/** Complex sign. */
DECLARE_FUNCTION_1P(csgn)
+/** Eta function: log(a*b) == log(a) + log(b) + eta(a, b). */
+DECLARE_FUNCTION_2P(eta)
+
/** Sine. */
DECLARE_FUNCTION_1P(sin)
/** Trilogarithm. */
DECLARE_FUNCTION_1P(Li3)
-// overloading at work: we cannot use the macros
+// overloading at work: we cannot use the macros here
/** Riemann's Zeta-function. */
extern const unsigned function_index_zeta1;
inline function zeta(const ex & p1) {
/** Beta-function. */
DECLARE_FUNCTION_2P(beta)
-// overloading at work: we cannot use the macros
+// 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) {