| |
| 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; |
| } |
| |