Description

I needed a multi-level counter, but I found that the counter documentation only really discusses single-level counter, which made it much harder than it should have been.

I wanted to index "questions" with numbers of the form S.C, where S is the section counter and C is a question-specific counter. (For example: 1.1, 1.2, then 2.1). Here is the code that I ended up writing:

#let question_counter = counter("question")
#question_counter.update((0, 0))
#show heading: it => {
  if it.level == 1 {
    question_counter.update((s, c) => (s+1, 0))
  }
}

#let question(body) = {
 question_counter.update((s, c) => (s, c+1))
 strong([ Question #context{ question_counter.display() } ])
 body
}

= Example usage
#question[Foo]
#question[Bar]

= More example
#question[Baz]

This required too much trial-and-error, I believe that the counter documentation should be improved to make this easy. For example:

1. There are no examples of update with multi-level counters.
2. The behavior of step on multi-level counters is not explained.
   • Does the indexing start at 0 or 1?
     Answer: it appears to start at 1.
   • is question_counter.step(level: 1) equivalent to question_counter.update((s, c) => (s+1, c)) or to question_counter.update((s, c) => (s+1, 0))?
     Answer: in my tests, neither, it appears to be unusable with 2-level counters.
3. I get weird errors if I remove the #question_counter.update((0, 0)) initialization, why? Is there a way to indicate that a counter is multi-level at creation time?