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74 lines
1.5 KiB
C
74 lines
1.5 KiB
C
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/* @(#)s_log2.c 5.1 93/09/24 */
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/* Modification from s_exp10.c Yaakov Selkowitz 2009. */
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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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FUNCTION
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<<log2>>, <<log2f>>---base 2 logarithm
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INDEX
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log2
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INDEX
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log2f
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ANSI_SYNOPSIS
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#include <math.h>
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double log2(double <[x]>);
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float log2f(float <[x]>);
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TRAD_SYNOPSIS
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#include <math.h>
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double log2(<[x]>);
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double <[x]>;
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float log2f(<[x]>);
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float <[x]>;
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DESCRIPTION
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<<log2>> returns the base 2 logarithm of <[x]>.
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<<log2f>> is identical, save that it takes and returns <<float>> values.
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RETURNS
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On success, <<log2>> and <<log2f>> return the calculated value.
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If the result underflows, the returned value is <<0>>. If the
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result overflows, the returned value is <<HUGE_VAL>>. In
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either case, <<errno>> is set to <<ERANGE>>.
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PORTABILITY
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<<log2>> and <<log2f>> are required by ISO/IEC 9899:1999 and the
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System V Interface Definition (Issue 6).
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*/
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/*
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* wrapper log2(x)
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*/
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#include "fdlibm.h"
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#include <errno.h>
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#include <math.h>
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#undef log2
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#ifndef _DOUBLE_IS_32BITS
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#ifdef __STDC__
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double log2(double x) /* wrapper log2 */
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#else
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double log2(x) /* wrapper log2 */
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double x;
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#endif
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{
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return (log(x) / M_LOG2_E);
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}
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#endif /* defined(_DOUBLE_IS_32BITS) */
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