st: mata orgtype

[Tomáš Houška <xbender@gmail.com>]

Dear Statalist,

I have a Stata macro generated by -levelsof- and I am trying to parse
it in mata with -tokens- so that I can run mata loops with it...
example:

levelsof product, local(product_id)
mata
prods=tokens(st_local("product_id"))
for(i = 1; i<=length(prods); i++) {
... commands including prods[i] ...
}
end

My problem is that on some types of variables, the resulting mata item
(in this case "prods") is a row vector, but sometimes it is a scalar
string. Once it is a scalar string, I cannot refer to items on
individual positions by -prods[i]- as I can do when it is a row
vector.
Is there a rule to which type gets created and when? Or is there a way
to make sure that row vector  gets created?
Thank you
Tomas
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