pow(3) - Linux manual page (original) (raw)
pow(3) Library Functions Manual pow(3)
NAME top
pow, powf, powl - power functionsLIBRARY 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_SOURCEDESCRIPTION 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)](../man7/math%5Ferror.7.html) 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](../man3/errno.3.html)_ is set to **EDOM**. An invalid floating-point exception
(**FE_INVALID**) is raised.
Pole error: _x_ is zero, and _y_ is negative
_[errno](../man3/errno.3.html)_ is set to **ERANGE** (but see BUGS). A divide-by-zero
floating-point exception (**FE_DIVBYZERO**) is raised.
Range error: the result overflows
_[errno](../man3/errno.3.html)_ is set to **ERANGE**. An overflow floating-point
exception (**FE_OVERFLOW**) is raised.
Range error: the result underflows
_[errno](../man3/errno.3.html)_ 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)](../man7/attributes.7.html).
┌──────────────────────────────────────┬───────────────┬─────────┐
│ **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](../man3/errno.3.html)_ 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)](../man3/cbrt.3.html), [cpow(3)](../man3/cpow.3.html), [sqrt(3)](../man3/sqrt.3.html)COLOPHON top
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man-pages@man7.orgLinux man-pages 6.10 2024-07-23 pow(3)
Pages that refer to this page:cbrt(3), cpow(3), pow10(3)