{"id":5050,"date":"2022-12-20T18:37:04","date_gmt":"2022-12-20T21:37:04","guid":{"rendered":"http:\/\/lode.uno\/linux-man\/index.php\/2022\/12\/20\/pow-man3p\/"},"modified":"2022-12-20T18:37:04","modified_gmt":"2022-12-20T21:37:04","slug":"pow-man3p","status":"publish","type":"post","link":"https:\/\/lode.uno\/linux-man\/2022\/12\/20\/pow-man3p\/","title":{"rendered":"POW (man3p)"},"content":{"rendered":"

POW<\/h1>\n

PROLOG<\/a>
NAME<\/a>
SYNOPSIS<\/a>
DESCRIPTION<\/a>
RETURN VALUE<\/a>
ERRORS<\/a>
EXAMPLES<\/a>
APPLICATION USAGE<\/a>
RATIONALE<\/a>
FUTURE DIRECTIONS<\/a>
SEE ALSO<\/a>
COPYRIGHT<\/a> <\/p>\n

\n

PROLOG <\/a> <\/h2>\n

This manual page is part of the POSIX Programmer\u2019s 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.<\/p>\n

NAME <\/a> <\/h2>\n

pow, powf, powl \u2014 power function<\/p>\n

SYNOPSIS <\/a> <\/h2>\n

#include <\/p>\n

double pow(double x<\/i>, double y<\/i>);
float powf(float x<\/i>, float y<\/i>);
long double powl(long double x<\/i>, long double y<\/i>);<\/p>\n

DESCRIPTION <\/a> <\/h2>\n

The functionality described on this reference page is aligned with the ISO\u00a0C standard. Any conflict between the requirements described here and the ISO\u00a0C standard is unintentional. This volume of POSIX.1-2017 defers to the ISO\u00a0C standard.<\/p>\n

These functions shall compute the value of x<\/i> raised to the power y<\/i>, x y<\/small><\/small><\/i> . If x<\/i> is negative, the application shall ensure that y<\/i> is an integer value.<\/p>\n

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

RETURN VALUE <\/a> <\/h2>\n

Upon successful completion, these functions shall return the value of x<\/i> raised to the power y<\/i>.<\/p>\n

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

If the correct value would cause overflow, a range error shall occur and pow<\/i>(), powf<\/i>(), and powl<\/i>() shall return \u00b1HUGE_VAL, \u00b1HUGE_VALF, and \u00b1HUGE_VALL, respectively, with the same sign as the correct value of the function.<\/p>\n

If the correct value would cause underflow, and is not representable, a range error may occur, and pow<\/i>(), powf<\/i>(), and powl<\/i>() 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.<\/p>\n

For y<\/i> < 0, if x<\/i> is zero, a pole error may occur and pow<\/i>(), powf<\/i>(), and powl<\/i>() shall return \u00b1HUGE_VAL, \u00b1HUGE_VALF, and \u00b1HUGE_VALL, respectively. On systems that support the IEC 60559 Floating-Point option, if x<\/i> is \u00b10, a pole error shall occur and pow<\/i>(), powf<\/i>(), and powl<\/i>() shall return \u00b1HUGE_VAL, \u00b1HUGE_VALF, and \u00b1HUGE_VALL, respectively if y<\/i> is an odd integer, or HUGE_VAL, HUGE_VALF, and HUGE_VALL, respectively if y<\/i> is not an odd integer.<\/p>\n

If x<\/i> or y<\/i> is a NaN, a NaN shall be returned (unless specified elsewhere in this description).<\/p>\n

For any value of y<\/i> (including NaN), if x<\/i> is +1, 1.0 shall be returned.<\/p>\n

For any value of x<\/i> (including NaN), if y<\/i> is \u00b10, 1.0 shall be returned.<\/p>\n

For any odd integer value of y<\/i> > 0, if x<\/i> is \u00b10, \u00b10 shall be returned.<\/p>\n

For y<\/i> > 0 and not an odd integer, if x<\/i> is \u00b10, +0 shall be returned.<\/p>\n

If x<\/i> is \u22121, and y<\/i> is \u00b1Inf, 1.0 shall be returned.<\/p>\n

For |x<\/i>| < 1, if y<\/i> is \u2212Inf, +Inf shall be returned.<\/p>\n

For |x<\/i>| > 1, if y<\/i> is \u2212Inf, +0 shall be returned.<\/p>\n

For |x<\/i>| < 1, if y<\/i> is +Inf, +0 shall be returned.<\/p>\n

For |x<\/i>| > 1, if y<\/i> is +Inf, +Inf shall be returned.<\/p>\n

For y<\/i> an odd integer < 0, if x<\/i> is \u2212Inf, \u22120 shall be returned.<\/p>\n

