illumos-gate New usr/src/man/man3m/pow.3m

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  12 .TH pow 3M "12 Jul 2006" "SunOS 5.11" "Mathematical Library Functions"
  13 .SH NAME
  14 pow, powf, powl \- power function
  15 .SH SYNOPSIS
  16 .LP
  17 .nf
  18 c99 [ \fIflag\fR... ] \fIfile\fR... \fB-lm\fR [ \fIlibrary\fR... ]
  19 #include <math.h>
  20 
  21 \fBdouble\fR \fBpow\fR(\fBdouble\fR x, \fBdouble\fR y);
  22 .fi
  23 
  24 .LP
  25 .nf
  26 \fBfloat\fR \fBpowf\fR(\fBfloat\fR x, \fBfloat\fR y);
  27 .fi
  28 
  29 .LP
  30 .nf
  31 \fBlong double\fR \fBpowl\fR(\fBlong double\fR x, \fBlong double\fR y);
  32 .fi
  33 
  34 .LP
  35 .nf
  36 cc [ \fIflag\fR... ] \fIfile\fR... \fB-lm\fR [ \fIlibrary\fR... ]
  37 #include <math.h>
  38 
  39 \fBdouble\fR \fBpow\fR(\fBdouble\fR x, \fBdouble\fR y);
  40 .fi
  41 
  42 .LP
  43 .nf
  44 \fBfloat\fR \fBpowf\fR(\fBfloat\fR x, \fBfloat\fR y);
  45 .fi
  46 
  47 .LP
  48 .nf
  49 \fBlong double\fR \fBpowl\fR(\fBlong double\fR x, \fBlong double\fR y);
  50 .fi
  51 
  52 .SH DESCRIPTION
  53 .sp
  54 .LP
  55 These functions compute the value of \fIx\fR raised to the power \fIy,\fR
  56 \fIx\fR^y>. If \fIx\fR is negative, \fIy\fR must be an integer value.
  57 .SH RETURN VALUES
  58 .sp
  59 .LP
  60 Upon successful completion, these functions return the value of \fIx\fR raised
  61 to the power \fIy\fR.
  62 .sp
  63 .LP
  64 For finite values of \fIx\fR < 0, and finite non-integer values of \fIy\fR, a
  65 domain error occurs and either a NaN (if representable), or an
  66 implementation-defined value is returned.
  67 .sp
  68 .LP
  69 If the correct value would cause overflow, a range error occurs and
  70 \fBpow()\fR, \fBpowf()\fR, and \fBpowl()\fR return \fBHUGE_VAL\fR,
  71 \fBHUGE_VALF\fR, and \fBHUGE_VALL\fR, respectively.
  72 .sp
  73 .LP
  74 If \fIx\fR or \fIy\fR is a NaN, a NaN is returned unless:
  75 .RS +4
  76 .TP
  77 .ie t \(bu
  78 .el o
  79 If \fIx\fR is +1 and \fIy\fR is NaN and the application was compiled with the
  80 \fBc99\fR compiler driver and is therefore SUSv3-conforming (see
  81 \fBstandards\fR(5)), 1.0 is returned.
  82 .RE
  83 .RS +4
  84 .TP
  85 .ie t \(bu
  86 .el o
  87 For any value of \fIx\fR (including NaN), if \fIy\fR is +0, 1.0 is returned.
  88 .RE
  89 .sp
  90 .LP
  91 For any odd integer value of \fIy\fR > 0, if \fIx\fR is \(+-0, \(+-0 is
  92 returned.
  93 .sp
  94 .LP
  95 For \fIy\fR > 0 and not an odd integer, if \fIx\fR is \(+-0, +0 is returned.
  96 .sp
  97 .LP
  98 If \fIx\fR is \(+-1 and \fIy\fR is \(+-Inf, and the application was compiled
  99 with the \fBcc\fR compiler driver, NaN is returned. If, however, the
 100 application was compiled with the \fBc99\fR compiler driver and is therefore
 101 SUSv3-conforming (see\fBstandards\fR(5)), 1.0 is returned.
 102 .sp
 103 .LP
 104 For |\fIx\fR| < 1, if \fIy\fR is \(miInf, +Inf is returned.
 105 .sp
 106 .LP
 107 For |\fIx\fR| > 1, if \fIy\fR is \(miInf, +0 is returned.
 108 .sp
 109 .LP
 110 For |\fIx\fR| < 1, if \fIy\fR is +Inf, +0 is returned.
 111 .sp
 112 .LP
 113 For |\fIx\fR| > 1, if \fIy\fR is +Inf, +Inf is returned.
 114 .sp
 115 .LP
 116 For \fIy\fR an odd integer < 0, if \fIx\fR is \(miInf, \(mi0 is returned.
 117 .sp
 118 .LP
 119 For \fIy\fR < 0 and not an odd integer, if \fIx\fR is \(miInf, +0 is returned.
 120 .sp
 121 .LP
 122 For \fIy\fR an odd integer > 0, if \fIx\fR is \(miInf, \(miInf is returned.
 123 .sp
 124 .LP
 125 For \fIy\fR > 0 and not an odd integer, if \fIx\fR is \(miInf, +Inf is
 126 returned.
