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3 | /* @(#)w_pow.c 5.2 93/10/01 */ |
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4 | /* |
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5 | * ==================================================== |
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6 | * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. |
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7 | * |
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8 | * Developed at SunPro, a Sun Microsystems, Inc. business. |
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9 | * Permission to use, copy, modify, and distribute this |
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10 | * software is freely granted, provided that this notice |
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11 | * is preserved. |
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12 | * ==================================================== |
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13 | */ |
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14 | |
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15 | /* |
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16 | FUNCTION |
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17 | <<pow>>, <<powf>>---x to the power y |
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18 | INDEX |
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19 | pow |
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20 | INDEX |
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21 | powf |
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22 | |
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23 | |
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24 | SYNOPSIS |
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25 | #include <math.h> |
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26 | double pow(double <[x]>, double <[y]>); |
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27 | float powf(float <[x]>, float <[y]>); |
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28 | |
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29 | DESCRIPTION |
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30 | <<pow>> and <<powf>> calculate <[x]> raised to the exponent <[y]>. |
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31 | @tex |
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32 | (That is, $x^y$.) |
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33 | @end tex |
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34 | |
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35 | RETURNS |
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36 | On success, <<pow>> and <<powf>> return the value calculated. |
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37 | |
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38 | When the argument values would produce overflow, <<pow>> |
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39 | returns <<HUGE_VAL>> and set <<errno>> to <<ERANGE>>. If the |
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40 | argument <[x]> passed to <<pow>> or <<powf>> is a negative |
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41 | noninteger, and <[y]> is also not an integer, then <<errno>> |
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42 | is set to <<EDOM>>. If <[x]> and <[y]> are both 0, then |
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43 | <<pow>> and <<powf>> return <<1>>. |
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44 | |
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45 | You can modify error handling for these functions using <<matherr>>. |
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46 | |
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47 | PORTABILITY |
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48 | <<pow>> is ANSI C. <<powf>> is an extension. */ |
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49 | |
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50 | /* |
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51 | * wrapper pow(x,y) return x**y |
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52 | */ |
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53 | |
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54 | #include "fdlibm.h" |
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55 | #include <errno.h> |
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56 | |
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57 | #ifndef _DOUBLE_IS_32BITS |
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58 | |
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59 | #ifdef __STDC__ |
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60 | double pow(double x, double y) /* wrapper pow */ |
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61 | #else |
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62 | double pow(x,y) /* wrapper pow */ |
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63 | double x,y; |
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64 | #endif |
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65 | { |
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66 | #ifdef _IEEE_LIBM |
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67 | return __ieee754_pow(x,y); |
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68 | #else |
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69 | double z; |
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70 | #ifndef HUGE_VAL |
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71 | #define HUGE_VAL inf |
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72 | double inf = 0.0; |
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73 | |
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74 | SET_HIGH_WORD(inf,0x7ff00000); /* set inf to infinite */ |
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75 | #endif |
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76 | struct exception exc; |
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77 | z=__ieee754_pow(x,y); |
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78 | if(_LIB_VERSION == _IEEE_|| isnan(y)) return z; |
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79 | if(isnan(x)) { |
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80 | if(y==0.0) { |
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81 | /* pow(NaN,0.0) */ |
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82 | /* error only if _LIB_VERSION == _SVID_ & _XOPEN_ */ |
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83 | exc.type = DOMAIN; |
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84 | exc.name = "pow"; |
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85 | exc.err = 0; |
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86 | exc.arg1 = x; |
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87 | exc.arg2 = y; |
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88 | exc.retval = 1.0; |
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89 | if (_LIB_VERSION == _IEEE_ || |
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90 | _LIB_VERSION == _POSIX_) exc.retval = 1.0; |
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91 | else if (!matherr(&exc)) { |
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92 | errno = EDOM; |
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93 | } |
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94 | if (exc.err != 0) |
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95 | errno = exc.err; |
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96 | return exc.retval; |
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97 | } else |
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98 | return z; |
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99 | } |
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100 | if(x==0.0){ |
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101 | if(y==0.0) { |
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102 | /* pow(0.0,0.0) */ |
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103 | /* error only if _LIB_VERSION == _SVID_ */ |
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104 | exc.type = DOMAIN; |
