[444] | 1 | |
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| 2 | /* @(#)w_exp.c 5.1 93/09/24 */ |
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| 3 | /* |
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| 4 | * ==================================================== |
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| 5 | * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. |
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| 6 | * |
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| 7 | * Developed at SunPro, a Sun Microsystems, Inc. business. |
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| 8 | * Permission to use, copy, modify, and distribute this |
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| 9 | * software is freely granted, provided that this notice |
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| 10 | * is preserved. |
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| 11 | * ==================================================== |
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| 12 | */ |
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| 13 | |
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| 14 | /* |
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| 15 | FUNCTION |
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| 16 | <<exp>>, <<expf>>---exponential |
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| 17 | INDEX |
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| 18 | exp |
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| 19 | INDEX |
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| 20 | expf |
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| 21 | |
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| 22 | SYNOPSIS |
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| 23 | #include <math.h> |
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| 24 | double exp(double <[x]>); |
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| 25 | float expf(float <[x]>); |
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| 26 | |
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| 27 | DESCRIPTION |
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| 28 | <<exp>> and <<expf>> calculate the exponential of <[x]>, that is, |
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| 29 | @ifnottex |
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| 30 | e raised to the power <[x]> (where e |
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| 31 | @end ifnottex |
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| 32 | @tex |
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| 33 | $e^x$ (where $e$ |
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| 34 | @end tex |
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| 35 | is the base of the natural system of logarithms, approximately 2.71828). |
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| 36 | |
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| 37 | You can use the (non-ANSI) function <<matherr>> to specify |
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| 38 | error handling for these functions. |
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| 39 | |
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| 40 | RETURNS |
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| 41 | On success, <<exp>> and <<expf>> return the calculated value. |
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| 42 | If the result underflows, the returned value is <<0>>. If the |
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| 43 | result overflows, the returned value is <<HUGE_VAL>>. In |
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| 44 | either case, <<errno>> is set to <<ERANGE>>. |
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| 45 | |
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| 46 | PORTABILITY |
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| 47 | <<exp>> is ANSI C. <<expf>> is an extension. |
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| 48 | |
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| 49 | */ |
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| 50 | |
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| 51 | /* |
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| 52 | * wrapper exp(x) |
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| 53 | */ |
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| 54 | |
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| 55 | #include "fdlibm.h" |
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| 56 | #include <errno.h> |
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| 57 | |
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| 58 | #ifndef _DOUBLE_IS_32BITS |
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| 59 | |
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| 60 | #ifdef __STDC__ |
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| 61 | static const double |
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| 62 | #else |
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| 63 | static double |
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| 64 | #endif |
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| 65 | o_threshold= 7.09782712893383973096e+02, /* 0x40862E42, 0xFEFA39EF */ |
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| 66 | u_threshold= -7.45133219101941108420e+02; /* 0xc0874910, 0xD52D3051 */ |
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| 67 | |
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| 68 | #ifdef __STDC__ |
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| 69 | double exp(double x) /* wrapper exp */ |
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| 70 | #else |
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| 71 | double exp(x) /* wrapper exp */ |
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| 72 | double x; |
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| 73 | #endif |
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| 74 | { |
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| 75 | #ifdef _IEEE_LIBM |
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| 76 | return __ieee754_exp(x); |
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| 77 | #else |
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| 78 | double z; |
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| 79 | struct exception exc; |
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| 80 | z = __ieee754_exp(x); |
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| 81 | if(_LIB_VERSION == _IEEE_) return z; |
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| 82 | if(finite(x)) { |
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| 83 | if(x>o_threshold) { |
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| 84 | /* exp(finite) overflow */ |
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| 85 | #ifndef HUGE_VAL |
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| 86 | #define HUGE_VAL inf |
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| 87 | double inf = 0.0; |
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| 88 | |
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| 89 | SET_HIGH_WORD(inf,0x7ff00000); /* set inf to infinite */ |
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| 90 | #endif |
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| 91 | exc.type = OVERFLOW; |
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| 92 | exc.name = "exp"; |
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| 93 | exc.err = 0; |
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| 94 | exc.arg1 = exc.arg2 = x; |
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| 95 | if (_LIB_VERSION == _SVID_) |
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| 96 | exc.retval = HUGE; |
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| 97 | else |
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| 98 | exc.retval = HUGE_VAL; |
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| 99 | if (_LIB_VERSION == _POSIX_) |
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| 100 | errno = ERANGE; |
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| 101 | else if (!matherr(&exc)) { |
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| 102 | errno = ERANGE; |
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| 103 | } |
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| 104 | if (exc.err != 0) |
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| 105 | errno = exc.err; |
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| 106 | return exc.retval; |
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| 107 | } else if(x<u_threshold) { |
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| 108 | /* exp(finite) underflow */ |
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| 109 | exc.type = UNDERFLOW; |
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| 110 | exc.name = "exp"; |
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| 111 | exc.err = 0; |
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| 112 | exc.arg1 = exc.arg2 = x; |
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| 113 | exc.retval = 0.0; |
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| 114 | if (_LIB_VERSION == _POSIX_) |
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| 115 | errno = ERANGE; |
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| 116 | else if (!matherr(&exc)) { |
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| 117 | errno = ERANGE; |
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| 118 | } |
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| 119 | if (exc.err != 0) |
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| 120 | errno = exc.err; |
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| 121 | return exc.retval; |
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| 122 | } |
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| 123 | } |
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| 124 | return z; |
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| 125 | #endif |
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| 126 | } |
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| 127 | |
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| 128 | #endif /* defined(_DOUBLE_IS_32BITS) */ |
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