Search Results

Search found 2945 results on 118 pages for 'scala designer'.

Page 11/118 | < Previous Page | 7 8 9 10 11 12 13 14 15 16 17 18  | Next Page >

  • Xamarin Designer for Android Webinar - Recording

    - by Wallym
    Here is some info on the recording of the webinar that I did last week for AppDev regarding the Xamarin Designer for Android.Basic Info: Android user interfaces can be created declaratively by using XML files, or programmatically in code. The Xamarin Android Designer allows developers to create and modify declarative layouts visually, without having to deal with the tedium of hand-editing XML files. The designer also provides real-time feedback, which lets the developer validate changes without having to redeploy the application in order to test a design. This can speed up UI development in Android tremendously. In this webinar, we'll take a look at UI Design in Mono for Android, the basics of the Xamarin Android Designer, and build a simple application with the designer.Here is the link:http://media.appdev.com/EDGE/LL/livelearn05232012.wmvI think it will only play in Internet Explorer.  Enjoy!

    Read the article

  • 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.

    Read the article

  • 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?

    Read the article

  • 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

    Read the article

  • 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.

    Read the article

  • 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?

    Read the article

  • Groovy / Scala / Java under the hood

    - by Jack
    I used Java for like 6-7 years, then some months ago I discovered Groovy and started to save a lot of typing.. then I wondered how certain things worked under the hood (because groovy performance is really poor) and understood that to give you dynamic typing every Groovy object is a MetaClass object that handles all the things that the JVM couldn't handle by itself. Of course this introduces a layer in the middle between what you write and what you execute that slows down everything. Then somedays ago I started getting some infos about Scala. How these two languages compare in their byte code translations? How much things they add to the normal structure that it would be obtained by plain Java code? I mean, Scala is static typed so wrapper of Java classes should be lighter, since many things are checked during compile time but I'm not sure about the real differences of what's going inside. (I'm not talking about the functional aspect of Scala compared to the other ones, that's a different thing) Can someone enlighten me? From WizardOfOdds it seems like that the only way to get less typing and same performance would be to write an intermediate translator that translates something in Java code (letting javac compile it) without alterating how things are executed, just adding synctatic sugar withour caring about other fallbacks of the language itself.

    Read the article

  • Yet another Haskell vs. Scala question

    - by Travis Brown
    I've been using Haskell for several months, and I love it—it's gradually become my tool of choice for everything from one-off file renaming scripts to larger XML processing programs. I'm definitely still a beginner, but I'm starting to feel comfortable with the language and the basics of the theory behind it. I'm a lowly graduate student in the humanities, so I'm not under a lot of institutional or administrative pressure to use specific tools for my work. It would be convenient for me in many ways, however, to switch to Scala (or Clojure). Most of the NLP and machine learning libraries that I work with on a daily basis (and that I've written in the past) are Java-based, and the primary project I'm working for uses a Java application server. I've been mostly disappointed by my initial interactions with Scala. Many aspects of the syntax (partial application, for example) still feel clunky to me compared to Haskell, and I miss libraries like Parsec and HXT and QuickCheck. I'm familiar with the advantages of the JVM platform, so practical questions like this one don't really help me. What I'm looking for is a motivational argument for moving to Scala. What does it do (that Haskell doesn't) that's really cool? What makes it fun or challenging or life-changing? Why should I get excited about writing it?

    Read the article

  • Different Scala Actor Implementations Overview

    - by Stefan K.
    I'm trying to find the 'right' actor implementation for my thesis. I realized there is a bunch of them and it's a bit confusing to pick one. Personally I'm especially interested in remote actors, but I guess a complete overview would be helpful to many others. This is a pretty general question, so feel free to answer just for the implementation you know about. I know about the following Scala Actor implementations (SAI). Please add the missing ones. Scala 2.7 (difference to) Scala 2.8 Akka (http://www.akkasource.org/) Lift (http://liftweb.net/) Scalaz (http://code.google.com/p/scalaz/) What are the target use-cases for these SAIs (lightweight vs. "heavy" enterprise framework)? do they support remote actors? What shortcomings do remote actors have in the SAIs? How is their performace? How active is there community? How easy are they to get started? How good is the documentation? How easy are they to extend? How stable are they? Which projects are using them? What are their shortcomings? What are their design principles? Are they thread based or event based (receive/ react) or both? Nested receiveS hotswapping the Actor’s message loop

