pow, powf, powl

Parameters

Return value

If no errors occur, base raised to the power of exponent ( base exponent ) is returned.

If a domain error occurs, an implementation-defined value is returned (NaN where supported).

If a pole error or a range error due to overflow occurs, ± HUGE_VAL , ±HUGE_VALF , or ±HUGE_VALL is returned.

If a range error occurs due to underflow, the correct result (after rounding) is returned.

Error handling

Errors are reported as specified in math_errhandling .

If base is finite and negative and exponent is finite and non-integer, a domain error occurs and a range error may occur.

If base is zero and exponent is zero, a domain error may occur.

If base is zero and exponent is negative, a domain error or a pole error may occur.

If the implementation supports IEEE floating-point arithmetic (IEC 60559),

• pow ( + 0 , exponent ) , where exponent is a negative odd integer, returns +∞ and raises FE_DIVBYZERO
• pow ( - 0 , exponent ) , where exponent is a negative odd integer, returns -∞ and raises FE_DIVBYZERO
• pow ( ± 0 , exponent ) , where exponent is negative, finite, and is an even integer or a non-integer, returns +∞ and raises FE_DIVBYZERO
• pow ( ± 0 , - ∞ ) returns +∞ and may raise FE_DIVBYZERO (until C23)
• pow ( + 0 , exponent ) , where exponent is a positive odd integer, returns +0
• pow ( - 0 , exponent ) , where exponent is a positive odd integer, returns -0
• pow ( ± 0 , exponent ) , where exponent is positive non-integer or a positive even integer, returns +0
• pow ( - 1 , ±∞ ) returns 1
• pow ( + 1 , exponent ) returns 1 for any exponent , even when exponent is NaN
• pow ( base, ± 0 ) returns 1 for any base , even when base is NaN
• pow ( base, exponent ) returns NaN and raises FE_INVALID if base is finite and negative and exponent is finite and non-integer.
• pow ( base, - ∞ ) returns +∞ for any |base|<1
• pow ( base, - ∞ ) returns +0 for any |base|>1
• pow ( base, + ∞ ) returns +0 for any |base|<1
• pow ( base, + ∞ ) returns +∞ for any |base|>1
• pow ( - ∞, exponent ) returns -0 if exponent is a negative odd integer
• pow ( - ∞, exponent ) returns +0 if exponent is a negative non-integer or negative even integer
• pow ( - ∞, exponent ) returns -∞ if exponent is a positive odd integer
• pow ( - ∞, exponent ) returns +∞ if exponent is a positive non-integer or positive even integer
• pow ( + ∞, exponent ) returns +0 for any negative exponent
• pow ( + ∞, exponent ) returns +∞ for any positive exponent
• except where specified above, if any argument is NaN, NaN is returned.

Notes

Although pow cannot be used to obtain a root of a negative number, cbrt is provided for the common case where exponent is 1 / 3 .

Example

#include <errno.h>
#include <fenv.h>
#include <math.h>
#include <stdio.h>
// #pragma STDC FENV_ACCESS ON
 
int main(void)
{
    // typical usage
    printf("pow(2, 10) = %f\n", pow(2, 10));
    printf("pow(2, 0.5) = %f\n", pow(2, 0.5));
    printf("pow(-2, -3) = %f\n", pow(-2, -3));
 
    // special values
    printf("pow(-1, NAN) = %f\n", pow(-1, NAN));
    printf("pow(+1, NAN) = %f\n", pow(+1, NAN));
    printf("pow(INFINITY, 2) = %f\n", pow(INFINITY, 2));
    printf("pow(INFINITY, -1) = %f\n", pow(INFINITY, -1));
 
    // error handling
    errno = 0; feclearexcept(FE_ALL_EXCEPT);
    printf("pow(-1, 1/3) = %f\n", pow(-1, 1.0 / 3));
    if (errno == EDOM)
        perror("    errno == EDOM");
    if (fetestexcept(FE_INVALID))
        puts("    FE_INVALID raised");
 
    feclearexcept(FE_ALL_EXCEPT);
    printf("pow(-0, -3) = %f\n", pow(-0.0, -3));
    if (fetestexcept(FE_DIVBYZERO))
        puts("    FE_DIVBYZERO raised");
}

pow(2, 10) = 1024.000000
pow(2, 0.5) = 1.414214
pow(-2, -3) = -0.125000
pow(-1, NAN) = nan
pow(+1, NAN) = 1.000000
pow(INFINITY, 2) = inf
pow(INFINITY, -1) = 0.000000
pow(-1, 1/3) = -nan
    errno == EDOM: Numerical argument out of domain
    FE_INVALID raised
pow(-0, -3) = -inf
    FE_DIVBYZERO raised

References

See also