I've noticed the following behavior in scala when trying to unwrap tuples into vals: scala> val (A, B, C) = (1, 2, 3) <console>:5: error: not found: value A val (A, B, C) = (1, 2, 3) ^ <console>:5: error: not found: value B val (A, B, C) = (1, 2, 3) ^ <console>:5: error: not found: value C ...
Maven Scala: I created a scala project using archetype: mvn org.apache.maven.plugins:maven-archetype-plugin:1.0-alpha-7:create \ -DarchetypeGroupId=org.scala-tools.archetypes \ -DarchetypeArtifactId=scala-archetype-simple \ -DarchetypeVersion=1.1 \ -DremoteRepositories=http://scala-tools.org/repo-releases \ -DgroupId...
In object O { // construction code and member initialization } construct, when is this code going to be run? ...
Passing messages around with actors is great. But I would like to have even easier code. Examples (Pseudo-code) val splicedList:List[List[Int]]=biglist.partition(100) val sum:Int=ActorPool.numberOfActors(5).getAllResults(splicedList,foldLeft(_+_)) where spliceIntoParts turns one big list into 100 small lists the numberofactors part, ...
If I have some traits like: trait A {...} trait B extends A{...} trait C1 extends B{...} trait C2 extends A{...} I can write class in two ways (C1 and C2 add same functionality) class Concrete1 extends B with C1 class Concrete2 extends B with C2 What variant is better(efficient)? ...
I want to have classes that can mix only specified traits: class Peter extends Human with Lawful with Evil class Mag extends Elf with Chaotic with Neutral Is in scala a way to do this? UPD: trait Law trait Lawful extends Law trait LNeutral extends Law trait Chaotic extends Law trait Moral trait Good extends Moral trait Neutral exte...
I am trying to build a project using the newest release candidate of Scala (scala-2.8.0.RC1) and Maven in Intellij CE (9.0.1) -- I cannot upgrade to 9.0.2 because it breaks the La Clojure plugin. If I change my pom.xml to use the scala-2.8.0.RC1, Intellij tells me that Array is not defined (highlights in red). If I change to scala-2.8.0...
Why does this code fail to compile, but compiles successfully when I uncomment the indicated line? (I'm using Scala 2.8 nightly). It seems that explicitly calling string2Wrapper allows it to be used implicitly from that point on. class A { import Implicits.string2Wrapper def foo() { //string2Wrapper("A") ==> "B" // <-- uncommen...
Hi all, I'm trying to implement a HashMap-based tree that'd support O(1) subtree lookup for a given root key. To that goal, I'm trying to do the following: scala> type Q = HashMap[Char, Q] <console>:6: error: illegal cyclic reference involving type Q type Q = HashMap[Char, Q] ^ So the question is, is...
assuming I running Scala 2.8.0 RC1, the following scala code should print out the content of the file "c:/hello.txt" for ( line<-Source.fromPath( "c:/hello.txt" ).getLines ) println( line ) However, when I run it, I get the following error <console>:10: error: missing arguments for method getLines in class Source; ...
Hi, using the CPS compiler-plugin of Scala 2.8, there are the two magic controls reset and shift. Reset delimits the continuation and shift captures the continuation. There is an example of using CPS with NIO, using nested resets as a type of "forking"...? I don't exactly understand the purpose of nesting the resets, what's the effect? ...
I'm studying the source code of the Scala 2.8 collection classes. I have questions about the hierarchy of scala.collection.Traversable. Look at the following declarations: package scala.collection trait Traversable[+A] extends TraversableLike[A, Traversable[A]] with GenericTraversableTemplate[A, Traversable] tr...
Using XScalaWT, this compiled under Scala 2.7: class NodeView(parent: Composite) extends Composite(parent) { var nodeName: Label = null this.contains( label( nodeName = _ ) ) } With 2.8.0 RC1, I get this error: type mismatch; found : main.scala.NodeView required: org.eclipse.swt.widgets.Label The types ...
What is the shortest / most elegant way to implement the following Scala code with an abstract attribute in Python? abstract class Controller { val path: String } A subclass of Controller is enforced to define "path" by the Scala compiler. A subclass would look like this: class MyController extends Controller { override va...
I am trying to create a producer/consumer type Scala app. The LoopControl just sends a message to the MessageReceiver continually. The MessageReceiver then delegates work to the MessageCreatorActor (whose work is to check a map for an object, and if not found create one and start it up). Each MessageActor created by this MessageCreatorA...
For Problem 4 of Project Euler How do I break out a loop? var largest=0 for(i<-999 to 1 by -1) { for (j<-i to 1 by -1) { val product=i*j if (largest>product) // I want to break out here else if(product.toString.equals(product.toString.reverse)) largest=largest max product } } And does anyone know how to turn nested for l...
In Scala 2.7, I want to use a method as a parameter of another method of the same class. I have a class and objects which are companions: class mM(var elem:Matrix){ //apply a function on a dimension rows (1) or cols (2) def app(func:Iterable[Double]=>Double)(dim : Int) : Matrix = { ... } //utility function ...
I am learning Parser Combinators in scala and seeing different ways of parsing.I mainly see three different kind of parsers ie.RegexpParsers,StandardTokenParsers and JavaTokenParsers.I am new to parsing and not getting the idea how we will choose the suitable Parser according to our requirement.Can any one please explain how these differ...
Hello Guys, I want to make a scala function which returns a scala tuple. I can do a function like this: def foo = (1,"hello","world") and this will work fine, but now I want to tell the compiler what I expect to be returned from the function instead of using the built in type inference (after all, I have no idea what a (1,"hello","w...
I try to find out why the call ∅ in scalaz.ListW.<^> works def <^>[B: Zero](f: NonEmptyList[A] => B): B = value match { case Nil => ∅ case h :: t => f(Scalaz.nel(h, t)) } My minimal theory is: trait X[T]{ def y : T } object X{ implicit object IntX extends X[Int]{ def y = 42 } implicit object StringX extends X[Strin...