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- 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;
- }
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