    Read the article

  • Scala newbie vproducer/consumer attempt running out of memory

    - by Nick
    I am trying to create a producer/consumer type Scala app. The LoopControl just sends a message to the MessageReceiver continually. The MessageReceiver then delegates work to the MessageCreatorActor (whose work is to check a map for an object, and if not found create one and start it up). Each MessageActor created by this MessageCreatorActor is associated with an Id. Eventually this is where I want to do business logic. But I run out of memory after 15 minutes. Its finding the cached actors,but quickly runs out of memory. Any help is appreciated. Or any one has any good code on producers consumers doing real stuff (not just adding numbers), please post. import scala.actors.Actor import java.util.HashMap import scala.actors.Actor._ case object LoopControl case object MessageReceiver case object MessageActor case object MessageActorCreator class MessageReceiver(msg: String) extends Actor { var messageActorMap = new HashMap[String, MessageActor] val messageCreatorActor = new MessageActorCreator(null, null) def act() { messageCreatorActor.start loop { react { case MessageActor(messageId) => if (msg.length() > 0) { var messageActor = messageActorMap.get(messageId); if(messageActor == null) { messageCreatorActor ! MessageActorCreator(messageId, messageActorMap) }else { messageActor ! MessageActor } } } } } } case class MessageActorCreator(msg:String, messageActorMap: HashMap[String, MessageActor]) extends Actor { def act() { loop { react { case MessageActorCreator(messageId, messageActorMap) => if(messageId != null ) { var messageActor = new MessageActor(messageId); messageActorMap.put(messageId, messageActor) println(messageActorMap) messageActor.start messageActor ! MessageActor } } } } } class LoopControl(messageReceiver:MessageReceiver) extends Actor { var count : Int = 0; def act() { while (true) { messageReceiver ! MessageActor ("00-122-0X95-FEC0" + count) //Thread.sleep(100) count = count +1; if(count > 5) { count = 0; } } } } case class MessageActor(msg: String) extends Actor { def act() { loop { react { case MessageActor => println() println("MessageActor: Got something-> " + msg) } } } } object messages extends Application { val messageReceiver = new MessageReceiver("bootstrap") val loopControl = new LoopControl(messageReceiver) messageReceiver.start loopControl.start }

    Read the article

  • Scala path dependent return type from parameter

    - by Rich Oliver
    In the following code using 2.10.0M3 in Eclipse plugin 2.1.0 for 2.10M3. I'm using the default setting which is targeting JVM 1.5 class GeomBase[T <: DTypes] { abstract class NewObjs { def newHex(gridR: GridBase, coodI: Cood): gridR.HexRT } class GridBase { selfGrid => type HexRT = HexG with T#HexTr def uniformRect (init: NewObjs) { val hexCood = Cood(2 ,2) val hex: HexRT = init.newHex(selfGrid, hexCood)// won't compile } } } Error message: Description Resource Path Location Type type mismatch; found: GeomBase.this.GridBase#HexG with T#HexTr required: GridBase.this.HexRT (which expands to) GridBase.this.HexG with T#HexTr GeomBase.scala Why does the compiler think the method returns the type projection GridBase#HexG when it should be this specific instance of GridBase? Edit transferred to a simpler code class in responce to comments now getting a different error message. package rStrat class TestClass { abstract class NewObjs { def newHex(gridR: GridBase): gridR.HexG } class GridBase { selfGrid => def uniformRect (init: NewObjs) { val hex: HexG = init.newHex(this) //error here } class HexG { val test12 = 5 } } } . Error line 11:Description Resource Path Location Type type mismatch; found : gridR.HexG required: GridBase.this.HexG possible cause: missing arguments for method or constructor TestClass.scala /SStrat/src/rStrat line 11 Scala Problem Update I've switched to 2.10.0M4 and updated the plug-in to the M4 version on a fresh version of Eclipse and switched to JVM 1.6 (and 1.7) but the problems are unchanged.

