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  • Can someone explain me implicit parameters in Scala?

    - by Oscar Reyes
    And more specifically how does the BigInt works for convert int to BigInt? In the source code it reads: ... implicit def int2bigInt(i: Int): BigInt = apply(i) ... How is this code invoked? I can understand how this other sample: "Date literals" works. In. val christmas = 24 Dec 2010 Defined by: implicit def dateLiterals(date: Int) = new { import java.util.Date def Dec(year: Int) = new Date(year, 11, date) } When int get's passed the message Dec with an int as parameter, the system looks for another method that can handle the request, in this case Dec(year:Int) Q1. Am I right in my understanding of Date literals? Q2. How does it apply to BigInt? Thanks

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  • Scala Lift - Robust method to protect files from hotlinking

    - by sirjamm
    I'm attempting to implement a way to stop hotlinking and/or un-authorised access to resources within my app. The method I'm trying to add is something I've used before in PHP apps. Basically a session is set when the page is first called. The images are added to the page via the image tag with the session value as a parameter: <img src="/files/image/[handle]?session=12345" /> When the image is requested the script checks to see if the session is set and matches the provided value. If the condition is not met the serving page returns null. Right at the end to the code I unset the session so further requests from outside the scope of the page will return null. What would be the best implementation of this method within the lift framework? Thanks in advance for any help, much appreciated :)

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  • assigning to local variables in scala template in play framework

    - by user3548344
    I am trying to define the local variables and assign to them as below : @defining((Json.parse(value), ("GGGGGG"))) {case (json:JsValue, lb)=> @{lb=json\\"myTestField"} } but getting the error reassignment to val. So I tried to declare lb as var like @defining((Json.parse(value), ("GGGGGG"))) {case (json:JsValue, lb:var)=> @{lb=json\\"myTestField"} } but getting the error identifier expected but 'var' found How can I assign to variable lb?

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  • Scala: custom control structures with several code blocks

    - by Vilius Normantas
    Is it possible to create a custom control structure with several code blocks, in the fashion of before { block1 } then { block2 } finally { block3 }? The question is about the sugar part only - I know the functionality can be easily achieved by passing the three blocks to a method, like doInSequence(block1, block2, block3). A real life example. For my testing utilities I'd like to create a structure like this: getTime(1000) { // Stuff I want to repeat 1000 times. } after { (n, t) => println("Average time: " + t / n) }

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  • Compiling Scala scripts. How works scalac?

    - by Arturo Herrero
    Groovy Groovy comes with a compiler called groovyc. For each script, groovyc generates a class that extends groovy.lang.Script, which contains a main method so that Java can execute it. The name of the compiled class matches the name of the script being compiled. For example, with this HelloWorld.groovy script: println "Hello World" That becomes something like this code: class HelloWorld extends Script { public static void main(String[] args) { println "Hello World" } } Scala Scala comes with a compiler called scalac. I don't know how it works. For example, with the same HelloWorld.scala script: println("Hello World") The code is not valid for scalac, because the compiler expected class or object definition, but works in Scala REPL interpreter. How is possible? Is it wrapped in a class before execution?

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  • Scala type system : basic type mismatch

    - by SiM
    I have a basic type system type mismatch problem: I have a class with a method def Create(nodeItem : NodeItem) = {p_nodeStart.addEndNode(nodeItem)} where p_nodeStart is NodeCache class NodeCache[END_T<:BaseNode] private(node: Node) extends BaseNode { def addEndNode(endNode : END_T) = {this.CACHE_HAS_ENDNODES.Create(endNode)} and the error its giving me is: error: type mismatch; found : nodes.NodeItem required: Nothing def Create(nodeItem : NodeItem) = {p_nodeStart.addEndNode(nodeItem)} while the NodeCache is defined as object NodeTrigger { def Create() { val nodeTimeCache = NodeCache.Create[NodeItem](node) and in object NodeCache object NodeCache { def Create[END_T<:BaseNode]() { val nodeCache = new NodeCache[END_T](node); Any ideas, how to fix the error?

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  • Can someone explain me implicit conversions in Scala?

    - by Oscar Reyes
    And more specifically how does the BigInt works for convert int to BigInt? In the source code it reads: ... implicit def int2bigInt(i: Int): BigInt = apply(i) ... How is this code invoked? I can understand how this other sample: "Date literals" works. In. val christmas = 24 Dec 2010 Defined by: implicit def dateLiterals(date: Int) = new { import java.util.Date def Dec(year: Int) = new Date(year, 11, date) } When int get's passed the message Dec with an int as parameter, the system looks for another method that can handle the request, in this case Dec(year:Int) Q1. Am I right in my understanding of Date literals? Q2. How does it apply to BigInt? Thanks

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  • How do I disable auto-compilation of Scala source in jEdit?

    - by Daniel
    I have always liked the auto-compilation feature of jEdit with Scala sources. Now, however, I'm using "mvn scala:cc" and JavaRebel with a Lift project, which provides better compilation than what jEdit does, and I'd like to disable jEdit's auto-compilation. How do I disable auto-compilation in jEdit, of Scala sources, in particular?

