// Copyright (c) 1999-2000 David Muse
// See the COPYING file for more information.

#ifndef RANDOMNUMBER_H
#define RANDOMNUMBER_H

// The randomnumber class provides methods for generating and scaling 
// random numbers.
//
// A common practice for generating random number sequences is to seed the
// first call to generateNumber() with the number of seconds since 1970 (see
// the datetime class) and seed each successive call with the previously
// generated number.
//
// Superfluous background:
//
// Random numbers are actually just a highly divergent series.  There is
// no such thing as true randomness.  Using the above described methodology, 
// if there is only one running process generating random numbers, successive 
// calls to generateNumber() will never return the same value until all 
// numbers between 0 and 2^32 have been returned.  At that point, the entire 
// sequence will repeat.  Calls to generateScaledNumber() may return the
// same value before all numbers in the range have been returned because
// it scales the result of generateNumber() which operates on a larger range.

class randomnumber {
        public:
                static  int     generateNumber(int seed);
                        // Generates a random number between 0 and 2^32, based
                        // on seed, and returns it.  
                        //
                        // It is ok to use the result of this method as the 
                        // seed for the next number.
                static  int     generateScaledNumber(int seed, 
                                                        int lower, int upper);
                        // Generates a random number between 0 and 2^32, based
                        // on seed, scales that value to be between
                        // lower and upper and returns it.
                        //
                        // It is NOT ok to use the result of this method as 
                        // the seed for the next number.
                static  int     scaleNumber(int number, int lower, int upper);
                        // Scales number to be between lower and upper and 
                        // returns it.
                        //
                        // It is NOT ok to use the result of this method as 
                        // the seed for the next number.

                static  int     getRandMax();
                        // Operating systems can generate random numbers
                        // between 0 and RAND_MAX.
                        // This method returns RAND_MAX.
                        // 
                        // RAND_MAX is usually 2^31-1 on 32 bit machines
                        // but there are exceptions where it is 2^15-1 or
                        // 2^32-1.
};

#endif