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/63401 <pre>Here are some functional programming job opportunities that were posted recently: Test Engineer at Klarna http://functionaljobs.com/jobs/146-test-engineer-at-klarna Cheers, Sean Murphy FunctionalJobs.com </pre> Functional Jobs 2013-05-20T06:00:02 http://comments.gmane.org/gmane.comp.lang.scala.user/63398 <pre>I just upgraded from 2.9.2 to 2.10.1, and I am getting warnings that I did not get before. Here's the relevant code: sealed trait ManeuverType object ManeuverType { // enumeration of maneuver types case object alt extends ManeuverType // altitude maneuver case object vec extends ManeuverType // horizontal "vector" maneuver case object spd extends ManeuverType // speed manevuer } And here are the warnings: [warn] /home/Maneuver.scala:12: dead code following this construct [warn] case object alt extends ManeuverType // altitude maneuver [warn] ^ [warn] /home/Maneuver.scala:13: dead code following this construct [warn] case object vec extends ManeuverType // horizontal "vector" maneuver [warn] ^ [warn] /home/Maneuver.scala:14: dead code following this construct [warn] case object spd extends ManeuverType // speed manevuer [warn] What changed in the language or compiler to cause these warnings? Thanks. --Russ P. ^ </pre> Russ P. 2013-05-20T03:33:48 http://comments.gmane.org/gmane.comp.lang.scala.user/63395 <pre>I've started an open-source project (SNMP4S&lt;https://github.com/barnesjd/snmp4s&gt;if you're interested), and I've run into a snag trying to accomplish my type-safety goals. I *think* what I need is some kind of variable-length tuple. A list won't work because the type of the contents are parameterized with different. A tuple accomplishes what I need, but I have to hand-write a function for every number of arguments I hope to support. It is much like Scala's limit on functions having at most 22 parameters. To avoid gory details of my project, suppose I wanted to have this Tuplizerclass below. I really like what the Consumer class looks like because each variable returned infers the correct type. However, I'd like to avoid hand-writing the 3 different functions and be able to support an arbitrary number of Options passed to f. class Tuplizer { def f[A](a:Option[A]):A = ??? def f[A, B](a:Option[A], b:Option[B]):(A,B) = ??? def f[A, B, C](a:Option[A], b:Option[B], c:Option[C]):(A,B,C) = ??? // ... } class Consumer { def t:Tuplizer = new Tuplizer def use = { val a = t.f(Some(1)) val (b, c) = t.f(Some("String"), Some(5)) val (d, e, f) = t.f(Some(7), Some("Other"), Some(true)) } } The best hint I've found towards accomplishing this is to use shapeless per this post &lt;http://stackoverflow.com/a/10487475&gt;. But I don't think that helps me get a varying number of args. Any good ideas? </pre> Joe Barnes 2013-05-19T20:58:47 http://comments.gmane.org/gmane.comp.lang.scala.user/63391 <pre>Hi all, it seems to me that ScalaLab based on the latest 2.11 build has improved response ("startup") time. Does compiler improvements introduced recently (after 2.11 M2) in 2.11? Stergios </pre> Stergios Papadimitriou 2013-05-19T13:02:02 http://comments.gmane.org/gmane.comp.lang.scala.user/63383 <pre>I have just released a newer version of the postgresql-async project, an async database connector for PostgreSQL written in Scala and I'm happy to announce that now there is also a mysql-async project that also offers an async connector for MySQL. Both projects use Netty as their network communication framework. The project aims to offer a simple way to talk to both PostgreSQL and MySQL in an async way and with a simple "send a statement, get a future result back" approach. It is not supposed to be a full replacement for JDBC or anything like that, it's just direct database access as simple as possible. Scala 2.10 is required due to the use of the new scala.concurrent.Promise and scala.concurrent.Future