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  • Why doesn't C++ allow you to request a pointer to the most derived class?

    - by Matthew Lowe
    (This question should probably be answered with a reference to Stroustrup.) It seems extremely useful to be able to request a pointer to the most derived class, as in the following: class Base { ... }; class DerivedA { ... }; class DerivedB { ... }; class Processor { public: void Do(Base* b) {...} void Do(DerivedA* d) {...} void Do(DerivedB* d) {...} }; list<Base*> things; Processor p; for(list<Base*>::iterator i=things.begin(), e=things.end(); i!=e; ++i) { p.Do(CAST_TO_MOST_DERIVED_CLASS(*i)); } But this mechanism isn't provided in c++. Why?

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  • Collision detection, visual C++

    - by hidden
    Hi, i am trying to do collision detection in visual C++ for a racing game. I found this site http://www.gamedev.net/reference/articles/article735.asp which seems like the thing i need. However i have no idea how to implement this in my code. The idea is that the players race around the course trying to find a tent with a red flag on it. When the collide witht this tent the game displays "player 1 wins" or whoever wins and then quits the game after 3 seconds. If you can help me please let me know as i am running out of time to get this to work. If you need me to send you the code then let me know that as well.

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  • What is the best way to declare a property?

    - by Simon
    Hi. We declare properties using the @property keyword and synthesize it in the implementation file. My question is, What if I declare a property using the @property keyword and also declare a variable in the interface block with the same name? For example, consider the following code, Interface: @interface myClass : NSObject { NSString *myClass_name; // LINE 1 } @property(nonatomic, retain) NSString *myClass_name; // LINE 2 @end Implementation: @implementation myClass @synthesize myClass_name // LINE 3 @end Declaring myClass_name in LINE 1 will make any problem? Like any reference problem or any unnecessary memory consumption problem?

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  • Detect double-tap on UISlider?

    - by Randy
    I can detect single/double-taps in specific views with: NSSet *myTouches = [event touchesForView:mySpecificView.view]; but I want to detect a double-tap on the button of a slider and can't find any reference to it. Is there a replacement for "touchesForView:" where I can enter the name of my slider? usage: I have three sliders with their default value being directly in the center of the slider. Once the position of the slider has changed, I want a quick way to individually reset each slider to its default position. I currently have each slider's containing view set to respond to a double-tap, updating each slider. It works fine, but doesn't seem natural. ie.I can't double-tap on the slider itself because the slider intercepts the taps and doesn't pass them on to the surrounding view. thanks in advance

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  • Creating attribute sets and attributes programatically magento

    - by digital_paki
    I am using the code listed on the following link =: http://www.magentocommerce.com/wiki/5_-_modules_and_development/catalog/programmatically_adding_attributes_and_attribute_sets Everything works until the point: // Just add a default group. else { $this->logInfo("Creating default group [{$this->groupName}] for set."); $modelGroup = Mage::getModel('eav/entity_attribute_group'); $modelGroup->setAttributeGroupName($this->groupName); $modelGroup->setAttributeSetId($id); // This is optional, and just a sorting index in the case of // multiple groups. // $modelGroup->setSortOrder(1); $model->setGroups(array($modelGroup)); } I am unsure where the object reference would need to be set from - I am attempting to have this as a separate file that can be automated - I am running this file by doing a require_once 'app/Mage.php'; Mage::app(); Any help in this would be greatly appreciated Thanks

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  • android spectrum analysis of streaming input

    - by TheBeeKeeper
    for a school project I am trying to make an android application that, once started, will perform a spectrum analysis of live audio received from the microphone or a bluetooth headset. I know I should be using FFT, and have been looking at moonblink's open source audio analyzer ( http://code.google.com/p/moonblink/wiki/Audalyzer ) but am not familiar with android development, and his code is turning out to be too difficult for me to work with. So I suppose my questions are, are there any easier java based, or open source android apps that do spectrum analysis I can reference? Or is there any helpful information that can be given, such as; steps that need be taken to get the microphone input, put it into an fft algorithm, then display a graph of frequency and pitch over time from its output? Any help would be appreciated, thanks.

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  • Wrap a list to add an empty row for UI binding.

    - by TheSean
    I am binding a List to a UI Control. My list does not contain a blank row, but I need to add one to allow the user to select blank. However, I'm using the same list in other parts of the application (users can edit/add/delete items) where it doesn't make sense to show a blank row. My idea is to create a wrapper around the list which adds a blank row just for the UI. The wrapper would hold a reference so that updates to the list (from other parts of the app) would be reflected in UI without any extra work. I have tried a few different ways, but nothing has worked out for me yet. Can anyone solve this problem?

