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  • Is a red-black tree my ideal data structure?

    - by Hugo van der Sanden
    I have a collection of items (big rationals) that I'll be processing. In each case, processing will consist of removing the smallest item in the collection, doing some work, and then adding 0-2 new items (which will always be larger than the removed item). The collection will be initialised with one item, and work will continue until it is empty. I'm not sure what size the collection is likely to reach, but I'd expect in the range 1M-100M items. I will not need to locate any item other than the smallest. I'm currently planning to use a red-black tree, possibly tweaked to keep a pointer to the smallest item. However I've never used one before, and I'm unsure whether my pattern of use fits its characteristics well. 1) Is there a danger the pattern of deletion from the left + random insertion will affect performance, eg by requiring a significantly higher number of rotations than random deletion would? Or will delete and insert operations still be O(log n) with this pattern of use? 2) Would some other data structure give me better performance, either because of the deletion pattern or taking advantage of the fact I only ever need to find the smallest item? Update: glad I asked, the binary heap is clearly a better solution for this case, and as promised turned out to be very easy to implement. Hugo

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  • Weird generics compile error.

    - by Jouke van der Maas
    I have two classes, a base class and a child class. In the base class i define a generic virtual method: protected virtual Bar Foo<T() where T : Bar {} Then in my child class i try to do this: protected override BarChild Foo() // BarChild inherits Bar { return base.Bar<T as BarChild() } Visual studio gives this weird error: The type 'T' cannot be used as type parameter 'T' in the generic type or method 'Foo()'. There is no boxing conversion or type parameter conversion from 'T' to 'Bar'. Repeating the where clause on the child's override also gives an error: Constraints for override and explicit interface implementation methods are inherited from the base method, so they cannot be specified directly So what am i doing wrong here?

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  • .Net SvcUtil: attributes must be optional

    - by Michel van Engelen
    Hi, I'm trying to generate C# code classes with SvcUtil.exe instead of Xsd.exe. The latter is giving me some problems. Command line: SvcUtil.exe myschema.xsd /dconly /ser:XmlSerializer Several SvcUtil problems are described and solved here: http://blog.shutupandcode.net/?p=761 One problem I can't solve is this one: Error: Type 'DatafieldDescription' in namespace '' cannot be imported. Attributes must be optional and from namespace 'http://schemas.microsoft.com/2003/10/Seri alization/'. Either change the schema so that the types can map to data contract types or use ImportXmlType or use a different serializer. ' I changed <xs:attribute name="Order" use="required"> to <xs:attribute name="Order" use="optional"> and <xs:attribute name="Order"> But the error remains. Is it possible to use attributes, or do I have to delete them all (in that case, this excercition is over)?

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  • Why do C# automatic properties not support default values like VB 2010?

    - by Rob van Groenewoud
    Looking at the new VB 2010 features, I stumbled upon support for Auto-Implemented Properties. Since I'm working with C#, this seemed quite familiar, but I noticed that VB did add a feature I would love to have in C#: setting a arbitrary default value for the auto-implemented property: I really like the clean usage of auto-properties in C#. This would save us the effort of introducing a backing field and hooking it up to the property everytime we simply need a default value, thereby cluttering up the code unnecessarily. I was wondering why this wasn't introduced in C# as well? What could be the rationale for not doing this? Is a syntax discussion going on, or are there technical limitations to implementing this?

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  • Returning a JSON view in combination with a boolean

    - by Rody van Sambeek
    What i would like to accomplish is that a partiel view contains a form. This form is posted using JQuery $.post. After a successfull post javascript picks up the result and uses JQuery's html() method to fill a container with the result. However now I don't want to return the Partial View, but a JSON object containing that partial view and some other object (Success - bool in this case). I tried it with the following code: [AcceptVerbs(HttpVerbs.Post)] public ActionResult Edit(int id, Item item) { if (ModelState.IsValid) { try { // ... return Json(new { Success = true, PartialView = PartialView("Edit", item) }); } catch(Exception ex) { // ... } } return Json(new { Success = false, PartialView = PartialView("Edit", item) }); } However I don't get the HTML in this JSON object and can't use html() to show the result. I tried using this method to render the partial as Html and send that. However this fails on the RenderControl(tw) method with a: The method or operation is not implemented.

