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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 || _POSIX_C_SOURCE >=	200112L;
	   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 do-
       main 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 the absolute value of	x is greater than 1, and y is positive	infin-
       ity, the	result is positive infinity.

       If x is negative	infinity, and y	is an odd integer less than 0, the re-
       sult 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 oc-
       curs  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.

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

BUGS
       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_IN-
       VALID)  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 oc-
       curs, 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 3.74 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/.

				  2010-09-12				POW(3)

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | CONFORMING TO | BUGS | SEE ALSO | COLOPHON

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