Hello everyone,
in Scala 2.8 how do I create an array of multiple dimensions? For example I want an integer or double matrix, something like double[][] in java.
I know for a fact that arrays have changed in 2.8 and that the old arrays are deprecated, but are there multiple ways to do it now and if yes, which is best?
Hoping for quick ...
In Scala 2.8 is there a way to overload constructors of a case class?
If yes, please put a snippet to explain, if not, please explain why?
...
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'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...
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...
Hello,
I have an asynchronous control-flow like the following:
ActorA ! DoA(dataA, callback1, callbackOnErrorA)
def callback1() = {
...
ActorB ! DoB(dataB, callback2, callbackOnErrorB)
}
def callback2() = {
ActorC ! DoC(dataC, callback3, callbackOnErrorC)
}
...
How would I divide this flow into several parts (continuations)...
I've been building out some annotated domain classes in Scala 2.8.0 using Hibernate Annotations 3.4.0. It's been working fine, except that there are certain annotations which take an array as a parameter. For example, here's a Java annotation that I want to express in Scala:
@OneToMany(mappedBy="passport_id", cascade=CascadeType.PERSIST...
I consider refactoring few method signatures that currently take parameter of type List or Set of concrete classes --List[Foo]-- to use repeated parameters instead: Foo*.
Update: Following reasoning is flawed, move along...
This would allow me to use the same method name and overload it based on the parameter type. This was not po...
@uncheckedVariance can be used to bridge the gap between Scala's declaration site variance annotations and Java's invariant generics.
scala> import java.util.Comparator
import java.util.Comparator
scala> trait Foo[T] extends Comparator[T]
defined trait Foo
scala> trait Foo[-T] extends Comparator[T]
<console>:5: error: contrav...
Does Scala have a version of Rubys' each_slice from the Array class?
...
I'm trying to match on an option group in Scala 2.8 (beta 1) with the following code:
import scala.xml._
val StatementPattern = """([\w\.]+)\s*:\s*([+-])?(\d+)""".r
def buildProperty(input: String): Node = input match {
case StatementPattern(name, value) => <propertyWithoutSign />
case StatementPattern(name, sign, value) => <p...
I'm looking to create a document like this:
<root/>
That I can add children to programatically. Theoretically, it would look like this:
val root_node_name = "root"
val doc = <{root_node_name}/>
But that doesn't seem to work:
error: not found: value <
So, what I tried instead was this:
val root_node_name = "root"
val doc = new s...
Hi,
We're looking at using actors in our Scala code quite soon. We're also thinking of moving to Scala 2.8 in the next few weeks. We've been keeping an eye on Akka but it doesn't currently support 2.8 and plans for it have slipped from the 0.7 release to 0.8
We would like distributed, supervised actors. Is there an alternative to Akka?...
How to do that without creating any new collections? Is there something better than this?
val m = scala.collection.mutable.Map[String, Long]("1" -> 1, "2" -> 2, "3" -> 3, "4" -> 4)
m.foreach(t => if (t._2 % 2 == 0) m.remove(t._1))
println(m)
P.S. in Scala 2.8
...
Newbie question since I'm not up to speed using
maven at all.
I'm trying to use scala + lift using scala 2.8, environment
is a win7 box if that matters.
I create a basic project using:
mvn archetype:generate -U -DarchetypeGroupId=net.liftweb -DarchetypeArtifactId=lift-archetype-basic -DarchetypeVersion=2.0-scala280-SNAPSHOT -Da...
In trying to write an API I'm struggling with Scala's collections in 2.8(.0-beta1).
Basically what I need is to write something that:
adds functionality to immutable sets of a certain type
where all methods like filter and map return a collection of the same type without having to override everything (which is why I went for 2.8 in th...
Following watching Nick Partidge's presentation on deriving scalaz, I got to looking at this example, which is just awesome:
import scalaz._
import Scalaz._
def even(x: Int) : Validation[NonEmptyList[String], Int]
= if (x % 2 ==0) x.success else "not even: %d".format(x).wrapNel.fail
println( even(3) <|*|> even(5) ) //prints: Failu...
There is a trait called Kleisli in the scalaz library. Looking at the code:
import scalaz._
import Scalaz._
type StringPair = (String, String)
val f: Int => List[String] = (i: Int) => List((i |+| 1).toString, (i |+| 2).toString)
val g: String => List[StringPair] = (s: String) => List("X" -> s, s -> "Y")
val k = kleisli(f) >=> k...
This question isn't meant as flame-bait! As it might be apparent, I've been looking at Scalaz recently. I'm trying to understand why I need some of the functionality that the library provides. Here's something:
import scalaz._
import Scalaz._
type NEL[A] = NonEmptyList[A]
val NEL = NonEmptyList
I put some println statements in my func...
scala> val m = Map(1 -> 2)
m: scala.collection.immutable.Map[Int,Int] = Map(1 -> 2)
scala> m.map{case (a, b) => (a+ 1, a+2, a+3)}
res42: scala.collection.immutable.Iterable[(Int, Int, Int)] = List((2,3,4))
What I want is for the result type to be List[(Int, Int, Int)]. The only way I found is:
scala> m.map{case (a, b) => (a+ 1, a+2...