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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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  • How to expose a Delphi set type via Soap

    - by Wouter van Nifterick
    I'm currently creating soap wrappers for some Delphi functions so that we can easily use them from PHP, C# and Delphi. I wonder what's the best way to expose sets. type TCountry = (countryUnknown,countryNL,countryD,countryB,countryS,countryFIN,countryF,countryE,countryP,countryPl,countryL); TCountrySet = set of TCountry; function GetValidCountrySet(const LicensePlate:string; const PossibleCountriesSet:TCountrySet):TCountrySet; I'm currently wrapping it like this for the soap server: type TCountryArray = array of TCountry; function TVehicleInfo.GetValidCountrySet(const LicensePlate:string; const PossibleCountriesSet:TCountryArray):TCountryArray; It works, but I need to write a lot of useless and ugly code to convert sets--arrays and arrays--sets. Is there an easier, more elegant, or more generic way to do this?

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  • Access generic type parameter at runtime?

    - by Bart van Heukelom
    Event dispatcher interface public interface EventDispatcher { <T> EventListener<T> addEventListener(EventListener<T> l); <T> void removeEventListener(EventListener<T> l); } Implementation public class DefaultEventDispatcher implements EventDispatcher { @SuppressWarnings("unchecked") private Map<Class, Set<EventListener>> listeners = new HashMap<Class, Set<EventListener>>(); public void addSupportedEvent(Class eventType) { listeners.put(eventType, new HashSet<EventListener>()); } @Override public <T> EventListener<T> addEventListener(EventListener<T> l) { Set<EventListener> lsts = listeners.get(T); // ****** error: cannot resolve T if (lsts == null) throw new RuntimeException("Unsupported event type"); if (!lsts.add(l)) throw new RuntimeException("Listener already added"); return l; } @Override public <T> void removeEventListener(EventListener<T> l) { Set<EventListener> lsts = listeners.get(T); // ************* same error if (lsts == null) throw new RuntimeException("Unsupported event type"); if (!lsts.remove(l)) throw new RuntimeException("Listener is not here"); } } Usage EventListener<ShapeAddEvent> l = addEventListener(new EventListener<ShapeAddEvent>() { @Override public void onEvent(ShapeAddEvent event) { // TODO Auto-generated method stub } }); removeEventListener(l); I've marked two errors with a comment above (in the implementation). Is there any way to get runtime access to this information?

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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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  • PHP autoloader: ignoring non-existing include

    - by Bart van Heukelom
    I have a problem with my autoloader: public function loadClass($className) { $file = str_replace(array('_', '\\'), '/', $className) . '.php'; include_once $file; } As you can see, it's quite simple. I just deduce the filename of the class and try to include it. I have a problem though; I get an exception when trying to load a non-existing class (because I have an error handler which throws exceptions). This is inconvenient, because it's also fired when you use class_exists() on a non-existing class. You don't want an exception there, just a "false" returned. I fixed this earlier by putting an @ before the include (supressing all errors). The big drawback with this, though, is that any parser/compiler errors (that are fatal) in this include won't show up (not even in the logs), resulting in a hard to find bug. What would be the best way to solve both problems at once? The easiest way would be to include something like this in the autoloader (pseudocode): foreach (path in the include_path) { if (is_readable(the path + the class name)) readable = true; } if (!readable) return; But I worry about the performance there. Would it hurt a lot? (Solved) Made it like this: public function loadClass($className) { $file = str_replace(array('_', '\\'), '/', $className) . '.php'; $paths = explode(PATH_SEPARATOR, get_include_path()); foreach ($paths as $path) { if (is_readable($path . '/' . $file)) { include_once $file; return; } } }

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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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  • 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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  • 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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  • 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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  • 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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  • 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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  • Modifying multiplying calculation to use delta time

    - by Bart van Heukelom
    function(deltaTime) { x = x * 0.9; } This function is called in a game loop. First assume that it's running at a constant 30 FPS, so deltaTime is always 1/30. Now the game is changed so deltaTime isn't always 1/30 but becomes variable. How can I incorporate deltaTime in the calculation of x to keep the "effect per second" the same?

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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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  • How to write custom (odd) authentication plugins for Wordpress, Joomla and MediaWiki?

    - by Bart van Heukelom
    On our network (a group of related websites - not a LAN) we have a common authentication system which works like this: On a network site ("consumer") the user clicks on a login link This redirects the user to a login page on our auth system ("RAS"). Upon successful login the user is directed back to the consumer site. Extra data is passed in the query string. This extra data does not include any information about the user yet. The consumer site's backend contacts RAS, with this extra data, to get the information about the logged in user (id, name, email, preferences, etc.). So as you can see, the consumer site knows nothing about the authentication method. It doesn't know if it's by username/password, fingerprint, smartcard, or winning a game of poker. This is the main problem I'm encountering when trying to find out how I could write custom authentication plugins for these packages, acting as consumer sites: Wordpress Joomla MediaWiki For example Joomla offers a pretty simple auth plugin system, but it depends on a username/password entered on the Joomla site. Any hints on where to start?

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