objects. Both drivers offer basic and prepared statement support, transformations for commonly used types and support for most of the types offered by the database. You can read the README's available to see how types are translated between db -&gt; Scala. You can read more about this release here -&gt; http://mauricio.github.io/2013/05/18/mysql-async-and-posrgresql-async-0.2.2-released.html And the Github project repo is here -&gt; https://github.com/mauricio/postgresql-async In case you're in a hurry, there is a small sample app using Play 2 + postgresql-async and deploying on Heroku here -&gt; http://mauricio.github.io/2013/04/29/async-database-access-with-postgresql-play-scala-and-heroku.html Feedback, bug reports, bug fixes and other improvements are all welcome :) - Maurício Linhares http://mauricio.github.io/ - http://twitter.com/#!/mauriciojr </pre> Maurício Linhares 2013-05-18T14:58:36 http://comments.gmane.org/gmane.comp.lang.scala.user/63367 <pre>Hello, I'm trying to parse ftp URI using scala regular expressions. My URI looks like this: val uri="ftp://user:password-WQCBuIXaXYjQT0dZR+AlfA&lt; at &gt;public.gmane.org/directory/file.xml" My regex looks like this (according to URI spec): val Regex = """^ftp://(.*):(.*)&lt; at &gt;(.*)/(.*)""".r However when I match by this regex URI is not parsed correctly: uri match { case Regex(userName,password,host,fileName) =&gt; ... } userName &gt; user password &gt; password host &gt; server.com/directory fileName &gt; file.xml I'm not sure why regex recognizes two forward slashes, but not one forward slash? I'd like to get this back: host &gt; server.com fileName &gt; directory/file.xml I'd appreciate any help in this matter. Regards, M </pre> mc 2013-05-17T18:19:56 http://comments.gmane.org/gmane.comp.lang.scala.user/63363 <pre>I Haskell you can declare a typeclass Bar having a “superclass” Foo as follows: class Foo a =&gt; Bar a See http://www.haskell.org/onlinereport/haskell2010/haskellch4.html#x10-750004.3 for reference. What is the best way to model this kind of relationship in Scala? We could use inheritance (as it is done in scalaz, IIRC): trait Foo[A] trait Bar[A] extends Foo[A] But to implement Bar you also would have to implement Foo’s members… Instead we’d like to reuse any available Foo implementation, maybe something like: class Bar[A : Foo] But then Foo wouldn’t be a superclass of Bar, the following wouldn’t compile: def f[A : Bar](a: A) = g(a) def g[A : Foo](a: A) = a I tried by defining an implicit conversion from Bar to Foo in Bar’s companion object but that doesn’t work either. Even if we explicitly import the conversion. Any other idea? </pre> Julien Richard-Foy 2013-05-17T15:24:26 http://comments.gmane.org/gmane.comp.lang.scala.user/63356 <pre>Hi everyone, in my quest to make Scala-the-language a bit smaller and simpler, I intend to deprecate and remove octal escape literals. The corresponding ticket is https://issues.scala-lang.org/browse/SI-7292. Some of the reasoning: - Considering that we live in a Unicode world, the usefulness of special syntactical shortcuts for characters between 0 and 255 is greatly diminished. - We already removed octal literals which are similarly confusing. I have never heard a *single* person complaining (or even asking) about what happened with octal literals. It's reasonable to assume that it will be the same for an even more obscure feature. - The parsing rules of octal escapes are unintuitive and misleading for unaware readers (e. g. it's not fixed-length like \uXXXX, but stops accepting symbols as soon as it encounters some char it doesn't like. Example: \377 parses as one octal escape literal, \378 parses as an octal escape and 8 (because 8 is not octal, duh), 400 parses as an octal escape and a 0 (400 would be valid octal number, but–for whatever reasons–the literal is capped to the first 255 numbers)). - Those who want it, can