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

       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 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

       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.

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) inputs than for
       other nearby inputs.  This affects only pow(), and not powf() nor powl().

       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.

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)