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  • scala 2.8 implict java collections conversions

    - by nablik
    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] [INFO] required: java.util.List[String] [INFO] def getFeatures() : java.util.List[String] = csv.attributes.toList [INFO]

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  • Have you actually convinced anybody to Scala?

    - by Lukasz Lew
    I had limited success myself. I was able to hype a few persons about Scala. But in fact none of them made a meaningful effort to try to switch (usually from Java). I would like to read both success and failure stories here. Both long tries and short ones. My goal is to find ways of presenting Scala to another person, friend, co-worker (not an audience) that will make them want to use this great language.

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  • maven and lift using scala 2.8 : lift-mapper missing?

    - by Bjorn J
    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 -DarchetypeRepository=http://scala-tools.org/repo-snapshots -DremoteRepositories=http://scala-tools.org/repo-snapshots -DgroupId=com.liftworkshop -DartifactId=todo -Dversion=1.0-SNAPSHOT So far so good, but then, I try to cd into my new project and do: mvn jetty:run I after quite a few downloads end up with a error like below: [ERROR] BUILD ERROR [INFO] ------------------------------------------------------------------------ [INFO] Failed to resolve artifact. Missing: ---------- 1) net.liftweb:lift-mapper:jar:2.0-scala280-SNAPSHOT Try downloading the file manually from the project website. Then, install it using the command: mvn install:install-file -DgroupId=net.liftweb -DartifactId=lift-mapper -D version=2.0-scala280-SNAPSHOT -Dpackaging=jar -Dfile=/path/to/file Alternatively, if you host your own repository you can deploy the file there: mvn deploy:deploy-file -DgroupId=net.liftweb -DartifactId=lift-mapper -Dve rsion=2.0-scala280-SNAPSHOT -Dpackaging=jar -Dfile=/path/to/file -Durl=[url] -Dr epositoryId=[id] Path to dependency: 1) com.liftworkshop:todo:war:1.0-SNAPSHOT 2) net.liftweb:lift-mapper:jar:2.0-scala280-SNAPSHOT ---------- 1 required artifact is missing. for artifact: com.liftworkshop:todo:war:1.0-SNAPSHOT from the specified remote repositories: scala-tools.snapshots (http://scala-tools.org/repo-snapshots), scala-tools.releases (http://scala-tools.org/repo-releases), central (http://repo1.maven.org/maven2) Any ideas?

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  • Adding multiple rss feeds to a script in SCALA InfoChannel Designer 5

    - by godleuf
    Okay, since it is impossible to talk to anyone on the phone or get support through Scala's "forum", I am going to take a shot and see if anyone out there is feeling my pain. I have a client that uses Scala's InfoChannel Designer and Content Manager. I have had to learn this software from scratch and I have to say it hasn't been easy. I think I am at a point where the overall design is set, but I need to implement a couple of things before I can make this happen. RSS feeds are my issue at this point. Multiple RSS feeds to be specific. I need a feed coming in for 3 areas of content: Wiki News (or equivalent), local weather and a stock ticker. I have learned how to setup a "crawl" using a script example available from Scala's file center and copying and pasting into my design. But from what I have learned first hand and through reading through other forums, you can not have a feed from 3 different sources or urls happening simultaneously. Doesn't seem like it would be an issue, but apparently it is. This small step has held up this project for far too long and I need to get it figured out. This doesn't even touch on my issue of feeding in streaming video as a background but I have gone over this in another question but with no luck thus far. If there is ANYONE out there who is in anything similar using this software, your feedback and/or suggestions would be greatly appreciated. Thanks you for allowing me to vent!

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  • simple scala question about httpparser

    - by kula
    hi all. i'm a scala newbee. i have one question. in my code ,i try to import httpparse library like this scalac -classpath /home/kula/code/201005/kookle/lib/htmlparser.jar crawler.scala and i run this code. scala main and it tell me that java.lang.NoClassDefFoundError: org/htmlparser/Parser at FetchActor$$anonfun$act$1$$anonfun$apply$1.apply(crawler.scala:21) at FetchActor$$anonfun$act$1$$anonfun$apply$1.apply(crawler.scala:13) at scala.actors.Reaction.run(Reaction.scala:78) at scala.actors.FJTask$Wrap.run(Unknown Source) at scala.actors.FJTaskRunner.scanWhileIdling(Unknown Source) at scala.actors.FJTaskRunner.run(Unknown Source) i check the file./home/kula/code/201005/kookle/lib/htmlparser.jar and it is no problem.anyone can tell me how cause this bug?

