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33 lines
841 B
C
33 lines
841 B
C
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/* @(#)s_logb.c 1.3 95/01/18 */
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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 SunSoft, 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 "math.h"
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double logb(double x) {
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int lx, ix;
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ix = (__HI(x)) & 0x7fffffff; /* high |x| */
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lx = __LO(x); /* low 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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