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  • Scala: Matching optional Regular Expression groups

    - by Brian Heylin
    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) => <propertyWithSign /> } val withSign = "property.name: +10" val withoutSign = "property.name: 10" buildProperty(withSign) // <propertyWithSign></propertyWithSign> buildProperty(withoutSign) // <propertyWithSign></propertyWithSign> But this is not working. What is the correct way to match optional regex groups?

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  • Why is Scala very complex?

    - by Anantha Kumaran
    I am a student. I learned java during the 2nd year. Now i am in fourth year. I got bored with java and i started to learn Scala. As i learn it, i found it being very complex (although i love it). My question may apply to all new complex language. Why scala is complex? is it because we need to create complex softwares? or i am the only one who thinks it is complex?

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  • Scala downwards or decreasing for loop?

    - by Felix
    In scala, you often use an iterator to do a for loop in an increasing order like: for(i <- 1 to 10){ code } How would you do it so it goes from 10 to 1? I guess 10 to 1 gives an empty iterator (like usual range mathematics)? I made a scala script which solves it by calling reverse on the iterator, but it's not nice in my opinion, is this the way to go: def nBeers(n:Int) = n match { case 0 => ("No more bottles of beer on the wall, no more bottles of beer."+ "\nGo to the store and buy some more, "+ "99 bottles of beer on the wall.\n") case _ => (n+" bottles of beer on the wall, "+n +" bottles of beer.\n"+"Take one down and pass it around, "+ (if((n-1)==0) "no more" else (n-1))+ " bottles of beer on the wall.\n") } for(b <- (0 to 99).reverse)println(nBeers(b)) ?? Any comments/suggestions?

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  • How do i change the Scala version that sbt works with?

    - by ashy_32bit
    Firing up the SBT console it reads : [info] Building project AYLIEN 1.0 against Scala 2.8.1 [info] using MyProject with sbt 0.7.4 and Scala 2.7.7 How can I make it use MyProject with sbt 0.7.4 and Scala 2.8.1 ? Please pay attenetion that I'm not asking about the Scala version that is used to build my project (it is the 2.8.1 as you can see), but I rather want to make sbt use MyProject with Scala 2.8.1. Apparently sbt uses it's own scala version to work with project definition (MyProject here) which is different than one it uses to actually build the project! or perhaps I'm missing something ... ?

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  • Scala: "Parameter type in structural refinement may not refer to an abstract type defined outside th

    - by raichoo
    Hi, I'm having a problem with scala generics. While the first function I defined here seems to be perfectly ok, the compiler complains about the second definition with: error: Parameter type in structural refinement may not refer to an abstract type defined outside that refinement def >>[B](a: C[B])(implicit m: Monad[C]): C[B] = { ^ What am I doing wrong here? trait Lifter[C[_]] { implicit def liftToMonad[A](c: C[A]) = new { def >>=[B](f: A => C[B])(implicit m: Monad[C]): C[B] = { m >>= (c, f) } def >>[B](a: C[B])(implicit m: Monad[C]): C[B] = { m >> a } } } IMPORTANT: This is NOT a question about Monads, it's a question about scala polymorphism in general. Regards, raichoo

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  • Remove redundant entries, scala way

    - by andersbohn
    Edit: Added the fact, that the list is sorted, and realizing 'duplicate' is misleading, replaced that with 'redundant' in the title. I have a sorted list of entries stating a production value in a given interval. Entries stating the exact same value at a later time adds no information and can safely be left out. case class Entry(minute:Int, production:Double) val entries = List(Entry(0, 100.0), Entry(5, 100.0), Entry(10, 100.0), Entry(20, 120.0), Entry(30, 100.0), Entry(180, 0.0)) Experimenting with the scala 2.8 collection functions, so far I have this working implementation: entries.foldRight(List[Entry]()) { (entry, list) => list match { case head :: tail if (entry.production == head.production) => entry :: tail case head :: tail => entry :: list case List() => entry :: List() } } res0: List[Entry] = List(Entry(0,100.0), Entry(20,120.0), Entry(30,100.0), Entry(180,0.0)) Any comments? Am I missing out on some scala magic?

