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  • Type-safe generic data structures in plain-old C?

    - by Bradford Larsen
    I have done far more C++ programming than "plain old C" programming. One thing I sorely miss when programming in plain C is type-safe generic data structures, which are provided in C++ via templates. For sake of concreteness, consider a generic singly linked list. In C++, it is a simple matter to define your own template class, and then instantiate it for the types you need. In C, I can think of a few ways of implementing a generic singly linked list: Write the linked list type(s) and supporting procedures once, using void pointers to go around the type system. Write preprocessor macros taking the necessary type names, etc, to generate a type-specific version of the data structure and supporting procedures. Use a more sophisticated, stand-alone tool to generate the code for the types you need. I don't like option 1, as it is subverts the type system, and would likely have worse performance than a specialized type-specific implementation. Using a uniform representation of the data structure for all types, and casting to/from void pointers, so far as I can see, necessitates an indirection that would be avoided by an implementation specialized for the element type. Option 2 doesn't require any extra tools, but it feels somewhat clunky, and could give bad compiler errors when used improperly. Option 3 could give better compiler error messages than option 2, as the specialized data structure code would reside in expanded form that could be opened in an editor and inspected by the programmer (as opposed to code generated by preprocessor macros). However, this option is the most heavyweight, a sort of "poor-man's templates". I have used this approach before, using a simple sed script to specialize a "templated" version of some C code. I would like to program my future "low-level" projects in C rather than C++, but have been frightened by the thought of rewriting common data structures for each specific type. What experience do people have with this issue? Are there good libraries of generic data structures and algorithms in C that do not go with Option 1 (i.e. casting to and from void pointers, which sacrifices type safety and adds a level of indirection)?

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  • How can I bind a LinkedList as ItemSource to ListView in WPF XAML?

    - by Jonas
    I'm learning WPF and would like to have a collection similar to a LinkedList, to where I can add and remove strings. And I want to have a ListView that listen to that collection with databinding. How can I do bind a simple list collection to a ListView in XAML? My idea (not working) is something like this: <Window ...> <Window.Resources> <LinkedList x:Key="myList"></LinkedList> <Window.Resources> <Grid> <ListView Height="100" HorizontalAlignment="Left" Margin="88,134,0,0" Name="listView1" VerticalAlignment="Top" Width="120" ItemsSource="{Binding Source={StaticResource myList}}"/> </Grid> </Window>

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  • How to take value from radio selection and pass that value into a hidden inputs value attribute?

    - by Matthew
    Hello guys, I need to know if this can be done and if so can someone push me in the right direction. Okay I have a series of radio buttons: <input type="radio" name="level_id" id="radio1" value="XXXX" class="radio1" /> <label for="radio1">choice 1</label> <input type="radio" name="level_id" id="radio2" value="XXXX" class="radio2" /> <label for="radio2">choice 2</label> <input type="radio" name="level_id" id="radio3" value="XXXX" class="radio3" /> <label for="radio3">choice 3</label> <label for="radio4">second choice1</label> <input type="radio" name="level_id" id="radio4" value="1" class="radio4" /> <label for="radio5">second choice2</label> <input type="radio" name="level_id" id="radio5" value="2" class="radio5" /> <label for="radio6">second choice3</label> <input type="radio" name="level_id" id="radio6" value="3" class="radio6" /> Now what I am looking to do is if someone selects CHOICE 1 and then selects SECOND CHOICE1 I would like to pass the value of SECOND CHOICE1 into the value of a hidden input. <input type="hidden" name="sub_source" id="sub_source" value="" /> So that when the form is ready to submit the value that gets passed would be: <input type="hidden" name="sub_source" id="sub_source" value="1" />

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  • Passing NULL value

    - by FFXIII
    Hi. I use an instance of NSXMLParser. I store found chars in NSMutableStrings that are stored in an NSMutableDictionary and these Dicts are then added to an NSMutableArray. When I test this everything seems normal: I count 1 array, x dictionnaries and x strings. In a detailview controller file I want to show my parsed results. I call the class where everthing is stored but I get (null) returned. This is what I do (wrong): XMLParser.h @interface XMLParser : NSObject { NSMutableArray *array; NSMUtableDictionary *dictionary; NSSMutabletring *element; } @property (nonatomic, retain) NSMutableArray *array; @property (nonatomic, retain) NSMutableDictionary *dictionary; @property (nonatomic, retain) NSMutableString *element; XMLParser.m @synthesize array, dictionary, element; //parsing goes on here & works fine //so 'element' is filled with content and stored in a dict in an array //and released at the end of the file In my controller file I do this: controller.h @class XMLParser; @interface controller : UIViewController { XMLParser *aXMLParser; } @property (nonatomic, retain) XMLParser *aXMLParser; controller.m #import "XMLParser.h" @synthesize aXMLParser; - (void)viewDidLoad { NSLog(@"test array: %@", aXMLParser.array); NSLog(@"test dict: %@", aXMLParser.dictionary); NSLog(@"test element: %@", aXMLParser.element); } When I test the value of my array, a dict or an element in the XMLParser.h file I get my result. What am I doing wrong so I can't call my results in my controller file? Any help is welcome, because I'm pretty stuck right now :/

