/* @(#)s_logb.c 1.3 95/01/18 */

/*

 * ====================================================

 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.

 *

 * Developed at SunSoft, a Sun Microsystems, Inc. business.

 * Permission to use, copy, modify, and distribute this

 * software is freely granted, provided that this notice 

 * is preserved.

 * ====================================================

 */

/*

 * double logb(x)

 * IEEE 754 logb. Included to pass IEEE test suite. Not recommend.

 * Use ilogb instead.

 */

#include "fdlibm.h"

#ifdef __STDC__

	double logb(double x)

#else

	double logb(x)

	double x;

#endif

{

	int lx,ix;

	ix = (__HI(x))&0x7fffffff;	/* high |x| */

	lx = __LO(x);			/* low 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); 

}