random.h

国外经典教材《程序设计抽象思想—C语言描述》一书中的关键性库文件

/*
 * File: random.h
 * Last modified on Fri Jul 22 16:44:36 1994 by eroberts
 * -----------------------------------------------------
 * Library package to produce pseudo-random numbers.
 */

#ifndef _random_h
#define _random_h

#include "genlib.h"
#include <stdlib.h>

/*
 * Constant: RAND_MAX
 * ------------------
 * Unfortunately, several libraries that supposedly conform to
 * the ANSI standard do not define RAND_MAX in <stdlib.h>.  To
 * reduce portability problems, this interface defines RAND_MAX
 * to be the largest positive integer if it is undefined.
 */

#ifndef RAND_MAX
#  define RAND_MAX ((int) ((unsigned) ~0 >> 1))
#endif

/*
 * Function: Randomize
 * Usage: Randomize();
 * -------------------
 * This function sets the random seed so that the random sequence
 * is unpredictable.  During the debugging phase, it is best not
 * to call this function, so that program behavior is repeatable.
 */

void Randomize(void);

/*
 * Function: RandomInteger
 * Usage: n = RandomInteger(low, high);
 * ------------------------------------
 * This function returns a random integer in the range low to high,
 * inclusive.
 */

int RandomInteger(int low, int high);

/*
 * Function: RandomReal
 * Usage: d = RandomReal(low, high);
 * ---------------------------------
 * This function returns a random real number in the half-open
 * interval [low .. high), meaning that the result is always
 * greater than or equal to low but strictly less than high.
 */

double RandomReal(double low, double high);

/*
 * Function: RandomChance
 * Usage: if (RandomChance(p)) . . .
 * ---------------------------------
 * The RandomChance function returns TRUE with the probability
 * indicated by p, which should be a floating-point number between
 * 0 (meaning never) and 1 (meaning always).  For example, calling
 * RandomChance(.30) returns TRUE 30 percent of the time.
 */

bool RandomChance(double p);

#endif