Erlang 8.11.2.2

gistfile1.erl

-module(circle).
-export([start/1]).

start(Msg) ->
    CPid = clasp(),
    Pid1 = shackle(CPid, CPid),
    Pid2 = shackle(Pid1, CPid),
    Pid3 = shackle(Pid2, CPid),
    send(Pid3,Msg).

clasp() ->
    spawn(fun() ->
		  loop(0, self()) end).

shackle(Pid, Root) ->
    spawn(fun() ->
		  loop(Pid, Root) end).

send(Pid,Msg) ->
    Pid ! {next, Msg}.

loop(Pid, Root) ->
    receive
	{next, Msg} when is_pid(Pid) ->
	    io:format("Send request received ~p~n", [Pid]),
	    Pid ! {next, Msg},
	    loop(Pid, Root);
	{next, Msg} when Pid == 0 ->
	    io:format("Arrived at shackle ~p~n", [Msg]),
	    Root ! {next, Msg}; 
	{next} ->
	    io:format("Default way~n")
    end.