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  • mysql, sqlite database source code

    - by Yang
    hi guys, i know implementing database is a huge topic, but i want to have a basic understanding of how database systems works (e.g. memory management, binary tree, transaction, sql parsing, multi-threading, partitions, etc) by investigating the source code of the database, since there are a few already proven very robust open source databases like mysql, sqlite and so on. however, the code are very complicated and i have no clue where to start. also i find that the old school database textbooks are only explaining the theory, not the implementation details. Can anyone suggest how should i get started and is there any books that emphasis on the technology and techniques of building dbms used in modern database industry? Thank in advance!

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  • DefaultSchedulerService in ASP.NET application

    - by Samir P
    Hi, My project has a requirement to implement look-ahead caching i.e. triggering another request on invokation of a specific request. The following details in short the implementation - HttpModule parses the SOAPRequest and matches entry in a configuration file for look-ahead candidate. If the request matches, it prepares the Parameters dictionary and starts appropriate workflow. Single workflow runtime is used across all requests is ensured through initializing the runtime instance at Application_Start event and stored in Application Dictionary. Using persistence service and DefaultScheduler service. We can't implement windows service model, as current requirement mandates passing the SOAPRequest parameters as arguments. ManualSchedulerService is not in contention due to synchronous nature of it's actual behaviour. Still the performance is pretty bad and product team is not happy. Can anybody suggest me better solution? Thanks, Samir

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  • Prefer extension methods for encapsulation and reusability?

    - by tzaman
    edit4: wikified, since this seems to have morphed more into a discussion than a specific question. In C++ programming, it's generally considered good practice to "prefer non-member non-friend functions" instead of instance methods. This has been recommended by Scott Meyers in this classic Dr. Dobbs article, and repeated by Herb Sutter and Andrei Alexandrescu in C++ Coding Standards (item 44); the general argument being that if a function can do its job solely by relying on the public interface exposed by the class, it actually increases encapsulation to have it be external. While this confuses the "packaging" of the class to some extent, the benefits are generally considered worth it. Now, ever since I've started programming in C#, I've had a feeling that here is the ultimate expression of the concept that they're trying to achieve with "non-member, non-friend functions that are part of a class interface". C# adds two crucial components to the mix - the first being interfaces, and the second extension methods: Interfaces allow a class to formally specify their public contract, the methods and properties that they're exposing to the world. Any other class can choose to implement the same interface and fulfill that same contract. Extension methods can be defined on an interface, providing any functionality that can be implemented via the interface to all implementers automatically. And best of all, because of the "instance syntax" sugar and IDE support, they can be called the same way as any other instance method, eliminating the cognitive overhead! So you get the encapsulation benefits of "non-member, non-friend" functions with the convenience of members. Seems like the best of both worlds to me; the .NET library itself providing a shining example in LINQ. However, everywhere I look I see people warning against extension method overuse; even the MSDN page itself states: In general, we recommend that you implement extension methods sparingly and only when you have to. (edit: Even in the current .NET library, I can see places where it would've been useful to have extensions instead of instance methods - for example, all of the utility functions of List<T> (Sort, BinarySearch, FindIndex, etc.) would be incredibly useful if they were lifted up to IList<T> - getting free bonus functionality like that adds a lot more benefit to implementing the interface.) So what's the verdict? Are extension methods the acme of encapsulation and code reuse, or am I just deluding myself? (edit2: In response to Tomas - while C# did start out with Java's (overly, imo) OO mentality, it seems to be embracing more multi-paradigm programming with every new release; the main thrust of this question is whether using extension methods to drive a style change (towards more generic / functional C#) is useful or worthwhile..) edit3: overridable extension methods The only real problem identified so far with this approach, is that you can't specialize extension methods if you need to. I've been thinking about the issue, and I think I've come up with a solution. Suppose I have an interface MyInterface, which I want to extend - I define my extension methods in a MyExtension static class, and pair it with another interface, call it MyExtensionOverrider. MyExtension methods are defined according to this pattern: public static int MyMethod(this MyInterface obj, int arg, bool attemptCast=true) { if (attemptCast && obj is MyExtensionOverrider) { return ((MyExtensionOverrider)obj).MyMethod(arg); } // regular implementation here } The override interface mirrors all of the methods defined in MyExtension, except without the this or attemptCast parameters: public interface MyExtensionOverrider { int MyMethod(int arg); string MyOtherMethod(); } Now, any class can implement the interface and get the default extension functionality: public class MyClass : MyInterface { ... } Anyone that wants to override it with specific implementations can additionally implement the override interface: public class MySpecializedClass : MyInterface, MyExtensionOverrider { public int MyMethod(int arg) { //specialized implementation for one method } public string MyOtherMethod() { // fallback to default for others MyExtension.MyOtherMethod(this, attemptCast: false); } } And there we go: extension methods provided on an interface, with the option of complete extensibility if needed. Fully general too, the interface itself doesn't need to know about the extension / override, and multiple extension / override pairs can be implemented without interfering with each other. I can see three problems with this approach - It's a little bit fragile - the extension methods and override interface have to be kept synchronized manually. It's a little bit ugly - implementing the override interface involves boilerplate for every function you don't want to specialize. It's a little bit slow - there's an extra bool comparison and cast attempt added to the mainline of every method. Still, all those notwithstanding, I think this is the best we can get until there's language support for interface functions. Thoughts?