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  • What is "elegant" code?

    - by Breton
    I see a lot of lip service and talk about the most "elegant" way to do this or that. I think if you spend enough time programming you begin to obtain a sort of intuitive feel for what it is we call "elegance". But I'm curious. Even if we can look at a bit of code, and say instinctively "That's elegant", or "That's messy", I wonder if any of us really understands what that means. Is there a precise definition for this "elegance" we keep referring to? If there is, what is it? Now, what I mean by a precise definition, is a series of statements which can be used to derive questions about a peice of code, or a program as a whole, and determine objectively, or as objectively as possible, whether that code is "elegant" or not. May I assert, that perhaps no such definition exists, and it's all just personal preference. In this case, I ask you a slightly different question: Is there a better word for "elegance", or a better set of attributes to use for judging code quality that is perhaps more objective than merely appealing to individual intuition and taste? Perhaps code quality is a matter of taste, and the answer to both of my questions is "no". But I can't help but feel that we could be doing better than just expressing wishy washy feelings about our code quality. For example, user interface design is something that to a broad range of people looks for all the world like a field of study that oughtta be 100% subjective matter of taste. But this is shockingly and brutally not the case, and there are in fact many objective measures that can be applied to a user interface to determine its quality. A series of tests could be written to give a definitive and repeatable score to user interface quality. (See GOMS, for instance). Now, okay. is Elegance simply "code quality" or is it something more? Is it something that can be measured? Or is it a matter of taste? Does our profession have room for taste? Maybe I'm asking the wrong questions altogether. Help me out here. Bonus Round If there is such a thing as elegance in code, and that concept is useful, do you think that justifies classifying the field of programming as an "Art" capital A, or merely a "craft". Or is it just an engineering field populated by a bunch of wishful thinking humans? Consider this question in the light of your thoughts about the elegance question. Please note that there is a distinction between code which is considered "art" in itself, and code that was written merely in the service of creating an artful program. When I ask this question, I ask if the code itself justifies calling programming an art. Bounty Note I liked the answers to this question so much, I think I'd like to make a photographic essay book from it. Released as a free PDF, and published on some kind of on demand printing service of course, such as "zazz" or "tiggle" or "printley" or something . I'd like some more answers, please!

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  • Delaying LINQ to SQL Select Query Execution

    - by Maxim Z.
    I'm building an ASP.NET MVC site that uses LINQ to SQL. In my search method that has some required and some optional parameters, I want to build a LINQ query while testing for the existence of those optional parameters. Here's what I'm currently thinking: using(var db = new DBDataContext()) { IQueryable<Listing> query = null; //Handle required parameter query = db.Listings.Where(l => l.Lat >= form.bounds.extent1.latitude && l.Lat <= form.bounds.extent2.latitude); //Handle optional parameter if (numStars != null) query = query.Where(l => l.Stars == (int)numStars); //Other parameters... //Execute query (does this happen here?) var result = query.ToList(); //Process query... Will this implementation "bundle" the where clauses and then execute the bundled query? If not, how should I implement this feature? Also, is there anything else that I can improve? Thanks in advance.

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  • WPD on XP, Vista, and 7 (need to transfer photo and video files)

    - by Bradley Dean
    I need to transfer files (still photos and videos) from any portable device that a user may connect (still camera, video camera, mobile phone, etc.) I don't need to worry about plain storage devices as these have drive letters. And I only care about existing files, I don't care about live video, preview video, taking new pictures, etc. I originally tried WIA, which works great except it can not transfer video files. So then I tried WPD, following along with dimeby8's tutorial: http://blogs.msdn.com/b/dimeby8/archive/2006/09/27/774259.aspx I haven't gotten the transfer working yet (I'm converting it over to C#), but I can at least see the device and enumerate the files in Win7. In XP I get nothing. It's pointed out in this thread that WPD won't enumerate devices on XP (see Lisa O [MSFT]'s post): http://social.msdn.microsoft.com/Forums/en/windowssdk/thread/56459945-b757-45df-8c9f-4ebdbbb18a2c So WIA is out because it won't do video. And WPD is out because it won't do XP. Has anyone gotten this to work? Am I missing something simple here? Thanks.