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  • What are the exact versions of stuff you have to install in order to be able to step-debug a Scala p

    - by Alex R
    How do YOU debug a Scala program? I mean YOU as in the person posting the Answer :) Please answer only from personal experience, not from stuff you've heard or read on the Internet. You should not believe everything you read on the Internet, especially tales of complex open-source software configurations that actually work :-) The are many Java tools which claim to support Scala in some way or another, but I have so far struck out in trying to get any one of them to actually let me set a breakpoint in Scala code and step through it. These are big, major open-source IDEs I'm talking about here. The main problem in getting a debugger to work seems to be the "version hell" with fast-changing IDEs, Plug-Ins, JDKs, and the Scala language itself. Hence, the more detailed re-statement of the question is appropriate: What is the exact version number of the IDE, Plug-In, JDK, Scala, and even Operating System, that you are successfully using? My question is related to this one, but wider in scope: http://stackoverflow.com/questions/2272705/how-to-debug-scala-code-when-outside-of-an-ide Thanks

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  • make a lazy var in scala

    - by ayvango
    Scala does not permit to create laze vars, only lazy vals. It make sense. But I've bumped on use case, where I'd like to have similar capability. I need a lazy variable holder. It may be assigned a value that should be calculated by time-consuming algorithm. But it may be later reassigned to another value and I'd like not to call first value calculation at all. Example assuming there is some magic var definition lazy var value : Int = _ val calc1 : () => Int = ... // some calculation val calc2 : () => Int = ... // other calculation value = calc1 value = calc2 val result : Int = value + 1 This piece of code should only call calc2(), not calc1 I have an idea how I can write this container with implicit conversions and and special container class. I'm curios if is there any embedded scala feature that doesn't require me write unnecessary code

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  • Remove duplicates in entries, scala way

    - by andersbohn
    I have a list of entries stating a production value in a given interval. Entries stating the exact same value at a later time adds no information and can safely be left out. case class Entry(minute:Int, production:Double) val entries = List(Entry(0, 100.0), Entry(5, 100.0), Entry(10, 100.0), Entry(20, 120.0), Entry(30, 100.0), Entry(180, 0.0)) Experimenting with the scala 2.8 collection functions, so far I have this working implementation: entries.foldRight(List[Entry]()) { (entry, list) => list match { case head :: tail if (entry.production == head.production) => entry :: tail case head :: tail => entry :: list case List() => entry :: List() } } res0: List[Entry] = List(Entry(0,100.0), Entry(20,120.0), Entry(30,100.0), Entry(180,0.0)) Any comments? Am I missing out on some scala magic?

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  • scala xml rewrite rule (or, simple pattern help)

    - by williamstw
    I'm missing some fairly simple syntax I gather. I'm trying to rewrite an element label to something else and keep everything else intact. object htmlRule extends RewriteRule { override def transform(n: Node): Seq[Node] = n match { case Elem(prefix, "document", attribs, scope, child@_*) => Elem(prefix, "html", attribs, scope, child) case other => other } } Now, I ask for an explanation of two things: 1) What exactly does "child@_*" mean in plain English? 2) How can I capture the value of "child@_*" and just let it pass right through to the new element? Currently, I get the following error, which makes sense. [error] found : Seq[scala.xml.Node] [error] required: scala.xml.Node [error] Elem(prefix, "html", attribs, scope, child) I'm not wedded to this either, so if there's a better way to simply change the element name of a specific node, let's here it... Thanks, --tim

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  • what good orm api will work well with scala or erlang

    - by Emotu Balogun
    I'm considering taking up scala programming but i'm really concerned about what will become of my ORM based applications. I currently use hibernate as my ORM and i find it a really reliable tool. I'd like to know if there's any ORM tool as efficient but written in scala, or will hibernate work seamlessly with it. i don't want to have to start writing endless sql queries again (like the days of JDBC). I also have the same thought about erlang. is there a good orm out there for erlang?? and can i use erlang with other DBMS like oracle and mysql with ORM

