/* Input validation loop (do-while) example taken from the ihypress.net Web site*/

#include <stdio.h>

int
main (void)
{
   char color;
 
   /* ask user for color */
do 
{
   printf ("Enter the color of the light (R,G,Y,A): ");
   scanf (" %c", &color); /* very important to leave space before %c here */

} while (color!='R' && color!='r' && color!='G' && color!='g'  \
 && color!='Y' && color!='y' && color!='A' && color!='a');
 
   /* test the alternatives */       
   switch (color)
   {
       /* red light */
       case 'R':
       case 'r':
                 printf ("STOP! \n");
                 break;
	
       /* yellow or amber light */
       case 'Y':
       case 'y':
       case 'A':
       case 'a':
                 printf ("CAUTION! \n");
                 break;
        
       /* green light */
       case 'G':
       case 'g':
                 printf ("GO! \n");
                 break;
 
       /* no default case necessary here */
   }

   return (0);
}