}
/** Derivatives of Psi-function (aka polygamma-functions). */
extern const unsigned function_index_psi2;
inline function psi(const ex & p1, const ex & p2) {
}
/** Derivatives of Psi-function (aka polygamma-functions). */
extern const unsigned function_index_psi2;
inline function psi(const ex & p1, const ex & p2) {