implement it via string interpolation - If one looks at some of our "competitors", they don't bothered to include it in the first place (and their literal syntax is even further removed from Java syntax). - In general, we need less magic to happen between what-the-developer-writes and what-the-compiler-sees. See the famous let's-convert-unicode-escapes-in-comments puzzler for a similar case where we are trying too hard to be Java. (Which–again–no other languages even considers emulating.) If you have never heard about them, all is fine. If you have a use-case where you think octal escape literals are absolutely critical, please speak up! Thanks, Simon </pre> Simon Ochsenreither 2013-05-17T13:01:18 http://comments.gmane.org/gmane.comp.lang.scala.user/63349 <pre>Hi group. I have a question about grouping 2 lists of case classes together, and in this example sorting employees into EmployeeDepartment. 1. case class EmployeeDepartment( &lt; at &gt;Key("_id") id:ObjectId, name:String) 2. case class Employees( &lt; at &gt;Key("_id") id:ObjectId, name:String, employeeDepartmentName:String) Basically, gettin a new list or map (don't know what would be better) looking like this: (EmployeeDepartment(12456, "Marketing department"), List( 123456, "Michael Larsson" ), List( 123456, "etc" )) Thanks </pre> Michael Larsson 2013-05-17T08:43:27 http://comments.gmane.org/gmane.comp.lang.scala.user/63343 <pre>Dear all, Sometimes I alias my type on existing classes for readability, ex : Type Hasher[T,K] = (T=&gt;K) And use it in class constructor as an implicit parameter. Would it be possible to annotate the type with an &lt; at &gt;implicitNotFound ? Thanks Best Regards Edmondo Porcu ______________________________________________________________________ This email has been scanned by the Symantec Email Security.cloud service. For more information please visit http://www.symanteccloud.com ______________________________________________________________________ </pre> Edmondo Porcu 2013-05-16T07:32:55 http://comments.gmane.org/gmane.comp.lang.scala.user/63332 <pre>Hi, This summer: Worst Bug Ever Part II - The Scala Version object listeners { A candy for the first person to find it. Cheers, David </pre> David Miguel Antunes 2013-05-15T18:40:28 http://comments.gmane.org/gmane.comp.lang.scala.user/63328 <pre>Hello, I use graphics2d to draw graphics. These graphics are scaled and translated with g.scale and g.translate. Also, I have a mouse click listener. I want to click at points in the graphics. To identify the correct position, I have to take into account the scaling and translating I've done to draw the graphics. How can this be done? listenTo(mouse.clicks) focusable = true reactions += { case event.MouseClicked(_, point, _, _, _) =&gt; { // need to scale &amp; translate point.x, point.y to corresponding position ... repaint } } </pre> Boris Hollas 2013-05-15T10:41:04 http://comments.gmane.org/gmane.comp.lang.scala.user/63319 <pre> Announcing Geodude + SBT Uber: I am announcing some very small open source projects. Over the last year developing Sportaneous, our team used an all Scala stack and wanted to contribute back a few simple utilities: Geodude *a library for reverse geocoding* This library makes it easy to reverse geo code and cache those values. Or use different providers for those values. Check out the github &lt;https://github.com/hjast/geodude&gt; for more information and examples import geodude._ val str = googleMaps.location("690 Prospect PL, Brooklyn, NY") .map(loc =&gt; "%s is at %s lat and %s lng" format(loc.name, loc.lat, loc.lng)) .getOrElse("Geocoding could not find address") println(str) Über sbt template G8 &amp; Go *A highly opinionated sbt template with tons of nice plugins, an admin console and dependencies ready to go!