ex_2023_12_15.erl

-module(ex_2023_12_15).
-compile(export_all).

%%% 2023-09-12
% Consider the infinite list of complete binary trees (from THAT haskell exercise): instead of infinite lists,
% we want to create processes which return the current element of the "virtual infinite list" with the message next,
% and terminate with the message stop.
% 1. Define a function btrees to create a process corresponding to the infinite tree of Exercise 2.1.
% 2. Define a function incbtrees to create a process corresponding to the infinite tree of Exercise 2.2.
% Notes: for security reasons, processes must only answer to their creating process; to define trees, you can use suitable
% tuples with atoms as customary in Erlang (e.g. {branch, {leaf, 1}, {leaf, 1}}).

btrees_child(Parent, Tree) ->
    NextTree =
        case Tree of
            {leaf, Value} -> {branch, {leaf, Value}, {leaf, Value}};
            {branch, V1, V2} -> {branch, {branch, V1, V2}, {branch, V1, V2}};
            V -> {leaf, V}
        end,
    receive
        {Parent, next} ->
            Parent ! NextTree,
            io:format("~p~n", [NextTree])
    after 5000 -> exit(ok)
    end,
    btrees_child(Parent, NextTree).

btrees(X) ->
    Self = self(),
    Pid = spawn(fun() -> btrees_child(Self, X) end),
    Pid ! {Self, next},
    Pid ! {Self, next},
    Pid ! {Self, next}.