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  • Young people using Emacs?

    - by bigmonachus
    I am a college student that has fallen in love with Emacs. I have used IDEs in the past, and although features like Intellisense made the switch to Emacs very hard, I now think that Emacs is much more powerful, and features like Intellisense can be pretty closely matched by various modes depending on language (and I am not referring to M-/). I am happily writing Elisp code for everything that I need that isn't provided by modes or by Emacs itself and I love the way that it adapts and molds to my needs. However, I do think that its main disadvantage is the fact that it has a pretty steep learning curve and that most new programmers will not even begin to learn it out of many common misconceptions. So, I want to know the opinions of young people (or any person who didn't start using Emacs before there were IDEs) that are Emacs users. Just to get some reassurance that Emacs is not dead within our Eclipse-loving generation =). (Opinions of users of any other highly extensible editor like Jedit are also welcome)

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  • What relational database innovations have there been in the last 10 years

    - by Simon Munro
    The SQL implementation of relational databases has been around in their current form for something like 25 years (since System R and Ingres). Even the main (loosely adhered to) standard is ANSI-92 (although there were later updates) is a good 15 years old. What innovations can you think of with SQL based databases in the last ten years or so. I am specifically excluding OLAP, Columnar and other non-relational (or at least non SQL) innovations. I also want to exclude 'application server' type features and bundling (like reporting tools) Although the basic approach has remained fairly static, I can think of: Availability Ability to handle larger sets of data Ease of maintenance and configuration Support for more advanced data types (blob, xml, unicode etc) Any others that you can think of?

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  • Guessing the time zone from an arbitrary "location" string?

    - by Thomas
    I'm trying to run some statistics over the Stack Overflow data dump, and for that I would like to know the time zone for each user. However, all I have to go on is the completely free-form "location" string. I'll stress that I'm only looking for an approximation of the time zone; of course, in general this is an unsolvable problem. However, many people fill out their country, state and/or city, which should give a pretty good indication. It's okay if it fails for other cases. It doesn't have to be reliable, it doesn't have to be accurate, it doesn't have to cover all bases. I don't want to waste too much time on this, so I'm wondering if there is some code out there that can make a reasonable guess. Any language, platform, API or library goes. Any ideas?

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  • Eliminating code duplication in a single file

    - by Jon
    Sadly, a project that I have been working on lately has a large amount of copy-and-paste code, even within single files. Are there any tools or techniques that can detect duplication or near-duplication within a single file? I have Beyond Compare 3 and it works well for comparing separate files, but I am at a loss for comparing single files. Thanks in advance. Edit: Thanks for all the great tools! I'll definitely check them out. This project is an ASP.NET/C# project, but I work with a variety of languages including Java; I'm interested in what tools are best (for any language) to remove duplication.

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  • Store in DB or not to store ?