* Check it out on github &lt;https://github.com/hjast/uber-sbt.g8&gt; Motivation - Easy way to upgrade libraries, easy access all the libraries (I use, but I expect to include more). - Since I use less than 20-30 libraries in my projects, actually having dependency listing part of template. This way it is both more readable and dependencies are autocompletable. - A console (since I go down into the console a lot). Basically any method you add to AdminConsole, you can call directly from console without having to import anything - Latest version of sbt + sbt plugins which I use - A way to basically let new programmers know which libraries they * should* use (anything in the Dependencies.scala) - logback + resource files for most scala projects To use g8r hjast/uberSBT cd uberSBT sbt gen-idea //Open up in IntelliJ To change dependencies either change in the Build.scala file. /** You can use any of the predefined dependencies or you can do traditional dep. adding **/ dependencies = Seq(lift.webkit, akka.actor, akka.camel) or in build.sbt libraryDependencies ++= akka.all To use console at sbt prompt console-admin Now anything added in AdminConsole can be called directly. List of Dependencies Included Please send a pull request to add any other dependencies to see missing (high quality libraries which could be used outside there own ecosystem.) Akka - akka.all [Seq] - akka.actor - akka.agent - akka.camel - akka.dataflow - akka.fileMailbox - akka.kernel - akka.mailboxesCommon - akka.osgi - akka.osgiAries - akka.remote - akka.slf4j - akka.transactor - akka.testkit - akka.zeromq Spray - spray.all [Seq] - spray.caching - spray.can - spray.client - spray.http - spray.httpx - spray.io - spray.routing - spray.servlet - spray.testkit - spray.util Lift - lift.all [Seq] - lift.webkit - lift.mapper - lift.record - lift.wizard - lift.json - lift.mongo - lift.mongoRecord Shapeless - shapeless.core - shapeless.spire - shapeless.scalaz - shapeless.scalacheck Testing - specs2 - junit Java - commonLang - servlet - jodaTime Numerical - saddle - spire NoSql - rogueAll [Seq] - rogueField - rogueCore - rogueLift Util - scalaLogging - scalaTime - logback - slf4j - logLady </pre> Reuben Doetsch 2013-05-14T23:33:28 http://comments.gmane.org/gmane.comp.lang.scala.user/63316 <pre>I'm attempting to extend the Function class with an implicit parameter, but I've not managed to appease the compiler. This is the code that I want to work: class MyFun extends ((Int, Int) =&gt; Int) { def apply(a:Int)(implicit b:Int):Int = a + b } And it doesn't compile: [error] MyFun.scala:21: class MyFun needs to be abstract, since method apply in trait Function2 of type (v1: Int, v2: Int)Int is not defined [error] class MyFun extends ((Int, Int) =&gt; Int) { [error] ^ I've tried a few variants without success: class MyFun extends ((Int, implicit Int) =&gt; Int) { def apply(a:Int)(implicit b:Int):Int = a + b } [error] MyFun.scala:21: identifier expected but 'implicit' found. [error] class MyFun extends ((Int, implicit Int) =&gt; Int) { [error] ^ [error] MyFun.scala:40: ')' expected but eof found. class MyFun extends ((Int)(implicit Int) =&gt; Int) { def apply(a:Int)(implicit b:Int):Int = a + b } [error] MyFun.scala:21: ')' expected but '(' found. [error] class MyFun extends ((Int)(implicit Int) =&gt; Int) { [error] ^ [error] MyFun.scala:21: ';' expected but '=&gt;' found. [error] class MyFun extends ((Int)(implicit Int) =&gt; Int) { [error] ^ Does anyone know how to do this? Thanks, Joe </pre> Joe Barnes 2013-05-14T21:02:45 http://comments.gmane.org/gmane.comp.lang.scala.user/63309 <pre>Dear hAkkers, We—the Akka committers—are pleased to be able to announce the availability of Akka 2.1.4. This is the fourth maintenance release of the 2.1 branch, containing documentation improvements and fixing several issues including: * CallingThreadDispatcher deadlock problems * Stack overflow while loading messages from persistent mailbox * More robust recovery in remoting in case of malformed messages * Proper deployment of typed