#keywords C, 랜덤, 함수

{{{#!c
#define A 16807L		/* multiplier (7**5) */
#define M 2147483647L	/* module (2**1-1) */

static long ln[16] = {0L,
			1973272912L, 747177549L, 20464843L,	640830765L, 1098742207L,
			78126602L, 84743774L, 831312807L, 124667236L, 1172177002L,
			1124933064L, 1223960546L, 1878892440L, 1449793615L, 553303732L};

static int strm = 1;		/* index of current stream */

/*-------------------------------------------------------------------*/
/* This implementation is for Intel 8086/8 and 80286/386 CPUs using  */
/* C compilers with 16-bit short integers and 32-bit long inegers.   */
/*-------------------------------------------------------------------*/
double ranf()
{
	short *p,*q,k;
	long Hi,Lo;
	p=(short *)&ln[strm];
	Hi=*(p+1) *A;
	*(p+1) = 0;
	Lo=ln[strm]*A;
	p=(short *)&Lo;
	Hi+= *(p+1);
	q=(short *)&Hi;
	*(p+1) = *q&0X7FFF;
	k= *(q+1) << 1;
	if(*q&0X7FFF) k++;
	Lo-=M;
	Lo+=k;
	if(Lo<0) Lo+=M;
	ln[strm]=Lo;
	return (double)Lo*4.656612875E-10;
}
}}}


보너스.
exponential random variables과 geometric random variables 생성 함수.
{{{#!c
double expntl(double ramda)
{
	return (-log(1-ranf())/ramda);
}

int geometric(double p)
{
	if (p > 1.0 || p <= 0.0)
	{
		printf("invalid number of parameter p(%lf)\n", p);
		return 0;
	}
	return (int)((log(1.0 - ranf())/log(1.0 - p)) + 1);
}
}}}