erlang

问题 I have the following Erlang code and it is giving the warning as follows, when i try to compile it, but that make sense. function need two arguments, but i need to patten match "everything else" rather x, y or z. -module(crop). -export([fall_velocity/2]). fall_velocity(P, D) when D >= 0 -> case P of x -> math:sqrt(2 * 9.8 * D); y -> math:sqrt(2 * 1.6 * D); z -> math:sqrt(2 * 3.71 * D); (_)-> io:format("no match:~p~n") end. crop.erl:9: Warning: wrong number of arguments in format call. I was

问题 When using rebar for release, I have to set an environment variable. It is a node list. For example: vm.args # -zarah cluster_nodes ['zarah_slave_a@yus-iMac.local','zarah_slave_b@yus-iMac.local','emacs@yus-iMac.local'] But when running, the shell gives the error message: ＊＊＊＊＊＊＊＊＊＊＊＊＊ {error_logger,{{2013,11,20},{10,47,28}},"application_controller: ~ts: ~ts~n",[["syntax error before: ","'.'"],"[zarah_slave_a@yus-iMac.local,zarah_slave_b@yus-iMac.local,emacs@yus-iMac.local]"]} Erlang R16B02

问题 As I'm learning Erlang just by reading books and doing my own exercises (NOT for homework), I'm struggling with even the most simple task that I mentioned in the title. Here's what I've done: I created a file called sum.erl with the following lines of code: -module(mysum). -export([mysum/1]). mysum(L) -> mysum(L, 0). mysum([H|T], acc) -> mysum(T, H + acc); mysum([], acc) -> acc. Then I compile: erl sum.erl which takes me to a shell. There, I typed: 1> L = [1, 3, 7]. [1, 3, 7] 2> mysum(L). **

问题 How to change the "eheap_alloc" size on windows? This is for to do load test of erlang server with several number of clients. My server is running successfully up to 100 clients but if it is 200, server works two minutes with good results and then after server crashed and resulted with abnormal termination by showing eheap_alloc: Cannot allocate 8414160 bytes of memory (of type "heap"). But in Linux it can work for all the clients successfully. How can I over come this problem? help me some

问题 I'm working with Windows Server 2012, Erlang 19.2, and RabbitMq 3.6.6. I'm having trouble configuring the connection between endpoints using TLS. I've tried every answer on SO, as well as all the RabbitMq docs here and here. Not sure what we're doing wrong. In the troubleshooting link here all tests pass except the "Attempt SSL connection to broker" piece. This is where the problem lies and I'm not sure why. When I go through the documentation on troubleshooting to see if you can get a peer

问题 I have a one_for_one supervisor that handles similar and totally independent children. When there is a problem with one child, repeatedly crashing and triggering: =SUPERVISOR REPORT==== 30-Mar-2011::13:10:42 === Supervisor: {local,gateway_sup} Context: shutdown Reason: reached_max_restart_intensity Offender: [{pid,<0.76.0>}, ... shutting itself down and also terminating all the innocent children that would just continue to run fine otherwise. How can I build a supervision tree out of standard

问题 I'm trying to write and compile a custom behaviour in Erlang . I cannot find any clear documentation on how to compile this behaviour. -module(bla). -export([start_link/0,behaviour_info/1]). behaviour_info(callbacks)-> [{init,1}]; behaviour_info(_Other)-> undefined. %% -callback init(Args :: term()) -> %% {ok, State :: term()} | {ok, State :: term(), timeout()} | %% {stop, Reason :: term()} | ignore. start_link()-> init([]). my command for comiling is : erlc.exe .\src\bla.erl resulting: bla

问题 I'm currently reading Programming Erlang! , at the end of Chapter 13, we want to create a keep-alive process, the example likes: on_exit(Pid, Fun) -> spawn(fun() -> Ref = monitor(process, Pid), receive {'DOWN', Ref, process, Pid, Info} -> Fun(Info) end end). keep_alive(Name, Fun) -> register(Name, Pid = spawn(Fun)), on_exit(Pid, fun(_Why) -> keep_alive(Name, Fun) end). but when between register/2 and on_exit/2 the process maybe exit, so the monitor will failed, I changed the keep_alive/2 like

问题 Why receive expression is sometimes called selective receive? What is the "save queue"? How the after section works? 回答1: There is a special "save queue" involved in the procedure that when you first encounter the receive expression you may ignore its presence. Optionally, there may be an after-section in the expression that complicates the procedure a little. The receive expression is best explained with a flowchart: receive pattern1 -> expressions1; pattern2 -> expressions2; pattern3 ->

问题 I created a mochiweb instance src/ |-- Makefile |-- room.erl |-- myserver.app |-- myserver.erl |-- myserver_app.erl |-- myserver_deps.erl |-- myserver_sup.erl |-- myserver_web.erl `-- uuid.erl in myserver_web.erl I am able to access the application config {ok, "0.0.1"} = application:get_key(vsn), However in room.erl , I am not able to access the application config (specifically the env list). undefined = application:get_key(vsn), The supervisor does not start the room, nor do I want it too. I