pow_ri.c

来自「在Linxu程序设计当中」· C语言 代码 · 共 42 行

#include "f2c.h"
#ifdef __cplusplus
extern "C" {
#endif

#ifdef KR_headers
double pow_ri(ap, bp) real *ap; integer *bp;
#else
double pow_ri(real *ap, integer *bp)
#endif
{
double pow, x;
integer n;
unsigned long u;

pow = 1;
x = *ap;
n = *bp;

if(n != 0)
	{
	if(n < 0)
		{
		n = -n;
		x = 1/x;
		}
	for(u = n; ; )
		{
		if(u & 01)
			pow *= x;
		if(u >>= 1)
			x *= x;
		else
			break;
		}
	}
return(pow);
}
#ifdef __cplusplus
}
#endif