text: #ifndef _util_h_
  #define _util_h_
  
  #ifndef __APPLE_CC__
      #include <GL/glew.h>
  #endif
  
  #include <GLFW/glfw3.h>
  
  typedef struct {
      unsigned int frames;
      double since;
  } FPS;
  
  int rand_int(int n);
  double rand_double();
  void update_fps(FPS *fps, int show);
  
  GLuint gen_buffer(GLenum target, GLsizei size, const void *data);
  GLuint make_shader(GLenum type, const char *source);
  GLuint load_shader(GLenum type, const char *path);
  GLuint make_program(GLuint shader1, GLuint shader2);
  GLuint load_program(const char *path1, const char *path2);
  void load_png_texture(const char *file_name);
  
  #endif
  