Missing parenthesis in display math within text within display math

Question

I'm trying to work out how to recursively nest text and math mode. The following example seems to fail to compile, and does not render the right):
% "text, {$$int$$}, text" is an arbitrary string provided by software I
% do not control, 
$$ operatorname{foo}left( text{text, {$$int$$}, text} right)$$

Is there a simple way to make this work?

egreg · Answer

The software you're using is flawed and there's essentially no safe method for making such generated code to work.
The problem is that text eventually makes an hbox in which the code is typeset using restricted horizontal mode where $$ has a peculiar behavior. Since display math makes no sense, TeX simply considers $$ as an empty math formula, when in restricted horizontal mode. So your int appears outside math mode and an error ensues.
TeX now tries to enter math mode before rescanning int, then finds the closing $ which ends math mode. It finds another one, which starts again math mode and now it finds a misplaced }. Another error.
Fix the software producing that code, which is bad LaTeX under many other respects. To begin with, $$ should never be used in LaTeX.

Missing parenthesis in display math within text within display math

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