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adglent is a Gleam library which can be used to setup testing code and a template for implementing solution to Advent of code problems.

NOTE: adglent only supports erlang target (default) for Gleam.


adglent is written in gleam and runs and tests solutions written in Gleam. Read more about gleam at

The easiest way to install gleam is to use asdf:

  1. Install asdf according to the instructions at the asdf website
  2. Install the gleam asdf plugin: asdf plugin-add gleam
  3. Install the latest asdf install gleam latest
  4. Use the latest gleam version globally: asdf global gleam latest

HINT: asdf can manage multiple versions of gleam and the version can be set globally and also locally (asdf local gleam <VERSION>) to use a specific gleam version in a project.


Start a new gleam project for your AOC soluctions with gleam new. In the project folder run:

gleam add --dev adglent



First log in to Advent of code and copy your personal session-cookie. The value can be found using developer tools in the browser (in Chrome: “Application->Cookies->>session” and copy the Cookie-value)

gleam run -m adglent/init

Input the AOC year, you personal AOC session cookie and select if showtime should be used for tests (otherwise it will assume the project uses gleeunit as is default for gleam new <project>)

NOTE: showtime is an alternate gleam test-runner. It is still quite new and havn’t been tested in as many project as gleeunit. It has a different way of formatting the test-results and also supports the possibility to run specific test-modules (which can be useful in AOC). showtime is a standalone project but have been embedded into adglent.

Add day

To start working on the solution for a specific day run:

gleam run -m adglent/day <NUM>

Where <NUM> is the day number of the day you want to solve a problem for.

Example (start solving 1st of December):

gleam run -m adglent/day 1

Adding a day will add tests in test/day<NUM>/day<NUM>_test.gleamand a src/day<NUM>/solve.gleam file where the solution can be implemented.

Furthermore it will also download the input for the problem to src/day<NUM>/input.txt

Before running the tests you need to provide one or more example. These can be found in the problem description for that day at the AOC website.

Add an example to a part of the problem by adding examples to the part1_examples or part2_examples lists.

Example (input “Hello Joe!” should give answer 613411):

const part1_examples: List(Example(Problem1AnswerType)) = [
  Example("Hello Joe!", "613411"),

The type of the answer for a part can be adjusted if needed by changing the type aliases Problem1AnswerType / Problem2AnswerType. Note that this will change the type that the part1 / part2 functions in solve.gleam expect to return.


To test all days in the project use:

gleam test

If you are using showtime you can test a single day by running:

gleam test -- --modules=day<NUM>/day<NUM>_test

Example (test solution for 1st of December):

gleam test -- modules=day1/day1_test

Get the answer

To get the (hopefully correct) answer after the tests are ok run:

gleam run -m day<NUM>/solve <PART>

where <NUM> is the day to solve and <PART> is the part of the problem (1 or 2) to solve.

This will run the solver and print the answer to stdout.

Module documentation

Module documentation can be found at

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