Escaping absolute value bars in Typst adds unnecessary space

[CoryMcCartan]

input.md:

$|x| > 0$

Actual:

> pandoc input.md --to typst
$\| x \| > 0$

Renders in Typst PDF as:

Expected:

$\|x\| > 0$

Or ideally $|x| > 0$, but I understand there are some reasons to not default to auto-scaling delimiters. Either renders as:

This is new behavior, I think because escaping all paired delimiters is relatively new in texmath?

[jgm]

One issue is this:

% texmath -t native
|x| = 0
[ ESymbol Open "|"
, EIdentifier "x"
, ESymbol Open "|"
, ESymbol Rel "="
, ENumber "0"
]

The second one is not recognized as a close delim. That's a bit of a tricky problem, though, and I don't think it's the root cause here.

The escaping is because, when rendering symbols we, look them up in the typst symbol map, and if they are not found there, we emit an escaped character:
https://github.com/jgm/texmath/blob/master/src/Text/TeXMath/Writers/Typst.hs#L122-L123

If that's undesirable; we could avoid it by special-casing certain characters.

However, we presumably want to distinguish between TeX

|x|

and TeX

\left|x\right|

The latter comes out in typst as

lr(|x|)

though maybe now

|x|

means the same thing?

One could argue that emitting

\|x\|

is correct because it preserves the distinction.