Sets are generally unordered.

So any order you observe is by accident and has to be considered an implementation detail.

If you need to maintain order, a MapSet is not the correct data structure to use.

Try using the -- operator on your lists directly instead.

This does what I need, so simple.
But trying to wrap my head around functional programming
wow

def prune(list, items) do
list – items
end

a variable for game_state

def get_guess(_tally = %{used: state}) do
letters_by_frequency = [
“e”,“a”,“r”,“i”,“o”,“t”,“n”,“s”,“l”,“c”,“u”,“d”,“p”,
“b”,“f”,“g”,“h”,“j”,“k”,“m”,“q”,“v”,“w”,“x”,“y”,“z”
]

prune(letters_by_frequency, state)
|> Enum.at(0)

end

Enjoy the journey!

Just to consider alternatives to accomplish the same thing: you could still represent the most common letters as a list, but use a set to track guesses. Then you might have a function like this:

def get_guess(by_frequency, used) do
  Enum.find(by_frequency, fn letter ->
    letter not in used
  end)
end

This isn’t necessarily “better” (and may actually be technically slower for small lists like you’re dealing with), but thought it might be worth seeing a different way of accomplishing the same thing. (BTW the above will also work if used is a list.)