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  • Is there an online identicon creator?

    - by wonsungi
    I thought the pictures associated with our profiles were automatically generated until they were manually changed. A lot of people have these cool identicons based on their IP address. How can I get my own identicon? I am looking for an online generator. Gravator does not seem to have any options to generate identicons. Edit: I will probably accept your answer if you just tell me how you made your identicon (and it did not involve downloading/installing stuff)

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  • Edit ePub eBooks with Your Favorite HTML Editor

    - by Matthew Guay
    ePub eBooks are increasingly popular today, but often they’ve been made by converting other file formats. Here’s how you can edit ePub books to remove irregularities and make them better for reading on your devices. ePub’s are actually a zip file containing images, XHTML files with your text, and more with the .epub extension. You can make them better by editing the XHTML files directly.  Code gurus can edit the code directly, but even if you’ve never edited HTML, you can still quickly make changes with a WYSIWYG editor. Extract the Files from your ePub eBook As mentioned before, ePub files are actually renamed zip files.  So first let’s get all of the files in your ePub eBook accessible.  Find an eBook you want to edit and then change the file extension to .zip. If you don’t see the file extensions, click Organize in the menu bar and select Folder and search options. Select the View tab, and then uncheck the box beside Hide extensions for known file types.  Click Ok, and then change the file type as above. Windows will warn you about changing the file type; click Yes to proceed. Now you can browse the files of the ePub file.  Notice that it contains mostly HTML or XHTML files and images.  Click Extract all files to save them all in a folder so you can easily edit them. Alternately, you can open the ePub file directly in your favorite file archival program such as 7-zip.  Browse to the location of your ePub file, double-click it, and it’ll automatically open even if you don’t change the file extension to zip.  Now you can extract the folder, or extract individual files as before.   Edit Your eBook in KompoZer The actual ebook contents are stored in HTML or XHTML files.  These may be stored on the top folder of you ePub file’s directory, or they may be stored in \OEBPS\text in the file. To change the contents of your eBook, you’ll want to edit these files.  Often there may be separate files for each chapter, so you may have to use trial and error to find the one you need to edit.  You could edit them by hand in Windows using Notepad if you don’t have an HTML editor installed. A better option would be to use an HTML editor.  Here we’ll use the free KompoZer program to edit the files just like we’d edit a document in Word. Download KompoZer (link below), and unzip the files.  Then open the new folder and launch kompozer.exe; you don’t even need to install it.  In fact, you could even store KompoZer on a flash drive so you could edit HTML files from any computer. In KompoZer, open the HTML or XHTML file from your eBook that you want to edit. Now you can edit the file just like you would edit a document in Word.  Remove extra and unneeded text, make titles stand out, correct misspellings … anything you want!  This is especially helpful if your ePub file was created by converting a PDF as these often have many small errors. Or, if you’d rather edit the code itself, select the Source tab and edit as you wish. When you’re done making the changes, make sure to save the file in the same location with the same file name. Recreate Your Edited ePub eBook Once you’ve made all the changes you wanted, it’s time to turn this folder of files back into ePub.  Make sure you change the name of the folder if it still has the same name as the original ePub or zip file so you don’t mix them up or have trouble with overwriting the old files. Zip the folder using Windows Explorer or your favorite archival utility.  If you are using another archival program, make sure to compress it as a zip folder; other compression methods will render the ePub unreadable by your eReader app. Now change the file extension again, this time back to .epub. Now you can read your eBook with your changes in your favorite reader program or app on your mobile device. Conclusion Whether you need to remove an odd, misplaced character or need to do fine editing, using an HTML editor is a great way to make your ePub eBooks look just like you want.  Also, with an editor like KompoZer it’s not even difficult. Download KompoZer Similar Articles Productive Geek Tips Change the Default Editor From Nano on Ubuntu LinuxConvert a PDF eBook to ePub Format for Your iPad, iPhone, or eReaderRead Mobi eBooks on Kindle for PCEdit Your Firefox Bookmarks Easier with Flat Bookmark EditorChange the Default Editor for Batch Files in Vista TouchFreeze Alternative in AutoHotkey The Icy Undertow Desktop Windows Home Server – Backup to LAN The Clear & Clean Desktop Use This Bookmarklet to Easily Get Albums Use AutoHotkey to Assign a Hotkey to a Specific Window Latest Software Reviews Tinyhacker Random Tips HippoRemote Pro 2.2 Xobni Plus for Outlook All My Movies 5.9 CloudBerry Online Backup 1.5 for Windows Home Server XPS file format & XPS Viewer Explained Microsoft Office Web Apps Guide Know if Someone Accessed Your Facebook Account Shop for Music with Windows Media Player 12 Access Free Documentaries at BBC Documentaries Rent Cameras In Bulk At CameraRenter

