http://blog.gmane.org/gmane.comp.lang.scala.user hourly 1 1901-01-01T00:00+00:00 http://gmane.org/img/gmane-25t.png http://gmane.org http://comments.gmane.org/gmane.comp.lang.scala.user/53621 <pre>How do I actually execute a Scala Swing program? I copied the example in chap. 34 "FirstSwingApp" into Scala shell on Windows. I then ran FirstSwingApp.top I was expecting to see a window pop up but nothing happened, except in shell it showed: res2: scala.swing.MainFrame = scala.swing.Frame$$anon $1[frame0,0,0,132x64,hidden ,layout=java.awt.BorderLayout,title=First Swing App,resizable,normal,defaultClos eOperation=HIDE_ON_CLOSE,rootPane=javax.swing.JRootPane[, 8,30,116x26,layout=java x.swing.JRootPane $RootLayout,alignmentX=0.0,alignmentY=0.0,border=,flags=1677767 3,maximumSize=,minimumSize=,preferredSize=],rootPaneCheckingEnabled=true] Please help. </pre> Michael 2012-05-26T20:05:05 http://comments.gmane.org/gmane.comp.lang.scala.user/53611 <pre> "scalac *.scala" ! results in error: source file '*.scala' could not be found Not sure, why it wont interpret the unix wild cards. Am wondering if this is a mac specific text encoding related issue. this is with scala 2.9.2 OS X 10.7 thanks Arun </pre> Arun Ramakrishnan 2012-05-26T02:25:19 http://comments.gmane.org/gmane.comp.lang.scala.user/53605 <pre>Hi all, Can someone explain why belinda is working fulltime instead of parttime in below code snippet? Thx in advance, Robby scala&gt; class Employee(employeeId: Integer, isFulltimeEmployed: Boolean) { | /** We can't register an employee without employeeId **/ | if (employeeId == null) { | throw new NullPointerException("employeeId was null") | } | /** we can override the primary constructor **/ | def this(employeeId: Integer) = this(employeeId, true) | override def toString() = employeeId + " works " + (if (isFullTimeEmployed) "fulltime" else "parttime") | } warning: there were 3 deprecation warnings; re-run with -deprecation for details defined class Employee scala&gt; scala&gt; val john = new Employee(12545, true) john: Employee = 12545 works fulltime scala&gt; val belinda = new Employee(32567, false) belinda: Employee = 32567 works fulltime scala&gt; val herman = new Employee(56784) herman: Employee = 56784 works fulltime scala&gt; val ivan = n</pre> Robby Pelssers 2012-05-25T20:44:11 http://comments.gmane.org/gmane.comp.lang.scala.user/53590 <pre>Hi, I am a Scala Noob and so far love the language. I am coming from a Perl background so the power of the language combined with the JVM still amazes me. Being from a Perl background one of the greatest things about Perl is the CPAN server that has everything you could possible need or want in Perl in one location. What are the thoughts of users and developers of have a CSAN(Central Scala Archive Network) for Scala open source code? I ask this because as I look around on the internet I am seeing more and more Scala projects popping up but the user/developer has to comb the internet to find great these. Finally, I think that Scala is going to continue to grow as its own language and not look to Java imports as much in the future as more users come aboard. -Dell </pre> Wendell Hatcher 2012-05-25T15:29:19 http://comments.gmane.org/gmane.comp.lang.scala.user/53584 <pre>http://www.scala-lang.org/node/10299 Quote from above Url: I do not really understand how you are supposed to develop real applications for the two platforms, considering that Java developers and .NET developers who are learning Scala, are used to reusing libraries friom their respective platform, e.g. log4j vs log4net, Hibernate vs NHibernate, Spring vs Spring.NET. For example, it does not seem very productive to create Scala abstraction layers for all popular third-part libraries you want to use. I mean, you might define an adapter trait that defines some SQL related methods you want to use, and then you can create one adapter implementation that reuses the Java Spring jar-file with the class 'org.springframework.jdbc.core.JdbcTemplate' while another adapter implementation reuses the Spring.NET assembly (dll-file) with the class 'Spring.Data.AdoTemplate'. Then somehow, I guess the shared Scala code would need to be able to determine which implementation to instantiate and include in the build script for </pre> jsamot 2012-05-25T12:53:34 http://comments.gmane.org/gmane.comp.lang.scala.user/53581 <pre>Hi, Do java.math.BigDecimal and