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  • Generic object load function for scala

    - by Isaac Oates
    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(s: Session) { def loadAddress(id: Long): Address = { return s.load(classOf[Address], id).asInstanceOf[Address]; } ... } So, now I can do this: val dl = new DataLoader(s) val addr = dl loadAddress(addr_id) Here's the question: How do I write a generic parametrized method which can load any object using this same pattern? i.e val addr = dl load[Address](addr_id) (or something along those lines.) I'm new to Scala so please forgive anything here that's especially hideous.

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  • What are the exact versions of stuff you had to install in order to be able to step-debug a Scala pr

    - by Alex R
    How do YOU debug a Scala program? I mean YOU as in the person posting the Answer :) Please answer only from personal experience, not from stuff you've heard or read on the Internet. You should not believe everything you read on the Internet, especially tales of complex open-source software configurations that actually work :-) The are many Java tools which claim to support Scala in some way or another, but I have so far struck out in trying to get any one of them to actually let me set a breakpoint in Scala code and step through it. These are big, major open-source IDEs I'm talking about here. The main problem in getting a debugger to work seems to be the "version hell" with fast-changing IDEs, Plug-Ins, JDKs, and the Scala language itself. Hence the second part of my question, which is really the most important part: What is the exact version number of the IDE, Plug-In, JDK, Scala, and even Operating System, that you are successfully using? My question is related to this one, but wider in scope: http://stackoverflow.com/questions/2272705/how-to-debug-scala-code-when-outside-of-an-ide Thanks

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  • Can I reproduce Scala's behavior for == ?

    - by JPP
    In Programming in Scala, I can read that the == operator behaves as if it was defined like this: final def == (that: Any): Boolean = if (null eq this) {null eq that} else {this equals that} But there must actually be compiler magic to avoid null pointer exceptions, right? Is there any way for me to replicate this behavior with pure Scala; i.e., have an operator/method return one thing if the receiver is null and another one if it isn't? What I mean is an actual implementation of null eq this. I suppose I can write a "pimp" and then define the method on the wrapper class, but is there a more direct way to do this?

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  • Merging elements in a scala list

    - by scompt.com
    I'm trying to port the following Java snippet to Scala. It takes a list of MyColor objects and merges all of the ones that are within a delta of each other. It seems like a problem that could be solved elegantly using some of Scala's functional bits. Any tips? List<MyColor> mergedColors = ...; MyColor lastColor = null; for(Color aColor : lotsOfColors) { if(lastColor != null) { if(lastColor.diff(aColor) < delta) { lastColor.merge(aColor); continue; } } lastColor = aColor; mergedColors.add(aColor); }

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  • Open Office APIs e Migração de Macros - 23/Fev/11

    - by Paulo Folgado
    AGENDAIntroduction on Oracle Open Office/OpenOffice.org API Oracle Open Office Basic IDE Hallo World and more Oracle Open Office dialog Programming Integrating Macros in Oracle Open Office Appetizer - Using JavaMicrosoft Office Macro MigrationEstimation Macro Migration effortMigrating Macros Migration pitfallsOs participantes deverão ter conhecimentos sólidos de Microsoft Office e de programação VBA.

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  • How to program macros on iWork 09?

    - by Luis
    Hi We have a simple macro that connects Access and Excel (Office 2007 on Windows) with some forms and we are trying to create the iWork version, but I cant find how to create a macro or something, does anyone knows some manual or links to do this? Im using iWork 09 on Snow Leopard. Thanks!

