I've implemented a Listenable/Listener trait that can be added to Actors. I'm wondering if it's possible to attach this style of trait to an actor without it having to explicitly call the listenerHandler method? Also I was expecting to find this functionality in the Akka library. Am I missing something or is there some reason that Akka ...
I have an xml file(from federal government's data.gov) which I'm trying to read with scala's xml handlers. val loadnode = scala.xml.XML.loadFile(filename) Apparently, there is an invalid xml character. Is there an option to just ignore invalid characters? or is my only option to clean it up first? org.xml.sax.SAXParseException: An ...
For example, how can I write an expression where the following is implicitly applied: implicit def intsToString(x: Int, y: Int) = "test" val s: String = ... //? Thanks ...
How does foldRight[B](B) from scaladoc match the actual call foldRight(0) args is an array of integers in string representation val elems = args map Integer.parseInt elems.foldRight(0) (_ + _) Scaladoc says: scala.Iterable.foldRight[B](B)((A, B) => B) : B Combines the elements of this list together using the binary function f, from ...
Here's a simplification of the classes I have: trait RequiredThings { val requiredThings: Seq[String] } class SimpleCalculator with RequiredThings { val requiredThings = List("a", "b") } class ComplicatedCalculator extends SimpleCalculator with RequiredThings { self: SimpleCalculator => override val requiredThings:List[String]...
We've been profiling our code recently and we've come across a few annoying hotspots. They're in the form assert(a == b, a + " is not equal to " + b) Because some of these asserts can be in code called a huge amount of times the string concat starts to add up. assert is defined as: def assert(assumption : Boolean, message : Any) = .....
I'm trying to port the following Java snippet to Scala. It takes a list of MyColor objects and merges all of the ones that are within a delta of each other. It seems like a problem that could be solved elegantly using some of Scala's functional bits. Any tips? List<MyColor> mergedColors = ...; MyColor lastColor = null; for(Color aColor ...
I was trying to solve Project Euler problem number 7 using scala 2.8 First solution implemented by me takes ~8 seconds def problem_7:Int = { var num = 17; var primes = new ArrayBuffer[Int](); primes += 2 primes += 3 primes += 5 primes += 7 primes += 11 primes += 13 while (primes.size < 10001){ ...
Assume you have a small project which on the surface looks like a good match for an ETL tool like Talend. But assume further, that you have never used Talend and furthermore, you do not trust "visual programming" tools in general and would rather code everything the old fashioned way (text on a nice IDE!) with the help of an appropriate...
I'm trying to use some Scala code and am having a hard time figuring out how to convert the Scala lists into standard Java lists. Any ideas? ...
I need to create a simple Chat system like facebook chat and a twitter-like app. What is the best concurrent program languages in this case ? Erlang, Haskell, Scala or anything else ? Thanks ^_^ ...
I'm starting on a Scala application which uses Hibernate (JPA) on the back end. In order to load an object, I use this line of code: val addr = s.load(classOf[Address], addr_id).asInstanceOf[Address]; Needless to say, that's a little painful. I wrote a helper class which looks like this: import org.hibernate.Session class DataLoader...
I've been converting some code from java to scala lately trying to teach myself the language. Suppose we have this scala class: class Person() { var name:String = "joebob" } Now I want to access it from java so I can't use dot-notation like I would if I was in scala. So I can get my var's contents by issuing: person = Person.new(...
I have two traits, one extending the other, each with an inner class, one extending the other, with the same names: trait A { class X { def x() = doSomething() } } trait B extends A { class X extends super.X { override def x() = doSomethingElse() } } class C extends B { val x = new X() // here B.X i...
I have read that Haskell parser combinators (in Parsec) can parse context sensitive grammars. Is this also true for Scala parser combinators? If so, is this what the "into" (aka ">>") function is for? What are some strengths/weaknesses of Scala's implementation of parser combinators, vs Haskell's? Do they accept the same class of gra...
I'm struggling to understand what precisely does it mean when a value has type A @cps[B,C] and what types of this form should I assign to my values when using the delimited continuations facility. I've looked at some sources: http://lamp.epfl.ch/~rompf/continuations-icfp09.pdf http://www.scala-lang.org/node/2096 http://dcsobral.blogs...
Here's the code I have: var commandsBuffer = List[String]() commandsBuffer ::= "cmd.exe" commandsBuffer ::= "/c" commandsBuffer ::= '"'+vcVarsAll.getAbsolutePath+'"' commandsBuffer ::= "&&" otherCommands.foreach(c => commandsBuffer ::= c) val asArray = commandsBuffer.reverse.toArray val processOutput = processutils.Proc.executeCommand(a...
I have problem with JavaConversions with 2.8 beta: import scala.collection.JavaConversions._ class Utils(dbFile : File, sep: String) extends IUtils { (...) def getFeatures() : java.util.List[String] = csv.attributes.toList } And then exception: [INFO] Utils.scala:20: error: type mismatch; [INFO] found : List[String] [IN...
Forgive me if this is a stupid question, but what makes actors so lightweight? To be honest, I'm not even sure how they work. Aren't they separate threads? 'Seems I have two questions. Thanks in advance :) ...
Let's say I have a MyObject instance which is not initialized: var a:MyObject = null is this the proper way to initialize it to null? ...