How to start the heading-numbering from 0?

Questions
,
1

Normally the first heading has the number 1 (which makes sense).
How can I have the first heading to be number 0 and the second number 1 and so on?

A simple #counter(heading).update(0) before the first heading does not work, because the counter already starts at 0, and #counter(heading).update(-1) gives a syntax error, because counters must be natural numbers.

1 Like
2

The command #counter(heading).update(0) doesn’t work because its value is already 0. You can verify this by running #context counter(heading).get() and checking the result.

As an alternative, you could define a numbering function that subtracts 1 from the input arguments before returning the results. For example:

#set heading(numbering: (..x) => numbering("1.", ..x.pos().map(n => n - 1)))

= hello
= test

This would output:

0. hello
1. test
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3

Thank you :) This works, but only for top level headings.
If I use this and include lower level headings this outputs

0. hello
0.0. One sublevel
0.1. next
0.1.0. two sublevels 
1. ...

But I want my top level headings to start with 0 but the levels beneath it with the usual 1.

So using your idea of subtracting one, but only for the first level and not the others, I tried instead of using the map function to just remove the first entry and add it again as follows.

#set heading(numbering: (..x) => {
   let numbers = x.pos()
   let n1 = numbers.at(0)
   numbers.remove(0)
   numbers.insert(0, int(n1 - 1))
   numbering("1.a", ..numbers)
}
)

This gives the error on the numbering line stating, can not join integer with a string. So somehow this operation destroys the possibility to use the normal numbering command. What am I doing wrong?

4

The problem is that the result of a Typst function is created by “joining” all expressions, and apart from the final numbering() call, numbers.remove(0) also returns a value!

There are a couple of ways around this:

  • you can opt out of this behavior by using return numbering(...)
  • you can prevent remove() from leaking by using let _ = ...
  • since remove() returns the element, you can use let n1 = numbers.remove(0)
  • you could also use numbers.at(0) -= 1
  • finally, you could destructure your numbers differently:
    #set heading(numbering: (n1, ..x) => numbering("1.a", n1 - 1, ..x))
4 Likes
5

Ah, that makes a lot of sense! Everyday I am learning something. Thank you! :)

2 Likes
6

It seems like in 0.14.0, an extra test was added to enforce the number to be positive.

I get this error: “number must be at least zero” by trying the previously mentioned techniques.

error: number must be at least zero
   ┌─ template.typ:37:55
   │
37 │   set heading(numbering: (n1, ..x) => numbering("1.a", n1 - 1, ..x))
   │                                                        ^^^^^^
7

The relevant issue on GitHub is still open. I will provide the link here in case someone wants more background information.

Start a counter with zero? · Issue #6662 · typst/typst

8

Something changed internally so that headings now see a counter value of 0 in the first layout iteration (it’s updated/fixed in later iterations). That’s not normally a visible change, but in this case it becomes noticeable in Typst 0.14.

You should be able to fix the problem by using calc.max(0, n1 - 1) so that the effective value never goes below 0.

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