st: syntax and gettoken with parentheses and equal signs

[Eric Lewis <erikylewis@gmail.com>]

Dear Statalist

I am trying to write an IV-type estimator that allows for parentheses
(for the first stage regression). I understand that gettoken with the
"bind" option can help with parentheses. However I am having a hard
time implementing that in practice. How can I use gettoken and/or
syntax in this setting?

e.g., I want a program that can define the macros lhs, exog, endog,
and inst based on arguments and the position of parentheses and the
equal sign.


program test_parentheses
     * example syntax y z1 z2 z3 (x1 x2 = z4 z5)

    * syntax and/or gettoken code:
     . . .

    display "`lhs'"
          * displays y
     display "`exog'"
          * displays z1 z2 z3
     display "`endog'"
          * displays x1 x2
     display "`inst'"
          * displays z4 z5
end

Currently I am taking the easy way out and using many options:
syntax [if] [in], lhs(varname) exog(varlist) endog(varlist) inst(varlist)

Thank you,
Eric
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