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  • How to change attribute on Scala XML Element

    - by Dave
    I have an XML file that I would like to map some attributes of in with a script. For example: <a> <b attr1 = "100" attr2 = "50"> </a> might have attributes scaled by a factor of two: <a> <b attr1 = "200" attr2 = "100"> </a> This page has a suggestion for adding attributes but doesn't detail a way to map a current attribute with a function (this way would make that very hard): http://www.scalaclass.com/book/export/html/1 What I've come up with is to manually create the XML (non-scala) linked-list... something like: // a typical match case for running thru XML elements: case Elem(prefix, e, attributes, scope, children @ _*) => { var newAttribs = attributes for(attr <- newAttribs) attr.key match { case "attr1" => newAttribs = attribs.append(new UnprefixedAttribute("attr1", (attr.value.head.text.toFloat * 2.0f).toString, attr.next)) case "attr2" => newAttribs = attribs.append(new UnprefixedAttribute("attr2", (attr.value.head.text.toFloat * 2.0f).toString, attr.next)) case _ => } Elem(prefix, e, newAttribs, scope, updateSubNode(children) : _*) // set new attribs and process the child elements } Its hideous, wordy, and needlessly re-orders the attributes in the output, which is bad for my current project due to some bad client code. Is there a scala-esque way to do this?

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  • How are Scala closures transformed to Java objects?

    - by iguana
    I'm currently looking at closure implementations in different languages. When it comes to Scala, however, I'm unable to find any documentation on how a closure is mapped to Java objects. It is well documented that Scala functions are mapped to FunctionN objects. I assume that the reference to the free variable of the closure must be stored somewhere in that function object (as it is done in C++0x, e.g.). I also tried compiling the following with scalac and then decompiling the class files with JD: object ClosureExample extends Application { def addN(n: Int) = (a: Int) => a + n var add5 = addN(5) println(add5(20)) } In the decompiled sources, I see an anonymous subtype of Function1, which ought to be my closure. But the apply() method is empty, and the anonymous class has no fields (which could potentially store the closure variables). I suppose the decompiler didn't manage to get the interesting part out of the class files... Now to the questions: Do you know how the transformation is done exactly? Do you know where it is documented? Do you have another idea how I could solve the mystery?

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  • Using variables inside macros in SQL

    - by Tim
    Hello I'm wanting to use variables inside my macro SQL on Teradata. I thought I could do something like the following: REPLACE MACRO DbName.MyMacro ( MacroNm VARCHAR(50) ) AS ( /* Variable to store last time the macro was run */ DECLARE V_LAST_RUN_DATE TIMESTAMP; /* Get last run date and store in V_LAST_RUN_DATE */ SELECT LastDate INTO V_LAST_RUN_DATE FROM DbName.RunLog WHERE MacroNm = :MacroNm; /* Update the last run date to now and save the old date in history */ EXECUTE MACRO DbName.RunLogUpdater( :MacroNm ,V_LAST_RUN_DATE ,CURRENT_TIMESTAMP ); ); However, that didn't work, so I thought of this instead: REPLACE MACRO DbName.MyMacro ( MacroNm VARCHAR(50) ) AS ( /* Variable to store last time the macro was run */ CREATE VOLATILE TABLE MacroVars AS ( SELECT LastDate AS V_LAST_RUN_DATE FROM DbName.RunLog WHERE MacroNm = :MacroNm; ) WITH DATA ON COMMIT PRESERVE ROWS; /* Update the last run date to now and save the old date in history */ EXECUTE MACRO DbName.RunLogUpdater( :MacroNm ,SELECT V_LAST_RUN_DATE FROM MacroVars ,CURRENT_TIMESTAMP ); ); I can do what I'm looking for with a Stored Procedure, however I want to avoid for performance. Do you have any ideas about this? Is there anything else I can try? Cheers Tim

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  • How to create contexts in shoulda macros

    - by Honza
    Asking this question again with smaller code sample: # this is a dummy shoulda macro that creates a context def self.macro_context context "macro" do yield end end # i am expecting this test to fail within the macro context context "some context" do macro_context do should "test" do fail end end end So what I would expect is to see: 1) Error: test: some context macro context should test. (TestClassName) But I am getting only this: So what I would expect is to see: 1) Error: test: some context should test. (TestClassName) Any idea what am I doing wrong?

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