  // A catch to handle a string.
    cout << s << endl;
  }

  y = v;                            // Now that we're done with error
                                    // handling, set y.
}  // 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. Zero or below will the assert ";
  cin  >> p;

  a.set(p);

  cout << "point a = ";
  a.print();

  cout << "Enter an x-coordinate. Zero or below will the exception handler ";
  cin  >> p;
  cout << "Enter a y-coordinate ";
  cin  >> q;
  
  a.set(p, q);

  cout << "now, point a = ";
  a.print();

} // end of main()