Create 2 process and send M messages back and forth between them

process.erl

% http://www.erlang.org/course/exercises.html#conc

-module(process).
-export([loop/0]).

loop() ->
        receive
                {From, Message} ->  io:format("received [~p] from [~p]~n", [Message, From]),
                loop()
        end.

process_function.erl

-module(process_function).
-compile(export_all).

start(M)        ->
                P1 = spawn(process, loop, []),
                P2 = spawn(process, loop, []),
                io:format("instantiated process ~p~n", [P1]),
                io:format("instantiated process ~p~n", [P2]),
                message(P1, P2, M),
                message(P2, P1, M).

message(From, To, M)    ->
                        [To ! {From, X} || X <- lists:seq(1,M)].