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  • Scala 2.8: _ behaviour changed?

    - by Alexey Romanov
    Using XScalaWT, this compiled under Scala 2.7: class NodeView(parent: Composite) extends Composite(parent) { var nodeName: Label = null this.contains( label( nodeName = _ ) ) } With 2.8.0 RC1, I get this error: type mismatch; found : main.scala.NodeView required: org.eclipse.swt.widgets.Label The types are: label(setups: (Label => Unit)*)(parent: Composite) : Label contains(setups: (W => Unit)*) : W So it looks like _ now binds to the outer function instead of inner. Is this change intentional?

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  • Method collect on Scala 2.7

    - by Brian Heylin
    I'm looking for a collect method in scala 2.7 but I can't seem to find an applicable call. Is there something equivalent to collect that I can use in scala? To be clear I'm looking to filter elements from a list and map those filtered to a new type.

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  • Boot.scala in lift..

    - by Dave
    I'm trying to modify the boot.scala in lift and running into a funny error. This is what I currently have: val entries = Menu(Loc("Home", List("index"), "Home")) :: Menu(Loc("StudentLogin", List("studentlogin"), "Student Login")) :: Menu(Loc("ProviderLogin", List("providerlogin"), "Provider Login")) LiftRules.setSiteMap(SiteMap(entries :_*)) I get this error: Boot.scala:29: error: value :: is not a member of net.liftweb.sitemap.Menu Menu(Loc("StudentLogin", List("studentlogin"), "Student Login")) :: any ideas about what I might be doing wrong? Thanks.

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  • graph library for scala

    - by Elazar Leibovich
    Is there a good library (or wrapper to Java library) for graphs, and/or graph algorithms in scala? This one seems to be quite dead. This is an example for the Dijkstra algorithm in scala, but I'm looking for a library a-la JGraphT.

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  • Scala traits and implicit conversion confusion

    - by pr1001
    The following lines work when I enter them by hand on the Scala REPL (2.7.7): trait myTrait { override def toString = "something" } implicit def myTraitToString(input: myTrait): String = input.toString object myObject extends myTrait val s: String = myObject However, if I try to compile file with it I get the following error: [error] myTrait.scala:37: expected start of definition [error] implicit def myTraitToString(input: myTrait): String = input.toString [error] ^ Why? Thanks!

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  • <:< operator in scala.

    - by scout
    Can anybody provide some details on <:< operator in scala. I think if(apple <:< fruit) //checks if apple is a subclass of fruit. Are there any other explanations? I see many definitions in the scala source file.

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  • Packaging and Deploying Scala Applications

    - by Dr. Guildo
    What is the simplest way to package a Scala application for use on a desktop PC? I'm guessing that would be in the form of a jar file. At the moment I'm using SBT to compile and run programs I'd be interested in solutions for machines that have Scala installed (and the library in their classpath), as well as those that only have Java. Thanks.

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  • Working with images in Scala

    - by dbyrne
    I am generating large PNG files from a Scala program. Currently, I am doing it the same way I would do it in java. I am creating a new BufferedImage and setting each pixel to the correct color. This works fine, but I am wondering if there are any good libraries for working with images in Scala? I am looking for something like Ruby's RMagick library.

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  • Deploying and hosting scala in the cloud?

    - by TiansHUo
    I am starting a web app considering scalability as one of the top priorities. What would be the benefits of this: cassandra scala lift vs the traditional LAMP on the cloud? Since from what I've read, please correct me, the cloud itself is scalable I have never seen anyone deploy scala on the cloud before. Is it worth the effort to learn the platform? Is it ready for production use?

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  • implementing java interface with scala class - type issue

    - by paintcan
    Why on earth won't this compile? Scala 2.8.0RC3: Java public interface X { void logClick(long ts, int cId, String s, double c); } Scala class Y extends X { def logClick(ts: Long, cId: Int,sid: java.lang.String,c: Double) : Unit = { ... } } Error class Y needs to be abstract, since method logClick in trait X of type (ts: Long,cId: Int,s: java.lang.String,c: Double)Unit is not defined

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  • Scala return type for tuple-functions

    - by Felix
    Hello Guys, I want to make a scala function which returns a scala tuple. I can do a function like this: def foo = (1,"hello","world") and this will work fine, but now I want to tell the compiler what I expect to be returned from the function instead of using the built in type inference (after all, I have no idea what a (1,"hello","world") is) I thought I remembered the classname being something like Tuple3[Int,String,String] but that doesnt work for me. Suggestions? :D (ps: I love stack overflow!)

