
// Copyright (c) 19992000 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 2^311 on 32 bit machines
// but there are exceptions where it is 2^151 or
// 2^321.
};
#endif
