pow(3M) Mathematical Library Functions pow(3M)NAME
pow, powf, powl - power function
SYNOPSIS
c99 [ flag... ] file... -lm [ library... ]
#include <math.h>
double pow(double x, double y);
float powf(float x, float y);
long double powl(long double x, long double y);
cc [ flag... ] file... -lm [ library... ]
#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
These functions compute the value of x raised to the power y, x**y. If
x is negative, y must be an integer value.
RETURN VALUES
Upon successful completion, these functions 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 occurs and either a NaN (if representable), or an imple‐
mentation-defined value is returned.
If the correct value would cause overflow, a range error occurs and
pow(), powf(), and powl() return HUGE_VAL, HUGE_VALF, and HUGE_VALL,
respectively.
If x or y is a NaN, a NaN is returned unless:
· If x is +1 and y is NaN and the application was compiled with the
c99 compiler driver and is therefore SUSv3-conforming (see stan‐
dards(5)), 1.0 is returned.
· For any value of x (including NaN), if y is +0, 1.0 is returned.
For any odd integer value of y > 0, if x is ±0, ±0 is returned.
For y > 0 and not an odd integer, if x is ±0, +0 is returned.
If x is ±1 and y is ±Inf, and the application was compiled with the cc
compiler driver, NaN is returned. If, however, the application was com‐
piled with the c99 compiler driver and is therefore SUSv3-conforming
(seestandards(5)), 1.0 is returned.
For |x| < 1, if y is −Inf, +Inf is returned.
For |x| > 1, if y is −Inf, +0 is returned.
For |x| < 1, if y is +Inf, +0 is returned.
For |x| > 1, if y is +Inf, +Inf is returned.
For y an odd integer < 0, if x is −Inf, −0 is returned.
For y < 0 and not an odd integer, if x is −Inf, +0 is returned.
For y an odd integer > 0, if x is −Inf, −Inf is returned.
For y > 0 and not an odd integer, if x is −Inf, +Inf is returned.
For y < 0, if x is +Inf, +0 is returned.
For y > 0, if x is +Inf, +Inf is returned.
For y an odd integer < 0, if x is ±0, a pole error occurs and
±HUGE_VAL, ±HUGE_VALF, and ±HUGE_VALL are returned for pow(), powf(),
and powl(), respectively.
For y < 0 and not an odd integer, if x is ±0, a pole error occurs and
HUGE_VAL, HUGE_VALF, and HUGE_VALL are returned for pow(), powf(), and
powl(), respectively.
For exceptional cases, matherr(3M) tabulates the values to be returned
by pow() as specified by SVID3 and XPG3.
ERRORS
These functions will fail if:
Domain Error The value of x is negative and y is a finite non-inte‐
ger.
If the integer expression (math_errhandling &
MATH_ERREXCEPT) is non-zero, the invalid floating-point
exception is raised.
The pow() function sets errno to EDOM if the value of x
is negative and y is non-integral.
Pole Error The value of x is 0 and y is negative.
If the integer expression (math_errhandling &
MATH_ERREXCEPT) is non-zero, the divide-by-zero float‐
ing-point exception is raised.
Range Error The result overflows.
If the integer expression (math_errhandling &
MATH_ERREXCEPT) is non-zero, the overflow floating-
point exception is raised.
The pow() function sets errno to EDOM if the value to
be returned would cause overflow.
USAGE
An application wanting to check for exceptions should call feclearex‐
cept(FE_ALL_EXCEPT) before calling these functions. On return, if
fetestexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is
non-zero, an exception has been raised. An application should either
examine the return value or check the floating point exception flags to
detect exceptions.
An application can also set errno to 0 before calling pow(). On return,
if errno is non-zero, an error has occurred. The powf() and powl()
functions do not set errno.
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
┌─────────────────────────────┬─────────────────────────────┐
│ ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
├─────────────────────────────┼─────────────────────────────┤
│Interface Stability │Standard │
├─────────────────────────────┼─────────────────────────────┤
│MT-Level │MT-Safe │
└─────────────────────────────┴─────────────────────────────┘
SEE ALSOexp(3M), feclearexcept(3M), fetestexcept(3M), isnan(3M), math.h(3HEAD),
matherr(3M), attributes(5), standards(5)NOTES
Prior to Solaris 2.6, there was a conflict between the pow() function
in this library and the pow() function in the libmp library. This con‐
flict was resolved by prepending mp_ to all functions in the libmp
library. See mp(3MP) for more information.
SunOS 5.10 12 Jul 2006 pow(3M)
