Circle2D class question

[kraigballa]

For part A the default center of the circle is (0,0) as declared by the constructor and the formula I use to calculate the distance from center to the specified point. So the x and y that the user enters is the actual point either inside, upon, or outside the circle.

[3hM2Nwbp]

#include <iostream>
#include <string>
#include "circle.h"
#include <cmath>
#include <iomanip>

using namespace std;

int main()
{
  Circle2D myCircle;     // Instantiate myCircle object
  double radius;
  double x;
  double y;
  char again;
  
  do
  {  
     cout << "This program will display whether or not the point and radius you specify are inside, outside, or upon the circle.\n";
	 /*cout << "Enter the radius: ";
	 cin >> radius;
	 myCircle.setRadius(radius);
	 cout << "\nEnter the x point: ";
	 cin >> x;
	 myCircle.setx(x);
	 cout << "\nEnter the y point: ";
	 cin >> y;
	 myCircle.setx(y); //should be sety(y) - that's why this->x was giving you the Y coordinate :-)
         So let's not set x or y on the circle and use the x and y points as the test points, leaving
         the circle's coordinates at (0, 0) with radius 1
         */

         cout << "\nEnter the X point: ";
         cin >> x;
         cout << "\nEnter the Y point: ";
         cin >> y;

	 // Display the results of the function contain

	 if (myCircle.contains(x, y) == true)
		 cout << "Your point is inside the circle.";
	 else
		 cout << "Your point is outside the circle.";


     cout << "\n\nWant to try again? (Y/N) ";
     cin >> again;
 
  }while(toupper(again) == 'Y');

  return 0;
}    

That should give you the expected result :)

There were a few logic problems, the first being setx(y) instead of sety(y), and the second being using the x and y inputs to change the circle you're testing.

[kraigballa]

Oh I get what you mean. By having setx(x) I am telling the object that "x" which is the center is now set to whatever they input. So in order to keep it as the default I need to not set x or y, but rather use the input directly with the function contains. I do need to keep setRadius though.

Now for part B. Here is a sample piece of code I made...am I at least on the right track?

int main()
{
  Circle2D myCircle;     // Instantiate myCircle object
  Circle2D myCircle2;   // for the first circle
  Circle2D myCircle3;   // for the second circle
  double radius;
  double x;
  double y;
  char again;
  
  do
  {  
     cout << "This program will display whether or not the point and radius you specify are inside, outside, or upon the circle.\n";

	 // The radius of default circle and a  point (x,y)..For part A
	 cout << "Enter the radius: ";
	 cin >> radius;
	 myCircle.setRadius(radius);
	 cout << "Enter the x point: ";
	 cin >> x;
	 cout << "Enter the y point: ";
	 cin >> y;

		 // Display the results of the function contain

	 if (myCircle.contains(x, y)) // No need to put true as the it is the default
		 cout << "Your point is inside the circle.";
	 else
		 cout << "Your point is outside the circle.";


	 // The first circle--For part B
	 cout << "\nEnter the radius: ";
	 cin >> radius;
	 myCircle2.setRadius(radius);
	 cout << "Enter the x coordinate for the center of circle 1: ";
	 cin >> x;
	 myCircle2.setx(x);
	 cout << "Enter the y coordinate for the center of circle 1: ";
	 cin >> y;
	 myCircle2.sety(y);

	 // The second circle--For part B
	 cout << "\nEnter the radius: ";
	 cin >> radius;
	 myCircle3.setRadius(radius);
	 cout << "Enter the x coordinate for the center of circle 2: ";
	 cin >> x;
	 myCircle3.setx(x);
	 cout << "Enter the y coordinate for the center of circle 2: ";
	 cin >> y;
	 myCircle3.sety(y);

	 // Display the results of the function contain

	 if (myCircle2.contains(myCircle3))
		 cout << "Circle 2 is inside of circle 1.";
	 else
		 cout << "Circle 2 is outside of circle 1.";


     cout << "\n\nWant to try again? (Y/N) ";
     cin >> again;
 
  }while(toupper(again) == 'Y');

  return 0;
}  

[3hM2Nwbp]

Yes, that code looks good. Now for the method Circle2D::contains(const Circle2D& otherCircle) method. I'm not sure if the class you're taking has covered const-correctness yet, but it's a good practice. If you haven't gotten to that yet, Circle2D::contains(Circle2D& otherCircle) works just as well in this academic case. Let me know if you need some help with the logic behind the circle-inside-circle part.

