NOTE:

These are a little sketchy...I'll fill in details 'soon'.

Random Whole Numbers

• random whole number between min and max inclusive: [min..max]
• rand() % (max - min + 1) + min

•    long rand_L(long min, long max)
     {
         return rand()%(max-min+1) + min;
     }
  

• But if RAND_MAX is SHRT_MAX instead of LONG_MAX, we won't get full values. A simple fix is:

     long rand_L(long min, long max)
     {
         return (RAND_MAX==LONG_MAX ? rand()
                                    : (long)rand()<<16 | rand())
                %(max-min+1) + min;
     }
  

Random Decimal Numbers

• random decimal values between min and max inclusive: [min..max]
• rand_range(0,X)/X.0 * (max - min) + min

•    // note:  the L on the 0 and 10000 makes sure those literals
     //        are of type long
     double rand_D(double min, double max)
     {
         return rand_L(0L, 10000L)/10000.0 * (max-min) + min;
     }
  

Random Character Values

• random character values between min and max inclusive: [min..max]
• ASCII_code = rand_L(min,max)

•    // note:  simply call long integer version by type-casting.
     //        return character by reversing the type-cast.
     char rand_C(char min, char max)
     {
         return (char)rand_L((long)min, (long)max);
     }
  

Random Action Occurance

• did an action known to have a P percent chance of occuring happen or not?
• rand_range(0,100) <= P*100

•    // note:  notice the L's again and that the range of decimals
     //        has been extended to 4 for better overall performance
     //        (not efficiency, but usefulness to an application)
     int event_occured(double probability)
     {
         return rand_L(0L, 10000L) <= probability*10000;
     }
  

• most commonly:

     int flip_coin(const double * chance_heads)  // fair coin
     {
         double chance = (chance_heads == NULL) ? 0.5 : *chance_heads;
         return event_occured(chance);
     }