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Last change
on this file was 2006, checked in by bird, 20 years ago |
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Initial revision
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Property cvs2svn:cvs-rev
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1.1
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Property svn:eol-style
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native
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Property svn:executable
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*
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File size:
959 bytes
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| 1 | /* @(#)s_logb.c 5.1 93/09/24 */
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| 2 | /*
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| 3 | * ====================================================
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| 4 | * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
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| 5 | *
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| 6 | * Developed at SunPro, a Sun Microsystems, Inc. business.
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| 7 | * Permission to use, copy, modify, and distribute this
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| 8 | * software is freely granted, provided that this notice
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| 9 | * is preserved.
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| 10 | * ====================================================
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| 11 | */
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| 12 |
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| 13 | #ifndef lint
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| 14 | static char rcsid[] = "$FreeBSD: src/lib/msun/src/s_logb.c,v 1.9 2003/07/23 04:53:46 peter Exp $";
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| 15 | #endif
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| 16 |
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| 17 | /*
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| 18 | * double logb(x)
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| 19 | * IEEE 754 logb. Included to pass IEEE test suite. Not recommend.
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| 20 | * Use ilogb instead.
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| 21 | */
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| 22 |
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| 23 | #include "math.h"
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| 24 | #include "math_private.h"
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| 25 |
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| 26 | double
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| 27 | logb(double x)
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| 28 | {
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| 29 | int32_t lx,ix;
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| 30 | EXTRACT_WORDS(ix,lx,x);
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| 31 | ix &= 0x7fffffff; /* high |x| */
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| 32 | if((ix|lx)==0) return -1.0/fabs(x);
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| 33 | if(ix>=0x7ff00000) return x*x;
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| 34 | if((ix>>=20)==0) /* IEEE 754 logb */
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| 35 | return -1022.0;
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| 36 | else
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| 37 | return (double) (ix-1023);
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| 38 | }
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