/*
	Evan Golub - 2004 - egolub@acm.org
*/


#include <GL/glut.h>
#include <math.h>
#include <iostream.h>


float radius;  //Global variable - Eeek!


void MyDisplay()
{
	glClear(GL_COLOR_BUFFER_BIT);

	glColor3f(1.0, 1.0, 1.0);
	glBegin(GL_LINES);
	glVertex2f(-1,0);  glVertex2f(1,0);
	glVertex2f(0,-1);  glVertex2f(0,1);
	glEnd();


	glColor3f(0.0, 0.0, 1.0);
	glBegin(GL_LINE_LOOP);
	glVertex2f(0,0);
	glVertex2f(0,0.5);
	glVertex2f(0.5,0.5);
	glVertex2f(0.5,0);
	glEnd();


	glColor3f(1.0, 0.5, 0.0);
	glPointSize(4);
	glBegin(GL_POINTS);
	glVertex2f(0,0);
	glEnd();


	glColor3f(1.0, 0.5, 0.75);
	glBegin(GL_LINE_LOOP);
	float angle;
	int numberOfSegments = 100;
	float PI = 3.141592;
         for(int i = 0; i < numberOfSegments; i++){
		angle = i*2*PI/numberOfSegments;
		glVertex2f(radius*cos(angle),radius*sin(angle));
	}
	glEnd();


	//glFlush();
	glutSwapBuffers();

}

int main(int argc, char **argv) {

	glutInit(&argc, argv);
	glutInitDisplayMode(GLUT_DOUBLE);
    	glutInitWindowSize(100,100);
    	glutCreateWindow("Test App");

	cout << "Enter a floating point value between 0 and 1 for the radius of the circle: ";
	cin >> radius;
	if ((radius < 0) || (radius > 1)) radius = 0.5;

	glutDisplayFunc(MyDisplay);

	glutMainLoop();
}