static inline int
cheb_eval_e(const cheb_series * cs,
const double x,
gsl_sf_result * result)
{
int j;
double d = 0.0;
double dd = 0.0;
double y = (2.0*x - cs->a - cs->b) / (cs->b - cs->a);
double y2 = 2.0 * y;
double e = 0.0;
for(j = cs->order; j>=1; j--) {
double temp = d;
d = y2*d - dd + cs->c[j];
e += fabs(y2*temp) + fabs(dd) + fabs(cs->c[j]);
dd = temp;
}
{
double temp = d;
d = y*d - dd + 0.5 * cs->c[0];
e += fabs(y*temp) + fabs(dd) + 0.5 * fabs(cs->c[0]);
}
result->val = d;
result->err = GSL_DBL_EPSILON * e + fabs(cs->c[cs->order]);
return GSL_SUCCESS;
}