/*FUNCTION<<random>>, <<srandom>>---pseudo-random numbers INDEX	randomINDEX	srandom SYNOPSIS	#define _XOPEN_SOURCE 500	#include <stdlib.h>	long int random(void);	void srandom(unsigned int <[seed]>);   DESCRIPTION<<random>> returns a different integer each time it is called; eachinteger is chosen by an algorithm designed to be unpredictable, sothat you can use <<random>> when you require a random number.The algorithm depends on a static variable called the ``random seed'';starting with a given value of the random seed always produces thesame sequence of numbers in successive calls to <<random>>. You can set the random seed using <<srandom>>; it does nothing beyondstoring its argument in the static variable used by <<rand>>.  You canexploit this to make the pseudo-random sequence less predictable, ifyou wish, by using some other unpredictable value (often the leastsignificant parts of a time-varying value) as the random seed beforebeginning a sequence of calls to <<rand>>; or, if you wish to ensure(for example, while debugging) that successive runs of your programuse the same ``random'' numbers, you can use <<srandom>> to set the samerandom seed at the outset. RETURNS<<random>> returns the next pseudo-random integer in sequence; it is anumber between <<0>> and <<RAND_MAX>> (inclusive). <<srandom>> does not return a result. NOTES<<random>> and <<srandom>> are unsafe for multi-threaded applications. _XOPEN_SOURCE may be any value >= 500. PORTABILITY<<random>> is required by XSI. This implementation uses the samealgorithm as <<rand>>. <<random>> requires no supporting OS subroutines.*/ #ifndef _REENT_ONLY #include <stdlib.h>#include <reent.h> voidsrandom (unsigned int seed){  struct _reent *reent = _REENT;   _REENT_CHECK_RAND48(reent);  _REENT_RAND_NEXT(reent) = seed;} long intrandom (void){  struct _reent *reent = _REENT;   /* This multiplier was obtained from Knuth, D.E., "The Art of     Computer Programming," Vol 2, Seminumerical Algorithms, Third     Edition, Addison-Wesley, 1998, p. 106 (line 26) & p. 108 */  _REENT_CHECK_RAND48(reent);  _REENT_RAND_NEXT(reent) =     _REENT_RAND_NEXT(reent) * __extension__ 6364136223846793005LL + 1;  return (long int)((_REENT_RAND_NEXT(reent) >> 32) & RAND_MAX);} #endif /* _REENT_ONLY */