#include <stdio.h>#include <gsl/gsl_poly.h>intmain (void){  int i;  /* coefficient of P(x) =  -1 + x^5  */  double a[6] = { -1, 0, 0, 0, 0, 1 };    double z[10];  gsl_poly_complex_workspace * w       = gsl_poly_complex_workspace_alloc (6);    gsl_poly_complex_solve (a, 6, w, z);  gsl_poly_complex_workspace_free (w);  for (i = 0; i < 5; i++)    {      printf ("z%d = %+.18f %+.18f\n",               i, z[2*i], z[2*i+1]);    }  return 0;}