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✨ A package to help you easily pretty print structured data

⚙️ This package works with both the Erlang and Javascript target


To add this package to your Gleam project:

gleam add glam

Pretty printing

When working with structured data (like JSON, XML, lists, ASTs, …) it can be useful to print it in a nice and tidy way. Of course, one could go the quick and dirty way and just string.inspect the data structure and call it a day. However, the result would hardly be readable for complex data structures.

On the other hand, handwriting a pretty printing function can be quite difficult (I sure have spent my fair share of time writing those) and error-prone: there are a lot of moving pieces to juggle and it’s easy for bugs to sneak in.

A pretty printing package like Glam provides some basic building blocks to describe the structure of your data and takes care of the heavy lifting of actually finding the best layout to format the data, gracefully handling line limits and indentation.

Getting started

If you want to get started with Glam, a great starting point is the learning materials page! There you’ll find a lot of step-by-step tutorials that will guide you through some awesome pretty printers and get you up and running with Glam.

By the end of the tutorials you’ll know most of the package’s API and you’ll have implemented pretty printers for lists, JSON and error messages:

pretty_list(["Gleam", "is", "fun!"])
|> doc.to_string(10) // Fit the list on lines of width 10

// [
//   "Gleam",
//   "is",   
//   "fun!",   
// ]

You can also have a look at the examples folder in the GitHub repo, there you’ll also find a JSON pretty printer.


If you think there’s any way to improve this package, or if you spot a bug don’t be afraid to open PRs, issues or requests of any kind! Any contribution is welcome 💜

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