Practice with Lists in Erlang

practice_lists.erl

%%%-------------------------------------------------------------------
%%% @author Aaron Lelevier
%%% @doc Practice with Lists in Erlang. It's been about a week since coding up some Erlang
%%% These functions are all in the [lists](http://erlang.org/doc/man/lists.html) module
%%% @end
%%% Created : 27. Sep 2020 2:26 PM
%%%-------------------------------------------------------------------
-module(practice).
-author("Aaron Lelevier").
-vsn(1.0).
-export([seq/2, zip/2, unzip/1]).
-compile(export_all).

seq(X, Y) ->
  seq(X, Y, []).

seq(X, Y, Acc) ->
  if
    X =< Y ->
      seq(X + 1, Y, [X | Acc]);
    true ->
      lists:reverse(Acc)
  end.

zip(L1, L2) ->
  zip(L1, L2, []).

zip([], [], Acc) -> lists:reverse(Acc);
zip([H1|T1], [H2|T2], Acc) ->
  zip(T1, T2, [{H1, H2}|Acc]).


unzip(L) ->
  unzip(L, [], []).

unzip([], Acc1, Acc2) -> {lists:reverse(Acc1), lists:reverse(Acc2)};
unzip([{A,B}|T], Acc1, Acc2) ->
  unzip(T, [A|Acc1], [B|Acc2]).