/** Riemann's Zeta-function. */
extern const unsigned function_index_zeta1;
inline function zeta(const ex & p1) {
/** Riemann's Zeta-function. */
extern const unsigned function_index_zeta1;
inline function zeta(const ex & p1) {
/** Psi-function (aka digamma-function). */
extern const unsigned function_index_psi1;
inline function psi(const ex & p1) {
/** Psi-function (aka digamma-function). */
extern const unsigned function_index_psi1;
inline function psi(const ex & p1) {