Newbie Scala Question: Say I want to do this [Java code] in Scala: public static double[] abs(double[] r, double[] im) { double t[] = new double[r.length]; for (int i = 0; i < t.length; ++i) { t[i] = Math.sqrt(r[i] * r[i] + im[i] * im[i]); } return t; } and also make it generic (since Scala efficiently do generic primit...
Hi all. I'm drawing a tab and I have the outline as I want it. I now want to fill the area I create but can't figure out how. This is the code that draws the border of the tab: val g2 = g.asInstanceOf[Graphics2D] g2.translate(x, y) val q = new CubicCurve2D.Float q.setCurve(0, h, 8, h, 6, 0, 16, 0) g2.setColor(Color.RED) g2...
Hi, I have the following classes/traits in Scala trait Write[-T] { def add(elem : T); } class ContraListWrapper[T] (var list : List[T]) extends Write[T] { def add(elem : T) = { list = elem :: list } } def bar(list : Write[Number]) = {} Invoking the method with a List of Object or list of Numbers works, thanks to contr...
Hi, When I'm writing this code, I've got a Compile error in Scala var s: Stack[_ <: Number] = new Stack[Integer]; s.push(new Integer(1)); //compile-error: type mismatch; found :Integer required: _$bqjyh where type _$bqjyh <: Number s.push(null); //compile-error: type mismatch; found : Null(null) required: _$2 where type _$2 <: Objec...
How one can access attributes with namespaces? My XML data are in a form val d = <z:Attachment rdf:about="#item_1"></z:Attachment> but the following does not match the attribute (d \\ "Attachment" \ "@about").toString If I remove the namespace component from the attribute's name then it works. val d = <z:Attachment about="#item_1"...
Hello, As I am in my starting career year in software development (C++ & C#) I now see my flaws and what I miss in this sphere. Because of that I came into some conclusions and made myself a plan to fill those gaps and increase my knowledge in software development. But the question I stumbled upon after making a tasks which I need to do...
In scalacheck's user guide there is "Generating Case Classes" paragraph. I modified example from it to use regular classes instead of case classes: import org.scalacheck._ import Gen._ import Arbitrary._ sealed abstract class Tree object Leaf extends Tree class Node(left:Tree, rigth:Tree, v:Int) extends Tree object Main { val genLe...
Hi, im new to scala and ran into the following problem: I want to get a subcollection of an existing collection that only contains elements of a specific type. The following works: class C(val name : String) class D(name : String) extends C(name) { } val collection = Set[C](new C("C1"),new D("D1"),new C("C2"),new D("D2")) collection.c...
Chained package clause were introduced in Scala 2.8, as described by Martin Odersky on the Scala site. I don't quite get the intuition behind this. Following was the example in the Scala book for the nested packages: package bobsrockets { package navigation { // In package bobsrockets.navigation class Navigator ...
I am using SBT (0.7.4) with Scala(2.7.7) to build my Scala project and sometimes I get following error when building the project. So far the only remedy seems to retry it or do a clean on the SBT shell which adds delay in build process. No definite pattern of occurrence of the error has emerged but it happens quite a lot when I am using...
Are there any good Scala-specific frameworks (for whatever purpose) and libraries worth taking a look out there other than Lift web framework? ...
Hi, In Scala variance can be defined with variance operators like + and - on the generic type argument. For example the List type is covariant in the standard library. class List[+A] So a function with a covariant list can be defined like this: def foo[A](list : List[A]) Also variance can be emulated with generic bounds. So we can...
What kind of constructs need 'scalac' compile and how to make an equivalent that will work in interpreter? Edit: I want to use scala instead of python as a scripting language. (with #!/usr/bin/scala) ...
haskell programmer. using F#. no typeclasses in F#. what to use when I need typeclasses? ...
I have Scala 2.8.0 installed and don't wish to use Scala 2.7. Whenever I try to use SBT, it begins downloading Scala 2.7.7. Even if I call it in a directory with a Scala 2.8 project. How to avoid this behaviour? There is no man page for SBT, neither I could find SBT configuration files in /etc or ~/. ...
How to use colours in console output in Scala or Java? ...
UserGuide of scalacheck project mentioned sized generators. The explanation code def matrix[T](g:Gen[T]):Gen[Seq[Seq[T]]] = Gen.sized {size => val side = scala.Math.sqrt(size).asInstanceOf[Int] //little change to prevent compile-time exception Gen.vectorOf(side, Gen.vectorOf(side, g)) } explained nothing for me. After some explorat...
What exactly is the difference between StandardTokenParsers and JavaTokenParsers? What is one good for and what is the other good for? In StandardTokenParsers I can define my keywords using lexical.reserved, but how exactly does that help me? BR Troels ...
I'm stuck on whether I should focus on Play or Lift for doing web development in Scala. Play looks very polished. The Scala-specific tutorial looks amazing. Furthermore, since I've been coding in MVC frameworks for a long time, it looks super familiar. However, it doesn't look like it can easily accomplish all the brilliant things th...
Hi stackoverflow. Having a background in Haskell I am currently trying to get familiar with Scala. I encountered some problems trying to translate a small, extensible expression language from Haskell into Scala. The underlying issue of writing a data type that is extensible with both new data-variants and operations is commonly known a...