+// overloading at work: we cannot use the macros here
+/** Riemann's Zeta-function. */
+extern const unsigned function_index_zeta1;
+template<typename T1>
+inline function zeta(const T1 & p1) {
+ return function(function_index_zeta1, ex(p1));
+}
+/** Derivatives of Riemann's Zeta-function. */
+extern const unsigned function_index_zeta2;
+template<typename T1, typename T2>
+inline function zeta(const T1 & p1, const T2 & p2) {
+ return function(function_index_zeta2, ex(p1), ex(p2));
+}
+
+/** Gamma-function. */
+DECLARE_FUNCTION_1P(lgamma)
+DECLARE_FUNCTION_1P(tgamma)