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  • Permutations distinct under given symmetry (Mathematica 8 group theory)

    - by Yaroslav Bulatov
    Given a list of integers like {2,1,1,0} I'd like to list all permutations of that list that are not equivalent under given group. For instance, using symmetry of the square, the result would be {{2, 1, 1, 0}, {2, 1, 0, 1}}. Approach below (Mathematica 8) generates all permutations, then weeds out the equivalent ones. I can't use it because I can't afford to generate all permutations, is there a more efficient way? Update: actually, the bottleneck is in DeleteCases. The following list {2, 2, 2, 2, 2, 2, 2, 1, 1, 1, 1, 1, 1, 0, 0, 0} has about a million permutations and takes 0.1 seconds to compute. Apparently there are supposed to be 1292 orderings after removing symmetries, but my approach doesn't finish in 10 minutes removeEquivalent[{}] := {}; removeEquivalent[list_] := ( Sow[First[list]]; equivalents = Permute[First[list], #] & /@ GroupElements[group]; DeleteCases[list, Alternatives @@ equivalents] ); nonequivalentPermutations[list_] := ( reaped = Reap@FixedPoint[removeEquivalent, Permutations@list]; reaped[[2, 1]] ); group = DihedralGroup[4]; nonequivalentPermutations[{2, 1, 1, 0}]

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  • Fixing Combinatorica redefinition of Element

    - by Yaroslav Bulatov
    My code relies on version of Element which works like MemberQ, but when I load Combinatorica, Element gets redefined to work like Part. What is the easiest way to fix this conflict? Specifically, what is the syntax to remove Combinatorica's definition from DownValues? Here's what I get for DownValues[Element] {HoldPattern[ Combinatorica`Private`a_List \[Element] \ {Combinatorica`Private`index___}] :> Combinatorica`Private`a[[Combinatorica`Private`index]], HoldPattern[Private`x_ \[Element] Private`list_List] :> MemberQ[Private`list, Private`x]}

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  • Django QuerySet filter method returns multiple entries for one record

    - by Yaroslav
    Trying to retrieve blogs (see model description below) that contain entries satisfying some criteria: Blog.objects.filter(entries__title__contains='entry') The results is: [<Blog: blog1>, <Blog: blog1>] The same blog object is retrieved twice because of JOIN performed to filter objects on related model. What is the right syntax for filtering only unique objects? Data model: class Blog(models.Model): name = models.CharField(max_length=100) def __unicode__(self): return self.name class Entry(models.Model): title = models.CharField(max_length=100) blog = models.ForeignKey(Blog, related_name='entries') def __unicode__(self): return self.title Sample data: b1 = Blog.objects.create(name='blog1') e1 = Entry.objects.create(title='entry 1', blog=b1) e1 = Entry.objects.create(title='entry 2', blog=b1)

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  • Duplex Contract GetCallbackChannel always returns a null-instance

