Erlang Programming Exercise: 4-1
I'm glad to be past chapter 3, and that I took the time to go through the exercises. I would highly suggest to anybody learning Erlang to do the same. They helped me learn the syntax of the language and to become much more comfortable in Erlang. I also found the erlang man pages to be very helpful. For example, to get the full documentation for the lists module you type "erl -man lists" in a shell.
Before jumping into the exercises for chapter four I went back and re-read the chapter. It's a nice reminder of how Erlang is different from the languages I use for work. I'm still having trouble trying to grok the activity vs task mentality, it's so different from what I'm used to.
Exercise 4-1 I found to be much easier than 3-10. The goal is to start up a process that prints out messages you send to it, but to have the interaction with that process through a public interface.
Here is the interface you are supposed to maintain:
echo:start() ⇒ ok echo:print(Term) ⇒ ok echo:stop() ⇒ ok
Since I've been naming my modules after the exercise chapter and number I changed 'echo' to four_one. Here is my solution:
-module(four_one).
-export([start/0,print/1,stop/0]).
-export([loop/0]).
start() ->
Pid = spawn(four_one,loop,[]),
register(four_one, Pid),
ok.
print(Term) ->
four_one ! {print, Term},
ok.
stop() ->
four_one ! stop,
ok.
loop() ->
receive
stop -> ok;
{print, Term} ->
io:format("~p~n", [Term]),
loop()
end.
Cheers,
Halzy
