Utilities for advent of code solution modules.

This module contains a set of macros and helper functions which should be used to generate solution modules for advent of code. When solving the problem for <day> of <year>, this module can be imported, after which the aoc/3 macro can be used to automatically generate a solution module. The intended use looks like this:

import AOC

aoc 2020, 1 do

  def p1 do
    input_stream()
    |>  ...
  end

  def p2 do
    input_stream()
    |>  ...
  end
end

Defining a module with the aoc/3 macro has a few advantages:

• The input_path, input_string and input_stream functions are generated and inserted into the generated module.
• The p1/0, p1/1, p1/2, p2/0, p2/1 and p2/2 functions can be used to call the p1 and p2 functions in this module, making the development experience a bit nicer.

Overall, the macros in these modules are intended to allow you to forego writing boilerplate code which is shared between all the solutions.

aoc/3 and use AOC

Internally, aoc/3 generates a module with a predefined name (Y<year>.D<day>) which contains a use AOC, day: <day>, year: <year> statement. In turn, the __using__/1 macro defined in this module is responsible for generating the input_* helper functions. Thus, if you prefer to use a different naming scheme than the one imposed by aoc/3, you can do something like the following:

defmodule MySolution do
  use AOC, day: <day>, year: <year>

  ...
end

When using AOC like this, you cannot use the p* helper functions, but you get access to the various input_* functions.

input_* functions

Inside the generated module, the following functions are available:

• input_path/0: Get the path to the input for the module's day / year.
• input_string/0: Use File.read!/1 to read input_path/0.
• input_stream/0: Use File.stream!/1 to read input_path/0 and map String.trim/1 over the stream.

Each of these functions is overridable. This makes it possible to add the example input to your module when testing your code, for instance, the following code can be used to use the example input for year 2020 day 1.

aoc 2020, 1 do
  def input_stream do
    [
      "1721",
      "979",
      "366",
      "299",
      "675",
      "1456"
    ]
  end

  ...
end

Besides the input_* functions, the following two functions are available:

• _aoc_day/0: Get the day of the module
• _aoc_year/0: Get the year of the module

p1(), p2() and others

Inside the body of aoc/3, it is intended that you define the solution to part 1 inside a p1 function and the solution to part 2 inside a p2 function. If you do this, the helpers defined in this module can be used to quickly call p1 or p2 for a given day and year from within iex.

day and year can be passed as arguments, if they are not passed as arguments, the :advent_of_code application environment is checked for the value of :day or :year (using Application.get_env/3). If the value is present, it is used, otherwise, the current day or year is used. Since the application environment is used, you can override day or year in your config/config.exs file.