pow(3p) — Linux manual page

PROLOG | NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | EXAMPLES | APPLICATION USAGE | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT

POW(3P)                 POSIX Programmer's Manual                POW(3P)

PROLOG         top

       This manual page is part of the POSIX Programmer's Manual.  The
       Linux implementation of this interface may differ (consult the
       corresponding Linux manual page for details of Linux behavior),
       or the interface may not be implemented on Linux.

NAME         top

       pow, powf, powl — power function

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);

DESCRIPTION         top

       The functionality described on this reference page is aligned
       with the ISO C standard. Any conflict between the requirements
       described here and the ISO C standard is unintentional. This
       volume of POSIX.1‐2017 defers to the ISO C standard.

       These functions shall compute the value of x raised to the power
       y, xy.  If x is negative, the application shall ensure that y is
       an integer value.

       An application wishing to check for error situations should set
       errno to zero and call feclearexcept(FE_ALL_EXCEPT) before
       calling these functions. On return, if errno is non-zero or
       fetestexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW |
       FE_UNDERFLOW) is non-zero, an error has occurred.

RETURN VALUE         top

       Upon successful completion, these functions shall return the
       value of x raised to the power y.

       For finite values of x < 0, and finite non-integer values of y, a
       domain error shall occur and either a NaN (if representable), or
       an implementation-defined value shall be returned.

       If the correct value would cause overflow, a range error shall
       occur and pow(), powf(), and powl() shall return ±HUGE_VAL,
       ±HUGE_VALF, and ±HUGE_VALL, respectively, with the same sign as
       the correct value of the function.

       If the correct value would cause underflow, and is not
       representable, a range error may occur, and pow(), powf(), and
       powl() shall return 0.0, or (if IEC 60559 Floating-Point is not
       supported) an implementation-defined value no greater in
       magnitude than DBL_MIN, FLT_MIN, and LDBL_MIN, respectively.

       For y < 0, if x is zero, a pole error may occur and pow(),
       powf(), and powl() shall return ±HUGE_VAL, ±HUGE_VALF, and
       ±HUGE_VALL, respectively.  On systems that support the IEC 60559
       Floating-Point option, if x is ±0, a pole error shall occur and
       pow(), powf(), and powl() shall return ±HUGE_VAL, ±HUGE_VALF, and
       ±HUGE_VALL, respectively if y is an odd integer, or HUGE_VAL,
       HUGE_VALF, and HUGE_VALL, respectively if y is not an odd
       integer.

       If x or y is a NaN, a NaN shall be returned (unless specified
       elsewhere in this description).

       For any value of y (including NaN), if x is +1, 1.0 shall be
       returned.

       For any value of x (including NaN), if y is ±0, 1.0 shall be
       returned.

       For any odd integer value of y > 0, if x is ±0, ±0 shall be
       returned.

       For y > 0 and not an odd integer, if x is ±0, +0 shall be
       returned.

       If x is -1, and y is ±Inf, 1.0 shall be returned.

       For |x| < 1, if y is -Inf, +Inf shall be returned.

       For |x| > 1, if y is -Inf, +0 shall be returned.

       For |x| < 1, if y is +Inf, +0 shall be returned.

       For |x| > 1, if y is +Inf, +Inf shall be returned.

       For y an odd integer < 0, if x is -Inf, -0 shall be returned.

       For y < 0 and not an odd integer, if x is -Inf, +0 shall be
       returned.

       For y an odd integer > 0, if x is -Inf, -Inf shall be returned.

       For y > 0 and not an odd integer, if x is -Inf, +Inf shall be
       returned.

       For y < 0, if x is +Inf, +0 shall be returned.

       For y > 0, if x is +Inf, +Inf shall be returned.

       If the correct value would cause underflow, and is representable,
       a range error may occur and the correct value shall be returned.

ERRORS         top

       These functions shall fail if:

       Domain Error
                   The value of x is negative and y is a finite non-
                   integer.

                   If the integer expression (math_errhandling &
                   MATH_ERRNO) is non-zero, then errno shall be set to
                   [EDOM].  If the integer expression (math_errhandling
                   & MATH_ERREXCEPT) is non-zero, then the invalid
                   floating-point exception shall be raised.

       Pole Error  The value of x is zero and y is negative.

                   If the integer expression (math_errhandling &
                   MATH_ERRNO) is non-zero, then errno shall be set to
                   [ERANGE].  If the integer expression
                   (math_errhandling & MATH_ERREXCEPT) is non-zero, then
                   the divide-by-zero floating-point exception shall be
                   raised.

       Range Error The result overflows.

                   If the integer expression (math_errhandling &
                   MATH_ERRNO) is non-zero, then errno shall be set to
                   [ERANGE].  If the integer expression
                   (math_errhandling & MATH_ERREXCEPT) is non-zero, then
                   the overflow floating-point exception shall be
                   raised.

       These functions may fail if:

       Pole Error  The value of x is zero and y is negative.

                   If the integer expression (math_errhandling &
                   MATH_ERRNO) is non-zero, then errno shall be set to
                   [ERANGE].  If the integer expression
                   (math_errhandling & MATH_ERREXCEPT) is non-zero, then
                   the divide-by-zero floating-point exception shall be
                   raised.

       Range Error The result underflows.

                   If the integer expression (math_errhandling &
                   MATH_ERRNO) is non-zero, then errno shall be set to
                   [ERANGE].  If the integer expression
                   (math_errhandling & MATH_ERREXCEPT) is non-zero, then
                   the underflow floating-point exception shall be
                   raised.

       The following sections are informative.

EXAMPLES         top

       None.

APPLICATION USAGE         top

       On error, the expressions (math_errhandling & MATH_ERRNO) and
       (math_errhandling & MATH_ERREXCEPT) are independent of each
       other, but at least one of them must be non-zero.

RATIONALE         top

       None.

FUTURE DIRECTIONS         top

       None.

SEE ALSO         top

       exp(3p), feclearexcept(3p), fetestexcept(3p), isnan(3p)

       The Base Definitions volume of POSIX.1‐2017, Section 4.20,
       Treatment of Error Conditions for Mathematical Functions,
       math.h(0p)

COPYRIGHT         top

       Portions of this text are reprinted and reproduced in electronic
       form from IEEE Std 1003.1-2017, Standard for Information
       Technology -- Portable Operating System Interface (POSIX), The
       Open Group Base Specifications Issue 7, 2018 Edition, Copyright
       (C) 2018 by the Institute of Electrical and Electronics
       Engineers, Inc and The Open Group.  In the event of any
       discrepancy between this version and the original IEEE and The
       Open Group Standard, the original IEEE and The Open Group
       Standard is the referee document. The original Standard can be
       obtained online at http://www.opengroup.org/unix/online.html .

       Any typographical or formatting errors that appear in this page
       are most likely to have been introduced during the conversion of
       the source files to man page format. To report such errors, see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .

IEEE/The Open Group               2017                           POW(3P)

Pages that refer to this page: math.h(0p)log10(3p)