actors ... and several smaller fixes IMPORTANT NOTE: Release 2.1.3 was broken due to a bug in the release scripts and build process, please use this release instead. There were no code changes between 2.1.3 and 2.1.4. This release is backwards binary compatible with version 2.1.0, 2.1.1, and 2.1.2, which means that the new JARs are a drop-in replacement for the old ones (but not the other way around). Always make sure to use at least the latest version required by any of your project’s dependencies. Known Issues Due to the restriction imposed by binary compatibility—which is kept for the patch releases within a minor release such as 2.1.x—not all known issues can be fixed. The currently known issues in the 2.1.x series are: * ActorSystem.shutdown() does not terminate all threads if akka.remote.netty.use-dispatcher-for-io is set to true </pre> Roland Kuhn 2013-05-14T14:10:30 http://comments.gmane.org/gmane.comp.lang.scala.user/63302 <pre>Hi, I watched "Raspberry Pi: Developing with Java Embedded Technology" ( https://www.youtube.com/watch?v=7DSp77OxzLg ) and just wondering whether AKKA and Scala are able to run in such devices? Mic </pre> Mic 2013-05-14T04:48:52 http://comments.gmane.org/gmane.comp.lang.scala.user/63301 <pre>Hopefully this is a really simple question. How should one check if an object is a Scala object? The way I would do it before was "base.isInstanceOf[scala.ScalaObject]" but ScalaObject is deprecated. Regards, Thomas </pre> Thomas Suckow 2013-05-14T02:06:58 http://comments.gmane.org/gmane.comp.lang.scala.user/63300 <pre>Kiama (http://kiama.googlecode.com) is a Scala library for language processing including attribute grammars, term rewriting, abstract state machines and pretty printing. The Kiama team are pleased to bring you the next release of the library which is now available from the SonaType OSS repository and should appear in Maven Central soon. Apart from the usual small enhancements and bug fixes, this release refactors the rewriting library to support different kinds of rewriters, notably a version that always memoises results. The big ticket item is a macro-based implementation of the core rewriting and attribution APIs to support improved debugging as well as domain-specific profiling (see https://code.google.com/p/kiama/wiki/Profiling for examples). The full release notes are available at: http://wiki.kiama.googlecode.com/hg/doc/1.5.0/notes.html cheers, Tony </pre> Tony Sloane 2013-05-14T01:56:15 http://comments.gmane.org/gmane.comp.lang.scala.user/63286 <pre>Hi, I want a macro used like `query("select * from foo")` to generate code like: case class Row( /* fields from DB */) val buf = new ListBuffer[Row] val rs = conn.prepareStatement(sql).executeQuery() while (rs.next) { buf += Row(rs.getString(1), rs.getInt(2), ... fields from DB ... ) // *** } lb.toList But from what I know so far, I must put that all in a single block expression, and that is generating type errors that I don't understand. The compilation failed with: MacroTests.scala:25: error: type mismatch; found : Row required: Row.type I can deduce that this comes from the line marked with *** above. So it didn't like my ListBuffer[Row] declaration. My tree looks like: Apply( Select( New( AppliedTypeTree( Ident(listBufferSym), List(Ident("Row")) // List(Ident(typeOf[Any].typeSymbol)) -- this get's it to run, but without desired type ) ), nme.CONSTRUCTOR ), List() ) To understand why it failed I tried to reify this: reify({ case class R(id: Int); val lb = new ListBuffer[R](); lb += R(1) }) In response, It printed a short story... &lt;console&gt;:12: error: Cannot materialize { [ lots of internally generated scala code ] } because: scala.reflect.macros.TypecheckException: type mismatch; found : $u.TypeTag[(some other)lb.type(in value res4) forSome { type (some other)lb.type(in value res4) &lt;: scala.collection.mutable.ListBuffer[(some other)R(in value