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105 | exc.name = "pow"; |
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106 | exc.err = 0; |
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107 | exc.arg1 = x; |
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108 | exc.arg2 = y; |
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109 | exc.retval = 0.0; |
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110 | if (_LIB_VERSION != _SVID_) exc.retval = 1.0; |
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111 | else if (!matherr(&exc)) { |
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112 | errno = EDOM; |
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113 | } |
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114 | if (exc.err != 0) |
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115 | errno = exc.err; |
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116 | return exc.retval; |
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117 | } |
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118 | if(finite(y)&&y<0.0) { |
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119 | /* 0**neg */ |
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120 | exc.type = DOMAIN; |
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121 | exc.name = "pow"; |
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122 | exc.err = 0; |
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123 | exc.arg1 = x; |
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124 | exc.arg2 = y; |
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125 | if (_LIB_VERSION == _SVID_) |
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126 | exc.retval = 0.0; |
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127 | else |
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128 | exc.retval = -HUGE_VAL; |
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129 | if (_LIB_VERSION == _POSIX_) |
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130 | errno = EDOM; |
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131 | else if (!matherr(&exc)) { |
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132 | errno = EDOM; |
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133 | } |
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134 | if (exc.err != 0) |
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135 | errno = exc.err; |
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136 | return exc.retval; |
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137 | } |
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138 | return z; |
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139 | } |
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140 | if(!finite(z)) { |
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141 | if(finite(x)&&finite(y)) { |
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142 | if(isnan(z)) { |
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143 | /* neg**non-integral */ |
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144 | exc.type = DOMAIN; |
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145 | exc.name = "pow"; |
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146 | exc.err = 0; |
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147 | exc.arg1 = x; |
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148 | exc.arg2 = y; |
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149 | if (_LIB_VERSION == _SVID_) |
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150 | exc.retval = 0.0; |
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151 | else |
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152 | exc.retval = 0.0/0.0; /* X/Open allow NaN */ |
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153 | if (_LIB_VERSION == _POSIX_) |
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154 | errno = EDOM; |
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155 | else if (!matherr(&exc)) { |
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156 | errno = EDOM; |
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157 | } |
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158 | if (exc.err != 0) |
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159 | errno = exc.err; |
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160 | return exc.retval; |
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161 | } else { |
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162 | /* pow(x,y) overflow */ |
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163 | exc.type = OVERFLOW; |
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164 | exc.name = "pow"; |
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165 | exc.err = 0; |
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166 | exc.arg1 = x; |
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167 | exc.arg2 = y; |
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168 | if (_LIB_VERSION == _SVID_) { |
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169 | exc.retval = HUGE; |
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170 | y *= 0.5; |
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171 | if(x<0.0&&rint(y)!=y) exc.retval = -HUGE; |
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172 | } else { |
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173 | exc.retval = HUGE_VAL; |
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174 | y *= 0.5; |
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175 | if(x<0.0&&rint(y)!=y) exc.retval = -HUGE_VAL; |
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176 | } |
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177 | if (_LIB_VERSION == _POSIX_) |
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178 | errno = ERANGE; |
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179 | else if (!matherr(&exc)) { |
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180 | errno = ERANGE; |
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181 | } |
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182 | if (exc.err != 0) |
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183 | errno = exc.err; |
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184 | return exc.retval; |
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185 | } |
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186 | } |
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187 | } |
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188 | if(z==0.0&&finite(x)&&finite(y)) { |
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189 | /* pow(x,y) underflow */ |
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190 | exc.type = UNDERFLOW; |
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191 | exc.name = "pow"; |
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192 | exc.err = 0; |
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193 | exc.arg1 = x; |
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194 | exc.arg2 = y; |
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195 | exc.retval = 0.0; |
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196 | if (_LIB_VERSION == _POSIX_) |
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197 | errno = ERANGE; |
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198 | else if (!matherr(&exc)) { |
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199 | errno = ERANGE; |
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200 | } |
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201 | if (exc.err != 0) |
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202 | errno = exc.err; |
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203 | return exc.retval; |
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204 | } |
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205 | return z; |
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206 | #endif |
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207 | } |
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208 | |
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209 | #endif /* defined(_DOUBLE_IS_32BITS) */ |
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