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  • Scala and Java Real-Time System

    - by portoalet
    Just wondering if anybody has run Scala app or web-app on Java Real-Time system? I assume because scala is bytecode compatible with regular JVM, then it should not take much effort to run it on a Real Time JVM such as Sun Java Real-Time System ?

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  • Operator precedence in scala

    - by Jeriho
    I like scala's propose of operator precedence but in some rare case unmodified rules may be inconvenient because you have restrictions in naming your methods. Is there in scala ways to define another rules for a class/file/etc? If not would it be resolved in future?

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  • Wanted: Good examples of Scala database persistence

    - by Rydell
    I'm would like to use Scala to persist data to a relational database, so what I am looking for are examples of CRUD operations using Scala. I would like to code on a lower level of abstraction than an ORM like Hibernate/Toplink (read:JDBC), but between us, I would like to see examples of all types. Thanks folks.

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  • MS Excel - Macros for consolidating values from multiple sheets into a single sheet

    - by SpikETidE
    Hi everyone... Consider i have 4 workbooks with the following structure... 1. Main.xlsx Name Jan Feb Mar A B C 2. Jan.xlsx Name Jan A 3.3 B 6.4 C 5.3 3. Feb.xlsx Name Feb A 1.3 B 3.4 C 5.5 4. Mar.xlsx Name Mar A 1.3 B 3.4 C 5.5 I need to combine them like 1. Main.xlsx Name Jan Feb Mar A 3.3 1.3 1.3 B 6.4 3.4 3.4 C 5.3 5.5 5.5 And i need to automate the process... And i guess i can do this with macros...? Can anyone suggest some way with which i can proceed with the macro? Thanks for your time....

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  • What's the best practice for async APIs that return futures on Scala?

    - by Maurício Linhares
    I have started a project to write an async PostgreSQL driver on Scala and to be async, I need to accept callbacks and use futures, but then accepting a callback and a future makes the code cumbersome because you always have to send a callback even if it is useless. Here's a test: "insert a row in the database" in { withHandler { (handler, future) => future.get(5, TimeUnit.SECONDS) handler.sendQuery( this.create ){ query => }.get( 5, TimeUnit.SECONDS ) handler.sendQuery( this.insert ){ query => }.get( 5, TimeUnit.SECONDS ).rowsAffected === 1 } } Sending the empty callback is horrible but I couldn't find a way to make it optional or anything like that, so right now I don't have a lot of ideas on how this external API should look like. It could be something like: handler.sendQuery( this.create ).addListener { query => println(query) } But then again, I'm not sure how people are organizing API's in this regard. Providing examples in other projects would also be great.

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  • Why appending to a list in Scala should have O(n) time complexity?

    - by Jubbat
    I am learning Scala at the moment and I just read that the execution time of the append operation for a list (:+) grows linearly with the size of the list. Appending to a list seems like a pretty common operation. Why should the idiomatic way to do this be prepending the components and then reversing the list? It can't also be a design failure as implementation could be changed at any point. From my point of view, both prepending and appending should be O(1). Is there any legitimate reason for this?

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  • dynamically create class in scala, should I use interpreter?

    - by Phil
    Hi, I want to create a class at run-time in Scala. For now, just consider a simple case where I want to make the equivalent of a java bean with some attributes, I only know these attributes at run time. How can I create the scala class? I am willing to create from scala source file if there is a way to compile it and load it at run time, I may want to as I sometimes have some complex function I want to add to the class. How can I do it? I worry that the scala interpreter which I read about is sandboxing the interpreted code that it loads so that it won't be available to the general application hosting the interpreter? If this is the case, then I wouldn't be able to use the dynamically loaded scala class. Anyway, the question is, how can I dynamically create a scala class at run time and use it in my application, best case is to load it from a scala source file at run time, something like interpreterSource("file.scala") and its loaded into my current runtime, second best case is some creation by calling methods ie. createClass(...) to create it at runtime. Thanks, Phil

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  • Visual Studio Macros on 64 bit fail with COM error

