Feature request: arbitrary inline counters

[AlbertLei]

As far as I can see, currently pandoc supports counters only for headers and lists (via example lists). Plus, the support for header counters is limited in that one cannot cross-reference the heading number.

It will be very useful to support arbitrary inline counters, like a simple span element.

I propose the following syntax.

Declaration Syntax

A counter is initialized or incremented by an empty Span containing a class (the counter group) and a unique ID (the reference anchor). Eg:

[]{.theorem #main}

Counters from different classes are numbered separately. So a separate state will be kept for each counter class.

Referencing Syntax

To reference the counter value (and add a link to the anchor),
we could utilize one of the following existing syntaxes:

• citation: @main
• Empty Link: [](#main). Or, use #main as shorthand?

Example

The following markdown block:

Theorem @thm:main: theorem body.
[]{#thm:main .theorem}

See also theorem @thm:foo below.

Theorem @thm:foo: theorem body.
[]{#thm:foo .theorem}

will be translated to the following markdown block:

Theorem [1](#thm:main): theorem body.
[]{#thm:main .theorem}

See also theorem [2](#thm:foo) below.

Theorem [2](#thm:foo): theorem body.
[]{#thm:foo .theorem}

Personal

Speaking for myself, I primarily write in pandoc markdown. This feature is less useful when I only care about latex,
but it becomes necessary when exporting to docx/HTML.

I currently rely on some preprocessor scripts to enable inline counters, and I've found them highly useful for my workflow.