\htmlId and subscripts / superscripts

[ashok-khanna]

If I try x_\htmlId{myId}{3} (e.g. in katex.org/#demo) I get the following error: KaTeX parse error: Got function '\htmlId' with no arguments as subscript at position 3: x_\̲h̲t̲m̲l̲I̲d̲{myId}{3}

Similar issue with ^. However this will work x_{\htmlId{myId}{3}}. Should I just use that or is there a way to fix the above? Also, does {} do anything in particular - couldn't find a link in the docs that describe it precisely. I assumed it was a grouping operator.

This is an awesome project, thank you!!!

[JacobBeaudry]

Hi Ashok,

That's the expected behaviour. As you guessed, the braces are basically groupers; they have various effects on the final output.

In general, KaTeX seeks to recreate LaTeX's behaviour, and LaTeX requires nested subscripts to be wrapped in braces, e.g.

• x_1_i

will cause an error, but

• x_{1_i}

will not. The same holds for any command that takes an argument, placed in a subscript, so

• x_\sin{x}

will give an error, because of \sin's argument, however,

• x_\oplus

will not, because \oplus does not take an argument.

In your case, the \htmlId{}{} command takes two arguments, so the error you're getting is the expected behaviour.

In general, until you're very comfortable with LaTeX, you can avoid a lot of confusing, hard-to-understand bugs if you always include the braces.

If you're new to TeX / LaTeX etc. I'd suggest taking a peek at the tex.se and overleaf sites.

At the former, you'll find detailed answers to a broad range of questions from some of the most knowledgeable members of the TeX community (just be sure to read the rules of the site before posting); at the latter, you'll find well-documented introductions and tutorials.

All the best,

Jacob

[ashok-khanna]

Thank you very much Jacob for the useful answer.