pow_ri.c

<B>Digital的Unix操作系统VAX 4.2源码</B>

#ifndef lint
static char	*sccsid = " @(#)pow_ri.c	1.2	(ULTRIX)	1/16/86";
#endif lint

/************************************************************************
 *									*
 *			Copyright (c) 1986 by				*
 *		Digital Equipment Corporation, Maynard, MA		*
 *			All rights reserved.				*
 *									*
 *   This software is furnished under a license and may be used and	*
 *   copied  only  in accordance with the terms of such license and	*
 *   with the  inclusion  of  the  above  copyright  notice.   This	*
 *   software  or  any  other copies thereof may not be provided or	*
 *   otherwise made available to any other person.  No title to and	*
 *   ownership of the software is hereby transferred.			*
 *									*
 *   This software is  derived  from  software  received  from  the	*
 *   University    of   California,   Berkeley,   and   from   Bell	*
 *   Laboratories.  Use, duplication, or disclosure is  subject  to	*
 *   restrictions  under  license  agreements  with  University  of	*
 *   California and with AT&T.						*
 *									*
 *   The information in this software is subject to change  without	*
 *   notice  and should not be construed as a commitment by Digital	*
 *   Equipment Corporation.						*
 *									*
 *   Digital assumes no responsibility for the use  or  reliability	*
 *   of its software on equipment which is not supplied by Digital.	*
 *									*
 ************************************************************************/

/************************************************************************
*
*			Modification History
*
*	David Metsky		10-Jan-86
*
* 001	Replaced old version with BSD 4.3 version as part of upgrade.
*
*	Based on: 	pow_ri.c	5.2		7/9/85
*
*************************************************************************/

float flt_retval;

float pow_ri(ap, bp)
float *ap;
long int *bp;
{
double pow, x;
long int n;

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

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