exc#1 concurrency

gistfile1.hrl

-module(processes).
-compile(export_all).

% Interaction between processes, Concurrency
%
% 1. Write a function which starts 2 processes, and sends a message M
% times forewards and backwards between them. After the messages have been
% sent the processes should terminate gracefully.

init(PingPongCount) ->
    spawn(?MODULE, pingpong, [PingPongCount]).

start(PingPongCount) ->
    [Pinger, Ponger] = [init(PingPongCount), init(PingPongCount)],
    Pinger ! {Pinger, serve_shoot, Ponger}.

pingpong(Count) ->
    receive
        {From, serve_shoot, Ponger} ->
            io:format("~p serving PING to ~p", [From, Ponger]),
            Ponger ! {From, ping},
            pingpong(Count);
        {From, ping} when Count >= 1 ->
            io:format("PING! ~p replying with pong! (~p)~n", [self(),
                Count]),
            From ! {self(), pong},
            pingpong(Count - 1);
        {From, pong} when Count > 1 ->
            io:format("PONG! ~p will send ping! (~p) ~n", [self(), Count]),
            From ! {self(), ping},
            pingpong(Count - 1);
        _ ->
            io:format("~p Game over. ~p ~n", [self(), Count]),
            ok
    end.