80 lines
1.7 KiB
C
80 lines
1.7 KiB
C
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/* @(#)w_log.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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FUNCTION
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<<log>>, <<logf>>---natural logarithms
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INDEX
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log
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INDEX
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logf
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SYNOPSIS
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#include <math.h>
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double log(double <[x]>);
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float logf(float <[x]>);
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DESCRIPTION
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Return the natural logarithm of <[x]>, that is, its logarithm base e
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(where e is the base of the natural system of logarithms, 2.71828@dots{}).
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<<log>> and <<logf>> are identical save for the return and argument types.
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RETURNS
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Normally, returns the calculated value. When <[x]> is zero, the
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returned value is <<-HUGE_VAL>> and <<errno>> is set to <<ERANGE>>.
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When <[x]> is negative, the returned value is NaN (not a number) and
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<<errno>> is set to <<EDOM>>.
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PORTABILITY
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<<log>> is ANSI. <<logf>> is an extension.
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*/
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/*
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* wrapper log(x)
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*/
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#include "fdlibm.h"
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#if __OBSOLETE_MATH
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#include <errno.h>
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#ifndef _DOUBLE_IS_32BITS
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#ifdef __STDC__
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double log(double x) /* wrapper log */
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#else
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double log(x) /* wrapper log */
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double x;
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#endif
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{
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#ifdef _IEEE_LIBM
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return __ieee754_log(x);
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#else
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double z;
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z = __ieee754_log(x);
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if(_LIB_VERSION == _IEEE_ || isnan(x) || x > 0.0) return z;
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if(x==0.0) {
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/* log(0) */
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errno = ERANGE;
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return -HUGE_VAL;
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} else {
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/* log(x<0) */
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errno = EDOM;
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return nan("");
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}
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#endif
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}
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#endif /* defined(_DOUBLE_IS_32BITS) */
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#endif /* __OBSOLETE_MATH */
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