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  • overwriting arguments in t-sql functions

    - by chuck taylor
    I was playing around with some code and realized that it is possible to overwrite the argument to a t-sql function. i.e., create function someFn(@date date) as begin if @date is null set @date = getdate() will set @date to be today's date if the argument was null. This appears only to make any sense if t-sql is treating their arguments as references not values. I realized that I don't actually know what the t-sql rules are for cases like this and was hoping someone could elaborate what is going on here. (I don't ever recall seeing any value vs. reference discussion with respect to t-sql code for that matter actually..)

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  • How do I access a DIV from javascript, if ASP.NET mangles its ID?

    - by Rising Star
    I have a web page that contains a "div" element. On the page, there is javascript to reference the div: document.getElementById('divId'). This was working fine until another developer redesigned the page to use an ASP master page. Now, document.getElementById('divId') returns null. It appears that ASP.net prepends some characters to the names of elements within contents forms when you use a master page. How can I know what the id of the div is when the page loads? Update Allow me to give a specific example to clarify the question: My page had a div with ID divNotice. After changing my page to use a master page, I see when I print the source to the page that renders that the div ID is ctl00_ContentPlaceHolder1_divNotice. My question is, how am I supposed to know what the div ID is going to be when the framework is done with it?

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  • Error while assigning the data to dataGrid Dataprovided

    - by sudeep kumar
    Hi , I was trying to acces the datagrid at runtime and want to assign the data to it like public function getGridData(reportsArray:ArrayCollection):void{ reportData = reportsArray; trace(" The length of the datagrid is "+reportData.length); graphDataGrid.dataProvider = reportData; invalidateDisplayList(); } but I was getting this error TypeError: Error #1009: Cannot access a property or method of a null object reference. at views.charts::ComparisonAnalysis/createDataGrid()[C:\FlexProjects\AdvancedMetering\views\charts\ComparisonAnalysis.mxml:32] at views.charts::ComparisonAnalysis/getGridData()[C:\FlexProjects\AdvancedMetering\views\charts\ComparisonAnalysis.mxml:26] at components.CustomReport::CustomReportSelector/getResultHandler()[C:\FlexProjects\AdvancedMetering\components\CustomReport\CustomReportSelector.mxml:147] at components.CustomReport::CustomReportSelector/__reportingBase_dataGridResultChanged()[C:\FlexProjects\AdvancedMetering\components\CustomReport\CustomReportSelector.mxml:203] at flash.events::EventDispatcher/dispatchEventFunction() at flash.events::EventDispatcher/dispatchEvent() at mx.core::UIComponent/dispatchEvent()[C:\autobuild\3.2.0\frameworks\projects\framework\src\mx\core\UIComponent.as:9298] at components.CustomReport::ReportingBase/getDataFromServer()[C:\FlexProjects\AdvancedMetering\components\CustomReport\ReportingBase.as:98] at components.CustomReport::ReportingBase/getResults()[C:\FlexProjects\AdvancedMetering\components\CustomReport\ReportingBase.as:78] at components.CustomReport::CustomReportSelector/getGraphData()[C:\FlexProjects\AdvancedMetering\components\CustomReport\CustomReportScripts.as:20] at components.CustomReport::CustomReportSelector/__getGraphandGridData_click()[C:\FlexProjects\AdvancedMetering\components\CustomReport\CustomReportSelector.mxml:248] Can someboedy please let me know what the problem it looks like the datagrid is not instantiated at this ppoint of time Sudee[

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  • Roundup of HTML 5 vulgarizations and resources

    - by ximus
    Hi everyone, HTML 5 is going to change the game not just for developers but will also come into the lives of professionals of all trades have an online presence, and web amateurs. These people are not web professionals but HTML and Flash have both been an important part of their general culture of the web. Vulgarization: to make (a technical or abstruse work) easier to understand and more widely known; popularize. (credits to reference.com) What links do you know of vulgarizations of HTML 5 that can help friends, family and colleagues better understand these up and coming changes of the web. Resources on all HTML5 subjects welcome; Fonts, animation, audio, video, offline capabilities, ... Here is a good start: Scribd presentation on their adoption of HTML 5

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  • DataGridView error when set DataSource

    - by user264464
    I got an error when run datagridview.DataSource = dataView; dataview is correct. I can see data inside it when I debug program. I got next error "Object reference not set to an instance of an object." Any Ideas? code: this.datagridview = new System.Windows.Forms.DataGridView(); ... DataSet ds = new DataSet(); XmlReaderSettings settings = new XmlReaderSettings(); StringReader stringReader = new StringReader(retString); XmlReader xmlReader = XmlReader.Create(stringReader, settings); ds.ReadXml(xmlReader); DataView dataView = ds.Tables[0].DefaultView; dataView is not null. I am able to view it when debug

