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/* @(#)s_logb.c 5.1 93/09/24 */
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/*
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 * ====================================================
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 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
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 *
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 * Developed at SunPro, a Sun Microsystems, Inc. business.
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 * Permission to use, copy, modify, and distribute this
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 * software is freely granted, provided that this notice
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 * is preserved.
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 * ====================================================
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 */
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#ifndef lint
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static char rcsid[] = "$\Id: s_logb.c,v 1.2.6.1 1997/02/23 11:03:20 joerg Exp $";
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#endif
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/*
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 * double logb(x)
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 * IEEE 754 logb. Included to pass IEEE test suite. Not recommend.
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 * Use ilogb instead.
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 */
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#include "math.h"
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#include "math_private.h"
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#ifdef __STDC__
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        double __generic_logb(double x)
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#else
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        double __generic_logb(x)
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        double x;
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#endif
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{
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        int32_t lx,ix;
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        EXTRACT_WORDS(ix,lx,x);
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        ix &= 0x7fffffff;                       /* high |x| */
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        if((ix|lx)==0) return -1.0/fabs(x);
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        if(ix>=0x7ff00000) return x*x;
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        if((ix>>=20)==0)                        /* IEEE 754 logb */
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                return -1022.0;
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        else
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                return (double) (ix-1023);
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}