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  • Generic object to object mapping with parametrized constructor

    - by Rody van Sambeek
    I have a data access layer which returns an IDataRecord. I have a WCF service that serves DataContracts (dto's). These DataContracts are initiated by a parametrized constructor containing the IDataRecord as follows: [DataContract] public class DataContractItem { [DataMember] public int ID; [DataMember] public string Title; public DataContractItem(IDataRecord record) { this.ID = Convert.ToInt32(record["ID"]); this.Title = record["title"].ToString(); } } Unfortanately I can't change the DAL, so I'm obliged to work with the IDataRecord as input. But in generat this works very well. The mappings are pretty simple most of the time, sometimes they are a bit more complex, but no rocket science. However, now I'd like to be able to use generics to instantiate the different DataContracts to simplify the WCF service methods. I want to be able to do something like: public T DoSomething<T>(IDataRecord record) { ... return new T(record); } So I'd tried to following solutions: Use a generic typed interface with a constructor. doesn't work: ofcourse we can't define a constructor in an interface Use a static method to instantiate the DataContract and create a typed interface containing this static method. doesn't work: ofcourse we can't define a static method in an interface Use a generic typed interface containing the new() constraint doesn't work: new() constraint cannot contain a parameter (the IDataRecord) Using a factory object to perform the mapping based on the DataContract Type. does work, but: not very clean, because I now have a switch statement with all mappings in one file. I can't find a real clean solution for this. Can somebody shed a light on this for me? The project is too small for any complex mapping techniques and too large for a "switch-based" factory implementation.

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  • Entity Framework v4 examples and tutorials of conceptual model mapping

    - by Rody van Sambeek
    In an application I'm writing I have a fairly complicated Database model. I'd like to use EF4 to map this to a whole lot nicer conceptual model. However all the tutorials I've read are with samples of 2 or 3 tables which all map 1 on 1 to the conceptual model. I'd like to learn how to correctly map the database model to a different conceptual model using VS 2010. However I can't find any good tutorials or (preferabally) instruction video's. Somebody got any tips, links or even books?

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  • Nested asynchronous calls do not seem to execute as expected

    - by Kristof Van Landschoot
    While trying out jQuery, I have a question that is probably a newbie mistake, but I cannot seem to find the solution. This is the code: $.get("index.html", function() { var i = 0; for (; i < 3; i++) { var lDiv = document.createElement('div'); lDiv.id = 'body-' + i; document.getElementById('body').appendChild(lDiv); $.get('index.html', function(data) { lDiv.innerHTML = "<p>Hello World " + i + "</p>"; }); } }); The output seems to be <div id='body-0'></div> <div id='body-1'></div> <div id='body-2'> <p>Hello World 3</p> </div> I expected the lDiv.innerHTML= code to be executed for each i, but apparently it is only executed for the last i? What am I overlooking?

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  • Why does my token return NULL and how can I fix it?(c++)

    - by Van
    I've created a program to get a string input from a user and parse it into tokens and move a robot according to the input. The program is supposed to recognize these inputs(where x is an integer): "forward x" "back x" "turn left x" "turn right x" and "stop". The program does what it's supposed to for all commands except for "stop". When I type "stop" the program prints out "whats happening?" because I've written a line which states: if(token == NULL) { cout << "whats happening?" << endl; } Why does token get NULL, and how can I fix this so it will read "stop" properly? here is the code: bool stopper = 0; void Navigator::manualDrive() { VideoStream video(&myRobot, 0);//allows user to see what robot sees video.startStream(); const int bufSize = 42; char uinput[bufSize]; char delim[] = " "; char *token; while(stopper == 0) { cout << "Enter your directions below: " << endl; cin.getline(uinput,bufSize); Navigator::parseInstruction(uinput); } } /* parseInstruction(char *c) -- parses cstring instructions received * and moves robot accordingly */ void Navigator::parseInstruction(char * uinput) { char delim[] = " "; char *token; // cout << "Enter your directions below: " << endl; // cin.getline (uinput, bufSize); token=strtok(uinput, delim); if(token == NULL) { cout << "whats happening?" << endl; } if(strcmp("forward", token) == 0) { int inches; token = strtok(NULL, delim); inches = atoi (token); double value = fabs(0.0735 * fabs(inches) - 0.0550); myRobot.forward(1, value); } else if(strcmp("back",token) == 0) { int inches; token = strtok(NULL, delim); inches = atoi (token); double value = fabs(0.0735 * fabs(inches) - 0.0550); myRobot.backward(1/*speed*/, value/*time*/); } else if(strcmp("turn",token) == 0) { int degrees; token = strtok(NULL, delim); if(strcmp("left",token) == 0) { token = strtok(uinput, delim); degrees = atoi (token); double value = fabs(0.00467 * degrees - 0.04); myRobot.turnLeft(1/*speed*/, value/*time*/); } else if(strcmp("right",token) == 0) { token = strtok(uinput, delim); degrees = atoi (token); double value = fabs(0.00467 * degrees - 0.04); myRobot.turnRight(1/*speed*/, value/*time*/); } } else if(strcmp("stop",token) == 0) { stopper = 1; } else { std::cerr << "Unknown command '" << token << "'\n"; } } /* autoDrive() -- reads in file from ifstream, parses * and moves robot according to instructions in file */ void Navigator::autoDrive(string filename) { const int bufSize = 42; char fLine[bufSize]; ifstream infile; infile.open("autodrive.txt", fstream::in); while (!infile.eof()) { infile.getline(fLine, bufSize); Navigator::parseInstruction(fLine); } infile.close(); } I need this to break out of the while loop and end manualDrive because in my driver program the next function called is autoDrive.

