### 7.27 Power Function

The following functions are equivalent to the function `gsl_pow_int` (see Small integer powers) with an error estimate. These functions are declared in the header file `gsl_sf_pow_int.h`.

Function: double gsl_sf_pow_int (double x, int n)
Function: int gsl_sf_pow_int_e (double x, int n, gsl_sf_result * result)

  These routines compute the power x^n for integer n. The power is computed using the minimum number of multiplications. For example, x^8 is computed as ((x^2)^2)^2, requiring only 3 multiplications. For reasons of efficiency, these functions do not check for overflow or underflow conditions.

    #include <gsl/gsl_sf_pow_int.h>
    /* compute 3.0**12 */
    double y = gsl_sf_pow_int(3.0, 12);