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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