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  • Colorbox not working in IE

    - by John Isaacks
    on This page in the center is a button that says "request price". I am using Colorbox so that when you click it, there is a lightbox-type popup of a Flash app. This works fine in FF and Chrome. However in IE it is just taking you directly to the page containing the flash rather then making it a popup. Does anyone have a clue why?

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  • WinForm Text Control that displays current character/character limit

    - by Refracted Paladin
    I need a way to display, like you see in some web apps, the current characters/character limit for a Text Control(i.e. 3/500). I usually see this as a label residing directly above or below the Text Control. How is this 'normally' accomplished? Should I override my Text Control somehow? Do I just manually add labels by every Text Control and 'bind' them to properties of the Text Control? Do I need to create a composite control that has the Text Control & Label Controls together to accomplish what I need? Any direction or help will be greatly appreciated.

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  • How to fit a custom graph to the boost graph library template?

    - by Michael
    I'm rusty on C++ templates and I'm using the boost graph library (a fatal combination). I've searched the web and can't find any direct instructions on how to take a custom graph structure and fit enough of it to BGL (boost graph library) that I can use boosts graph traversing algorithms. Anyone familiar enough with the library to help me out?

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  • How to use DLL reference with an ActiveX <object> via JavaScript

    - by John Factorial
    My question: how can I set an ActiveX object's property via JavaScript to an enum value found in a non-ActiveX DLL? Problem description: I am instantiating an ActiveX object with the following object tag: <object classid="clsid:F338193D-2491-4D7B-80CE-03487041A278" id="VideoCapture1" width="500" height="500"></object> (This is the guid for the 3rd party ActiveX I'm using, "VisioForge_Video_Capture_4.VFVideoCapture4X") I have example C# code for using this ActiveX, which I am porting to JavaScript. Code like this works just fine: VideoCapture1.Debug_Mode = true; var devcount = VideoCapture1.Video_CaptureDevices_GetCount(); var devs = []; for (var i =0; i < devcount; ++i) { devs[devs.length] = VideoCapture1.Video_CaptureDevices_GetItem(i); } ... etc ... However, VideoCapture1 has some settings which refer to a DLL enum, like so (C# code): VideoCapture1.Mode = VisioForge_Video_Capture_4.TxVFMode.Mode_Video_Preview; I can see in Visual Web Developer that TxVFMode.Mode_Video_Preview is value 1 in the enum. However, the following JS does not appear to set the Mode properly: VideoCapture1.Mode = 1; Does anyone know how I can set VideoCapture1.Mode to the enum value found in the TxVFMode? PS: In Visual Web Developer, when I "Go to definition" on TxVFMode, I get the Guid for the enum. I thought I could create an with this Guid or instantiate a VisioForge_Video_Capture_4.TxVFMode in JS, but neither gives me a usable object.

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  • JSLint reports unexpected use of '&' and '|' -- I'd like to clean this

    - by Zhami
    I'm trying to get my Javascript code 100% JSLint clean. I've got some JS code that I've lifted from elsewhere to create a UUID. That code has the following line: s[16] = hexDigits.substr((s[16] & 0x3) | 0x8, 1); This line incites JSLint to generate two error messages: 1) Unexpected use of '&' 2) Unexpected use of '|' I don't understand why -- I'd appreciate counsel regarding how to recode to eliminate the error message.