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  • Is the Scala 2.8 collections library a case of "the longest suicide note in history" ?

    - by oxbow_lakes
    First note the inflammatory subject title is a quotation made about the manifesto of a UK political party in the early 1980s. This question is subjective but it is a genuine question, I've made it CW and I'd like some opinions on the matter. Despite whatever my wife and coworkers keep telling me, I don't think I'm an idiot: I have a good degree in mathematics from the University of Oxford and I've been programming commercially for almost 12 years and in Scala for about a year (also commercially). I have just started to look at the Scala collections library re-implementation which is coming in the imminent 2.8 release. Those familiar with the library from 2.7 will notice that the library, from a usage perspective, has changed little. For example... > List("Paris", "London").map(_.length) res0: List[Int] List(5, 6) ...would work in either versions. The library is eminently useable: in fact it's fantastic. However, those previously unfamiliar with Scala and poking around to get a feel for the language now have to make sense of method signatures like: def map[B, That](f: A => B)(implicit bf: CanBuildFrom[Repr, B, That]): That For such simple functionality, this is a daunting signature and one which I find myself struggling to understand. Not that I think Scala was ever likely to be the next Java (or /C/C++/C#) - I don't believe its creators were aiming it at that market - but I think it is/was certainly feasible for Scala to become the next Ruby or Python (i.e. to gain a significant commercial user-base) Is this going to put people off coming to Scala? Is this going to give Scala a bad name in the commercial world as an academic plaything that only dedicated PhD students can understand? Are CTOs and heads of software going to get scared off? Was the library re-design a sensible idea? If you're using Scala commercially, are you worried about this? Are you planning to adopt 2.8 immediately or wait to see what happens? Steve Yegge once attacked Scala (mistakenly in my opinion) for what he saw as its overcomplicated type-system. I worry that someone is going to have a field day spreading fud with this API (similarly to how Josh Bloch scared the JCP out of adding closures to Java). Note - I should be clear that, whilst I believe that Josh Bloch was influential in the rejection of the BGGA closures proposal, I don't ascribe this to anything other than his honestly-held beliefs that the proposal represented a mistake.

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  • Stuck at "Hello World" with IntelliJ IDEA 9.0.1 for Scala

    - by Alex R
    I've been using Eclipse since 2.x and and IDEs in general for over 20 years (since Turbo Pascal and Turbo C in the late '80s!). (that preamble is supposed to imply, "I'm not an idiot" ... LOL :-] ) I'm trying to use the debugger in IntelliJ 9.0.1. I've resigned myself to an old standby: class hello { def main(a: Array[String]) = println("got args: " + a) } Alas, I'm unable to get even this simple Scala example to run. I'd like to eventually put a breakpoint in it, but for now just running it would be great. I have Java 1.6u20 and the Scala plug-in 0.3.473 (January 2010). The error below summarizes my experience: What possibly could I be doing wrong? Thanks

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  • Scala methods ending in _=

    - by Alexey Romanov
    I seem to remember Scala treating methods ending in _= specially, so something like this: object X { var x: Int = 0; def y_=(n : Int) { x = n }} X.y = 1 should call X.y_=(1). However, in 2.8.0 RC1, I get an error message: <console>:6: error: value y is not a member of object X X.y = 1 ^ Interestingly, just trying to call the method without parentheses fails as well: scala> X.y_= 1 <console>:1: error: ';' expected but integer literal found. X.y_= 1 ^ Am I misremembering something which does actually exist or did I just invent it out of whole cloth?

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  • Scala case class generated field value

    - by Petteri Hietavirta
    I have an existing Scala application and it uses case classes which are then persisted in MongoDB. I need to introduce a new field to a case class but the value of it is derived from existing field. For example, there is phone number and I want to add normalised phone number while keeping the original phone number. I'll update the existing records in MongoDB but I would need to add this normalisation feature to existing save and update code. So, is there any nice shortcut in Scala to add a "hook" to a certain field of a case class? For example, in Java one could modify setter of the phone number.

