text: #ifndef GLFUNCTIONS_H
  #define GLFUNCTIONS_H
  
  #include <utility>
  #include <cstdio>
  #include <cstdlib>
  #include <fstream>
  #include <iostream>
  #include <string>
  #include <iterator>
  #include <stdlib.h>
  
  #include <GL/glew.h>
  #include <GL/glut.h>
  #include <GL/gl.h>
  #include <GL/glu.h>
  
  
  extern int old_x;
  extern int dx;
  extern double _dx;
  
  void handleKeypress(unsigned char key, int x, int y);
  
  void Sphere(int x, int y, int z, int r);
  
  void initRendering();
  
  void handleResize(int w, int h);
  
  void motionFunc(int x, int y);
  
  void mouseFunc(int button, int state, int x, int y);
  
  void drawScene();
  
  
  #endif // GLFUNCTIONS_H
  