    - by bruce.kinchin
    I'm doing some javascript development and found a cool macro to region my code ("Using #region Directive With JavaScript Files in Visual Studio"). I used this on my 32 bit box, and it worked first time. (Visual Studio 2008 SP1, Win7) For easy of reference the macro is: Option Strict Off Option Explicit Off Imports System Imports EnvDTE Imports EnvDTE80 Imports System.Diagnostics Imports System.Collections Public Module JsMacros Sub OutlineRegions() Dim selection As EnvDTE.TextSelection = DTE.ActiveDocument.Selection Const REGION_START As String = "//#region" Const REGION_END As String = "//#endregion" DTE.ExecuteCommand("Edit.StopOutlining") selection.SelectAll() Dim text As String = selection.Text selection.StartOfDocument(True) Dim startIndex As Integer Dim endIndex As Integer Dim lastIndex As Integer = 0 Dim startRegions As Stack = New Stack() Do startIndex = text.IndexOf(REGION_START, lastIndex) endIndex = text.IndexOf(REGION_END, lastIndex) If startIndex = -1 AndAlso endIndex = -1 Then Exit Do End If If startIndex <> -1 AndAlso startIndex < endIndex Then startRegions.Push(startIndex) lastIndex = startIndex + 1 Else ' Outline region ... selection.MoveToLineAndOffset(CalcLineNumber(text, CInt(startRegions.Pop())), text.Length) selection.MoveToLineAndOffset(CalcLineNumber(text, endIndex) + 1, 1, True) selection.OutlineSection() lastIndex = endIndex + 1 End If Loop selection.StartOfDocument() End Sub Private Function CalcLineNumber(ByVal text As String, ByVal index As Integer) Dim lineNumber As Integer = 1 Dim i As Integer = 0 While i < index If text.Chars(i) = vbCr Then lineNumber += 1 i += 1 End If i += 1 End While Return lineNumber End Function End Module I then tried to use the same macro on two separate 64 bit machines (Win7 x64), identical other than the 64 bit OS version and it fails to work. Stepping through it with the Visual Studio Macros IDE, it fails the first time on the DTE.ExecuteCommand("Edit.StopOutlining") line with a COM error (Error HRESULT E_FAIL has been returned from a call to a COM component). If I attempt to run it a second time, I can run it from the Macro Editor with no issue, but not from within Visual Studio with the macro explorer 'run macro' command. I have reviewed the following articles without finding anything helpful: Stackoverflow: Visual Studio 2008 macro only works from the Macro IDE, not the Macro Explorer Recorded macro does not run; Failing on DTE.ExecuteCommand Am I missing something dumb?

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  • JSP or .ascx equivalent for Scala?

    - by Daniel Worthington
    I'm working on a small MVC "framework" (it's really very small) in Scala. I'd like to be able to write my view files as Scala code so I can get lots of help from the compiler. Pre-compiling is great, but what I really want is a way to have the servlet container automatically compile certain files (my view files) on request so I don't have to shut down Jetty and compile all my source files at once, then start it up again just to see small changes to my HTML. I do this a lot with .ascx files in .NET (the file will contain just one scriptlet tag with a bunch of C# code inside which writes out markup using an XmlWriter) and I love this workflow. You just make changes and then refresh your browser, but it's still getting compiled! I don't have a lot of experience with Java, but it seems possible to do this with JSP as well. I'm wondering if this sort of thing is possible in Scala. I have looked into building this myself (see more info here: http://www.nabble.com/Compiler-API-td12050645.html) but I would rather use something else if it's out there.

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  • Project Euler 7 Scala Problem

    - by Nishu
    I was trying to solve Project Euler problem number 7 using scala 2.8 First solution implemented by me takes ~8 seconds def problem_7:Int = { var num = 17; var primes = new ArrayBuffer[Int](); primes += 2 primes += 3 primes += 5 primes += 7 primes += 11 primes += 13 while (primes.size < 10001){ if (isPrime(num, primes)) primes += num if (isPrime(num+2, primes)) primes += num+2 num += 6 } return primes.last; } def isPrime(num:Int, primes:ArrayBuffer[Int]):Boolean = { // if n == 2 return false; // if n == 3 return false; var r = Math.sqrt(num) for (i <- primes){ if(i <= r ){ if (num % i == 0) return false; } } return true; } Later I tried the same problem without storing prime numbers in array buffer. This take .118 seconds. def problem_7_alt:Int = { var limit = 10001; var count = 6; var num:Int = 17; while(count < limit){ if (isPrime2(num)) count += 1; if (isPrime2(num+2)) count += 1; num += 6; } return num; } def isPrime2(n:Int):Boolean = { // if n == 2 return false; // if n == 3 return false; var r = Math.sqrt(n) var f = 5; while (f <= r){ if (n % f == 0) { return false; } else if (n % (f+2) == 0) { return false; } f += 6; } return true; } I tried using various mutable array/list implementations in Scala but was not able to make solution one faster. I do not think that storing Int in a array of size 10001 can make program slow. Is there some better way to use lists/arrays in scala?

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