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  • Track pageviews in Google Analytics on partial url of Grails application

    - by Pieter van Gent
    For my Grails application I want to set up Google Analytics to track only "partial" url's. I 'll explain: a typical Grails url consists of the following parts: domain + application-name + controller + action + id e.g. www.mydomain.com/myapp/controller/action/12345 As far as I understand for Google Analytics the page to be tracked is identified by the entire url. For my purpose I'm not interested in the id part of the url: I want to know which actions have been performed, but I need not know for which id the action was executed. And of course I would like a generic solution, because I have multiple controllers and multiple actions... Maybe some kind of filter stating "I want to track pages 3 levels deep (/myapp/controller/action)" would do? Or a filter stating "exclude everything from url after the last /"? Any help would be much appreciated. Kind regards, Pieter

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  • Why can't I share a variable between two content sections in an ASP.NET MVC View?

    - by Dave Van den Eynde
    I have an ASP.NET MVC View with the typical TitleContent and MainContent, with a fairly complicated title that I want to calculate once and then share between these two content sections, like so: <%@ Page Title="" Language="C#" MasterPageFile="~/Views/Shared/Site.Master" Inherits="System.Web.Mvc.ViewPage<dynamic>" %> <% var complicatedTitle = string.Format("{0} - {1}", Model.FirstThing, Model.SecondThing); %> <asp:Content ID="Content1" ContentPlaceHolderID="TitleContent" runat="server"> <%: complicatedTitle %> </asp:Content> <asp:Content ID="Content2" ContentPlaceHolderID="MainContent" runat="server"> <h2><%: complicatedTitle %></h2> </asp:Content> This, however, doesn't work, as the resulting error message would say that only Content controls are allowed directly in a content page that contains Content controls. The calculation definately belongs in the view. How do you solve this problem?

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  • Generate an ID via COM interop

    - by Erik van Brakel
    At the moment, we've got an unmaintanable ball of code which offers an interface to a third party application. The third party application has a COM assembly which MUST be used to create new entries. This process involves two steps: generate a new object (basically an ID), and update that object with new field values. Because COM interop is so slow, we only use that to generate the ID (and related objects) in the database. The actual update is done using a regular SQL query. What I am trying to figure out if it's possible to use NHibernate to do some of the heavy lifting for us, without bypassing the COM assembly. Here's the code for saving something to the database as I envision it: using(var s = sessionFactory.OpenSession()) using(var t = s.BeginTransaction()) { MyEntity entity = new MyEntity(); s.Save(entity); t.Commit(); } Regular NH code I'd say. Now, this is where it gets tricky. I think I have to supply my own implementation of NHibernate.Id.IIdentifierGenerator which calls the COM assembly in the Generate method. That's not a problem. What IS a problem is that the COM assembly requires initialisation, which does take a bit of time. It also doesn't like multiple instances in the same process, for some reason. What I would like to know is if there's a way to properly access an external service in the generator code. I'm free to use any technique I want, so if it involves something like an IoC container that's no problem. The thing I am looking for is where exactly to hook-up my code so I can access the things I need in my generator, without having to resort to using singletons or other nasty stuff.

