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

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

NAME         top

       pow, powf, powl - power functions

SYNOPSIS         top

       #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         top

       These functions return the value of x raised to the power of y.

RETURN VALUE         top

       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         top

       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         top

       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         top

       C99, POSIX.1-2001, POSIX.1-2008.

       The variant returning double also conforms to SVr4, 4.3BSD, C89.

BUGS         top

       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         top

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

COLOPHON         top

       This page is part of release 4.08 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/.

                                 2016-03-15                           POW(3)