Pragmatic Forums | Posts in topic 'question about 'irc lite''

question about 'irc lite' posted by Joe Armstrong @ Sun, 04 Nov 2007 19:53:30 +0000

Joe Armstrong — Sun, 04 Nov 2007 19:53:30 +0000

You’re quite right – the call to controller/2 is the key to understanding everything.
I say this on page 194 – but it probably wasn’t clear enough. In retrospect I think the IRC
code is a little tricky to follow – the graphics detracts from the algorithm (thought it does
give a hint as to how to make a GUI in Erlang).

There is a much simpler example in the difficult to find “getting started” document at
the main Erlang web site – this describes a form of instant messenger – which is somewhat simpler than the IRC example.

http://www.erlang.org/doc/getting_started/conc_prog.html#3.5

Cheers

/Joe Armstrong

question about 'irc lite' posted by Ittay Dror @ Sat, 03 Nov 2007 09:27:12 +0000

Ittay Dror — Sat, 03 Nov 2007 09:27:12 +0000

Maybe I found the answer. Does the call ‘controller(C, self())’ in chat_group.erl means that all messages from C will now be routed to the chat_group process (by lib_chan_mm)? If so, I think this function (controller) should be explained in the previous chapter. Also, I think the message diagram should define where each message goes (‘login’ goes to the chat_server process, ‘relay’ goes to the group controller)

Another minor question is about server_loop’s handling of the login message. When it receives it and there’s no group controller, it creates one, but forgets about the message. So I assume this relies on the client’s behavior of resending login messages until acknowledged? If so, I think this should be pointed out (and why? why not start the group controller and then send it the login message?

Thank you,
Ittay

question about 'irc lite' posted by Ittay Dror @ Sat, 03 Nov 2007 09:06:53 +0000

Ittay Dror — Sat, 03 Nov 2007 09:06:53 +0000

Hi,

I’m reading the book and I enjoy it very much. Good book, excellent language!

However, I have a problem understanding the chat server example on chapter 11.

In the code I see that when a string is typed into Widget it is sent with ‘lib_chan_mm:send(MM, {relay, Nick, Str})’. I understand this is received by mod_chat_controller which then forward it with ‘chat_server ! {mm, MM, Msg}’. so Msg is ‘{relay, Nick, Str}’. But when I look at server_loop, I see it only handles login messages by forwarding them to the group controller. Other messages seem to just be printed to the console (‘Msg’ pattern in server_loop).

What have I missed?

Thank you,
Ittay