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():
           _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
               || /* Since glibc 2.19: */ _DEFAULT_SOURCE
               || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

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 5.05 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 https://www.kernel.org/doc/man-pages/.

                                            2017-09-15                                     POW(3)