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• scala integer weirdness

  - by williamstw

  Suppose you inadvertently use Integer instead of Int, as in this code: import scala.collection.mutable.Map val contributors = Map[String,Integer]() val count = contributors.getOrElseUpdate("john",0) contributors.put("john",count+1) println(contributors) Compiler output: (fragment of test.scala):7: error: type mismatch; found : Int(1) required: String contributors.put("john",count+1) ^ Why "required: String"?

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• Starting inets/httpd with custom application

  - by williamstw

  I've got a module that I'm attempting to turn into a proper OTP application. Currently, the module has start/0 which starts a genserver which supplies configuration data read from a config file. It then calls inets:start(httpd,config:lookup(httpd_conf)). I gather that I need to move the starting of these out into the .app file's (application list) but I'm not sure how to get my config data into the inets:start function (or pass in httpd)? Thanks, --tim

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• Sharing [config] data across modules,functions

  - by williamstw

  I have some configuration data in a config file that I read off disk when the app starts. I need to make that configuration data available to other functions/modules in the application. I started down the path of looking into ets/mnesia to store the data on startup to make it shared among all processes, but then my inner voice cautioned me that there must be a more functional, erlang-y way to do this. The only alternate approach I've come up with so far is setting up a module that has an actor loop that reads the data on startup and responds to messages like {Key, From} and responds by From ! {ok,Value}. Then, I gave up and decided to ask... Thanks, --tim

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• erlang io:format, and a hanging web application

  - by williamstw

  While I'm learning a new language, I'll typically put lots of silly println's to see what values are where at specific times. It usually suffices because the languages typically have available a tostring equivalent. In trying that same approach with erlang, my webapp just "hangs" when there's a value attempted to be printed that's not a list. This happens when variable being printed is a tuple instead of a list. There's no error, exception, nothing... just doesn't respond. Now, I'm muddling through by being careful about what I'm writing out and as I learn more, things are getting better. But I wonder, is there a way to more reliably to [blindly] print a value to stdout? Thanks, --tim

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• Retrieving values from Env in mod_esi or webtools

  - by williamstw

  A complete noob question, but how exactly do I get values (e.g. path_info) from inside the callback? From the docs, I thought it was a list of tuples, which I thought would make it accessible via lists:keyfind, but I've had no luck. So far, all the examples I've found only show how to print everything with io_lib but not how to access the values by key... Thanks, --tim The docs: Module:Function(SessionID, Env, Input)- _ Types SessionID = term() Env = [EnvironmentDirectives] ++ ParsedHeader EnvironmentDirectives = {Key, Value} Key = query_string | content_length | server_software | gateway_interface | server_protocol | server_port | request_method | remote_addr | script_name. <v>Input = string()

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• Scala match/compare enumerations

  - by williamstw

  I have an enumeration that I want to use in pattern matches in an actor. I'm not getting what i'd expect and, now, I'm suspecting I'm missing something simple. My enumeration, object Ops extends Enumeration { val Create = Value("create") val Delete = Value("delete") } Then, I create an Ops from a String: val op = Ops.valueOf("create") Inside my match, I have: case (Ops.Create, ...) But Ops.Create doesn't seem to equal ops.valueOf("create") The former is just an atom 'create' and the later is Some(create) Hopefully, this is enough info for someone to tell me what I'm missing... Thanks

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• scala xml rewrite rule (or, simple pattern help)

  - by williamstw

  I'm missing some fairly simple syntax I gather. I'm trying to rewrite an element label to something else and keep everything else intact. object htmlRule extends RewriteRule { override def transform(n: Node): Seq[Node] = n match { case Elem(prefix, "document", attribs, scope, child@_*) => Elem(prefix, "html", attribs, scope, child) case other => other } } Now, I ask for an explanation of two things: 1) What exactly does "child@_*" mean in plain English? 2) How can I capture the value of "child@_*" and just let it pass right through to the new element? Currently, I get the following error, which makes sense. [error] found : Seq[scala.xml.Node] [error] required: scala.xml.Node [error] Elem(prefix, "html", attribs, scope, child) I'm not wedded to this either, so if there's a better way to simply change the element name of a specific node, let's here it... Thanks, --tim

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