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.TH POW 3M "Jul 12, 2006" "SunOS 5.11" "Mathematical Library Functions"
.SH NAME
pow, powf, powl \- power function
.SH SYNOPSIS
.LP
.nf
c99 [ \fIflag\fR... ] \fIfile\fR... \fB-lm\fR [ \fIlibrary\fR... ]
#include <math.h>

\fBdouble\fR \fBpow\fR(\fBdouble\fR x, \fBdouble\fR y);
.fi

.LP
.nf
\fBfloat\fR \fBpowf\fR(\fBfloat\fR x, \fBfloat\fR y);
.fi

.LP
.nf
\fBlong double\fR \fBpowl\fR(\fBlong double\fR x, \fBlong double\fR y);
.fi

.LP
.nf
cc [ \fIflag\fR... ] \fIfile\fR... \fB-lm\fR [ \fIlibrary\fR... ]
#include <math.h>

\fBdouble\fR \fBpow\fR(\fBdouble\fR x, \fBdouble\fR y);
.fi

.LP
.nf
\fBfloat\fR \fBpowf\fR(\fBfloat\fR x, \fBfloat\fR y);
.fi

.LP
.nf
\fBlong double\fR \fBpowl\fR(\fBlong double\fR x, \fBlong double\fR y);
.fi

.SH DESCRIPTION
.sp
.LP
These functions compute the value of \fIx\fR raised to the power \fIy,\fR
\fIx\fR^y>. If \fIx\fR is negative, \fIy\fR must be an integer value.
.SH RETURN VALUES
.sp
.LP
Upon successful completion, these functions return the value of \fIx\fR raised
to the power \fIy\fR.
.sp
.LP
For finite values of \fIx\fR < 0, and finite non-integer values of \fIy\fR, a
domain error occurs and either a NaN (if representable), or an
implementation-defined value is returned.
.sp
.LP
If the correct value would cause overflow, a range error occurs and
\fBpow()\fR, \fBpowf()\fR, and \fBpowl()\fR return \fBHUGE_VAL\fR,
\fBHUGE_VALF\fR, and \fBHUGE_VALL\fR, respectively.
.sp
.LP
If \fIx\fR or \fIy\fR is a NaN, a NaN is returned unless:
.RS +4
.TP
.ie t \(bu
.el o
If \fIx\fR is +1 and \fIy\fR is NaN and the application was compiled with the
\fBc99\fR compiler driver and is therefore SUSv3-conforming (see
\fBstandards\fR(7)), 1.0 is returned.
.RE
.RS +4
.TP
.ie t \(bu
.el o
For any value of \fIx\fR (including NaN), if \fIy\fR is +0, 1.0 is returned.
.RE
.sp
.LP
For any odd integer value of \fIy\fR > 0, if \fIx\fR is \(+-0, \(+-0 is
returned.
.sp
.LP
For \fIy\fR > 0 and not an odd integer, if \fIx\fR is \(+-0, +0 is returned.
.sp
.LP
If \fIx\fR is \(+-1 and \fIy\fR is \(+-Inf, and the application was compiled
with the \fBcc\fR compiler driver, NaN is returned. If, however, the
application was compiled with the \fBc99\fR compiler driver and is therefore
SUSv3-conforming (see \fBstandards\fR(7)), 1.0 is returned.
.sp
.LP
For |\fIx\fR| < 1, if \fIy\fR is \(miInf, +Inf is returned.
.sp
.LP
For |\fIx\fR| > 1, if \fIy\fR is \(miInf, +0 is returned.
.sp
.LP
For |\fIx\fR| < 1, if \fIy\fR is +Inf, +0 is returned.
.sp
.LP
For |\fIx\fR| > 1, if \fIy\fR is +Inf, +Inf is returned.
.sp
.LP
For \fIy\fR an odd integer < 0, if \fIx\fR is \(miInf, \(mi0 is returned.
.sp
.LP
For \fIy\fR < 0 and not an odd integer, if \fIx\fR is \(miInf, +0 is returned.
.sp
.LP
For \fIy\fR an odd integer > 0, if \fIx\fR is \(miInf, \(miInf is returned.
.sp
.LP
For \fIy\fR > 0 and not an odd integer, if \fIx\fR is \(miInf, +Inf is
returned.
.sp
.LP
For \fIy\fR < 0, if \fIx\fR is +Inf, +0 is returned.
.sp
.LP
For \fIy\fR > 0, if \fIx\fR is +Inf, +Inf is returned.
.sp
.LP
For \fIy\fR an odd integer < 0, if \fIx\fR is \(+-0, a pole error occurs and
\(+-\fBHUGE_VAL\fR, \(+-\fBHUGE_VALF\fR, and \(+-\fBHUGE_VALL\fR are returned
for \fBpow()\fR, \fBpowf()\fR, and \fBpowl()\fR, respectively.
.sp
.LP
For \fIy\fR < 0 and not an odd integer, if \fIx\fR is \(+-0, a pole error
occurs and \fBHUGE_VAL\fR, \fBHUGE_VALF\fR, and \fBHUGE_VALL\fR are returned
for \fBpow()\fR, \fBpowf()\fR, and \fBpowl()\fR, respectively.
.sp
.LP
For exceptional cases, \fBmatherr\fR(3M) tabulates the values to be returned by
\fBpow()\fR as specified by SVID3 and XPG3.
.SH ERRORS
.sp
.LP
These functions will fail if:
.sp
.ne 2
.mk
.na
\fBDomain Error\fR
.ad
.RS 16n
.rt
The value of \fIx\fR is negative and \fIy\fR is a finite non-integer.
.sp
If the integer expression (\fBmath_errhandling\fR & \fBMATH_ERREXCEPT\fR) is
non-zero, the invalid floating-point exception is raised.
.sp
The \fBpow()\fR function sets \fBerrno\fR to \fBEDOM\fR if the value of \fIx\fR
is negative and \fIy\fR is non-integral.
.RE

