static inline int
cheb_eval_mode_e(const cheb_series * cs,
const double x,
gsl_mode_t mode,
gsl_sf_result * result)
{
int j;
double d = 0.0;
double dd = 0.0;
double y = (2.*x - cs->a - cs->b) / (cs->b - cs->a);
double y2 = 2.0 * y;
int eval_order;
if(GSL_MODE_PREC(mode) == GSL_PREC_DOUBLE)
eval_order = cs->order;
else
eval_order = cs->order_sp;
for(j = eval_order; j>=1; j--) {
double temp = d;
d = y2*d - dd + cs->c[j];
dd = temp;
}
result->val = y*d - dd + 0.5 * cs->c[0];
result->err = GSL_DBL_EPSILON * fabs(result->val) + fabs(cs->c[eval_order]);
return GSL_SUCCESS;
}