Lesson 2 - Scripting

Create your own functions¶

Even though Typst is a markup language (!= a programming language), it embeds a scripting language that lets us add logic (if/else statements, for loops, etc.) and create reusable components/functions.

Let's look at an example:

#let say-hello(s) = {
  [Hello, my friend '#s', how are you?]
}

#say-hello("Joseph")

#say-hello("Justine")

Two greeting lines addressed to Joseph and Justine

Once again we use the let keyword, and then we wrap the output of the function inside curly braces.

Note

There is no return keyword in Typst: everything in your function will be rendered.

Functions with default arguments¶

Functions can have as many arguments as we want, and some of them can have default values:

#let custom-box(label, fill: red) = {
   box(fill: fill, width: 4cm, inset: 5pt, text(weight: "bold", label))
}

#custom-box("Life is good")
#custom-box("Life is good", fill: green)

Two bold "Life is good" boxes, one red and one green

Variadic arguments¶

You can make your function accept any number of arguments by using variadic arguments:

#let custom-stack(..args) = {
  box(fill: red, inset: 5pt, stack(
      dir: ttb,
      spacing: 10pt,
      ..args
   ))
}

#custom-stack("hey", "you")
#custom-stack("we can add a", circle(fill: blue), "circle")

Two red boxes stacking text, with the second one including a blue circle between words

We can still apply changes to each argument passed. For example, let's add a black border around each of them:

#let custom-stack(..args) = {
  box(fill: red, inset: 5pt, stack(
    dir: ttb,
    spacing: 10pt,
    ..args.pos().map(val => box(stroke: 0.5pt + black, val)),
  ))
}

#custom-stack("hey", "you")
#custom-stack("we can add a", circle(fill: blue), "circle")

Two red boxes stacking text, with each item outlined by a black border and the second box including a blue circle between words

The pos() method converts it to an array, and map() applies a function to each element (val becomes box(stroke: 0.5pt + black, val)).

`if`/`else`¶

You can use if/else statements, which, for example, can be useful for creating flexible functions:

#let greet(name, vip: false) = {
  if vip {
    [Welcome back, esteemed #name!]
  } else {
    [Hello #name!]
  }
}

#greet("Joseph")

#greet("Justine", vip: true)

Greeting lines for Joseph and VIP guest Justine

`for` loops¶

You can use for loops to repeat content or iterate over a list:

#let name-list(names) = {
  for name in names {
    [• Hello #name \ ]
  }
}

#name-list(("Joseph", "Justine", "Alex", "Victoria"))

Bulleted list greeting Joseph, Justine, Alex, and Victoria

Question

Having questions? Feedback? Feel free to ask!