#include <stdio.h>
#include <stdlib.h>

enum days {sunday, monday, tuesday, wednesday, thursday, 
           friday, saturday};

enum colors {red, green, blue, yellow};

int day_function (enum days some_day){
  /* some day calculation */
  return 2;
}

int color_function (enum colors some_color){
  /* some color calculation */
  return 1;
}

int main(void){

  enum days some_day = sunday;
  enum colors some_color = yellow;

  day_function(some_color);     /* Passing a color in place of a day   */
  color_function(some_day);     /* Passing a day in place of a color   */
                                /* No compile time, nor run time error */
  return 0;
}