POW(3) Library Functions Manual POW(3)

pow — power function

#include <math.h>

double pow(double x, double y);

The pow() function computes the value of x raised to the power y, x y . If x is negative, y must be an integer value.

An application wishing to check for error situations should set errno to 0 before calling pow(). If errno is non-zero on return, or the return value is NaN, an error has occurred.

Upon successful completion, pow() returns the value of x raised to the power y.

If x is 0 and y is 0, 1.0 is returned.

If y is NaN, or y is non-zero and x is NaN, NaN is returned and errno may be set to [EDOM]. If y is 0.0 and x is NaN, either 1.0 is returned, or NaN is returned and errno may be set to [EDOM].

If x is 0.0 and y is negative, -HUGE_VAL is returned and errno may be set to [EDOM] or [ERANGE].

If the correct value would cause overflow, ±HUGE_VAL is returned, and errno is set to [ERANGE].

If the correct value would cause underflow, 0 is returned and errno may be set to [ERANGE].

The pow() function will fail if:

The value of x is negative and y is non-integral.
The value to be returned would have caused overflow.

The pow() function may fail if:

The value of x is 0.0 and y is negative, or y is NaN.
The correct value would cause underflow.

No other errors will occur.

None.

None.

None.

exp(3) , isnan(3) , <math.h> .

Derived from Issue 1 of the SVID.

February 1997 posix.fail