Erlang Programming/Behaviors/gen server

Example program for the OTP behaviour, gen_server. Here is an example program using gen_server to create a simple text game. -module(rock). -author("Eric Evers"). -behaviour(gen_server). % --------------------------------------------------------------- % Example of a gen_server % Purpose: a tutorial on gen_server % Program: a program that plays "rock, paper, scissors" % in spanish and english % Topics covered: % * starting a gen_server % * stoping a gen_server % * using a gen_server to play a simple game % * make a call within a call % * use calls and casts % % For more information see: % % References: % Author: Ericsson AB % Document: Erlang documentation % Section: OTP Design Principles % Page: Gen_Server Behaviour % ---------------------------------------------------------------- % % - for internal use -export([init/1, handle_call/3, handle_cast/2]). -export([handle_info/2, terminate/2, code_change/3]). % - quick halt (note: casts are Asynchronous) -export([stop/0]). % - for external use (note: calls are Synchronous) -export([start/0, translate/1, juego/1, list/0, play/1]). % @start the server start() -> gen_server:start_link({local, ?MODULE}, ?MODULE, [], []). list() -> gen_server:call(?MODULE, {list}). translate(Word) -> gen_server:call(?MODULE, {translate, Word}). % % use juego to play the game using spanish words juego(Word) -> gen_server:call(?MODULE, {juego, Word}). % use play to play the game using english words play(Word) -> gen_server:call(?MODULE, {play, Word}). % % init init([]) -> Dictionary = dict:from_list( [{rock,roca},{paper,papel},{scissors,tijeras}]), {ok, Dictionary}. % % handle_call handle_call({list}, _From, Dictionary) -> Response = dict:to_list(Dictionary), {reply, Response, Dictionary}; % % Here we make a call within a call handle_call({play, Word}, _From, Dictionary) -> Status = dict:is_key(Word, Dictionary), if Status == true -> SWord = dict:fetch(Word, Dictionary), {reply, Response, _} = handle_call({juego, SWord}, _From, Dictionary); true -> Response = your_word_is_not_valid end, {reply, Response, Dictionary}; % handle_call({juego, Word}, _From, Dictionary) -> List = dict:to_list(Dictionary), {_English, Spanish} = lists:unzip(List), Indexes = lists:seq(1, length(Spanish)), Enumerated = lists:zip(Spanish, Indexes), Enumerated_dictionary = dict:from_list(Enumerated), {_H,_M,S} = time(), N = (S rem length(Spanish)) + 1, Pick = lists:nth(N, Spanish), io:format("you play: ~w \n",[Word]), P = dict:fetch(Word, Enumerated_dictionary), Delta = ((N+3)-P) rem 3, Response = case Delta of 0 -> {'I',picked,Pick,its_a,draw}; 1 -> {'I',picked,Pick,you,loose}; 2 -> {'I',picked,Pick,you,win}; true -> {unknown, result} end, {reply, Response, Dictionary}; % handle_call({translate, Word}, _From, Dictionary) -> Response = case dict:is_key(Word, Dictionary) of true -> dict:fetch(Word, Dictionary); false -> {word_not_known, Word} end, {reply, Response, Dictionary}; % handle_call(_Message, _From, Dictionary) -> {reply, error, Dictionary}. % - stop() -> gen_server:cast(?MODULE, stop). % terminate(normal, _State) -> ok. % handle_cast(stop, State) -> {stop, normal, State}; % % - lets keep the compiler quiet with all the call-backs handle_cast(_Message, Dictionary) -> {noreply, Dictionary}. handle_info(_Message, Dictionary) -> {noreply, Dictionary}. code_change(_OldVersion, Dictionary, _Extra) -> {ok, Dictionary}. % - sample output ----------------------------- % c(rock). % <compile is done> % rock:start(). % <server started> % % 67> rock:juego(tijeras). % you play: tijeras % {'I',picked,roca,you,loose} % % 68> rock:juego(tijeras). % you play: tijeras % {'I',picked,papel,you,win} % % 69> rock:juego(tijeras). % you play: tijeras % {'I',picked,tijeras,its_a,draw} % ----------------------------------------------------