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  • updated validation example for web api

    - by MonkeyBonkey
    I tried the validation example code for web api on the latest mvc 4 download and I'm getting some errors. Does anyone have an updated example of the ValidationActionFilter class. Here's the original code public class ValidationActionFilter : ActionFilterAttribute { public override void OnActionExecuting(HttpActionContext context) { var modelState = context.ModelState; if (!modelState.IsValid) { dynamic errors = new JsonObject(); foreach (var key in modelState.Keys) { var state = modelState[key]; if (state.Errors.Any()) { errors[key] = state.Errors.First().ErrorMessage; } } context.Response = new HttpResponseMessage<JsonValue>(errors, HttpStatusCode.BadRequest); } } } I'm getting an error on HttpResponseMessage The non-generic type 'System.Net.Http.HttpResponseMessage' cannot be used with type arguments Also it looks like I need to add a Json reference, but should I be using JSON.net instead? An example of this using Json.net?

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  • Tutorial on Consuming a WCF service in ASP.Net web site?

    - by Robert
    I'm attempting to create my first WCF service. I've created the service and now I'm trying to call it from a asp.net (vb) web site and I've tried adding a web reference to it and using the scvutil.exe to consume the service. So far neither have worked. It's not letting me declare the service in my code. If someone could point me to a good tutorial on how to consume a WCF service in an ASP.Net web site that would be great. I've found numorous on how to use them with AJAX or silverlight or windows apps but nothing on using it in just a plain old website.

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  • JSON Syntax, what is this?

    - by danp
    I understand concepts of JSON ok, but after starting to use ebay's api, I came across a notation which I've not seen before, and was wondering if anyone could explain what's going on with it? { "findItemsByKeywordsResponse": [ { "ack": [ "Success" ], "version": [ "1.5.0" ], "timestamp": [ "2010-06-16T08:42:21.468Z" ], "searchResult": [ { "@count": "0" } ], "paginationOutput": [ { "pageNumber": [ "0" ], "entriesPerPage": [ "10" ], "totalPages": [ "0" ], "totalEntries": [ "0" ] } ] } ] } What's the "@count" thing? I noticed when I reference it in chrome, it throws an error: But in Firefox not. JSON Lint reports it's valid, as I'd expect... ;)

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  • When did the idea of macros (user-defined code transformation) appear?

    - by Jay
    I have read McCarthy's 1960 paper on LISP and found no reference to anything that's similar to user-defined macros or normal order evaluation. I was wondering when marcos first appeared in programming language history (and also in Lisp history): When was the idea of user-defined code transformation (before interpretation or compilation) first described (theoretically)? What was the first programming language implementation to have Lisp-like macros (by "Lisp-like" I mean "using a readable Turing-complete language to do code-transformation")? (including non-Lisps -- Forth for example is quite old, but I'm not sure if the first Forth implementation already had "IMMEDIATE") What was the first Lisp dialect to have macros? Thank you!

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  • Visaul Studio 2010, TlbImp generates .net 4.0 interops in 2.0 projects

    - by DJScrib
    In a C# project we add a reference to a COM object via the Add References setup pointing to a COM object which results in the IDE auto-generating the interop assembly. So this is fine and good, but we are building based on .net 3.5 SP1 aka CLR 2.0, and the generated interops are using the 4.0 CLR making them incompatiable. Is there a way to prevent this? I assume the other option is in our build script to try using tlbimp.exe with the /references parameter? to point to mscorlib v2.0? Anyhow, I'm hoping there's a flag somewhere to allow this.

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  • Action method expected parameter named Id and nothing otherwise

    - by codingbiz
    The Error The parameters dictionary contains a null entry for parameter 'UserId' of non-nullable type 'System.Int64' for method 'System.Web.Mvc.ActionResult Predict(Int64)' in 'sportingbiz.Controllers.PredictionController'. An optional parameter must be a reference type, a nullable type, or be declared as an optional parameter. Parameter name: parameters This does not work. Throws the error mentioned above http://mysite/User/Profile/15 This works http://mysite/User/Profile/?UserID=15 The Controller Action public ActionResult Profile(long UserID) { } When I changed the parameter name to Id it works. I think it's because Id was specified in the route collection (Global.asax). Is it possible to tell MVC that UserId should map to Id without changing it in the Global.asax

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  • How should flushing be handled in a doctrine EntityManager instance shared across different services in symfony2?

