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

   1
   2 /* @(#)w_exp.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         <<exp>>, <<expf>>---exponential
  17 INDEX
  18         exp
  19 INDEX
  20         expf
  21
  22 ANSI_SYNOPSIS
  23         #include <math.h>
  24         double exp(double <[x]>);
  25         float expf(float <[x]>);
  26
  27 TRAD_SYNOPSIS
  28         #include <math.h>
  29         double exp(<[x]>);
  30         double <[x]>;
  31
  32         float expf(<[x]>);
  33         float <[x]>;
  34
  35 DESCRIPTION
  36         <<exp>> and <<expf>> calculate the exponential of <[x]>, that is,
  37         @ifnottex
  38         e raised to the power <[x]> (where e
  39         @end ifnottex
  40         @tex
  41         $e^x$ (where $e$
  42         @end tex
  43         is the base of the natural system of logarithms, approximately 2.71828).
  44
  45         You can use the (non-ANSI) function <<matherr>> to specify
  46         error handling for these functions.
  47
  48 RETURNS
  49         On success, <<exp>> and <<expf>> return the calculated value.
  50         If the result underflows, the returned value is <<0>>.  If the
  51         result overflows, the returned value is <<HUGE_VAL>>.  In
  52         either case, <<errno>> is set to <<ERANGE>>.
  53
  54 PORTABILITY
  55         <<exp>> is ANSI C.  <<expf>> is an extension.
  56
  57 */
  58
  59 /*
  60  * wrapper exp(x)
  61  */
  62
  63 #include "fdlibm.h"
  64 #include <errno.h>
  65
  66 #ifndef _DOUBLE_IS_32BITS
  67
  68 #ifdef __STDC__
  69 static const double
  70 #else
  71 static double
  72 #endif
  73 o_threshold=  7.09782712893383973096e+02,  /* 0x40862E42, 0xFEFA39EF */
  74 u_threshold= -7.45133219101941108420e+02;  /* 0xc0874910, 0xD52D3051 */
  75
  76 #ifdef __STDC__
  77         double exp(double x)            /* wrapper exp */
  78 #else
  79         double exp(x)                   /* wrapper exp */
  80         double x;
  81 #endif
  82 {
  83 #ifdef _IEEE_LIBM
  84         return __ieee754_exp(x);
  85 #else
  86         double z;
  87         struct exception exc;
  88         z = __ieee754_exp(x);
  89         if(_LIB_VERSION == _IEEE_) return z;
  90         if(finite(x)) {
  91             if(x>o_threshold) {
  92                 /* exp(finite) overflow */
  93 #ifndef HUGE_VAL
  94 #define HUGE_VAL inf
  95                 double inf = 0.0;
  96
  97                 SET_HIGH_WORD(inf,0x7ff00000);  /* set inf to infinite */
  98 #endif
  99                 exc.type = OVERFLOW;
 100                 exc.name = "exp";
 101                 exc.err = 0;
 102                 exc.arg1 = exc.arg2 = x;
 103                 if (_LIB_VERSION == _SVID_)
 104                   exc.retval = HUGE;
 105                 else
 106                   exc.retval = HUGE_VAL;
 107                 if (_LIB_VERSION == _POSIX_)
 108                   errno = ERANGE;
 109                 else if (!matherr(&exc)) {
 110                         errno = ERANGE;
 111                 }
 112                 if (exc.err != 0)
 113                    errno = exc.err;
 114                 return exc.retval;
 115             } else if(x<u_threshold) {
 116                 /* exp(finite) underflow */
 117                 exc.type = UNDERFLOW;
 118                 exc.name = "exp";
 119                 exc.err = 0;
 120                 exc.arg1 = exc.arg2 = x;
 121                 exc.retval = 0.0;
 122                 if (_LIB_VERSION == _POSIX_)
 123                   errno = ERANGE;
 124                 else if (!matherr(&exc)) {
 125                         errno = ERANGE;
 126                 }
 127                 if (exc.err != 0)
 128                    errno = exc.err;
 129                 return exc.retval;
 130             }
 131         }
 132         return z;
 133 #endif
 134 }
 135
 136 #endif /* defined(_DOUBLE_IS_32BITS) */