int gsl_sf_erfc_e(double x, gsl_sf_result * result)
{
const double ax = fabs(x);
double e_val, e_err;
/* CHECK_POINTER(result) */
if (ax <= 1.0) {
double t = 2.0 * ax - 1.0;
gsl_sf_result c;
cheb_eval_e(&erfc_xlt1_cs, t, &c);
e_val = c.val;
e_err = c.err;
} else if (ax <= 5.0) {
double ex2 = exp(-x * x);
double t = 0.5 * (ax - 3.0);
gsl_sf_result c;
cheb_eval_e(&erfc_x15_cs, t, &c);
e_val = ex2 * c.val;
e_err = ex2 * (c.err + 2.0 * fabs(x) * GSL_DBL_EPSILON);
} else if (ax < 10.0) {
double exterm = exp(-x * x) / ax;
double t = (2.0 * ax - 15.0) / 5.0;
gsl_sf_result c;
cheb_eval_e(&erfc_x510_cs, t, &c);
e_val = exterm * c.val;
e_err =
exterm * (c.err + 2.0 * fabs(x) * GSL_DBL_EPSILON +
GSL_DBL_EPSILON);
} else {
e_val = erfc8(ax);
e_err = (x * x + 1.0) * GSL_DBL_EPSILON * fabs(e_val);
}
if (x < 0.0) {
result->val = 2.0 - e_val;
result->err = e_err;
result->err += 2.0 * GSL_DBL_EPSILON * fabs(result->val);
} else {
result->val = e_val;
result->err = e_err;
result->err += 2.0 * GSL_DBL_EPSILON * fabs(result->val);
}
return GSL_SUCCESS;
}
nr_double_t fspecial::erfc (nr_double_t x) {
const nr_double_t ax = fabs (x);
nr_double_t val;
if (ax <= 1.0) {
nr_double_t t = 2.0 * ax - 1.0;
val = cheb_eval (&erfc_xlt1_cs, t);
}
else if (ax <= 5.0) {
nr_double_t ex2 = exp (-x * x);
nr_double_t t = 0.5 * (ax - 3.0);
val = ex2 * cheb_eval (&erfc_x15_cs, t);
}
else if (ax < 10.0) {
nr_double_t ex = exp(-x * x) / ax;
nr_double_t t = (2.0 * ax - 15.0) / 5.0;
val = ex * cheb_eval (&erfc_x510_cs, t);
}
else {
val = erfc8 (ax);
}
return (x < 0.0) ? 2.0 - val : val;
}