    - by Jbm
    I have defined several services in symfony 2 which persist changes to the database. These services have the doctrine instance as one of their dependencies: a.given.service: class: Acme\TestBundle\Service\AGivenService arguments: [@doctrine] If I have two different services and both of them persist objects through the EntityManager, which is obtained like this from the doctrine instance: $em = $doctrine->getEntityManager(); Would all services always share the same EntityManager? If so, how should I handle flushing if I wanted to handle all the changes in a single transaction? I have checked this: http://docs.doctrine-project.org/projects/doctrine-orm/en/2.0.x/reference/transactions-and-concurrency.html and it explains how to handle different transactions in a request, but I want to achieve the opposite, which is having different changes in different services handled as a single transaction. Is there a better approach to handle multiple changes in different services? For now my best bet is having a front-end service in charge of calling the other services and doing the flushing afterwards. Backend services would persist objects but would not do any flushing.

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  • Struts 1 - problem in showing ActionMessages through a JSP page

    - by Yatendra Goel
    I am using Struts 1.3.10. I am trying to display ActionMessage and ActionError set by Action class through a JSP page. The problem is that the ActionErrors are displaying well but ActionMessages are not displaying. When I debug the application, I found that the messages (reference variable of ActionMessages) contains messages. I also saved those messages through saveMessages(request, messages) method of Action class. So, I think that the problem is in the JSP code through which I am trying to display those messages. The JSP code is as follows: <logic:messagesPresent> <ul id="messsages"> <html:messages id="msg" message="true"> <li><bean:write name="msg"/> </li> </html:messages> </ul> </logic:messagesPresent>

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  • How to expose a control collection to a property grid at design time

    - by Stefano Delendati
    I have a custom control that with a property that is a collection of custom object. This custom object hava a reference to some component/controls. When at design time I tray to add an item to the collection and select the object, VS tells me that the control is not serializable. This is the code (simplified version - but not to much): public class ViewRefObj { public control view { get; set; } public ViewRefObj() { } } private List<ViewRefObj> _controls=new List<ViewRefObj>(); public List<ViewRefObj> Views { get { return _controls; } }

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  • Lua Tables w/ Changing Variables - Mental Block

    - by bottles
    I always assumed that changing the value of k from "x" to 20 would eliminate "x". So why then in this example are we able to go back and reference "x"? a = {} k = "x" a[k] = 10 print(a[k]) ---> Returns 10 print(a["x"]) ---> Returns 10 a[20] = "great" k = 20 print(a[k]) ---> "great" a["x"] = a["x"] + 1 print(a["x"]) --> 11 Why does that last print command work, and return 11? I thought we set k = 20. Why is "x" even in the picture?

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  • GQL Query with __key__ in List of KEYs

    - by bossylobster
    In the GQL reference [1], it is encouraged to use the IN keyword with a list of values, and to construct a Key from hand the GQL query SELECT * FROM MyModel WHERE __key__ = KEY('MyModel', 'my_model_key') will succeed. However, using the code you would expect to work: SELECT * FROM MyModel WHERE __key__ IN (KEY('MyModel', 'my_model_key1'), KEY('MyModel', 'my_model_key2')) in the Datastore Viewer, there is a complaint of "Invalid GQL query string." What is the correct way to format such a query? [1] http://code.google.com/appengine/docs/python/datastore/gqlreference.html PS I know there are more efficient ways to do this in Python (without constructing a GQL query) and using the remote_api, but each call to the remote_api counts against quota. In an environment where quota is not (necessarily) free, quick and dirty queries are very helpful.

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  • C# app that uses Excel Interop, easy switch between 2003 2007?

    - by user320781
    I have an app written that just does really basic I/O on a spreadsheet. Read in a bunch of cells, do some sorting, and dump the output back into another spreadsheet. Works great on my machine. I have Office 2003 installed. When it runs on someone elses machine with 2007, it bombs, presumably due to the different versions of the Interop assemblies. I was hoping someone knew a way to dynamically change which/where the assembly is loaded from depending on the office version (getting the office version is easy from the registry). Sifting thru the rest of the internet, i didnt see anything to indicate that was possible :( . I tried installing the 2007 PIAs, but when i try to add a reference, they dont show up and i have no idea where to browse for them (they arent in the c:\windows\assemblies\; maybe the install didnt work). Am I going to have to get a machine with 2007 installed to build on every time i need to make updates?

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  • Creating simple c++.net wrapper. Step-by-step

    - by sfx
    I've a c++ project. I admit that I'm a complete ZERO in c++. But still I need to write a c++.net wrapper so I could work with an unmanaged c++ library using it. So what I have: 1) unmanaged project's header files. 2) unmanaged project's libraries (.dll's and .lib's) 3) an empty C++.NET project which I plan to use as a wrapper for my c# application How can I start? I don't even know how to set a reference to an unmanaged library. S.O.S.

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