43 lines
937 B
C
43 lines
937 B
C
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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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/*
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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 "fdlibm.h"
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#ifndef _DOUBLE_IS_32BITS
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#ifdef __STDC__
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double logb(double x)
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#else
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double 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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}
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#endif /* _DOUBLE_IS_32BITS */
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