Converting List of String to List of Int

Questions / Help
1

I am trying to learn some elixir with this years advent of code (no spoilers please).

Ex: I have in a file

four9one
bbzhsmnmtf8kftwosevenxfkssgrcjthree
6pkkcddsixsixjgnjvdtjtwo
4four45seven7nine7two
rcssix4

When I run my function I see the expected numbers individually but not as a List.

iex(69)> AdventOfCode2023.day_one
99
88
66
47
44
cXB/, # What is this? In my head I think it should be [99, 88, 66, 47, 44]

I am just confused at what is happening in my function. I don’t just want a solution to the problem itself.

  def day_one do
    numbers =
      File.read!(Path.expand("./lib/data/day1.data"))
      |> String.split("\r\n", trim: true)
      |> Enum.take(5)
      |> Enum.map(fn raw ->
        word = String.replace(raw, ~r/\D/, "")

        if String.length(word) === 1 do
          IO.puts(String.to_integer(word <> word))
          String.to_integer(word <> word)
        else
          IO.puts(String.to_integer(String.first(word) <> String.last(word)))
          String.to_integer(String.first(word) <> String.last(word))
        end
      end)

    IO.puts(numbers)
  end
2

Charlist. It is just different representation, just like 0xFF == 255.

1 Like
3

I guess my next question would be why is it a charlist and not [99, 88, 66, 47, 44]

4

You have it described in the link I have posted. It is exactly the same thing, just different representation.

2 Likes
5

Every newcomer is confused by this notation…

iex> 'hello world' |> IO.inspect(charlists: :as_list)
[104, 101, 108, 108, 111, 32, 119, 111, 114, 108, 100]
~c"hello world"

It’s coming from Erlang… where charlist is used as “string”
Every time there is a list that could potentially be something readable, it will print it like this

4 Likes
6

I see, I miss understood the first time I read it.

7

FWIW @Marzdor you can override this behaviour in IEx by adding this to your $HOME/.iex.exs file:

IEx.configure(inspect: [charlists: :as_lists])

You can also pass charlists: :as_lists to any IO.inspect/2 call, or set this project-wide by adding this code somewhere:

inspect_opts_default_inspect_fun = Inspect.Opts.default_inspect_fun()
Inspect.Opts.default_inspect_fun(fn value, opts ->
  opts = Map.put(opts, :charlists, :as_lists)
  inspect_opts_default_inspect_fun.(value, opts)
end)
2 Likes
8

Thank you for the tip.