How do you escape dollar signs?

[kulst]

I want to use the $ sign multiple times in a field. For example:

## Back
Initial state: \(($S,w)\)
Final state: \(($,$)\)

Currently this produces:

<p data-original-markdown="SW5pdGlhbCBzdGF0ZTogXCgoJFMsdylcKTxiciAvPkZpbmFsIHN0YXRlOiBcKCgkLCQpXCk=">Initial state: <anki-mathjax>(\(S,w)\</anki-mathjax>
Final state: \<anki-mathjax>(</anki-mathjax>,$)\)</p>

I would like to get something like this:

<p data-original-markdown="SW5pdGlhbCBzdGF0ZTogXCgoJFMsdylcKTxiciAvPkZpbmFsIHN0YXRlOiBcKCgkLCQpXCk=">Initial state: <anki-mathjax>($S,w)</anki-mathjax>
Final state: <anki-mathjax>($,$)</anki-mathjax></p>

I could not find a way to escape the dollar sign.

Having only one dollar sign in the field is working fine.

[kulst]

I think you could make \$ escape the dollar sign by changing the regex

pattern = re.compile(r"\$\$(.*?)\$\$|\$(.*?)\$", re.DOTALL)

into

pattern = re.compile(
    r"(?<!\\)(?:\\\\)*\$\$((?:\\.|[^\\$]|\$(?!\$))*)\$\$|(?<!\\)(?:\\\\)*\$((?:\\.|[^\\$])*)\$",
    re.DOTALL)

This should match only if the first dollar sign is preceded by an even number of backslashes (including zero) and only capture if it finds 2 (1) unescaped dollar signs.

After injecting the placeholders we can replace the escaped $-signs so they show up normally. Overall something like this:

pattern = re.compile(
    r"(?<!\\)(?:\\\\)*\$\$((?:\\.|[^\\$]|\$(?!\$))*)\$\$|(?<!\\)(?:\\\\)*\$((?:\\.|[^\\$])*)\$",
    re.DOTALL)
lines_joined = "\n".join(lines)
lines_processed = pattern.sub(replacer, lines_joined)
pattern = re.compile(r"(?<!\\)(?:\\\\)*\\(\$)", re.DOTALL)
lines_processed = pattern.sub("$", lines_joined)
return lines_processed.split("\n")

[kulst]

Hm, this turns out to be more complicated than I thought.

In principle what I want to do in the preprocessor is:

1. Match against \\[..\\], \\(..\\), $$..$$ and $..$ but only if the dollars are not escaped and consider multiple backslashes before.
2. Replace those matches like it is done already
3. In the remaining string replace \$ by $, again consider multiple backslashes before the dollar sign

I need to think about it a bit to get the regex for 1 correct.

[lervag]

Interesting - I more or less agree that this should be supported and that we can support it by preceding with backslashes. Now, perhaps we should not overcomplicate it? Let's not consider multiple backslashes, only a single one. Then we could consider the multiple backslash-situation afterwards?