EP Exercise 4-2: The Process Ring

My solution for Exercise 4-2 in the book Erlang Programming

%%
%% Erlang Programming Exercise 4-2
%%

-module(ring).
-export([start/3,create_node/3,stop/0]).

create_node(M,N,Msg) ->
    io:format("Creating node ~w (~w)~n", [N,self()]),
    if
        N-1 > 0  -> NextPid = spawn(ring,create_node,[M,N-1,Msg]);
        N-1 == 0 -> NextPid = head
    end,
    print_m_times(NextPid,N,Msg,M),
    loop(NextPid).

start(M, N, Msg) ->
    io:format("Spawning ~w nodes!~n",[N]),
    Pid = spawn(ring,create_node,[M,N,Msg]),
    register(head, Pid),
    ok. 

stop() ->
    head ! quit,
    ok. 

loop(NextPid) ->
    receive
        {print, Pid, NodeNum, MsgContents} when Pid /= self() ->
            io:format("(~w) msg from node ~w: ~s~n",[self(),NodeNum,MsgContents]),
            NextPid ! {print, Pid, NodeNum, MsgContents},
            loop(NextPid);
        quit ->
            NextPid ! quit,
            io:format("Destroying node (~w)~n", [self()]),
            true
    end.

print_m_times(_,_,_,0) ->
    true;
print_m_times(NextPid,FromNode,Msg,M_Times) ->
    NextPid ! {print, self(), FromNode, Msg},
    print_m_times(NextPid,FromNode,Msg,M_Times-1).

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