defmodule ArrangeOpeningCombos do def remove_illegal_third_moves_after_e4(potential_line) do [one, w1, b1, two, w2, b2, three, w3, b3, four, w4, b4] = potential_line illegal_moves_map = %{ "Bd3" => [ "a5", "b5", "c5", "d3", "d4", "d5", "e5", "f5", "g5", "h5", "Nd2", "Ba3", "Bb2", "Bc2", "Be3", "Bf4", "Bf5", "Bg5", "Bg6", "Bh6" ] } cond do w2 == "Bd3" -> illegal_moves_list = Map.get(illegal_moves_map, "Bd3") if w3 not in illegal_moves_list do "(#{one} #{w1} #{b1} #{two} #{w2} #{b2} #{three} #{w3} #{b3} #{four} #{w4} #{b4}) " end true -> "(#{one} #{w1} #{b1} #{two} #{w2} #{b2} #{three} #{w3} #{b3} #{four} #{w4} #{b4}) " # potential_line end end def remove_illegal_second_moves_after_e4(possible_line) do [one, w1, b1, two, w2, b2, three, w3, b3, four, w4, b4] = possible_line list_of_illegal_second_moves_after_e4 = [ "a5", "b5", "c5", "d5", "e5", "f5", "g5", "h5", "Nd2", "Ba3", "Bb2", "Bd2", "Be3", "Bf4", "Bg5", "Bg2", "Bh3", "Bh6" ] if w2 not in list_of_illegal_second_moves_after_e4 do [one, w1, b1, two, w2, b2, three, w3, b3, four, w4, b4] end |> remove_illegal_third_moves_after_e4() end def remove_illegal_second_moves_after_d4(possible_line) do [one, w1, b1, two, w2, b2, three, w3, b3, four, w4, b4] = possible_line list_of_illegal_second_moves_after_d4 = [ "a5", "b5", "c5", "d5", "e5", "f5", "g5", "h5", "Ne2", "Ba3", "Ba6", "Bb2", "Bb5", "Bc4", "Bd3", "Be2", "Bg2", "Bh3" ] if w2 not in list_of_illegal_second_moves_after_d4 do "(#{one} #{w1} #{b1} #{two} #{w2} #{b2} #{three} #{w3} #{b3} #{four} #{w4} #{b4}) " end # |> remove_illegal_third_moves_after_d4() end def scrub_moves_list(moves_list) do Enum.map( moves_list, fn [one, w1, b1, two, w2, b2, three, w3, b3, four, w4, b4] = possible_line -> cond do w1 == "e4" -> remove_illegal_second_moves_after_e4(possible_line) w1 == "d4" -> remove_illegal_second_moves_after_d4(possible_line) true -> "(#{one} #{w1} #{b1} #{two} #{w2} #{b2} #{three} #{w3} #{b3} #{four} #{w4} #{b4}) " end end ) end def permute([]), do: [[]] def permute(list) do for x <- list, y <- permute(list -- [x]), do: [x | y] end def go(opening_moves_string) do [ one, white1, black1, two, white2, black2, three, white3, black3, four, white4, black4 ] = String.split(opening_moves_string) move_numbering = [one, two, three, four] whites_moves_list = [white1, white2, white3, white4] blacks_moves_list = [black1, black2, black3, black4] permutations = permute(whites_moves_list) combinations_list = Enum.map( permutations, fn moves_list -> Enum.zip(move_numbering, moves_list) |> Enum.zip(blacks_moves_list) |> Enum.flat_map(fn {{number, whites_move}, blacks_move} -> [number, whites_move, blacks_move] end) end ) Enum.map( combinations_list, fn [ one, w1, b1, two, w2, b2, three, w3, b3, four, w4, b4 ] -> illegal_first_moves = [ "a5", "b5", "c5", "d5", "e5", "f5", "g5", "h5", "Ne2", "Nd2", "Ba3", "Ba6", "Bb2", "Bb5", "Bc4", "Bd3", "Be2", "Bd2", "Be3", "Bf4", "Bg5", "Bg2", "Bh3", "Bh6" ] if w1 not in illegal_first_moves do [one, w1, b1, two, w2, b2, three, w3, b3, four, w4, b4] end end ) |> Enum.reject(&is_nil(&1)) |> scrub_moves_list() |> Enum.reject(&is_nil(&1)) |> IO.puts() end end Output: Interactive Elixir (1.10.3) - press Ctrl+C to exit (type h() ENTER for help) Elixir is ready iex(1)> ArrangeOpeningCombos.go("1. e4 e6 2. d4 Ke7 3. Bd3 f6 4. Ne2 Kf7") (1. e4 e6 2. d4 Ke7 3. Bd3 f6 4. Ne2 Kf7) (1. e4 e6 2. d4 Ke7 3. Ne2 f6 4. Bd3 Kf7) (1. e4 e6 2. Bd3 Ke7 3. Ne2 f6 4. d4 Kf7) (1. e4 e6 2. Ne2 Ke7 3. d4 f6 4. Bd3 Kf7) (1. e4 e6 2. Ne2 Ke7 3. Bd3 f6 4. d4 Kf7) (1. d4 e6 2. e4 Ke7 3. Bd3 f6 4. Ne2 Kf7) (1. d4 e6 2. e4 Ke7 3. Ne2 f6 4. Bd3 Kf7) :ok Ok, so, I’ve been learning Elixir for about a year now despite having zero programming experience - thanks so much to everyone on here who’s so kindly and generously helped me along the way :slight_smile: :slight_smile: :wink: - and I’d like to get a sense of where I’m at, what I’m doing correctly, what bad habits I’ve picked up along the way, if any, and how I can write code that is more efficient, readable and idiomatic while conforming to best practices. To that end I’ve put together this toy project. Any and all tips, suggestions, recommendations (and encouragements :slight_smile: ) are warmly welcomed. Thanks again guys! :slight_smile:

