%%Пример для вопроса №8: Как запрограммировать на Erlang конечный автомат?
%%"Дверь с кодовым замком"
-module(code_lock).
-behaviour(gen_fsm).

-export([start_link/1]).
-export([button/1]).
-export([init/1, locked/2, open/2]).

start_link(Code) ->
   gen_fsm:start_link({local, code_lock}, code_lock, Code, []).

button(Digit) ->
   gen_fsm:send_event(code_lock, {button, Digit}).

init(Code) ->
   {ok, locked, {[], Code}}.

locked({button, Digit}, {SoFar, Code}) ->
   case [Digit|SoFar] of
       Code ->
           do_unlock(),
           {next_state, open, {[], Code}, 3000};
       Incomplete when length(Incomplete)<length(Code) ->
           {next_state, locked, {Incomplete, Code}};
       _Wrong ->
           {next_state, locked, {[], Code}}
   end.

open(timeout, State) ->
   do_lock(),
   {next_state, locked, State}.

do_lock() ->
   io::format("door closed").

do_unlock() ->
   io::format("door opened").