toolchain/gcc/newlib/libm/math/w_log.c

   1
   2 /* @(#)w_log.c 5.1 93/09/24 */
   3 /*
   4  * ====================================================
   5  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
   6  *
   7  * Developed at SunPro, a Sun Microsystems, Inc. business.
   8  * Permission to use, copy, modify, and distribute this
   9  * software is freely granted, provided that this notice
  10  * is preserved.
  11  * ====================================================
  12  */
  13
  14 /*
  15 FUNCTION
  16        <<log>>, <<logf>>---natural logarithms
  17
  18 INDEX
  19     log
  20 INDEX
  21     logf
  22
  23 ANSI_SYNOPSIS
  24        #include <math.h>
  25        double log(double <[x]>);
  26        float logf(float <[x]>);
  27
  28 TRAD_SYNOPSIS
  29        #include <math.h>
  30        double log(<[x]>);
  31        double <[x]>;
  32
  33        float logf(<[x]>);
  34        float <[x]>;
  35
  36 DESCRIPTION
  37 Return the natural logarithm of <[x]>, that is, its logarithm base e
  38 (where e is the base of the natural system of logarithms, 2.71828@dots{}).
  39 <<log>> and <<logf>> are identical save for the return and argument types.
  40
  41 You can use the (non-ANSI) function <<matherr>> to specify error
  42 handling for these functions.
  43
  44 RETURNS
  45 Normally, returns the calculated value.  When <[x]> is zero, the
  46 returned value is <<-HUGE_VAL>> and <<errno>> is set to <<ERANGE>>.
  47 When <[x]> is negative, the returned value is <<-HUGE_VAL>> and
  48 <<errno>> is set to <<EDOM>>.  You can control the error behavior via
  49 <<matherr>>.
  50
  51 PORTABILITY
  52 <<log>> is ANSI, <<logf>> is an extension.
  53 */
  54
  55 /*
  56  * wrapper log(x)
  57  */
  58
  59 #include "fdlibm.h"
  60 #include <errno.h>
  61
  62 #ifndef _DOUBLE_IS_32BITS
  63
  64 #ifdef __STDC__
  65         double log(double x)            /* wrapper log */
  66 #else
  67         double log(x)                   /* wrapper log */
  68         double x;
  69 #endif
  70 {
  71 #ifdef _IEEE_LIBM
  72         return __ieee754_log(x);
  73 #else
  74         double z;
  75         struct exception exc;
  76         z = __ieee754_log(x);
  77         if(_LIB_VERSION == _IEEE_ || isnan(x) || x > 0.0) return z;
  78 #ifndef HUGE_VAL
  79 #define HUGE_VAL inf
  80         double inf = 0.0;
  81
  82         SET_HIGH_WORD(inf,0x7ff00000);  /* set inf to infinite */
  83 #endif
  84         exc.name = "log";
  85         exc.err = 0;
  86         exc.arg1 = x;
  87         exc.arg2 = x;
  88         if (_LIB_VERSION == _SVID_)
  89            exc.retval = -HUGE;
  90         else
  91            exc.retval = -HUGE_VAL;
  92         if(x==0.0) {
  93             /* log(0) */
  94             exc.type = SING;
  95             if (_LIB_VERSION == _POSIX_)
  96                errno = ERANGE;
  97             else if (!matherr(&exc)) {
  98                errno = EDOM;
  99             }
 100         } else {
 101             /* log(x<0) */
 102             exc.type = DOMAIN;
 103             if (_LIB_VERSION == _POSIX_)
 104                errno = EDOM;
 105             else if (!matherr(&exc)) {
 106                errno = EDOM;
 107             }
 108         }
 109         if (exc.err != 0)
 110            errno = exc.err;
 111         return exc.retval;
 112 #endif
 113 }
 114
 115 #endif /* defined(_DOUBLE_IS_32BITS) */