-/** Psi-function (aka polygamma-function). */
-//DECLARE_FUNCTION_1P(psi)
-DECLARE_FUNCTION_2P(psi)
-
+/** Beta-function. */
+DECLARE_FUNCTION_2P(beta)
+
+// overloading at work: we cannot use the macros here
+/** Psi-function (aka digamma-function). */
+extern const unsigned function_index_psi1;
+inline function psi(const ex & p1) {
+ return function(function_index_psi1, p1);
+}
+/** Derivatives of Psi-function (aka polygamma-functions). */
+extern const unsigned function_index_psi2;
+inline function psi(const ex & p1, const ex & p2) {
+ return function(function_index_psi2, p1, p2);
+}
+