#include <GL/glut.h>
#include <stdio.h>
#include <stdlib.h>

#define RND ((float)rand( )/RAND_MAX)

#define True  1
#define False 0
#define WINSIZE 500
#define ROWSIZE 2000

void display(void);
void idle(void);
void init(void);
int  main(int argc, char** argv);

float j;
int row[ROWSIZE], old_row[ROWSIZE];

int rule(int left, int top, int right)
{
    if(!left & (top | right))
    {
        return True;
    }
    else if(left & !top & !right)
    {
        return True;
    }
    else
    {
        return False;
    }
}

void display( )
{
    int i, out, tmp;
    glPointSize(0.5);
    glBegin(GL_POINTS);
        for(i = 0; i < ROWSIZE; i++)
        {
            if(i == 0)
            {
                out = rule(0, row[i], row[i+1]);
            }
            else if(i == ROWSIZE-1)
            {
                out = rule(row[i-1], row[i], 0);
            }
            else
            {
                out = rule(row[i-1], row[i], row[i+1]);
            }
            if(out)
            {
                glColor3f(0.3, 0.9, 0.1);
            }
            else
            {
                glColor3f(0.3, 0.3, 0.3);
            }
            old_row[i] = out;
            glVertex3f(ROWSIZE/4 - i*0.4, j, 0.0);
        }
        for(i = 0; i < ROWSIZE; i++)
        {
            tmp    = row[i];
            row[i] = old_row[i];
            old_row[i] = tmp;
        }
    glEnd( );
    glutSwapBuffers( );
/*    int k = rule(True, True, True);*/
/*    printf("%d\n", k);*/
    j -= 0.6;
}

void idle( )
{
    glutPostRedisplay( );
}

void init( )
{
    int i;
    glClearColor(0.0, 0.0, 0.0, 0.0);
    glMatrixMode(GL_FLAT);
    glLoadIdentity( );
    glOrtho(- WINSIZE/2, WINSIZE/2, - WINSIZE/2, WINSIZE/2, -2.0, 2.0);
    glClear(GL_COLOR_BUFFER_BIT);
    j = WINSIZE/2.0 + 20;
    for(i = 0; i < ROWSIZE; i++)
    {
        row[i]     = 0;
        old_row[i] = 0;
    }
    row[ROWSIZE/2] = 1;
}

int main(int argc, char** argv)
{
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB);
    glutInitWindowSize(WINSIZE, WINSIZE);
    glutInitWindowPosition(0,0);
    glutCreateWindow("Rule 30 Cellular Automata");
    init( );
    glutDisplayFunc(display);
    glutIdleFunc(idle);
    glutMainLoop( );
    return 0;
}