fcn_desc(fcnp func, int num) : p(func), num_params(num), is_ginac(false), serial(0) {}
fcn_desc(fcnp2 func, int num, int ser) : p((fcnp)func), num_params(num), is_ginac(true), serial(ser) {}
fcn_desc(fcnp func, int num) : p(func), num_params(num), is_ginac(false), serial(0) {}
fcn_desc(fcnp2 func, int num, int ser) : p((fcnp)func), num_params(num), is_ginac(true), serial(ser) {}