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);