erlang

Right now I am doing Process ! Message, but as i googled a bit, a message queue size is only limited to memory. I have a tree of processes where leaves generate messages and feed up to the root and i need to limit queue or switch to some another method of doing the same. more of it, sometimes Process gets messages from one leaf and sometimes from two leaves. In the second case I need different finite queues for eave leaf. There are no built-in mechanisms to limit the size of the message queue for a process. The usual solution to this problem in erlang is to introduce a flow control protocol

In the following code , server is listening to port 2345. After accepting connection from client it returns {ok, Socket} start() -> {ok, Listen} = gen_tcp:listen(2345, [binary, {packet, 4}, {reuseaddr, true}, {active, true}]), {ok, Socket} = gen_tcp:accept(Listen). I want to get client's IP and port, how can I get them by analyzing socket? Use inet:peername/1 . The description of the function from documentation: peername(Socket) -> {ok, {Address, Port}} | {error, posix()} Types: Socket = socket() Address = ip_address() Port = integer() >= 0 Returns the address and port for the other end of a

I'm coding a unit test where a (rather lengthy) binary is generated, and I want to assert that the generated binary equals the one I expect to be generated. I'm running eunit through " rebar eunit ". Thing is, when this assertion fails, the output is abreviated with " ... ", and I want to see the complete output so I can spot where the difference is. I'm now using " ?debugFmt() " as a temporary solution, but I'd like to know if there's an alternative to it (a config option or argument somewhere that can be applied to " ?_assertEqual() " so the output is only shown when the assertion fails).

I'm very new to Erlang. I tried to find out if a list index is out of bounds (before trying it) so i wanted to do an if clause with something like if lists:flatlength(A) < DestinationIndex .... I discovered that those function results cannot be used in if guards so i used case instead. This results in a nested case statement case Destination < 1 of true -> {ok,NumberOfJumps+1}; false -> case lists:flatlength(A) < Destination of true -> doSomething; false -> case lists:member(Destination,VisitedIndices) of true -> doSomething; false -> doSomethingElse end end end. I found this bad in terms of

Simple question... This code .. client() -> SomeHostInNet = "localhost" % to make it runnable on one machine {ok, Sock} = gen_tcp:connect(SomeHostInNet, 5678, [binary, {packet, 0}]), ok = gen_tcp:send(Sock, "Some Data"), ok = gen_tcp:close(Sock). is very clear except that I don't quite understand what [binary, {packet,0}] means ? Any one cares to explain ? MadSeb As per the gen_tcp:connect documentation: [binary, {packet, 0}] is the list of options that's passed to the connect function. binary means that the data that is sent/received on the socket is in binary format (as opposed to, say, list

I am trying to have a function that ensures the table I need is already created and if not to create it. Here's the sample: ensure_table_exists(Table, MnesiaTables, Nodes) -> case lists:member(Table, MnesiaTables) of true -> throw({error, db_might_have_already_been_created}); false -> mnesia:create_table(Table, [{disc_copies, Nodes}, {attributes, record_info(fields, Table)}]), ok end. The issue is that when compiling I get the error: illegal record info . It might have to do that record_info is resolved at compile time or that the second argument to record info should actually be a record that

I went through the documentation of the trace/3 BIF in Erlang. However, one observation I have made is that it cannot be used for tracing the consuming of messages from the mailbox. The flag 'receive' only traces when messages are added to a process's mailbox. Is there any way one can trace events such as reading from the mailbox using the receive construct? If not, is there any reason why this isn't possible? It seems very strange that one can trace most kind of events in a program and the reading of messages from a mailbox is not traceable. There is no such tool. You can only hope for call

Over the holidays, my family loves to play Boggle. Problem is, I'm terrible at Boggle. So I did what any good programmer would do: wrote a program to play for me. At the core of the algorithm is a simple prefix trie , where each node is a dict of references to the next letters. This is the trie:add implementation: add([], Trie) -> dict:store(stop, true, Trie); add([Ch|Rest], Trie) -> % setdefault(Key, Default, Dict) -> % case dict:find(Key, Dict) of % { ok, Val } -> { Dict, Val } % error -> { dict:new(), Default } % end. { NewTrie, SubTrie } = setdefault(Ch, dict:new(), Trie), NewSubTrie = add