    Read the article

  • Commenting out portions of code in Scala

    - by akauppi
    I am looking for a C(++) #if 0 -like way of being able to comment out whole pieces of Scala source code, for keeping around experimental or expired code for a while. I tried out a couple of alternatives and would like to hear what you use, and if you have come up with something better? // Simply block-marking N lines by '//' is one way... // <tags> """ anything My editor makes this easy, but it's not really The Thing. It gets easily mixed with actual one-line comments. Then I figured there's native XML support, so: <!-- ... did not work --> Wrapping in XML works, unless you have <tags> within the block: class none { val a= <ignore> ... cannot have //<tags> <here> (not even in end-of-line comments!) </ignore> } The same for multi-line strings seems kind of best, but there's an awful lot of boilerplate (not fashionable in Scala) to please the compiler (less if you're doing this within a class or an object): object none { val ignore= """ This seems like ... <truly> <anything goes> but three "'s of course """ } The 'right' way to do this might be: /*** /* ... works but not properly syntax highlighed in SubEthaEdit (or StackOverflow) */ ***/ ..but that matches the /* and */ only, not i.e. /*** to ***/. This means the comments within the block need to be balanced. And - the current Scala syntax highlighting mode for SubEthaEdit fails miserably on this. As a comparison, Lua has --[==[ matching ]==] and so forth. I think I'm spoilt? So - is there some useful trick I'm overseeing?

    Read the article

  • Crazy VS Designer Errors

    - by BlueRaja
    Here's a strange one. After renaming a class, one of my forms began giving me errors in the designer, refusing to open. Funny thing is, the form worked just fine when I ran the program. I began reverting my changes to deduce the problem. I have now reverted completely back to the last commit - in which I know the form was working in the designer - cleaned the solution, and deleted the bin/ and obj/ folders, as well as the *.suo file for good measure. The form still does not display in designer. Here are the errors it gives: Could not find 'MyNamespace.MyControl'. Please make sure that the assembly that contains this type is referenced. If this type is a part of your development project, make sure that the project has been successfully built. The variable 'myControl1' is either undeclared or was never assigned. The variable is both declared and assigned, and MyControl builds fine (again, the form works fine when the program is actually run). Stranger still, if I try to create a new form and drag a MyControl onto it, I get this Entity-Framework error: Failed to create component 'MyControl'. The error message follows: 'System.ArgumentException: The specified named connection is either not found in the configuration, not intended to be used with the EntityClient provider, or not valid. at System.Data.EntityClient.EntityConnection.ChangeConnectionString(String newConnectionString) at System.Data.EntityClient.EntityConnection..ctor(String connectionString) at System.Data.Objects.ObjectContect.CreateEntityConnection(String connectionString) etc. etc. There is nothing wrong with my connection string: it worked before, and, again, it works when I actually run the program (the control already exists on the old form from the previous commit). Any ideas whatsoever? I am completely at a loss. [Edit] The only significant code: MyControl.cs public MyControl() { _entities = new MyEFEntities(); //Entity-framework generated class } MyForm.Designer.cs private void InitializeComponent() { this.myControl1 = new MyNamespace.MyControl(); ... this.Controls.Add(this.myControl1); } MyEFDatabase.Designer.cs public MyEFEntities() : base("name=MyEFEntities", "MyEFEntities") { ... } App.Config <connectionStrings> <add name="MyEFEntities" connectionString="metadata=res://*/MyEFDatabase.csdl|res://*/MyEFDatabase.ssdl|res://*/MyEFDatabase.msl;provider=System.Data.SqlClient;provider connection string=&quot;Data Source=MyDatabaseServer;Initial Catalog=MyDatabase;Integrated Security=True;MultipleActiveResultSets=True&quot;" providerName="System.Data.EntityClient" /> </connectionStrings> I've tried the "replace &quot; with '" trick - didn't help. [Edit2] It is happening to new projects also, but not immediately. Only after fiddling around a bit (it has something to do with adding a many-to-one relationship that EF did not figure out on its own), but I can't figure out the exact steps to reproduce.

    Read the article

  • How to read Scala code with lots of implicits?