scala.math.BigDecimal differ in a sense of functionality? Please see the output of REPL; is it the expected behavior? Welcome to Scala version 2.9.2 (OpenJDK Client VM, Java 1.8.0-ea). Type in expressions to have them evaluated. Type :help for more information. scala&gt; new java.math.BigDecimal(10).pow(50).remainder(new java.math.BigDecimal(45)) res0: java.math.BigDecimal = 10 scala&gt; BigDecimal(10).pow(50).remainder(BigDecimal(6)) java.lang.ArithmeticException: Division impossible at java.math.BigDecimal.divideToIntegralValue(BigDecimal.java:1863) at java.math.BigDecimal.divideAndRemainder(BigDecimal.java:1995) at java.math.BigDecimal.remainder(BigDecimal.java:1929) at scala.math.BigDecimal.remainder(BigDecimal.scala:255) at .&lt;init&gt;(&lt;console&gt;:8) at .&lt;clinit&gt;(&lt;console&gt;) at .&lt;init&gt;(&lt;console&gt;:11) at .&lt;clinit&gt;(&lt;console&gt;) at $print(&lt;console&gt;) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Meth</pre> Viktoras Agejevas 2012-05-25T12:25:05 http://comments.gmane.org/gmane.comp.lang.scala.user/53577 <pre>Hi Scala folks, I cannot manage to explain to myself the following behavior. Roughly, I'm trying to use pattern matching to test if my variable is instance of some traits. The problem arises when I try to match with different traits that are mixins in the same object. Here is a minimal example: trait A trait B extends A trait C extends A val ab = new A with B val ac = new A with C val abc = new A with B with C def f1(a:Any)=a match { case i:B if i==1 =&gt; -1 case i:B if i == None =&gt; 0 case i:C =&gt; 1 case _ =&gt; 2 } def f2(a:Any)=a match { case i:C =&gt; 1 case i:B if i==1 =&gt; -1 case i:B if i == None =&gt; 0 case _ =&gt; 2 } defined trait A defined trait B defined trait C ab: java.lang.Object with A with B = $anon$3&lt; at &gt;5b784ece ac: java.lang.Object with A with C = $anon$4&lt; at &gt;377de54c abc: java.lang.Object with A </pre> Marc-Antoine Nüssli 2012-05-25T11:10:40 http://comments.gmane.org/gmane.comp.lang.scala.user/53576 <pre> Hi, I'm having trouble understanding some aspects of Scala's type inference. At the moment I'm not sure whether I just ran into a couple of corner cases of the Scala spec or if there possibly is some bug somewhere in Scala. I have the following code (Scala 2.9.2): trait RE In the repl, I get: scala&gt; val r = new RR r: RR = RR&lt; at &gt;79bd18e4 &lt;console&gt;:16: error: inferred type arguments [Nothing,RR] do not conform to val p = new P(r) The error message is somewhat unspecific, as it does not say which of the type arguments does not conform. I'm also surprised, that the left argument is inferred as Nothing instead of RA. I think (maybe naively) that this should be possible at least in principle, as the compiler has all necessary type information. So, I decide that the first argument is the problem and I change the definition of P to introduce a dummy parameter: class P[A &lt;: FE, B &lt;: F[A]](b: B, a: A) extends R[PS] { def o = new PS } I get: scala&gt; val r = new RR Indeed, the problem seems t</pre> MP 2012-05-25T11:09:54 http://comments.gmane.org/gmane.comp.lang.scala.user/53568 <pre>I'm just like to revive a pretty ancient thread [1] about interest in a collection of Scala puzzlers by pointing out that http://scalapuzzlers.com is finally live. Feedback, comments and, of course, submissions much appreciated! ap [1] http://www.scala-lang.org/node/3247 </pre> Andrew Phillips 2012-05-24T23:59:53 http://comments.gmane.org/gmane.comp.lang.scala.user/53546 <pre>Dear all, I'm trying to model the following AST: An expression is either an operation or a value. An operation is reducible to a value via `eval` method. Concrete operations have expressions as parameters. It should be possible to restrict those parameters to expressions that evaluate to some concrete types of values. The problem: a method that processes a map[String, Value] doesn't compile (Scala 2.9.2): scala&gt; :paste // Entering paste mode (ctrl-D to finish) sealed abstract class Expr[T &lt;: Value[_]] {def eval: T} sealed abstract class Op[T &lt;: Value[_]] extends Expr[T] sealed abstract class Value[T &lt;: Value[_]] extends Expr[T] {def eval = this.asInstanceOf[T]} def rename(s: String): String = "xxx" def process(m: Map[String, Value[_]]): Map[String, Value[_]] = m map {t =&gt; (rename(t._1), t._2)} // Exiting paste mode, now interpreting. &lt;console&gt;:12: error: type