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File: [cvs.NetBSD.org] / src / lib / libm / src / s_logb.c (download)

Revision 1.9, Thu Oct 9 11:32:48 1997 UTC (26 years, 5 months ago) by lukem
Branch: MAIN
CVS Tags: netbsd-1-4-base, netbsd-1-4-RELEASE, netbsd-1-4-PATCH003, netbsd-1-4-PATCH002, netbsd-1-4-PATCH001, netbsd-1-4, netbsd-1-3-base, netbsd-1-3-RELEASE, netbsd-1-3-PATCH003-CANDIDATE2, netbsd-1-3-PATCH003-CANDIDATE1, netbsd-1-3-PATCH003-CANDIDATE0, netbsd-1-3-PATCH003, netbsd-1-3-PATCH002, netbsd-1-3-PATCH001, netbsd-1-3-BETA, netbsd-1-3
Changes since 1.8: +2 -1 lines

rcsid facism, WARNSify

/* @(#)s_logb.c 5.1 93/09/24 */
/*
 * ====================================================
 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
 *
 * Developed at SunPro, a Sun Microsystems, Inc. business.
 * Permission to use, copy, modify, and distribute this
 * software is freely granted, provided that this notice 
 * is preserved.
 * ====================================================
 */

#include <sys/cdefs.h>
#if defined(LIBM_SCCS) && !defined(lint)
__RCSID("$NetBSD: s_logb.c,v 1.9 1997/10/09 11:32:48 lukem Exp $");
#endif

/*
 * double logb(x)
 * IEEE 754 logb. Included to pass IEEE test suite. Not recommend.
 * Use ilogb instead.
 */

#include "math.h"
#include "math_private.h"

#ifdef __STDC__
	double logb(double x)
#else
	double logb(x)
	double x;
#endif
{
	int32_t lx,ix;
	EXTRACT_WORDS(ix,lx,x);
	ix &= 0x7fffffff;			/* high |x| */
	if((ix|lx)==0) return -1.0/fabs(x);
	if(ix>=0x7ff00000) return x*x;
	if((ix>>=20)==0) 			/* IEEE 754 logb */
		return -1022.0; 
	else
		return (double) (ix-1023); 
}