[image] Maxximiliann: illegal_moves_map = %{ "Bd3" => [ "a5", "b5", "c5", "d3", "d4", "d5", "e5", "f5", "g5", "h5", "Nd2", "Ba3", "Bb2", "Bc2", "Be3", "Bf4", "Bf5", "Bg5", "Bg6", "Bh6" ] } With Elixir formatter this is better: defmodule Example do @illegal_moves %{ "Bd3" => ~w[a5 b5 c5 d3 d4 d5 e5 f5 g5 h5 Nd2 Ba3 Bb2 Bc2 Be3 Bf4 Bf5 Bg5 Bg6 Bh6] } end as that your list would not be expanded in so many lines … [image] Maxximiliann: "(#{one} #{w1} #{b1} #{two} #{w2} #{b2} #{three} #{w3} #{b3} #{four} #{w4} #{b4}) " Shorter: "(" <> Enum.join(possible_line, " ") <> ") " [image] Maxximiliann: Map.get(illegal_moves_map, "Bd3") Optionally: illegal_moves_map["Bd3"] [image] Maxximiliann: Enum.map( moves_list, fn [one, w1, b1, two, w2, b2, three, w3, b3, four, w4, b4] = possible_line -> cond do w1 == "e4" -> remove_illegal_second_moves_after_e4(possible_line) w1 == "d4" -> remove_illegal_second_moves_after_d4(possible_line) true -> "(#{one} #{w1} #{b1} #{two} #{w2} #{b2} #{three} #{w3} #{b3} #{four} #{w4} #{b4}) " end end ) You may use pattern matching for this like: Enum.map(moves_list, fn [_one, w1 | _rest] = possible_line when w1 in ~w[e4 d4] -> remove_illegal_second_moves_after(possible_line, w1) possible_line -> "(" <> Enum.join(possible_line, " ") <> ") " end) [image] Maxximiliann: fn moves_list -> Enum.zip(move_numbering, moves_list) |> Enum.zip(blacks_moves_list) |> Enum.flat_map(fn {{number, whites_move}, blacks_move} -> [number, whites_move, blacks_move] end) end Much better: fn moves_list -> [move_numbering, moves_list, blacks_moves_list] |> Enum.zip() |> Enum.flat_map(&Tuple.to_list/1) end [image] Maxximiliann: |> scrub_moves_list() |> Enum.reject(&is_nil(&1)) scrub_moves_list/1 always returns list, so second Enum.reject/2 is not needed. Also you can write &is_nil/1. Finally having "(" <> Enum.join(possible_line, " ") <> ") " multiple times we may want to create a helper function for that.

Great stuff, thanks so very, very much! :slight_smile:

Elixir Programming Language Forum

Learning Elixir - Year One

Questions & Help Questions

Maxximiliann December 15, 2020, 2:36am 3

Great stuff, thanks so very, very much!