pow(3) — Linux manual page

NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | ATTRIBUTES | STANDARDS | HISTORY | BUGS | SEE ALSO

pow(3)                  Library Functions Manual                  pow(3)

NAME         top

       pow, powf, powl - power functions

LIBRARY         top

       Math library (libm, -lm)

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);

   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 <= 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 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 with the appropriate sign is returned.

       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.

       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 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 a finite value less than 0, and y is a finite noninteger,
       a domain error occurs, and a NaN is returned.

       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.

       Except as specified above, if x or y is a NaN, the result is a
       NaN.

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 │
       └─────────────────────────────────────┴───────────────┴─────────┘

STANDARDS         top

       C11, POSIX.1-2008.

HISTORY         top

       C99, POSIX.1-2001.

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

BUGS         top

   Historical bugs (now fixed)
       Before glibc 2.28, on some architectures (e.g., x86-64) pow() may
       be more than 10,000 times slower for some inputs than for other
       nearby inputs.  This affects only pow(), and not powf() nor
       powl().  This problem was fixed in glibc 2.28.

       A number of bugs in the glibc implementation of pow() were fixed
       in glibc 2.16.

       In glibc 2.9 and earlier, when a pole error occurs, errno is set
       to EDOM instead of the POSIX-mandated ERANGE.  Since glibc 2.10,
       glibc does the right thing.

       In glibc 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)

Linux man-pages (unreleased)     (date)                           pow(3)

Pages that refer to this page: cbrt(3)cpow(3)pow10(3)