Scala annotations, what actually is that?
I don't know Java. I started learning Scala. I can't imagine what and what for annotations are? Could someone explain me? ...
scala
Is there a way to extend Scala's RichString?
Since scala.runtime.RichString is declared as final, you can't extend it like class MyString extends RichString. I'd like to 'pimp the library' and simply add another method. How would I do this? ...
Design patterns for functional-oo hybrid languages?
Is there already any collection of best practices for languages like Scala? I've found a work on design patterns for functional languages here. There's GoF design patterns for oo languages. But are there any patterns for functional-oo hybrids? All I've seen is this list. Does anyone know any more? ...
What's the Scala for a declaration of "Class<? extends SomeType>"
I'm obviously missing something about why the following does not compile: trait SomeTrait{ def homepageClass[A <: SomeType]: Class[A] } class SomeOtherType extends SomeType object SomeObject extends SomeTrait{ def homepageClass = classOf[SomeOtherType] } ...
How to set up implicit conversion to allow arithmetic between numeric types?
I'd like to implement a class C to store values of various numeric types, as well as boolean. Furthermore, I'd like to be able to operate on instances of this class, between types, converting where necessary Int --> Double and Boolean -> Int, i.e., to be able to add Boolean + Boolean, Int + Boolean, Boolean + Int, Int + Double, Double + ...
Is it possible for an optional argument value to depend on another argument in Scala
Does anyone know if something like this is possible in Scala: case class Thing(property:String) def f(thing:Thing, prop:String = thing.property) = println(prop) The above code doesn't compile; giving the error error: not found: value thing at thing.property The following shows the expected behaviour: f(Thing("abc"), "123") // print...
How to declare scala method so that it can be called from Java using varargs style
I have 2 simple methods in a scala library class: class Foo { def bar(args : String*) : Unit = println("Foo.bar with: " + args) def bar(args : Array[String]) : Unit = bar(args.toSeq : _*) } This all compiles nicely. I then put this in a library foo.jar and try and compile the following piece of Java: import Foo public class Test ...
scala empty array
What is the canonical way to get an empty array in Scala? new Array[String](0) is too verbose. ...
What lexer to build a lexer/parser in Scala
Hi there, I'm currently looking for a lexer/parser that generate Scala code from a BNF grammar (a ocamlyacc file with precedence and associativity) and I'm quite confused to find.. almost nothing: For parsing, I found scala-bison (that I have a lot of trouble to deal with). All the other tools are just Java parser imported into Scala (l...
What Is the Concept of "Weak Conformance" in Scala?
I just recently encountered the term "Weak Conformance" (in retronym's answer to How to set up implicit conversion to allow arithmetic between numeric types?). What is it? ...
Java GAE maven configuration problem? just another VerifyError
My project works absolutely fine on the Google Server but I get a VerifyError: java.lang.VerifyError: (class: org/restlet/ext/servlet/ServerServlet, method: createServer signature: (Ljavax/servlet/http/HttpServletRequest;) Lorg/restlet/engine/http/HttpServerHelper;) Incompatible object argument for function call UPDATE Through ex...
Do methods ending with _! have a special meaning in Scala?
Do methods ending with _! such as delete_! or i_is_! have a special meaning? Are they "just names"? Do they follow some convention? There's even bulkDelete_!!. (The specific context is Lift if it makes a difference.) ...
relationship between path-dependent inner types in Scala
Warning: I'm cross-posting from #scala The book Programming in Scala states that path-dependent types are different depending on the exact instance of the path in question. If so, I don't understand why all the following predicates return true: class Outer { val in = new Inner class Inner } val o1 = new Outer val o2 = new Outer o...
scala SocketServer
what is the purpose of scala.tools.util.SocketServer? ...
scala equivalent of java public field
In java, I have a class like this: public class MyClass extends Properties { public StringProperty prop1 = new StringProperty(this, "default value for prop1"); public StringProperty prop2 = new StringProperty(this, "prop2 default val"); }//MyClass The parent class "Properties" uses reflection to look for all public fields in...
how to make implicit conversion of types used in my Interpreter
I am writing an interpreter and tried to use solution from how-to-set-up-implicit-conversion-to-allow-arithmetic-between-numeric-types for the same problem I need to be able to add Boolean + Boolean, Int + Boolean, Boolean + Int, Int + Double, Double + Double etc. So I used WeakConformance and C classes from that solution sealed trait...
What is the fastest way to sum a collection in Scala
I've tried different collections in Scala to sum it's elements and they are much slower than Java sums it's arrays (with for cycle). Is there a way for Scala to be as fast as Java arrays? I've heard that in scala 2.8 arrays will be same as in java, but they are much slower in practice ...
Scala matching a specific node in xml
I have xml that looks like this: val xml = <plugins> <plugin type="x">plugin x</plugin> <plugin type="y">plugin y</plugin> </plugins> I am trying to write a match statement that finds the plugin with the attribute type="x". I tried: xml match { case <plugin type="x">{contents}</plugin> => println(contents) case _ => println(...
Is it possible to recover the name of the function from within the function in scala?
I'd like to do something like def getMeASammy() {println "getMeASammy"} def getMeADrink() {println "getMeADrink"} def getMeASub() {println "getMeASub"} But, I don't want to explicitly type out the name of the function. ...
Difference between Scala trait and C++ concepts
What is the difference between Scala traits Haskell type class and C++0x Concepts? ...