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  • Using a variable as identifier in a json array

    - by Robbert van den Bogerd
    Hi folks! I'm wondering if it is possible to use assigned variables as identifier in a json array. When I tried this, I was getting some unexpected results: (Code is simplified, parameters are passed in a different way) var parameter = 'animal'; var value = 'pony'; Util.urlAppendParameters (url, {parameter : value}); Util.urlAppendParameters = function(url, parameters) { for (var x in parameters) { alert(x); } } Now the alert popup says: 'parameter' instead of 'animal'. I know I could use a different method (creating an array and assigning every parameter on a new line), but I want to keep my code compact. So my question is: Is it possible to use a variable as an identifier in the json array, and if so, could you please tell me how? Thanks in advance!

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  • How to 'convert' char to function in C

    - by Tim van Elsloo
    Hi, void someFunction() { char *function = "anotherFunction"; const char *params[] = {"aVal","bVal","cVal"}; // How can I call the *function with the *params? } void anotherFunction(char *aKey, char *bKey, char *cKey) { // Do something with *aKey, *bKey and *cKey; } Does someone know how to call the *function with the *params? Thanks in advance, Tim

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  • How to 'do' ByVal in C#

    - by Jouke van der Maas
    As I understand it, C# passes parameters into methods by reference. In vb.net, you can specify this with ByVal and ByRef. The default is ByVal. Is this for compatibility with vb6, or is it just random? Also, how can I specify what to use in C#? I kind of like the idea of passing parameters by value.

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  • How to set up source control in VS2010

    - by Jouke van der Maas
    Hi, I want to set up source control for my project, but it seems like I need a server for this. I've never done this before, and I couldn't find anything helpfull yet. Is there any way to host a server locally so Visual studio can use it? Or do you know any online (free) servers I can use? By the way, if source control is not actually what i should use for keeping track of changes in my files, please suggest a better option. Thanks in advance.

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  • Basic Profanity Filter in Objective C for iPhone

    - by David van Dugteren
    How have you like minded individuals tackled the basic challenge of filtering profanity, obviously one can't possibly tackle every scenario but it would be nice to have one at the most basic level as a first line of defense. In Obj-c I've got NSString *tokens = [text componentsSeparatedByString:@" "]; And then I loop through each token to see if any of the keywords (I've got about 400 in a list) are found within each token. Realising False positives are also a problem, if the word is a perfect match, its flagged as profanity otherwise if more than 3 words with profanity are found without being perfect matches it is also flagged as profanity. Later on I will use a webservice that tackles the problem more precisely, but I really just need something basic. So if you wrote the word penis it would go yup naughty naughty, bad word written.

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  • Byte from string/int in C++

    - by Tim van Elsloo
    Hi, I'm a beginning user in C++ and I want to know how to do this: How can I 'create' a byte from a string/int. So for example I've: string some_byte = "202"; When I would save that byte to a file, I want that the file is 1 byte instead of 3 bytes. How is that possible? Thanks in advance, Tim

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  • How can you remove a field from a word document?

    - by Kevin van Zanten
    Dear reader, I'm working on a project where the user can insert data into a document using fields, document properties and variables. The user also needs to be able to remove the data from the document. So far, I've managed to remove the document property and variable, but I'm not sure how I would go about removing the field (that's already inserted into the document). Please advise. Yours sincerely, Kevin

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  • XSS as attack vector even if XSS data not stored?

    - by Klaas van Schelven
    I have a question about XSS Can forms be used as a vector for XSS even if the data is not stored in the database and used at a later point? i.e. in php the code would be this: <form input="text" value="<?= @$_POST['my_field'] ?>" name='my_field'> Showing an alert box (demonstrate that JS can be run) on your own browser is trivial with the code above. But is this exploitable across browsers as well? The only scenario I see is where you trick someone into visiting a certain page, i.e. a combination of CSRF and XSS. "Stored in a database and used at a later point": the scenario I understand about CSS is where you're able to post data to a site that runs JavaScript and is shown on a page in a browser that has greater/different privileges than your own. But, to be clear, this is not wat I'm talking about above.

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  • Netbeans 7.2 won't open on OS X

    - by Mark van Wyk
    I installed Netbeans on OSX Mountain Lion running JDK 7. Everything was working fine. Then my machine for no reason crashed. After this I could no longer open Netbeans anymore. If I try to start Netbeans from the commandline: /Applications/NetBeans/NetBeans 7.2.app/Contents/MacOS/netbeans Then it works fine. From there I can select Netbeans About and confirm that my userdir and cachedir is: User directory: /Users/<user>/Library/Application Support/NetBeans/7.2 Cache directory: /Users/<user>/Library/Caches/NetBeans/7.2 So, I deleted these directories and tried again, but alas, I can only start netbeans via the commandline. Ideas appreciated...

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