| POW(3M) | Mathematical Library Functions | POW(3M) |
pow, powf, powl - power function
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);
These functions compute the value of x raised to the power y, x^y>. If x is negative, y must be an integer value.
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 implementation-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:
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 compiled with the c99 compiler driver and is therefore SUSv3-conforming (see standards(7)), 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.
These functions will fail if:
Domain Error
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
If the integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero, the divide-by-zero floating-point exception is raised.
Range Error
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.
An application wanting to check for exceptions should call feclearexcept(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.
See attributes(7) for descriptions of the following attributes:
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
| Interface Stability | Standard |
| MT-Level | MT-Safe |
math.h(3HEAD), exp(3M), feclearexcept(3M), fetestexcept(3M), isnan(3M), matherr(3M), attributes(7), standards(7)
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 conflict was resolved by prepending mp_ to all functions in the libmp library. See mp(3MP) for more information.
| July 12, 2006 | SunOS 5.11 |