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  • Scala factory pattern returns unusable abstract type

    - by GGGforce
    Please let me know how to make the following bit of code work as intended. The problem is that the Scala compiler doesn't understand that my factory is returning a concrete class, so my object can't be used later. Can TypeTags or type parameters help? Or do I need to refactor the code some other way? I'm (obviously) new to Scala. trait Animal trait DomesticatedAnimal extends Animal trait Pet extends DomesticatedAnimal {var name: String = _} class Wolf extends Animal class Cow extends DomesticatedAnimal class Dog extends Pet object Animal { def apply(aType: String) = { aType match { case "wolf" => new Wolf case "cow" => new Cow case "dog" => new Dog } } } def name(a: Pet, name: String) { a.name = name println(a +"'s name is: " + a.name) } val d = Animal("dog") name(d, "fred") The last line of code fails because the compiler thinks d is an Animal, not a Dog.

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  • Decision for Unchecked Exceptions in Scala

    - by Jatin
    As a java programmer, I have always been critical of Unchecked Exceptions. Mostly programmers use it as an en-route to coding easiness only to create trouble later. Also the programs (though untidy) with checked exceptions are much robust compared to unchecked counterparts. Surprisingly in Scala, there is nothing called Checked Exceptions. All the Java checked and unchecked are unchecked in Scala. What is the motivation behind this decision? For me it opens wide range of problems when using any external code. And if by chance the documentation is poor, it results in KILL.

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  • Is Clojure, Scala and other restrained by the JVM vs CLR

    - by jia93
    The Java implementors seem slow to adopt language improvements, for example compare C# with full closures, expression trees, LINQ etc.. to Java, and even the push back of some stuff to Java 8 will still leave it behind the current implementation of C#. However since I dont intend to use either Java or C# that particular language war isnt of interest too much, im more concerned with the JVM vs CLR. Is this lagging-behind also applicable to the JVM? Will Scala, Clojure etc.. will they be able to continue to innovate or score optimal performance in the face of slowly progressing underlying VM such as JVM? Is Clojure/Scala restrained at present by JVM limitations?

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  • Common idiom in Java to Scala, traverse/Iterate Java list into Scala list

    - by Berlin Brown
    I am processing a XML document and iterating through nodes. I want to iterate through the nodes and build a new List of some type. How would I do this with Scala: Here is my XML traverse code: def findClassRef(xmlNode: Elem) = { xmlNode\"classDef" foreach { (entry) => val name = entry \ "@name" val classid = entry \ "@classId" println(name + "//" + classid) } } Where the line of println is, I want to append elements to a list.

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  • what's the right way to use scala.io.Source?

    - by woods
    In many examples, it is described that you can use scala.io.Source to read a whole file like this: val str = scala.io.Source.fromFile("test.txt").mkString() But closing the underlying stream is not mentioned. Why does Scala not provide a convenient way to do that such as with clause in Python? It looks useful but not difficult. Is there any other better way to do that safely in Scala, i means to read a whole file?

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  • How do I use continuations on Scala 2.8?

    - by Seth Tisue
    Scala 2.8.0.RC1 includes the continuations plugin on trunk for the first time, but the details of how to use it have changed from previous releases, so it's difficult to follow the blog entries and SO answers out there that talk about continuations but were written for previous versions.

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  • What's the new way to iterate over a Java Map in Scala 2.8.0?

    - by Alex R
    How does scala.collection.JavaConversions supercede the answers given here: http://stackoverflow.com/questions/495741/iterating-over-java-collections-in-scala (doesn't work because the "jcl" package is gone) and here http://www.eishay.com/2009/05/iterating-over-map-with-scala.html (doesn't work me in a complicated test which I'll try to boil down and post here later) The latter is actually a Scala Map question but I think I need to know both answers in order to iterate over a java.util.Map. Thanks

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  • Extending existing data structure in Scala.

    - by Lukasz Lew
    I have a normal tree defined in Scala. sealed abstract class Tree case class Node (...) extends Tree case class Leaf (...) extends Tree Now I want to add a member variable to all nodes and leaves in the tree. Is it possible with extend keyword or do I have to modify the tree classes by adding [T]?

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