 127 .sp
 128 .LP
 129 For \fIy\fR < 0, if \fIx\fR is +Inf, +0 is returned.
 130 .sp
 131 .LP
 132 For \fIy\fR > 0, if \fIx\fR is +Inf, +Inf is returned.
 133 .sp
 134 .LP
 135 For \fIy\fR an odd integer < 0, if \fIx\fR is \(+-0, a pole error occurs and
 136 \(+-\fBHUGE_VAL\fR, \(+-\fBHUGE_VALF\fR, and \(+-\fBHUGE_VALL\fR are returned
 137 for \fBpow()\fR, \fBpowf()\fR, and \fBpowl()\fR, respectively.
 138 .sp
 139 .LP
 140 For \fIy\fR < 0 and not an odd integer, if \fIx\fR is \(+-0, a pole error
 141 occurs and \fBHUGE_VAL\fR, \fBHUGE_VALF\fR, and \fBHUGE_VALL\fR are returned
 142 for \fBpow()\fR, \fBpowf()\fR, and \fBpowl()\fR, respectively.
 143 .sp
 144 .LP
 145 For exceptional cases, \fBmatherr\fR(3M) tabulates the values to be returned by
 146 \fBpow()\fR as specified by SVID3 and XPG3.
 147 .SH ERRORS
 148 .sp
 149 .LP
 150 These functions will fail if:
 151 .sp
 152 .ne 2
 153 .mk
 154 .na
 155 \fBDomain Error\fR
 156 .ad
 157 .RS 16n
 158 .rt  
 159 The value of \fIx\fR is negative and \fIy\fR is a finite non-integer.
 160 .sp
 161 If the integer expression (\fBmath_errhandling\fR & \fBMATH_ERREXCEPT\fR) is
 162 non-zero, the invalid floating-point exception is raised.
 163 .sp
 164 The \fBpow()\fR function sets \fBerrno\fR to \fBEDOM\fR if the value of \fIx\fR
 165 is negative and \fIy\fR is non-integral.
 166 .RE
 167 
 168 .sp
 169 .ne 2
 170 .mk
 171 .na
 172 \fBPole Error\fR
 173 .ad
 174 .RS 16n
 175 .rt  
 176 The value of \fIx\fR is 0 and \fIy\fR is negative.
 177 .sp
 178 If the integer expression (\fBmath_errhandling\fR & \fBMATH_ERREXCEPT\fR) is
 179 non-zero, the divide-by-zero floating-point exception is raised.
 180 .RE
 181 
 182 .sp
 183 .ne 2
 184 .mk
 185 .na
 186 \fBRange Error\fR
 187 .ad
 188 .RS 16n
 189 .rt  
 190 The result overflows.
 191 .sp
 192 If the integer expression (\fBmath_errhandling\fR & \fBMATH_ERREXCEPT\fR) is
 193 non-zero, the overflow floating-point exception is raised.
 194 .sp
 195 The \fBpow()\fR function sets \fBerrno\fR to \fBEDOM\fR if the value to be
 196 returned would cause overflow.
 197 .RE
 198 
 199 .SH USAGE
 200 .sp
 201 .LP
 202 An application wanting to check for exceptions should call
 203 \fBfeclearexcept\fR(\fBFE_ALL_EXCEPT\fR) before calling these functions. On
 204 return, if \fBfetestexcept\fR(\fBFE_INVALID\fR | \fBFE_DIVBYZERO\fR |
 205 \fBFE_OVERFLOW\fR | \fBFE_UNDERFLOW\fR) is non-zero, an exception has been
 206 raised. An application should either examine the return value or check the
 207 floating point exception flags to detect exceptions.
 208 .sp
 209 .LP
 210 An application can also set \fBerrno\fR to 0 before calling \fBpow()\fR. On
 211 return, if \fBerrno\fR is non-zero, an error has occurred. The \fBpowf()\fR and
 212 \fBpowl()\fR functions do not set \fBerrno\fR.
 213 .SH ATTRIBUTES
 214 .sp
 215 .LP
 216 See \fBattributes\fR(5) for descriptions of the following attributes:
 217 .sp
 218 
 219 .sp
 220 .TS
 221 tab() box;
 222 cw(2.75i) |cw(2.75i) 
 223 lw(2.75i) |lw(2.75i) 
 224 .
 225 ATTRIBUTE TYPEATTRIBUTE VALUE
 226 _
 227 Interface StabilityStandard
 228 _
 229 MT-LevelMT-Safe
 230 .TE
 231 
 232 .SH SEE ALSO
 233 .sp
 234 .LP
 235 \fBexp\fR(3M), \fBfeclearexcept\fR(3M), \fBfetestexcept\fR(3M),
 236 \fBisnan\fR(3M), \fBmath.h\fR(3HEAD), \fBmatherr\fR(3M), \fBattributes\fR(5),
 237 \fBstandards\fR(5)
 238 .SH NOTES
 239 .sp
 240 .LP
 241 Prior to Solaris 2.6,  there was a conflict between the \fBpow()\fR function in
 242 this library and the \fBpow()\fR function in the \fBlibmp\fR library. This
 243 conflict was resolved by prepending \fBmp_\fR to all functions in the
 244 \fBlibmp\fR library. See \fBmp\fR(3MP) for more information.