# pow

```       #include <math.h>

double pow(double x, double y);
float powf(float x, float y);
long double powl(long double x, long double y);

Link with -lm.

Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

powf(), powl():
_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600 ||
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L;
or cc -std=c99

DESCRIPTION
These functions return the value of x raised to the power of y.

RETURN VALUE
On success, these functions return the value of x to the power of y.

If x is a finite value less than 0, and y is  a  finite  noninteger,  a
domain error occurs, and a NaN is returned.

If the result overflows, a range error occurs, and the functions return
HUGE_VAL, HUGE_VALF, or HUGE_VALL, respectively,  with  the  mathemati-
cally correct sign.

If  result  underflows, and is not representable, a range error occurs,
and 0.0 is returned.

Except as specified below, if x or y is a NaN, the result is a NaN.

If x is +1, the result is 1.0 (even if y is a NaN).

If y is 0, the result is 1.0 (even if x is a NaN).

If x is +0 (-0), and y is an odd integer greater than 0, the result  is
+0 (-0).

If  x  is 0, and y greater than 0 and not an odd integer, the result is
+0.

If x is -1, and y is positive infinity or negative infinity, the result
is 1.0.

If  the absolute value of x is less than 1, and y is negative infinity,
the result is positive infinity.

If the absolute value of x is greater than 1, and y is negative  infin-
ity, the result is +0.

If  the absolute value of x is less than 1, and y is positive infinity,
the result is +0.

If x is negative infinity, and y greater than 0 and not an odd integer,
the result is positive infinity.

If x is positive infinity, and y less than 0, the result is +0.

If x is positive infinity, and y greater than 0, the result is positive
infinity.

If x is +0 or -0, and y is an odd integer less than  0,  a  pole  error
occurs  and  HUGE_VAL,  HUGE_VALF,  or HUGE_VALL, is returned, with the
same sign as x.

If x is +0 or -0, and y is less than 0 and not an odd integer,  a  pole
error occurs and +HUGE_VAL, +HUGE_VALF, or +HUGE_VALL, is returned.

ERRORS
See  math_error(7) for information on how to determine whether an error
has occurred when calling these functions.

The following errors can occur:

Domain error: x is negative, and y is a finite noninteger
errno is set  to  EDOM.   An  invalid  floating-point  exception
(FE_INVALID) is raised.

Pole error: x is zero, and y is negative
errno  is set to ERANGE (but see BUGS).  A divide-by-zero float-
ing-point exception (FE_DIVBYZERO) is raised.

Range error: the result overflows
errno is set to ERANGE.  An  overflow  floating-point  exception
(FE_OVERFLOW) is raised.

Range error: the result underflows
errno  is  set to ERANGE.  An underflow floating-point exception
(FE_UNDERFLOW) is raised.

ATTRIBUTES
For  an  explanation  of  the  terms  used   in   this   section,   see
attributes(7).

+----------------------+---------------+---------+
|Interface             | Attribute     | Value   |
+----------------------+---------------+---------+
|pow(), powf(), powl() | Thread safety | MT-Safe |
+----------------------+---------------+---------+
CONFORMING TO
C99, POSIX.1-2001, POSIX.1-2008.

The variant returning double also conforms to SVr4, 4.3BSD, C89.

BUGS
On  64-bits, pow() may be more than 10,000 times slower for some (rare)

In  version  2.3.2  and  earlier,  when  an overflow or underflow error
occurs, glibc's pow() generates a bogus invalid  floating-point  excep-
tion (FE_INVALID) in addition to the overflow or underflow exception.

SEE ALSO
cbrt(3), cpow(3), sqrt(3)

COLOPHON
This  page  is  part of release 4.04 of the Linux man-pages project.  A
description of the project, information about reporting bugs,  and  the
latest     version     of     this    page,    can    be    found    at
http://www.kernel.org/doc/man-pages/.

2015-04-19                            POW(3)```