How to push or insert into arrays?

Questions
1

OK, guys, this feels odd to ask, but I do not understand the following:

With self.remove(int) I can remove an element from an array.

#let a = (1, 2, 3)
#a.remove(0)

That works perfectly fine and the output type is int.
If I want to add an element to an array - say add the element “4” to a - following the Typst doc (self.push(any)) I would think you’d go for

#a.push(4)

That does not generate an error message, but neither does it render any output. The type of a.push(4) however is none.

Same goes for

#a.insert(0, 4)

No error, no rendered output, type none.

To be honest, I do not understand why?

Any explanation is appreciated.

Cheers,
Amman

2

I can’t explain it, but perhaps you’ll find it out yourself by trying this:

#let a = (1, 2, 3)
#a.push(4)
#a
1 Like
3

Thank you! I somehow thought that when using the push definition the variable is not automatically modified. So I was messing around with

#let a = (1, 2, 3)
#let b = a.push(4)

which did not work. I somehow did not try your approach, but, hey!, it works. Thanks a lot!

4

For what it’s worth, this is a totally reasonable assumption to make. Almost all typst functions are pure, meaning they can’t modify values outside their scope, see Function Type – Typst Documentation

In particular, all user-defined functions must be pure (though you can make them non-pure through states and counters)