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

NAME

       pow, powf, powl - power functions

SYNOPSIS

       #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; or cc -std=c99

DESCRIPTION

       The pow() function returns 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 mathemat-
       ically 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

       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

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

BUGS

       For a pole error, errno is set to EDOM; POSIX.1 says it should be set to ERANGE.

       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.

SEE ALSO

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

COLOPHON

       This page is part of release 3.25 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/.

								    2008-08-10								    POW(3)