How to write a multi-line set builder?

Questions
1

A set builder notation with multiple lines can be wrote in latex with array:
https://i.sstatic.net/TJ9lj.png.
How can this be done in typst?

2

Hi and welcome to the forum!

The technique i’ve been using is to use cases, although admittedly it’s a bit hacky:

$
cal(Z) = {
  z
  cases(
    delim: "|",
    1 <= z_((k, m))^l <= ...,
    forall k in cal(K)\, ...
  )
}
$

image

3 Likes
3

My first approach would be like this, with stack and nested equations.

$ cal(Z) = lr({z mid(|) #align(left)[#stack(spacing: 0.4em, dir: ttb, $A, B, C$, $a, b, c$)]}) $

This doesn’t feel so elegant, maybe because of the need to ensure left alignment or the nested equations in equation.

bild

Now that I compare, I think using cases is better!

Edit: We can define a “math version of stack” and salvage the syntax. I think this is a win for typst!

#let mstack(..args) = $#align(left)[#stack(spacing: 0.4em, dir: ttb, ..args)]$

$ cal(Z) = lr(\{z mid(|) mstack(A#sym.comma B "and" C, a#sym.comma b "and" c) \}) $
1 Like
4

Disclaimer: This solution is equivalent to the one by @aarnent. He was just ~1 minute faster :cry:
You can use math.cases() to get the multiple lines. And then you just wrap everything in curly brackets. Note that you have to use sym.comma (or \,) since the regular comma will be interpreted as a new case.

#set math.cases(delim: "|")

$
  cal(Z) = {
    z cases(
      #h(0.5em) 1 <= z_((k,m))^l <= ... ,
      #h(0.5em) forall k in cal(K) #sym.comma forall m in cal(M)_k #sym.comma ...
    )
  }
$

forum_3336_mulitline-set
forum_3336_mulitline-set1472Ă—367 79.6 KB

4 Likes
5

you can get around this by using a new equation for each case, like this:

$
  cal(Z) = {
    z #math.cases(
      $#h(0.5em) 1 <= z_((k,m))^l <= ...$,
      $#h(0.5em) forall k in cal(K), forall m in cal(M)_k, ...$,
    )
  }
$

 

instead of $       cases(a,   b  ) $
use        $ #math.cases($a$, $b$) $

this means the the cases call is in code mode, so each parameter needs to be wrapped in $...$ – in return, each equation is isolated from math mode’s comma parsing.