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<P><FONT SIZE=2>Hi, Vlad!<BR>
<BR>
Try the following:<BR>
<BR>
First the loop: (can be a single registered process (better than passing PIDs around) or<BR>
a stand alone gen_server (which has certain qualities you might wanna have in your module..)):<BR>
<BR>
<BR>
loop() -><BR>
receive<BR>
{input, Data} -><BR>
processInput(Data),<BR>
loop();<BR>
AnyMessage -><BR>
store(AnyMessage),<BR>
loop<BR>
after 2300 -> <BR>
timeOutRoutine(),<BR>
loop()<BR>
end. <BR>
<BR>
Then a loop-state in order to verify the loops' state and<BR>
to store messages that are not caught by the reseive-pattern:<BR>
<BR>
State = [{active, true}, {pending, []}]<BR>
<BR>
the adapted loop function and the list-related helperz:<BR>
<BR>
loop(State) -><BR>
receive<BR>
activate -> <BR>
NewState = replaceVariable(State, {active, true}),<BR>
loop(NewState);<BR>
deactivate -><BR>
NewState = replaceVariable(State, {active, false}),<BR>
loop(NewState);<BR>
{input, Data} -><BR>
case getValue(State, active) of<BR>
false -><BR>
loop(State);<BR>
true -><BR>
processInput(Data),<BR>
loop(State)<BR>
end;<BR>
AnyMessage -><BR>
case getValue(State, active) of<BR>
false -><BR>
loop(State);<BR>
true -><BR>
%% now storing the msg in the loop's state:<BR>
NewState = replaceVariable(State, {pending, AnyMessage}),<BR>
loop(State)<BR>
end<BR>
after 2300 -> <BR>
timeOutRoutine(),<BR>
loop()<BR>
end.<BR>
<BR>
%% getValue<BR>
<BR>
getValue([], Key) -><BR>
value_not_found;<BR>
<BR>
getValue([{Key, Value}, Rest], Key) -><BR>
Value;<BR>
<BR>
getValue([{_OtherKey, _OtherValue}, Rest], Key) -><BR>
getValue(Rest, Key).<BR>
<BR>
%% replaceVariable<BR>
<BR>
replaceVariable({SuperVarKey, VarList}, {VarKey, NewValue}) -><BR>
{SuperVarKey, replaceVariable(VarList, {VarKey, NewValue})};<BR>
<BR>
replaceVariable(VarList, {Key, Value}) -><BR>
replaceVariable(VarList, {Key, Value}, []).<BR>
<BR>
<BR>
replaceVariable([], {_VarKey, _NewValue}, _Acc) -><BR>
void;<BR>
<BR>
replaceVariable([{VarKey, _OldValue} | Rest], {VarKey, NewValue}, Acc) -><BR>
lists:append([ lists:append([Acc, [{VarKey, NewValue}]]), Rest]);<BR>
<BR>
<BR>
replaceVariable([{OtherVarKey, OtherValue} | Rest], {VarKey, NewValue}, Acc) -><BR>
replaceVariable(Rest, {VarKey, NewValue}, lists:append([Acc, [{OtherVarKey, OtherValue}]])).<BR>
<BR>
<BR>
Obviously there are many ways to Rome, you can also use a dets/ets or mnesia to store wanted/unwanted messages instead of<BR>
saving it to the loop's state. Or you could use a gen_server instead that has some additional features with a native<BR>
server state that might suit your needs a lil' better.<BR>
<BR>
Best Regards,<BR>
<BR>
Christoph Grasl<BR>
Embedded Software Entwickler<BR>
<BR>
KEYTRONIX<BR>
Gesellschaft für industrielle Elektronik und Informationstechnologie mbH<BR>
<BR>
Ungargasse 64-66/1/109<BR>
A-1030 WIEN<BR>
<BR>
E-Mail: c.grasl@keytronix.com<BR>
Tel.: +43 (1) 718 06 60 - 323<BR>
Mobil: +43 (664) 8556456<BR>
WWW: <A HREF="http://www.keytronix.com">http://www.keytronix.com</A><BR>
<BR>
HG Wien FN 261131t<BR>
<BR>
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-----Ursprüngliche Nachricht-----<BR>
Von: erlang-questions-bounces@erlang.org im Auftrag von Vlad Dumitrescu<BR>
Gesendet: Di 05.08.2008 08:59<BR>
An: erlang-questions<BR>
Betreff: [erlang-questions] Selective receive issue<BR>
<BR>
Hi all,<BR>
<BR>
I have an example of a receive where I don't seem to be able to use the<BR>
usual "dump any unrecognized messages" catch-all clause. I think it is also<BR>
an example where channels could be useful, but the main question is whether<BR>
I am missing the obvious or not.<BR>
<BR>
I have a process that takes {input, Data} messages from its mailbox and<BR>
processes them (not necessarily one at a time). Flow control is implemented<BR>
as a pair of 'start'/'stop' messages. The way I implemented the main loop is<BR>
(simplified)<BR>
<BR>
receive<BR>
start->Running = true, loop();<BR>
stop->Running = false, loop()<BR>
after 0 -><BR>
if Running -> process_one_step(), loop();<BR>
true -> loop()<BR>
end<BR>
end,<BR>
<BR>
where the process_one_step() function may call<BR>
<BR>
receive<BR>
{input, Data} -> ...<BR>
end<BR>
<BR>
one or several times (it is configurable by the clients).<BR>
<BR>
It seems to me that there is no place where I can put a '_->...;' clause<BR>
without creating problems. So I'd like to ask if anyone sees another way to<BR>
structure this that will allow rogue messages to be discarded.<BR>
<BR>
------<BR>
A solution that requires an EEP :-) is to introduce an extension to the<BR>
receive statement that will explicitly keep matched messages in the<BR>
mailbox. For example<BR>
<BR>
receive<BR>
Pattern -> keep(), loop();<BR>
Msg -> process(Msg), loop()<BR>
end<BR>
<BR>
keep() is the extension that says "leave the message in the mailbox and<BR>
proceed". This way process() will be called with all messages except those<BR>
matching Pattern<BR>
<BR>
Would something like that be useful, or are there already ways to achieve<BR>
the same effect?<BR>
<BR>
best regards,<BR>
Vlad<BR>
<BR>
</FONT>
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