For y<\/i> < 0 and not an odd integer, if x<\/i> is \u2212Inf, +0 shall be returned.<\/p>\n

For y<\/i> an odd integer > 0, if x<\/i> is \u2212Inf, \u2212Inf shall be returned.<\/p>\n

For y<\/i> > 0 and not an odd integer, if x<\/i> is \u2212Inf, +Inf shall be returned.<\/p>\n

For y<\/i> < 0, if x<\/i> is +Inf, +0 shall be returned.<\/p>\n

For y<\/i> > 0, if x<\/i> is +Inf, +Inf shall be returned.<\/p>\n

If the correct value would cause underflow, and is representable, a range error may occur and the correct value shall be returned.<\/p>\n

ERRORS <\/a> <\/h2>\n

These functions shall fail if:
Domain\u00a0Error<\/p>\n

The value of x<\/i> is negative and y<\/i> is a finite non-integer.<\/p>\n

If the integer expression (math_errhandling<\/i> & MATH_ERRNO) is non-zero, then errno<\/i> shall be set to [EDOM]<\/b>. If the integer expression (math_errhandling<\/i> & MATH_ERREXCEPT) is non-zero, then the invalid floating-point exception shall be raised.<\/p>\n\n\n
<\/td>\n\n

Pole\u00a0Error<\/p>\n<\/td>\n

<\/td>\n\n

The value of x<\/i> is zero and y<\/i> is negative.<\/p>\n<\/td>\n

 <\/td>\n<\/tr>\n<\/table>\n

If the integer expression (math_errhandling<\/i> & MATH_ERRNO) is non-zero, then errno<\/i> shall be set to [ERANGE]<\/b>. If the integer expression (math_errhandling<\/i> & MATH_ERREXCEPT) is non-zero, then the divide-by-zero floating-point exception shall be raised.<\/p>\n\n\n
<\/td>\n\n

Range\u00a0Error<\/p>\n<\/td>\n

<\/td>\n\n

The result overflows.<\/p>\n<\/td>\n

 <\/td>\n<\/tr>\n<\/table>\n

If the integer expression (math_errhandling<\/i> & MATH_ERRNO) is non-zero, then errno<\/i> shall be set to [ERANGE]<\/b>. If the integer expression (math_errhandling<\/i> & MATH_ERREXCEPT) is non-zero, then the overflow floating-point exception shall be raised.<\/p>\n

These functions may fail if:<\/p>\n\n\n
<\/td>\n\n

Pole\u00a0Error<\/p>\n<\/td>\n

<\/td>\n\n

The value of x<\/i> is zero and y<\/i> is negative.<\/p>\n<\/td>\n

 <\/td>\n<\/tr>\n<\/table>\n

If the integer expression (math_errhandling<\/i> & MATH_ERRNO) is non-zero, then errno<\/i> shall be set to [ERANGE]<\/b>. If the integer expression (math_errhandling<\/i> & MATH_ERREXCEPT) is non-zero, then the divide-by-zero floating-point exception shall be raised.<\/p>\n\n\n
<\/td>\n\n

Range\u00a0Error<\/p>\n<\/td>\n

<\/td>\n\n

The result underflows.<\/p>\n<\/td>\n

 <\/td>\n<\/tr>\n<\/table>\n

If the integer expression (math_errhandling<\/i> & MATH_ERRNO) is non-zero, then errno<\/i> shall be set to [ERANGE]<\/b>. If the integer expression (math_errhandling<\/i> & MATH_ERREXCEPT) is non-zero, then the underflow floating-point exception shall be raised.<\/p>\n

The following sections are informative.<\/i><\/p>\n

EXAMPLES <\/a> <\/h2>\n

None.<\/p>\n

APPLICATION USAGE <\/a> <\/h2>\n

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

RATIONALE <\/a> <\/h2>\n

None.<\/p>\n

FUTURE DIRECTIONS <\/a> <\/h2>\n

None.<\/p>\n

SEE ALSO <\/a> <\/h2>\n

exp<\/i>(), feclearexcept<\/i>(), fetestexcept<\/i>(), isnan<\/i>()<\/p>\n

The Base Definitions volume of POSIX.1-2017, Section 4.20<\/i>, Treatment of Error Conditions for Mathematical Functions<\/i>, <\/b><\/p>\n

COPYRIGHT <\/a> <\/h2>\n

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 .<\/p>\n

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 .<\/p>\n

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