[kraigballa]

Yes, we did go over const but I'm not sure which class objects to use them on. Also since I use setx(x) and sety(y) for both objects (myCircle2 and myCircle3) will myCircle3 overwrite myCircle2?

How do I get the values for both objects (myCircle2 and myCircle3)? I can see how to get one...but both without overwriting I'm not sure.

bool Circle2D::contains(Circle2D &myCircle)
{
double pointX = x;
double pointY = y;
double circleRadius = radius;

// What next?
}

Thanks a lot for the help!!

[3hM2Nwbp]

Alright, we'll have 6 pieces of information for finding if a circle is inside another one; the radius, x, and y of each circle. The math is nearly the same as bool Circle2D::contains(double x, double y)

bool Circle2D::contains(Circle2D& otherCircle)
{
  //otherCircle.getradius() - Info 1
  //otherCircle.getx()        - Info 2
  //otherCircle.gety()        - Info 3
  //this->getradius()             - Info 4
  //this->getx()               - Info 5
  //this->gety()               - Info 6
  /*
    The distance between the centers of the circles plus the radius of 'otherCircle'
    must be less than the radius of `this` circle for 'otherCircle' to be inside `this` circle.
  */
}

[kraigballa]

What is otherCircle, and what does this-> point to? I would think that it would be...

bool Circle2D::contains(Circle2D& otherCircle)
{
  //myCircle2.getradius() - Info 1
  //myCircle2.getx()        - Info 2
  //myCircle2.gety()        - Info 3
  //myCircle3.getradius()             - Info 4
  //myCircle3.getx()               - Info 5
  //myCircle3.gety()               - Info 6
  /*
    The distance between the centers of the circles plus the radius of 'otherCircle'
    must be less than the radius of `this` circle for 'otherCircle' to be inside `this` circle.
  */
}

[3hM2Nwbp]

Consider the following code

Circle2D myCircle2;
Circle2D myCircle3;
myCircle2.contains(myCircle3); //Inside the method, myCircle2 is pointed at by `this`, and myCircle3 is 'otherCircle'
//Think of it as this method being 'inside' of myCircle2, and referring to itself as `this`

//Now this code
Circle2D myCircle2
Circle2D myCircle3
myCircle3.contains(myCircle2); //Inside the method, myCircle3 is pointed at by `this`, and myCircle2 is 'otherCircle' 

[kraigballa]

Ah I see...so 'this' points to the object that is being used rather than the parameters of the function it is performing. And the parameters are passed like any other...

Do I need to perform the 'sets' for these objects, or just do it inside of the member function section? For instance:

 // The first circle--For part B
	 cout << "\nEnter the radius: ";
	 cin >> radius;
	 myCircle2.setRadius(radius);
	 cout << "Enter the x coordinate for the center of circle 1: ";
	 cin >> x;
	 myCircle2.setx(x);
	 cout << "Enter the y coordinate for the center of circle 1: ";
	 cin >> y;
	 myCircle2.sety(y);

	 // The second circle--For part B
	 cout << "\nEnter the radius: ";
	 cin >> radius;
	 myCircle3.setRadius(radius);
	 cout << "Enter the x coordinate for the center of circle 2: ";
	 cin >> x;
	 myCircle3.setx(x);
	 cout << "Enter the y coordinate for the center of circle 2: ";
	 cin >> y;
	 myCircle3.sety(y);