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  • Passing additional data value to strongly typed partial views in ASP.NET MVC

    - by fearofawhackplanet
    I have an OrderForm domain class, which has property subclasses, something like: interface IOrderForm { int OrderId { get; } ICustomerDetails CustomerDetails { get; set; } IDeliveryDetails DeliveryDetails{ get; set; } IPaymentsDetails PaymentsDetails { get; set; } IOrderDetails OrderDetails { get; set; } } My "Details" view is strongly typed inheriting from IOrderForm. I then have a strongly type partial for rendering each section: <div id="CustomerDetails"> <% Html.RenderPartial("CustomerDetails", Model.CustomerDetails); %> </div> <div id="DeliveryDetails"> <% Html.RenderPartial("DeliveryDetails", Model.DeliveryDetails); %> </div> ... etc This works ok up to this point, but I'm trying to add some nice ajax bits for updating some parts of the order form, and I've realised that each of my partial views also needs access to the IOrderForm.OrderId. Whats the easiest way to give my partials access to this value?

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  • SQLAlchemy DetachedInstanceError with regular attribute (not a relation)

    - by haridsv
    I just started using SQLAlchemy and get a DetachedInstanceError and can't find much information on this anywhere. I am using the instance outside a session, so it is natural that SQLAlchemy is unable to load any relations if they are not already loaded, however, the attribute I am accessing is not a relation, in fact this object has no relations at all. I found solutions such as eager loading, but I can't apply to this because this is not a relation. I even tried "touching" this attribute before closing the session, but it still doesn't prevent the exception. What could be causing this exception for a non-relational property even after it has been successfully accessed once before? Any help in debugging this issue is appreciated. I will meanwhile try to get a reproducible stand-alone scenario and update here. Update: This is the actual exception message with a few stacks: File "/home/hari/bin/lib/python2.6/site-packages/SQLAlchemy-0.6.1-py2.6.egg/sqlalchemy/orm/attributes.py", line 159, in __get__ return self.impl.get(instance_state(instance), instance_dict(instance)) File "/home/hari/bin/lib/python2.6/site-packages/SQLAlchemy-0.6.1-py2.6.egg/sqlalchemy/orm/attributes.py", line 377, in get value = callable_(passive=passive) File "/home/hari/bin/lib/python2.6/site-packages/SQLAlchemy-0.6.1-py2.6.egg/sqlalchemy/orm/state.py", line 280, in __call__ self.manager.deferred_scalar_loader(self, toload) File "/home/hari/bin/lib/python2.6/site-packages/SQLAlchemy-0.6.1-py2.6.egg/sqlalchemy/orm/mapper.py", line 2323, in _load_scalar_attributes (state_str(state))) DetachedInstanceError: Instance <ReportingJob at 0xa41cd8c> is not bound to a Session; attribute refresh operation cannot proceed The partial model looks like this: metadata = MetaData() ModelBase = declarative_base(metadata=metadata) class ReportingJob(ModelBase): __tablename__ = 'reporting_job' job_id = Column(BigInteger, Sequence('job_id_sequence'), primary_key=True) client_id = Column(BigInteger, nullable=True) And the field client_id is what is causing this exception with a usage like the below: Query: jobs = session \ .query(ReportingJob) \ .filter(ReportingJob.job_id == job_id) \ .all() if jobs: # FIXME(Hari): Workaround for the attribute getting lazy-loaded. jobs[0].client_id return jobs[0] This is what triggers the exception later out of the session scope: msg = msg + ", client_id: %s" % job.client_id

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  • Git using wrong email address when talking to Heroku

    - by David
    git clone [email protected]:myapp.git Results in a "myoldemailaddress not authorized to access myapp" myoldemailaddress was an email address I was using on an old heroku account, but it seems to be stuck using it, I can use my new one. I've removed the .heroku directory, and regenerated it, it has the correct user name and password, I can see my apps listed I've uploaded my key (I've regenerated my several times now) ssh-keygen -t rsa -C mynewaddress I uninstalled and reinstalled heroku on a different user in the same machine it works just fine. Something about my account has my old address, but I can't figure out where.

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  • What is the maximum number of virtualhosts Apache can handle?

    - by FractalizeR
    Hello. What is the maximum number of VirtualHosts Apache can handle on a single machine (I don't mean anything related to load, let's suppose it's irrelevant for the question). And we take only Apache without any proxifying things like nginx. I am asking because on one forum one guy reported that his Apache works unstable with the number of sites more than 400 on a single machine. If you have a config, that handles more than 400, please tell me here. Thanks.

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  • Idea for Networking Projects ?

    - by Vishwanath dalvi
    I'm appearing for final year B.E (Degree) Information technology,I want idea for networking projects that i can Implement in final year using Cisco microsoft or Linux based technology any idea that can be implemented and can help in future for networking ....

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