How to write 2 equations on top of each other with a brace?

Questions
1

Hello!

Would anyone know how to make this in Typst?

image

Specifically how to have to blocks

Kind regards

2

Certainly, you would use the cases function in math mode, which takes comma-separated cases. Note the & for aligning, and the quoted "/" and "," since they have special meanings. Another option is escaping them like \/ and \, or using their names slash and comma.

delta(r_i - r_j) = cases(
  0 ","             &quad r_i - r_j >= epsilon "/" 2,
  1 "/" epsilon "," &quad r_i - r_j <  epsilon "/" 2
)

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image783Ă—217 19.2 KB

2 Likes
3

Amazing!

How to correctly specify the gap between each line and can I get the “,” at the end in some smart way?

Kind regards

4

You can do the following for the spacing as described in the documentation (Cases Function – Typst Documentation)

#set math.cases(gap: 1em)

There doesn’t seem to be a simple way to achieve that effect with the comma. You could probably manually place it all with a grid, but alignment would be tricky.

5

Yeah, ended up doing this:

  #set math.cases(gap: 1em)
  $
    delta(r_i - r_j) = cases(
      0 ","             &quad r_i - r_j >= epsilon "/" 2,
      1 "/" epsilon "," &quad r_i - r_j <  epsilon "/" 2
    ) #h(4pt) ,

  $ <eq:sph2>

But weird that I cannot set gap inside the function call, have to set it globally? Seems counterintuitive

The “,” was done through h-space

Kind regards

6

Manually placing just the comma does seem to be a good solution, I hadn’t thought of that. With more cases it will probably require a grid.

To make this easier you could define a custom function like so.

#set math.cases(gap: 1em)
#let commas(num) = pad(
  left: 0.2em,
  bottom: 1em,
  grid(columns: 1, row-gutter: 1.5em, ..(",",) * num)
)
$
delta(r_i - r_j) = cases(
  0 ","             &quad r_i - r_j > epsilon slash 2,
  1 ","             &quad r_i - r_j = epsilon slash 2,
  1 "/" epsilon "," &quad r_i - r_j < epsilon slash 2
) #commas(2)
$

Still kind of a workaround, but a less painful one.

7

You can set it in the function call by adding gap: #1em as a named argument to cases. Function calls in math are a hybrid between math markup and code: They support named arguments, but for them to be interpreted as code rather than math, you still need to enter code mode with the hash.