    - by Yaroslav
    Hi! Here is the server code: using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.ServiceModel; using System.Runtime.Serialization; using System.ServiceModel.Description; namespace Console_Chat { [ServiceContract(SessionMode = SessionMode.Required, CallbackContract = typeof(IMyCallbackContract))] public interface IMyService { [OperationContract(IsOneWay = true)] void NewMessageToServer(string msg); [OperationContract(IsOneWay = false)] bool ServerIsResponsible(); } [ServiceContract] public interface IMyCallbackContract { [OperationContract(IsOneWay = true)] void NewMessageToClient(string msg); [OperationContract(IsOneWay = true)] void ClientIsResponsible(); } [ServiceBehavior(InstanceContextMode = InstanceContextMode.PerSession)] public class MyService : IMyService { public IMyCallbackContract callback = null; /* { get { return OperationContext.Current.GetCallbackChannel<IMyCallbackContract>(); } } */ public MyService() { callback = OperationContext.Current.GetCallbackChannel<IMyCallbackContract>(); } public void NewMessageToServer(string msg) { Console.WriteLine(msg); } public void NewMessageToClient( string msg) { callback.NewMessageToClient(msg); } public bool ServerIsResponsible() { return true; } } class Server { static void Main(string[] args) { String msg = "none"; ServiceMetadataBehavior behavior = new ServiceMetadataBehavior(); ServiceHost serviceHost = new ServiceHost( typeof(MyService), new Uri("http://localhost:8080/")); serviceHost.Description.Behaviors.Add(behavior); serviceHost.AddServiceEndpoint( typeof(IMetadataExchange), MetadataExchangeBindings.CreateMexHttpBinding(), "mex"); serviceHost.AddServiceEndpoint( typeof(IMyService), new WSDualHttpBinding(), "ServiceEndpoint" ); serviceHost.Open(); Console.WriteLine("Server is up and running"); MyService server = new MyService(); server.NewMessageToClient("Hey client!"); /* do { msg = Console.ReadLine(); // callback.NewMessageToClient(msg); } while (msg != "ex"); */ Console.ReadLine(); } } } Here is the client's: using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.ServiceModel; using System.Runtime.Serialization; using System.ServiceModel.Description; using Console_Chat_Client.MyHTTPServiceReference; namespace Console_Chat_Client { [ServiceContract(SessionMode = SessionMode.Required, CallbackContract = typeof(IMyCallbackContract))] public interface IMyService { [OperationContract(IsOneWay = true)] void NewMessageToServer(string msg); [OperationContract(IsOneWay = false)] bool ServerIsResponsible(); } [ServiceContract] public interface IMyCallbackContract { [OperationContract(IsOneWay = true)] void NewMessageToClient(string msg); [OperationContract(IsOneWay = true)] void ClientIsResponsible(); } public class MyCallback : Console_Chat_Client.MyHTTPServiceReference.IMyServiceCallback { static InstanceContext ctx = new InstanceContext(new MyCallback()); static MyServiceClient client = new MyServiceClient(ctx); public void NewMessageToClient(string msg) { Console.WriteLine(msg); } public void ClientIsResponsible() { } class Client { static void Main(string[] args) { String msg = "none"; client.NewMessageToServer(String.Format("Hello server!")); do { msg = Console.ReadLine(); if (msg != "ex") client.NewMessageToServer(msg); else client.NewMessageToServer(String.Format("Client terminated")); } while (msg != "ex"); } } } } callback = OperationContext.Current.GetCallbackChannel(); This line constanly throws a NullReferenceException, what's the problem? Thanks!

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  • Xaml parse exception is thrown when i define a duplex contract

    - by Yaroslav
    Hi! I've got a WPF application containing a WCF service. The Xaml code is pretty simple: Enter your text here Send Address: Here is the service: namespace WpfApplication1 { [ServiceContract(CallbackContract=typeof(IMyCallbackContract))] public interface IMyService { [OperationContract(IsOneWay = true)] void NewMessageToServer(string msg); [OperationContract(IsOneWay = true)] bool ServerIsResponsible(); } [ServiceContract] public interface IMyCallbackContract { [OperationContract] void NewMessageToClient(string msg); [OperationContract] void ClientIsResponsible(); } /// <summary> /// Interaction logic for Window1.xaml /// </summary> public partial class Window1 : Window { public Window1() { InitializeComponent(); ServiceMetadataBehavior behavior = new ServiceMetadataBehavior(); //behavior.HttpGetEnabled = true; //behavior. ServiceHost serviceHost = new ServiceHost( typeof(MyService), new Uri("net.tcp://localhost:8080/")); serviceHost.Description.Behaviors.Add(behavior); serviceHost.AddServiceEndpoint( typeof(IMetadataExchange), MetadataExchangeBindings.CreateMexTcpBinding(), "mex"); serviceHost.AddServiceEndpoint( typeof(IMyService), new NetTcpBinding(), "ServiceEndpoint"); serviceHost.Open(); MessageBox.Show( "server is up"); // label1.Content = label1.Content + String.Format(" net.tcp://localhost:8080/"); } } public class MyService : IMyService { public void NewMessageToServer(string msg) { } public bool ServerIsResponsible() { return true; } } } I am getting a Xaml parse exception in Line 1, what can be the problem? Thanks!

