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```POW(3)                    Linux Programmer's Manual                   POW(3)
```

## NAME         top

```       pow, powf, powl - power functions
```

## SYNOPSIS         top

```       #include <math.h>

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

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         top

```       The pow() function returns the value of x raised to the power of y.
```

## RETURN VALUE         top

```       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
mathematically 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
infinity, the result is +0.

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

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

If x is negative infinity, and y is an odd integer less than 0, the
result is -0.

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

If x is negative infinity, and y is an odd integer greater than 0,
the result is negative infinity.

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         top

```       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
floating-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.
```

## CONFORMING TO         top

```       C99, POSIX.1-2001.  The variant returning double also conforms to
SVr4, 4.3BSD, C89.
```

## BUGS         top

```       In glibc 2.9 and earlier, when a pole error occurs, errno is set to
EDOM instead of the POSIX-mandated ERANGE.  Since version 2.10, glibc
does the right thing.

If x is negative, then large negative or positive y values yield a
NaN as the function result, with errno set to EDOM, and an invalid
(FE_INVALID) floating-point exception.  For example, with pow(), one
sees this behavior when the absolute value of y is greater than about
9.223373e18.

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

```       cbrt(3), cpow(3), sqrt(3)
```

## COLOPHON         top

```       This page is part of release 3.51 of the Linux man-pages project.  A
description of the project, and information about reporting bugs, can
be found at http://www.kernel.org/doc/man-pages/.

2010-09-12                           POW(3)
```