    - by Petr Pudlák
    Consider the following code fragment (adapted from http://stackoverflow.com/a/12265946/1333025): // Using scalaz 6 import scalaz._, Scalaz._ object Example extends App { case class Container(i: Int) def compute(s: String): State[Container, Int] = state { case Container(i) => (Container(i + 1), s.toInt + i) } val d = List("1", "2", "3") type ContainerState[X] = State[Container, X] println( d.traverse[ContainerState, Int](compute) ! Container(0) ) } I understand what it does on high level. But I wanted to trace what exactly happens during the call to d.traverse at the end. Clearly, List doesn't have traverse, so it must be implicitly converted to another type that does. Even though I spent a considerable amount of time trying to find out, I wasn't very successful. First I found that there is a method in scalaz.Traversable traverse[F[_], A, B] (f: (A) => F[B], t: T[A])(implicit arg0: Applicative[F]): F[T[B]] but clearly this is not it (although it's most likely that "my" traverse is implemented using this one). After a lot of searching, I grepped scalaz source codes and I found scalaz.MA's method traverse[F[_], B] (f: (A) => F[B])(implicit a: Applicative[F], t: Traverse[M]): F[M[B]] which seems to be very close. Still I'm missing to what List is converted in my example and if it uses MA.traverse or something else. The question is: What procedure should I follow to find out what exactly is called at d.traverse? Having even such a simple code that is so hard analyze seems to me like a big problem. Am I missing something very simple? How should I proceed when I want to understand such code that uses a lot of imported implicits? Is there some way to ask the compiler what implicits it used? Or is there something like Hoogle for Scala so that I can search for a method just by its name?

    Read the article

  • How can I improve the workflow between developer and designer with Expression Blend?

    - by Amenti
    We use WPF and Expression Blend 4. I'm trying to improve our workflow by tutoring one of our designers to use it for styling and animation. Slowly but surely I get the impression Blend in itself is to technical for the designer in question. I myself use it only occasionally (it's great for Visual States for instance) because a lot of things are easier done in code or not possible at all in Blend alone. It seems a developer with design experience is a lot more productive with it than a sole designer. Are there any good resources or advice as to how I can improve this workflow?

    Read the article

  • How to improve workflow between developer and designer with Expression Blend?

    - by Amenti
    We use WPF and Expression Blend 4. I'm trying to improve our workflow by tutoring one of our designers to use it for styling and animation. Slowly but surely I get the impression Blend in itself is to technical for the designer in question. I myself use it only occasionally (it's great for Visual States for instance) because a lot of things are easier done in code or not possible at all in Blend alone. It seems a developer with design experience is a lot more productive with it than a sole designer. Are there any good online resources or advice you could give me how to improve this situation?

    Read the article

  • “Could not find type” error loading a form in the Designer

    - by Vaccano
    This is the exact same question as this one: “Could not find type” error loading a form in the Designer Before anyone goes closing my question please read that one. You will realize that it did not get a real answer. I hope to get a full answer (rather than a workaround) from this question. When I create a class that descends from Control and uses generics, that class fails to load in the designer. Here is and example: class OwnerDrawnListBox<T> : System.Windows.Forms.Control { private readonly List<T> _items; // Other list box private stuff here public OwnerDrawnListBox() { _items = new List<T>(); } // More List box code } I then use this in my designer: private OwnerDrawnListBox<Bag> lstAvailable; private void InitializeComponent() { // Used to be System.Windows.Forms.ListBox(); this.lstAvailable = new ARUP.ScanTrack.Mobile.OwnerDrawnListBox<Bag>(); // Other items } If the generic class is subclassed (to a non-generic) then the referenced question says that it works fine (ie if I made Class BagOwnerDrawListBox: OwnerDrawnListBox<Bag>). What I want to know is there a way to "fix" this so that the generic item is accepted by the designer? Side Note: I am using the Compact Framework.

    Read the article

  • Streaming Video In Scala InfoChannel Designer 5

    - by godleuf
    I am having the hardest time finding urls to use in Scala Designer 5 showing video streams. I am new at this program, but there is an option to run a video as a background. I have found a couple of samples to link to, but nothing great thus far. Anyone out there using this program and wanting to do the same? Thanks.