mismatch; found : scala.collection.immutable.Iterable[(java.lang.String, Value[_$4]) forSome { type _$4 }] required: Map[</pre> Eugen Labun 2012-05-24T11:21:30 http://comments.gmane.org/gmane.comp.lang.scala.user/53545 <pre> I'm rather confused by this: Welcome to Scala version 2.9.2 (Java HotSpot(TM) Server VM, Java 1.6.0_18).Type in expressions to have them evaluated.Type :help for more information. scala&gt; import math.Ordering.Implicits._import math.Ordering.Implicits._ scala&gt; "a" min "b"&lt;console&gt;:11: error: type mismatch; found : java.lang.String("b") required: Ordering[?] "a" min "b" ^ And yet... scala&gt; implicitly[Ordering[String]]res1: Ordering[String] = scala.math.Ordering$String$&lt; at &gt;19dbc3b what does it means "required: Ordering[?]". Is this a bug? Chris </pre> Chris Marshall 2012-05-24T11:10:48 http://comments.gmane.org/gmane.comp.lang.scala.user/53539 <pre>I've seen some references &lt; at &gt;deprecated("Scala Actors are beeing removed from the standard library. Please refer to the migration guide.", "2.10") Does anyone know where to find this guide, if it exists? Google fails me. best regards, Scott Morrison </pre> Scott Morrison 2012-05-24T06:01:00 http://comments.gmane.org/gmane.comp.lang.scala.user/53537 <pre>Hi, I want to use a Java TreeMap with a Comparator to sort the entries in the Map in order of their values, in Scala 2.9.2. I have the following code. var map = new TreeMap[String, Int](cmp) val cmp: Comparator[String] = new Comparator[String] { def compare(a: String, b: String): Int = map.get(a).compare(map.get(b)) } map.put("name",1) map.put("email",3) map.put("key",89) println(map firstKey) But when I run the above segment I get the output as email where as I was expecting key as the output. What am I doing wrong? Thanks, Sankha </pre> Sankha Narayan Guria 2012-05-24T03:34:17 http://comments.gmane.org/gmane.comp.lang.scala.user/53536 <pre>Hi all, I just discovered to my dismay that it's not possible to write a method that takes a GenSeq argument, and then have (for example) .map calls on that argument be run in parallel depending on whether the passed argument was actually a ParSeq or not! To see this, note that (0 until 1000).par.asInstanceOf[scala.collection.GenSeq[Int]].map({ _ + 1 }) doesn't actually run the map in parallel. This is because of the implementation of ParIterableLike.map&lt;https://github.com/scala/scala/blob/v2.9.2/src/library/scala/collection/parallel/ParIterableLike.scala#L504&gt;is def map[S, That](f: T =&gt; S)(implicit bf: CanBuildFrom[Repr, S, That]): That = bf ifParallel { pbf =&gt; executeAndWaitResult(new Map[S, That](f, pbf, splitter) mapResult { _.result }) } otherwise seq.map(f)(bf2seq(bf)) and once you've "forgotten" from the ParSeq down to a GenSeq, there's no longer any way for the compiler to provide an implicit CanBuildFrom argument which is parallel. In the snippet above, the implicit CanBuildFrom</pre> Scott Morrison 2012-05-24T01:19:27 http://comments.gmane.org/gmane.comp.lang.scala.user/53535 <pre>The following two refiy invocations create expressions representing an immutable and mutable map respectively: and they seem to work as expected when evaluated: But when I use show or showRaw, they give exactly the same results: I would have expected that show and showRaw would give different results? In particular, I would expect that instead of newTypeName("HashMap") one would make reference to collection.immutable.HashMap and the other would make reference to collection.mutable.HashMap? -- paul.butcher-&gt;msgCount++ Snetterton, Castle Combe, Cadwell Park... Who says I have a one track mind? http://www.paulbutcher.com/ LinkedIn: http://www.linkedin.com/in/paulbutcher MSN: paul-q9qwgYRQEc9WkMItezQGDw&lt; at &gt;public.gmane.org AIM: paulrabutcher Skype: paulrabutcher </pre> Paul Butcher 2012-05-23T22:27:32 http://comments.gmane.org/gmane.comp.lang.scala.user/53531 <pre>Hi, I'm trying to convert traits with type parameters (together with self types) to traits with abstract type members. Here's an example: object TP { trait A[X,AA &lt;: A[X,AA]] { self: AA =&gt; def a: AA = this } trait A1[X,AA &lt;: A1[X,AA]] extends A[X,AA] { self: AA =&gt; def a1: AA = this } } Note that traits A and A1 in object TP (Type Parameters) have self type references. It is important that methods a and a1 return different abstract traits, with different type bounds. (a: AA &lt;: A and