| NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | CONFORMING TO | BUGS | SEE ALSO | COLOPHON | The Linux Programming Interface |
POW(3) Linux Programmer's Manual POW(3)
pow, powf, powl - power functions
#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
The pow() function returns the value of x raised to the power of y.
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.
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.
C99, POSIX.1-2001. The variant returning double also conforms to SVr4,
4.3BSD, C89.
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)
This page is part of release 3.32 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)
HTML rendering created 2010-12-03 by Michael Kerrisk, author of The Linux Programming Interface