    Read the article

  • java.lang.NoSuchMethodError: main when starting HelloWorld with Eclipse Scala plugin

    - by Matt Sheppard
    I've just been playing with Scala, and installed the Eclipse plugin as described at http://www.scala-lang.org/node/94, but after entering the "Hello World" test example and setting up the run configuration as described, I get the following error Exception in thread "main" java.lang.NoSuchMethodError: main For reference the code is package hello object HelloWorld extends Application { println("Hello World!") } I've tinkered a bit with the obvious solutions (adding a main method, adding a singleton object with a main method) but I'm clearly doing something wrong. Can anyone get their test example to work, or point out what I am doing wrong?

    Read the article

  • Scala Actors with Java interop to underlying COM libraries

    - by wheaties
    I'm working on a JVM project which uses ESRI components (COM based, wrapped with JIntegra.) The client has requested the JAR files we produce work on the JVM and be accessible to Java code. I'd like to use Scala but I'm worried about how well the library will play with Scala's actors. Particularly I'm worried about the different mechanisms COM and Java employ to pass objects from one thread to another. Does anyone have any experience with this? Will they play nice? Edit: for clarification I noticed that when performing I/O on the ESRI DB that the CPU utilization is roughly 15%. I'd like to read each row and pass that row over to another actor for parsing. Then I could have several threads reading from the DB at once. The problem is that each row retrieved using ESRI's library is actually a Java wrapped COM object.

    Read the article

  • .NET custom form designer: How to implement IMenuCommandService?

    - by jonny
    I've got a report form designer written long ago for a database project. It used a lot of winapi magic hence i was forced to rewrite some parts 'in proper way'. Thanks to some articles from MSDN magazine (here and here) and CodeProject i was able to implement designer surface, toolbox and undo/redo engine. Every resource i discovered on the topic so far is a bit outdated. Can you point to fresh/comprehensive article? Code from article mentioned above seems not working. MenuCommandService.ShowContextMenu is called but nothing appears since there aren't any DesignerVerbs in globalVerbs collection. Should i add 'standard' ones, corresponded to designer actions such as cut/paste, manually? If yes, how can i accomplish this?

    Read the article

  • How many Scala web-frameworks are there?

    - by Prikrutil
    Hello! I've just started learning Scala and the first thing I'm going to implement is a tiny web-application. I've been using Erlang for the last year to implement server-side software, but I've never wrote web-applications before. It will be a great experience. Here is my question: are there web-frameworks for Scala except for Lift? Don't get me wrong, Lift looks awesome. I just want to know how many frameworks there are so that I can then choose between them. It's always a good to have a choice, but I the only thing I found was Lift.

    Read the article

  • Visual studio winform designer shows design errors as text rather than html

    - by Miki Watts
    All of the sudden, visual studio displays designer errors as plain html text, for example: <DIV id="div1" class="ErrorStyle" width="100%"><span style="font-weight: 600"><br>Object reference not set to an instance of an object. </span><br><a href="" instead of displaying the usual html formatted. I haven't been able to find anything similar to it on google. Before getting this problem, when I tried opening the winform designer, I would get the run/save/cancel dialog of internet explorer for a .tmp file, instead of the designer window. That went away when I found out that I had notepad assigned to the .tmp file type and removed that. Any ideas how to fix this?