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  • google docs for asp.net mvc

    - by Yaroslav Yakovlev
    Where can I get code example of using google docs with asp.net mvc? I need to upload documents and make it possible for people to download them. Also would be just great to make it possible to see the documents like I see them on google docs and be able to edit (probably use iFrame) but would like to get working example or some tips to get started. Code pieces are greatly appreciated, upvoted and marked as answer ;-), but I~ll be enought with a good starting points. P.S. I~m aware of google have docs for their api :-). Just looking for other places to start from. Codeproject article or github repo of api used with asp.net mvc would be the best.

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  • Match subpatterns in any order

    - by Yaroslav
    I have long regexp with two complicated subpatters inside. How i can match that subpatterns in any order? Simplified example: /(apple)?\s?(banana)?\s?(orange)?\s?(kiwi)?/ and i want to match both of apple banana orange kiwi apple orange banana kiwi It is very simplified example. In my case banana and orange is long complicated subpatterns and i don't want to do something like /(apple)?\s?((banana)?\s?(orange)?|(orange)?\s?(banana)?)\s?(kiwi)?/ Is it possible to group subpatterns like chars in character class? UPD Real data as requested: 14:24 26,37 Mb 108.53 01:19:02 06.07 24.39 19:39 46:00 my strings much longer, but it is significant part. Here you can see two lines what i need to match. First has two values: length (14 min 24 sec) and size 26.37 Mb. Second one has three values but in different order: size 108.53 Mb, length 01 h 19 m 02 s and date June, 07 Third one has two size and length Fourth has only length There are couple more variations and i need to parse all values. I have a regexp that pretty close except i can't figure out how to match patterns in different order without writing it twice. (?<size>\d{1,3}\[.,]\d{1,2}\s+(?:Mb)?)?\s? (?<length>(?:(?:01:)?\d{1,2}:\d{2}))?\s* (?<date>\d{2}\.\d{2}))? NOTE: that is only part of big regexp that forks fine already.

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  • Can I rewrite the whole url?

    - by Yaroslav Yakovlev
    I need to rewrite the whole url. E.g. I have a http://UrlToRewrite.com/default.aspx?myParams=myvalues and I need it to be http://SingleUrl.com Is it possible to make such a thing with default url rewriters? Another question is, is it possible to make the same thing, but depending on the parameter destination url will be http://SingleUrl1.com and http://SingleUrl2.com.

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  • Is there a way to force ContourPlot re-check all the points on the each stage of it's recursion algorithm?

    - by Alexey Popkov
    Hello, Thanks to this excellent analysis of the Plot algorithm by Yaroslav Bulatov, I now understand the reason why Plot3D and ContourPlot fail to draw smoothly functions with breaks and discontinuities. For example, in the following case ContourPlot fails to draw contour x^2 + y^2 = 1 at all: ContourPlot[Abs[x^2 + y^2 - 1], {x, -1, 1}, {y, -1, 1}, Contours -> {0}] It is because the algorithm does not go deeply into the region near x^2 + y^2 = 1. It "drops" this region on an initial stage and do not tries to investigate it further. Increasing MaxRecursion does nothing in this sense. And even undocumented option Method -> {Refinement -> {ControlValue -> .01 \[Degree]}} does not help (but makes Plot3D a little bit smoother). The above function is just a simple example. In real life I'm working with very complicated implicit functions that cannot be solved analytically. Is there a way to get ContourPlot to go deeply into such regions near breaks and discontinuities?

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