| 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 | @ifinfo
|
|---|
| 38 | e raised to the power <[x]> (where e
|
|---|
| 39 | @end ifinfo
|
|---|
| 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) */
|
|---|