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  • Scala - Enumeration vs. Case-Classes

    - by tzofia
    I've created akka actor called LogActor. The LogActors's receive method handling messages from other actors and logging them to the specified log level. I can distinguish between the different levels in 2 ways. The first one: import LogLevel._ object LogLevel extends Enumeration { type LogLevel = Value val Error, Warning, Info, Debug = Value } case class LogMessage(level : LogLevel, msg : String) The second: (EDIT) abstract class LogMessage(msg : String) case class LogMessageError(msg : String) extends LogMessage(msg) case class LogMessageWarning(msg : String) extends LogMessage(msg) case class LogMessageInfo(msg : String) extends LogMessage(msg) case class LogMessageDebug(msg : String) extends LogMessage(msg) Which way is more efficient? does it take less time to match case class or to match enum value? (I read this question but there isn't any answer referring to the runtime issue)

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  • Self-type mismatch in Scala

    - by Alexey Romanov
    Given this: abstract class ViewPresenterPair { type V <: View type P <: Presenter trait View {self: V => val presenter: P } trait Presenter {self: P => var view: V } } I am trying to define an implementation in this way: case class SensorViewPresenter[T] extends ViewPresenterPair { type V = SensorView[T] type P = SensorPresenter[T] trait SensorView[T] extends View { } class SensorViewImpl[T](val presenter: P) extends SensorView[T] { presenter.view = this } class SensorPresenter[T] extends Presenter { var view: V } } Which gives me the following errors: error: illegal inheritance; self-type SensorViewPresenter.this.SensorView[T] does not conform to SensorViewPresenter.this.View's selftype SensorViewPresenter.this.V trait SensorView[T] extends View { ^ <console>:13: error: type mismatch; found : SensorViewPresenter.this.SensorViewImpl[T] required: SensorViewPresenter.this.V presenter.view = this ^ <console>:16: error: illegal inheritance; self-type SensorViewPresenter.this.SensorPresenter[T] does not conform to SensorViewPresenter.this.Presenter's selftype SensorViewPresenter.this.P class SensorPresenter[T] extends Presenter { ^ I don't understand why. After all, V is just an alias for SensorView[T], and the paths are the same, so how can it not conform?

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  • Scala capture group using regex

    - by Geo
    Let's say I have this code: val string = "one493two483three" val pattern = """two(\d+)three""".r pattern.findAllIn(string).foreach(println) I expected findAllIn to only return 483, but instead, it returned two483three. I know I could use unapply to extract only that part, but I'd have to have a pattern for the entire string, something like: val pattern = """one.*two(\d+)three""".r val pattern(aMatch) = string println(aMatch) // prints 483 Is there another way of achieving this, without using the classes from java.util directly, and without using unapply?

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  • Scala parser combinators: how to parse "if(x)" if x can contain a ")"

    - by Germán
    I'm trying to get this to work: def emptyCond: Parser[Cond] = ("if" ~ "(") ~> regularStr <~ ")" ^^ { case s => Cond("",Nil,Nil) } where regularStr is defined to accept a number of things, including ")". Of course, I want this to be an acceptable input: if(foo()). But for any if(x) it is taking the ")" as part of the regularStr and so this parser never succeeds. What am I missing?

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  • Another Java vs. Scala perspective - is this typical?

    - by Alex R
    I have been reading about Scala for a while and even wrote some small programs to better understand some of the more exoteric features. Today I decided to do my first "real project", translating some 60 lines of ugly Java code to Scala to rewrite it using the better pattern-matching features (why? because the Java version was becoming hard to maintain due to excessive combination of regex and conditionals). About halfway through the editing process, Eclipse thew up this error: I get the general impression that the Scala IDE in Eclipse is a lot buggier and less complete than its Java equivalent. Is this correct or do I just have a bad installation? Is there a better IDE for Scala?

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  • scala sbt with pk11 or steps

    - by portoalet
    I am quite frustrated with sbt and pk11/steps I am just trying to run "jetty-run", but i got so many dependency errors, it's not fun anymore. I am stuck with unresolved dependencies for sjson 0.3 Does anyone know which mvn repo can I get sjson 0.3 from?

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  • Is there a good date/time API available for Scala?

    - by Erik Engbrecht
    I'm looking for something akin to JodaTime or JSR 310 for Scala that leverages nice Scala features such as operator overloading and doesn't rely on implicit conversions (I have an irrational fear of implicit conversions). I'm aware of http://github.com/jorgeortiz85/scala-time, but it just pimps JodaTime with implicits.

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  • Can someone exaplain me implicit parameters in Scala?

    - by Oscar Reyes
    And more specifically how does the BigInt works for convert int to BigInt? In the source code it reads: ... implicit def int2bigInt(i: Int): BigInt = apply(i) ... How is this code invoked? I can understand how this other sample: "Date literals" works. In. val christmas = 24 Dec 2010 Defined by: implicit def dateLiterals(date: Int) = new { import java.util.Date def Dec(year: Int) = new Date(year, 11, date) } When int get's passed the message Dec with an int as parameter, the system looks for another method that can handle the request, in this case Dec(year:Int) Q1. Am I right in my understanding of Date literals? Q2. How does it apply to BigInt? Thanks

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  • Scala contiguous match

    - by drypot
    pathTokens match { case List("post") => ("post", "index") case List("search") => ("search", "index") case List() => ("home", "index") } match { case (controller, action) => loadController(http, controller, action) case _ => null } I wanted contiguous match. but got compile error. :( (pathTokens match { case List("post") => ("post", "index") case List("search") => ("search", "index") case List() => ("home", "index") }) match { case (controller, action) => loadController(http, controller, action) case _ => null } When I wrapped first match with parenparenthesis, it worked ok. Why I need parenthesis here ?

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  • automatic xml conversion in scala

    - by Jeff Bowman
    Let's say I have the following class: class Person(val firstName:String, val lastName:String) Is there an automatic way to generate xml from this class without having to hand create a toXml() method? Ideally the output would be something like: <Person <firstNameJohn</firstName <lastNameSmith</lastName </Person It seems like there should be a way to do this without having to write all that out manually. Perhaps there is a trait I haven't found yet?

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  • Scala: how to specify varargs as type?

    - by IttayD
    Instead of def foo(configuration: (String, String)*) I'd like to be able to write: type Configuration = (String, String)* def foo(configuration: Configuration) The main use case is to provide an easy method signature when overriding in subclasses

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