res4)] with Singleton; type (some other)R(in value res4) &lt;: Product with Serializable{val id: Int; def copy(id: Int): (some other)R(in value res4); def copy$default$1: Int} }] required: $u.WeakTypeTag[lb.type(in value res4) forSome { type lb.type(in value res4) &lt;: scala.collection.mutable.ListBuffer[R(in value res4)] with Singleton; type R(in value res4) &lt;: Product with Serializable{val id: Int; def copy(id: Int): R(in value res4); def copy$default$1: Int} }] I don't understand that. I haven't learned about 'forSome' yet. Any suggestions? Is there a way for the macro to introduce multiple expressions without wrapping them in a block? (And let me know if there a more appropriate mailing list for this.) thank you, Rob </pre> Rob Nikander 2013-05-13T20:12:05 http://comments.gmane.org/gmane.comp.lang.scala.user/63282 <pre>Hi, It seems like the reflection function showRaw is reporting a modifier that doesn't exist. I'm trying to write a macro that generates a case class definition, among other things. To see what the AST should look like, I open a scala prompt and run: scala&gt; import scala.reflect.runtime.universe._ scala&gt; reify( { case class Foo(name: String, id: Long, count: Int) } ) res2: ... scala&gt; showRaw(res2) res3: String = Expr(Block(List(ClassDef(Modifiers(CASE), newTypeName("Foo"), List(), Template(List(Ident(scala.Product), Ident(scala.Serializable)), emptyValDef, List(ValDef(Modifiers(CASEACCESSOR | PARAMACCESSOR), newTermName("name"), ... But there is nothing called CASEACCESSOR or PARAMACCESSOR in: http://www.scala-lang.org/api/2.10.1/index.html#scala.reflect.api.FlagSets$FlagValues How do I build this tree? Any ideas? Thank you, Rob </pre> Rob Nikander 2013-05-13T17:34:39 http://comments.gmane.org/gmane.comp.lang.scala.user/63280 <pre> *trait *Elt[Element &lt;: Elt[Element,Ret],Ret] { self:Element=&gt; } *trait *EltBuilder[Element&lt;:Elt[Element,Ret],Ret] { *def *apply(parent: Element, childBuilder: EltBuilder[Element,Ret]): Element } *trait *Motor[-Element&lt;:Elt[_,Ret],Ret] { *def *onEnd(self: Element): Ret } *class *Core[R] { *type *Bld = EltBuilder[Element,Ret] *type *Ret = R *trait *Element *extends *Elt[Element,Ret] { *val *parent:Element *val *childBuilder:Bld } *trait *Mot *extends *Motor[Element,Ret] *with *Access { *class *Elt(val parent:Element, val childBuilder:Bld) extends Element { def onEnd(): Ret = Mot.this.onEnd(this) } *val *builder:Bld = *new *Bld { *def *apply(parent: Element, childBuilder:Bld) = *new * Elt(parent,childBuilder) } } *trait *Access { *type *Ret = Core.*this*.Ret *type *Bld = Core.*this*.Bld *type *Element = Core.*this*.Element /** To define! */ *type *Elt&lt;:Element *def *builder:Bld } } *trait *ExtCore[R] *extends *Core[R] { *type *Data *def *getData(parent:Element):Data *trait *Element extends *super*.Element { *val *data:Data } *trait *Mot *extends super*.Mot *with *Motor[Element,Ret] *with *Access { *class *Elt(parent:Element, childBuilder:Bld, *val *data:Data) *extends* *super*.Elt(parent,childBuilder) *with *ExtCore.*this* .Element *override val *builder:Bld = *new *Bld { *def *apply(parent: Element, childBuilder:Bld) = *new *Elt(parent,childBuilder, getData(parent)) } } } The line is red shows for the parent parameter: *type mismatch; found : Mot.this.Element (which expands to) ExtCore.this.Element required: ExtCore.this.Element* Elt is a generic element type EltBuilder is a generic builder for Elt Motor is a processor class for Elt Core is a simple implementation, containing trait Mot with an almost full implementation ExtCore is a refinement of Core, which adds some information to the basic Elt defined in Core. For various reasons, it is difficult to impossible to change variances (i.e. Elt is not covariant) I'm stuck on this. Thanks. Yves </pre> yves 2013-05-13T14:27:09 Search the mailing list at Gmane query http://search.gmane.org/?group=$group=gmane.comp.lang.scala.user