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[/] [or1k/] [trunk/] [newlib-1.10.0/] [newlib/] [libm/] [math/] [w_log.c] - Blame information for rev 1773

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1 1010 ivang 
 
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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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ANSI_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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TRAD_SYNOPSIS
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       #include <math.h>
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       double log(<[x]>);
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       double <[x]>;
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       float logf(<[x]>);
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       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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You can use the (non-ANSI) function <<matherr>> to specify error
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handling for these functions.
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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 <<-HUGE_VAL>> and
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<<errno>> is set to <<EDOM>>.  You can control the error behavior via
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<<matherr>>.
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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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#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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        struct exception exc;
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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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#ifndef HUGE_VAL
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#define HUGE_VAL inf
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        double inf = 0.0;
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        SET_HIGH_WORD(inf,0x7ff00000);  /* set inf to infinite */
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#endif
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        exc.name = "log";
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        exc.err = 0;
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        exc.arg1 = x;
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        exc.arg2 = x;
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        if (_LIB_VERSION == _SVID_)
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           exc.retval = -HUGE;
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        else
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           exc.retval = -HUGE_VAL;
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        if(x==0.0) {
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            /* log(0) */
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            exc.type = SING;
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            if (_LIB_VERSION == _POSIX_)
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               errno = ERANGE;
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            else if (!matherr(&exc)) {
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               errno = EDOM;
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            }
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        } else {
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            /* log(x<0) */
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            exc.type = DOMAIN;
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            if (_LIB_VERSION == _POSIX_)
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               errno = EDOM;
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            else if (!matherr(&exc)) {
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               errno = EDOM;
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            }
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        }
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        if (exc.err != 0)
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           errno = exc.err;
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        return exc.retval;
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#endif
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}
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#endif /* defined(_DOUBLE_IS_32BITS) */

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