    Read the article

  • Threading extra state through a parser in Scala

    - by Travis Brown
    I'll give you the tl;dr up front I'm trying to use the state monad transformer in Scalaz 7 to thread extra state through a parser, and I'm having trouble doing anything useful without writing a lot of t m a -> t m b versions of m a -> m b methods. An example parsing problem Suppose I have a string containing nested parentheses with digits inside them: val input = "((617)((0)(32)))" I also have a stream of fresh variable names (characters, in this case): val names = Stream('a' to 'z': _*) I want to pull a name off the top of the stream and assign it to each parenthetical expression as I parse it, and then map that name to a string representing the contents of the parentheses, with the nested parenthetical expressions (if any) replaced by their names. To make this more concrete, here's what I'd want the output to look like for the example input above: val target = Map( 'a' -> "617", 'b' -> "0", 'c' -> "32", 'd' -> "bc", 'e' -> "ad" ) There may be either a string of digits or arbitrarily many sub-expressions at a given level, but these two kinds of content won't be mixed in a single parenthetical expression. To keep things simple, we'll assume that the stream of names will never contain either duplicates or digits, and that it will always contain enough names for our input. Using parser combinators with a bit of mutable state The example above is a slightly simplified version of the parsing problem in this Stack Overflow question. I answered that question with a solution that looked roughly like this: import scala.util.parsing.combinator._ class ParenParser(names: Iterator[Char]) extends RegexParsers { def paren: Parser[List[(Char, String)]] = "(" ~> contents <~ ")" ^^ { case (s, m) => (names.next -> s) :: m } def contents: Parser[(String, List[(Char, String)])] = "\\d+".r ^^ (_ -> Nil) | rep1(paren) ^^ ( ps => ps.map(_.head._1).mkString -> ps.flatten ) def parse(s: String) = parseAll(paren, s).map(_.toMap) } It's not too bad, but I'd prefer to avoid the mutable state. What I want Haskell's Parsec library makes adding user state to a parser trivially easy: import Control.Applicative ((*>), (<$>), (<*)) import Data.Map (fromList) import Text.Parsec paren = do (s, m) <- char '(' *> contents <* char ')' h : t <- getState putState t return $ (h, s) : m where contents = flip (,) [] <$> many1 digit <|> (\ps -> (map (fst . head) ps, concat ps)) <$> many1 paren main = print $ runParser (fromList <$> paren) ['a'..'z'] "example" "((617)((0)(32)))" This is a fairly straightforward translation of my Scala parser above, but without mutable state. What I've tried I'm trying to get as close to the Parsec solution as I can using Scalaz's state monad transformer, so instead of Parser[A] I'm working with StateT[Parser, Stream[Char], A]. I have a "solution" that allows me to write the following: import scala.util.parsing.combinator._ import scalaz._, Scalaz._ object ParenParser extends ExtraStateParsers[Stream[Char]] with RegexParsers { protected implicit def monadInstance = parserMonad(this) def paren: ESP[List[(Char, String)]] = (lift("(" ) ~> contents <~ lift(")")).flatMap { case (s, m) => get.flatMap( names => put(names.tail).map(_ => (names.head -> s) :: m) ) } def contents: ESP[(String, List[(Char, String)])] = lift("\\d+".r ^^ (_ -> Nil)) | rep1(paren).map( ps => ps.map(_.head._1).mkString -> ps.flatten ) def parse(s: String, names: Stream[Char]) = parseAll(paren.eval(names), s).map(_.toMap) } This works, and it's not that much less concise than either the mutable state version or the Parsec version. But my ExtraStateParsers is ugly as sin—I don't want to try your patience more than I already have, so I won't include it here (although here's a link, if you really want it). I've had to write new versions of every Parser and Parsers method I use above for my ExtraStateParsers and ESP types (rep1, ~>, <~, and |, in case you're counting). If I had needed to use other combinators, I'd have had to write new state transformer-level versions of them as well. Is there a cleaner way to do this? I'd love to see an example of a Scalaz 7's state monad transformer being used to thread state through a parser, but Scala 6 or Haskell examples would also be useful.

    Read the article

  • Concrete Implementation of Generic Form Not Working in Designer

    - by Dov
    I have a base class, defined as below (I'm also using DevExpress components): public abstract partial class BaseFormClass<R> : XtraForm where R : DataRow { ... } Contrary to what I've read from elsewhere, I'm still able to design this class. I didn't have to create a concrete class from it to do so. But, when I create a concrete class descended from it (as below), that class won't work in the designer. public partial class ConcreteFormClass : BaseFormClass<StronglyTypedRow> { ... } I get this message: The designer could not be shown for this file because none of the classes within it can be designed. The designer inspected the following classes in the file: ConcreteFormClass --- The base class 'BaseFormClass' could not be loaded. Ensure the assembly has been referenced and that all projects have been built. Has anyone seen this before? Any sort of known workaround?

    Read the article

< Previous Page | 7 8 9 10 11 12 13 14 15 16 17 18  | Next Page >