a1: AA &lt;: A1) I've tried to translate TP to AT (Abstract Types) but that doesn't compile: object AT { trait A { type AA &lt;: A def a: AA = this } trait A1 extends A { type AA &lt;: A1 def a1: AA = this } } How to translate TP without using type parameters? or more generally: Can traits with type parameters can always be translated to traits with abstract type members, and vice versa. or specifically: Can https://github.com/rapido/oer/blob/master/src</pre> Robbert van Dalen 2012-05-23T19:10:24 http://comments.gmane.org/gmane.comp.lang.scala.user/53529 <pre>Http://www.virtual-clouddrive.org - Data emancipation for the rest of us. Feel free to ask for help - this is important to me on a moral level. Based on Voldemort for the metadata stores that actually protect you with a Lift front end (that could use a tasteful designer :-). All written in Scala. Enjoy, Maarten </pre> maarten 2012-05-23T18:13:17 http://comments.gmane.org/gmane.comp.lang.scala.user/53521 <pre>Hi all, Scala is a great language with first-class functions and support for functional programming. The IFL conference is interested to hear from researchers engaged in the implementation and application of functional and function-based programming languages. You can show what Scala can do in this area by submitting either a draft paper or an extended abstract describing work to be presented at the symposium. ------------------------------------------------------------------------------- CALL FOR PAPERS 24th Symposium on Implementation and Application of Functional Languages (IFL 2012) University of Oxford, UK, August 30-September 1, 2012 http://www.cs.ox.ac.uk/conferences/IFL2012/ This year IFL will be hosted by the University of Oxford, within the idyllic setting of the dreaming spires and picturesque colleges, which have been the home to academic endeavour and research for over nine centuries. The sympo</pre> Daniel James 2012-05-23T10:52:21 http://comments.gmane.org/gmane.comp.lang.scala.user/53513 <pre>Not sure how many users here use hadoop. But, I am writing to this group as the test case i have is the HelloWorld of MapReduce, the word count and believe its more of a Scala/Java interop issue. I narrowed it down to my Map task implementation. I say this because when i reference and use a Java implementation of a equivalent( seemingly so) Java version, everything works fine. Java version public class TokenCounterMapperJava extends Mapper&lt;LongWritable, Text, Scala version class TokenCounterMapper extends Mapper[LongWritable, Text, Text, Here is a link to the full page of code in Scala. https://gist.github.com/2773592 I get the following error. FYI, I get this error when i run it locally, not even on a cluster. ############ java.io.IOException: Type mismatch in key from map: expected org.apache.hadoop.io.Text, recieved org.apache.hadoop.io.LongWritable at org.apache.hadoop.mapred.MapTask$MapOutputBuffer.collect(MapTask.java:871) at org.apache.hadoop.mapred.MapTask$NewOutputCollector.write(MapTas</pre> Arun Ramakrishnan 2012-05-23T07:02:49 http://comments.gmane.org/gmane.comp.lang.scala.user/53509 <pre>Hi, I run across a very weird situation (using scala 2.9.1). Following code crashes at last line. For some reason Sub1 does not crash while almost identical Sub2 does with java.lang.NullPointerException: abstract class Base { val t:String val n=t.head def p=println(t,n) } //cannot use "case class" since no arguments class Sub1(val t:String) extends Base { } class Sub2 extends Base { val t="" } //this does not crash new Sub1("bb") //this crashes new Sub2() What could be a reason of different behaviour? Thx, Andy </pre> Andy Coolware 2012-05-23T05:30:53 http://comments.gmane.org/gmane.comp.lang.scala.user/53507 <pre>Hi! I'm working with OSGI and Apache Karaf. I cannot install scala-compiler as a bundle because it depends on org.apache.ant. I get the following message: Unresolved constraint in bundle scala-compiler [81]: Unable to resolve 81.0: missing requirement [81.0] osgi.wiring.bundle; (osgi.wiring.bundle=org.apache.ant) I tried with ant 1.8.3 distribution without success. Don't know what am I supposed to install then (which is the bundle "org.apache.ant" I'm supposed to install? Where can I get it?) Any help would be appreciated. </pre> oscarvarto 2012-05-23T01:50:15 Search the mailing list at Gmane query http://search.gmane.org/?group=$group=gmane.comp.lang.scala.user