+
+static ex zeta1_eval(const ex & x)
+{
+ if (x.info(info_flags::numeric)) {
+ const numeric &y = ex_to<numeric>(x);
+ // trap integer arguments:
+ if (y.is_integer()) {
+ if (y.is_zero())
+ return _ex_1_2;
+ if (y.is_equal(_num1))
+ throw(std::domain_error("zeta(1): infinity"));
+ if (y.info(info_flags::posint)) {
+ if (y.info(info_flags::odd))
+ return zeta(x).hold();
+ else
+ return abs(bernoulli(y))*pow(Pi,y)*pow(_num2,y-_num1)/factorial(y);
+ } else {
+ if (y.info(info_flags::odd))
+ return -bernoulli(_num1-y)/(_num1-y);
+ else
+ return _ex0;
+ }
+ }
+ // zeta(float)
+ if (y.info(info_flags::numeric) && !y.info(info_flags::crational))
+ return zeta1_evalf(x);
+ }
+ return zeta(x).hold();
+}
+
+static ex zeta1_deriv(const ex & x, unsigned deriv_param)