gistfile1.erl

-module(tut15).
-export([start/0, ping/2, pong/0]).
ping(0, Pong_PID) ->
    Pong_PID ! finished,
    io:format("ping finished~n", []);

ping(N, Pong_PID) ->
    Pong_PID ! {ping, self()},
    receive
       pong ->
       :format("Ping received pong~n", [])
    end,

ping(N - 1, Pong_PID).
    pong() ->
        receive
            finished ->
                io:format("Pong finished~n", []);
                {ping, Ping_PID} ->
                    io:format("Pong received ping~n", []),
                    Ping_PID ! pong,
                    pong()
                end.
    start() ->
        Pong_PID = spawn(tut15, pong, []),
        spawn(tut15, ping, [3, Pong_PID]).




------------
OUTPUT
>> start().

Pong received ping
Ping received pong
Pong received ping
Ping received pong
Pong received ping
Ping received pong
ping finished
Pong finished