Manpages - pow.3

pow, powf, powl - power functions

  #include <math.h>

  double pow(double x, double y);
  float powf(float x, float y);
  long double powl(long double x, long double y);

Link with -lm.

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_SOURCE

These functions return the value of x raised to the power of y.

On success, these functions return the value of x to the power of y.

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 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 is returned.

Except as specified below, if x or y is a NaN, the result is a NaN.

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 +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 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.

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.

See *math_error*(7) 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 is set to EDOM. An invalid floating-point exception (FE_INVALID) is raised.
• errno is set to ERANGE (but see BUGS). A divide-by-zero floating-point exception (FE_DIVBYZERO) is raised.
• errno is set to ERANGE. An overflow floating-point exception (FE_OVERFLOW) is raised.
• errno is set to ERANGE. An underflow floating-point exception (FE_UNDERFLOW) is raised.

For an explanation of the terms used in this section, see *attributes*(7).

Interface	Attribute	Value
*pow*(), *powf*(), *powl*()	Thread safety	MT-Safe

C99, POSIX.1-2001, POSIX.1-2008.

The variant returning double also conforms to SVr4, 4.3BSD, C89.

*cbrt*(3), *cpow*(3), *sqrt*(3)

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