.sp
.ne 2
.mk
.na
\fBPole Error\fR
.ad
.RS 16n
.rt
The value of \fIx\fR is 0 and \fIy\fR is negative.
.sp
If the integer expression (\fBmath_errhandling\fR & \fBMATH_ERREXCEPT\fR) is
non-zero, the divide-by-zero floating-point exception is raised.
.RE

.sp
.ne 2
.mk
.na
\fBRange Error\fR
.ad
.RS 16n
.rt
The result overflows.
.sp
If the integer expression (\fBmath_errhandling\fR & \fBMATH_ERREXCEPT\fR) is
non-zero, the overflow floating-point exception is raised.
.sp
The \fBpow()\fR function sets \fBerrno\fR to \fBEDOM\fR if the value to be
returned would cause overflow.
.RE

.SH USAGE
.sp
.LP
An application wanting to check for exceptions should call
\fBfeclearexcept\fR(\fBFE_ALL_EXCEPT\fR) before calling these functions. On
return, if \fBfetestexcept\fR(\fBFE_INVALID\fR | \fBFE_DIVBYZERO\fR |
\fBFE_OVERFLOW\fR | \fBFE_UNDERFLOW\fR) is non-zero, an exception has been
raised. An application should either examine the return value or check the
floating point exception flags to detect exceptions.
.sp
.LP
An application can also set \fBerrno\fR to 0 before calling \fBpow()\fR. On
return, if \fBerrno\fR is non-zero, an error has occurred. The \fBpowf()\fR and
\fBpowl()\fR functions do not set \fBerrno\fR.
.SH ATTRIBUTES
.sp
.LP
See \fBattributes\fR(7) for descriptions of the following attributes:
.sp

.sp
.TS
tab(	) box;
cw(2.75i) |cw(2.75i)
lw(2.75i) |lw(2.75i)
.
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
Interface Stability	Standard
_
MT-Level	MT-Safe
.TE

.SH SEE ALSO
.sp
.LP
.BR math.h (3HEAD),
.BR exp (3M),
.BR feclearexcept (3M),
.BR fetestexcept (3M),
.BR isnan (3M),
.BR matherr (3M),
.BR attributes (7),
.BR standards (7)
.SH NOTES
.sp
.LP
Prior to Solaris 2.6,  there was a conflict between the \fBpow()\fR function in
this library and the \fBpow()\fR function in the \fBlibmp\fR library. This
conflict was resolved by prepending \fBmp_\fR to all functions in the
\fBlibmp\fR library. See \fBmp\fR(3MP) for more information.