A Mata written log-likelihood function with extra variables

[Minchul Park]

I am writing an ado file where I use the

ml

command with a mata-written log-likelihood function.

Specifically, my code is like below:

// my_fun command
program define my_fun
               version 18
               syntax varlist
               gettoken y xvars: varlist
               ml model my_log_like_fun() (Eq.1: something) (Eq.2: something) ... (Eq.q: something)
               ml maximize
end

// the mata written log-likelihood function
mata:
void my_log_like_fun (transmorphic scalar ML, real rowvector b, real colvector lnf)
{
               depvar = moptimize_util_depvar(ML, 1)
               xb        = moptimize_util_xb(ML, b, 1)
               something others

                lnf       = expression
}
end

Here, my two questions are like below.

First, in the "my_log_like_fun" (specifically in expression), I need to use variables, say varlist2, that does not appear in Eq. 1 - Eq. q. But, I am not sure how to do that.

Second, since the varlist2 are intrinsically different from the variables in the "varlist", I want to know how to distinguish the variable in the "syntax" line.
For example, in the "ivregress" command, the syntax is "ivregress estimator depvar [varlist1] (varlist2 = varlist_iv) ... ".
Like the "ivregress" command, I want to make a command in that we can specify "varlist2" and the "varlist2" is used in the "my_log_like_fun".

How can I do that?
Thank you