Apply show rule only inside math mode

[NicoWeio]

I'm currently using #show "L": math.cal, but this (obviously) applies to all L's, not just those in equations.
I know I could do something like #let LL = $cal(L)$, but a) I'd prefer the show rule for its brevity and b) this seems to be a more general shortcoming of the current Typst compiler.

[Enivex]

This is what you're looking for

#show math.equation: it =>{
  show "L" : math.cal
  it
}

[NicoWeio]

Nested show rules – I didn't even know that was possible. But now that I see it, it makes total sense! Thanks!

[NicoWeio]

There is one pitfall with this approach – it also applies to strings inside an equation:

#show math.equation: it =>{
  show "L" : math.cal
  it
}

$
L "is the Lagrangian."
$

Any idea how to handle that?

[EpicEricEE]

You could use a regex instead and only match when really only "L" is given by using start (^) and end ($) anchors:

#show math.equation: it => {
  show regex("^L$"): math.cal
  it
}

In a similar fashion, you could also use regex("\bL\b") instead, where \b means "word boundary".