How can I separate a preamble (with functions and formatting rules) from my main typ file?

Questions
1

Hi,
I want to split my typ file in 2 files: one preamble and one main file.
I tried import, include … but nothing seems to work. I put below an example of the problem: if I use this file, it’s working my text is blue and I have number on heading.
But if I put the first part in preamble.typ (the first part finish before the first import), I am unable to get the same result. As you see in comment, I tried different thing but without getting the expected output.
Do you have ideas where is the problem please ? Many thanks.
Tom

#let chapter-counter = counter("chapter")
#chapter-counter.update(0)

#set page(margin: 2cm)                 // Set page margin globally
#set heading(numbering: "I.1.a.i")     // Set a custom numbering format for headings
#set text(fill: blue, size: 14pt)     // Set global text color and size

// Function to define a chapter
#let define-chapter(title) = {
  pagebreak(weak: true)
  context {
    align(center)[
      #block(inset: 2em, breakable: false)[
        #set text(size: 24pt, weight: "bold")
        #smallcaps[Chapter]
        #v(0cm)
        #title
      ]
    ]
  }

}

// #import "preamble.typ": define-chapter
// #import "preamble.typ": *
// #include("preamble.typ")
#define-chapter("Introduction to Typst")
= Test <test>
#lorem(700)
2

Check this post:

3

The tutorial page Making a Template should be helpful in your case.

Citing from that tutorial:

In Typst, templates are functions in which you can wrap your whole document.

So if you #import something (a function) from a template it is not applied automatically. You have to call it (e.g. for your custom chapter function), or wrap your whole document in it (e.g. for the text set rules).

4

Hi @tom1, welcome and thank you for your question! I have changed your post’s title to bring it in line with the question guidelines and thus make it easier to understand from the title:

Good titles are questions you would ask your friend about Typst.

I also added the templates tag, as it makes your question easier to find.

5

Many thanks for your replies.
Currently I have not enough time to understand the overall process to convert to a template, but I find a solution which seems working except for the number of the chapter but I think I forgot to add it.

I hope the solution will be interesting for some people.

Listing of template_test.typ:

// Counter for chapters
#let chapter-counter = counter("chapter")

// Function to define a chapter
#let define-chapter(title) = {
  pagebreak(weak: true)
  context {
    align(center)[
      #block(inset: 2em, breakable: false)[
        #set text(size: 24pt, weight: "bold")
        #smallcaps[Chapter]
        #v(0cm)
        #title
      ]
    ]
  }
}

// Initialize document with all styles
#let init(doc) = {
  // Initialize counter
  chapter-counter.update(0)
  
  // Set document styles
  set page(margin: 2cm)
  set heading(numbering: "I.1.a.i")
  set text(fill: blue, size: 14pt)
  
  // Return the styled document
  doc
}

Listing of main.typ:

#import "template_test.typ": init, define-chapter

#show: doc => init(doc)

#define-chapter("Introduction to Typst")
= Test <test>
#lorem(700)

Tom