    - by eugeneK
    There are few string lists in my web application that i don't know where to store in DB or just class. ie. I have 7 major browsers with which users enter the site. I want to save these stats thus i need to create browser column in UserLogin database. I don't want to waste space and resources so i can save full browser name in each login row. So i either need to save browserID field and hook it up with Browsers table which will store names following db normalization rules or to have sort of Dataholder abstract class which has a list of browsers from which i can retrieve browser name by it's ID... The question what should i do ? These few data lists i have contain no more than 200 items each so i think it makes sense to have them as abstract class but again i don't know whether MS-SQL will handle multiple joins so well. Think of idea when i have user with country,ip,language,browser and few more stats .. thanks

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  • Best way to represent Gender in a class library used in multilingual applications

    - by Hauge
    I'm creating class library with some commonly used classes like persons, addresses etc. This library will be used in an multilingual application, and I am looking for the most convenient way to represent a persons gender. Ideally I would like to be able to code like this: Person person = new Person { Gender = Genders.Male, FirstName = "Nice", LastName = "Dude" } if (person.Gender == Genders.Male) Console.WriteLine("person is Male"); Console.WriteLine(person.Gender); //Should output: Male Console.WriteLine(person.Gender.ToString("da-DK")); //Should output the name of the gender in the language provided List<Gender> genders = Genders.GetAll(); foreach(Gender gender in genders) { Console.WriteLine(gender.ToString()); Console.WriteLine(gender.ToString("da-DK")); } What would you do? An enumeration and a specialized Gender class, but what about the localization then? Regards Jesper Hauge

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  • Classic ASP Request.Form removes spaces?

    - by alex
    I'm trying to figure this oddity out... in classic ASP i seem to be losing spaces in Request.Form values... ie, Request.Form("json") is {"project":{"...","administrator":"AlexGorbatchev", "anonymousViewUrl":null,"assets":[],"availableFrom":"6/10/20104:15PM"... However, CStr(Request.Form) is json={"project":{"__type":"...":"Alex Gorbatchev", "anonymousViewUrl":null,"assets":[],"availableFrom":"6/10/2010 4:15 PM"... Here's the entire code :) <%@ language="VBSCRIPT"%> <% Response.Write(CStr(Request.Form("json"))) Response.Write(CStr(Request.Form)) %> Somebody please tell me I haven't lost all my marbles...

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  • Technologies used in Remote Administration applications(not RD)

    - by Michael
    I want to know what kind of technologies are used nowadays as underlying screen capture engine for remote administration software like VNC pcAnywhere TeamViewer RAC Remote Administrator etc.. The programming language is not so important as just to know whether a driver needs to be developed which is polling video memory 30 times per second or there are any com objects built in the Windows kernel to help doing this? I'm not interested in 3rd party components for doing this. Do I have to use DirectX facilities? Just want some start point to develop my own screen stream capture engine, which will be less CPU hog.

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  • Using multilingual and localeurl in django

    - by Dmitry A. Erokhin
    Using dajngo-multilingual and localeurl. Small sample of my main page view: def main(request): #View for http://www.mysite.com/ name = Dog.objects.all()[0].full_name #this is a translated field return render_to_response("home.html", {"name" : name}) Entering http://www.mysite.com/ redirects me to http://www.mysite.com/ru/ and "name" variable gets russian localization. For now it's ok... But... Entering http://www.mysite.com/en/ shows me same russian loclized variable. During my experiments with debuger I've discovered: request.LANGUAGE_CODE is changing properly according to /en/ or /ru/ url suffix (thanx to localeurl) invoking multilingual.languages.set_default_language() makes "name" variable change loclization The question is: should I change language of django-multilingual to request.LANGUAGE_CODE in each of my view myself, or it must be solved automaticly and I've done something wrong?

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  • C++ namespace alias and forward declaration

    - by Dave
    I am using a C++ third party library that places all of its classes in a versioned namespace, let's call it tplib_v44. They also define a generic namespace alias: namespace tplib = tplib_v44; If a forward-declare a member of the library in my own .h file using the generic namespace... namespace tplib { class SomeClassInTpLib; } ... I get compiler errors on the header in the third-party library (which is being included later in my .cpp implementation file): error C2386: 'tplib' : a symbol with this name already exists in the current scope If I use the version-specific namespace, then everything works fine, but then ... what's the point? What's the best way to deal with this?

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  • Function parameter types in Python

    - by Leif Andersen
    Unless I'm mistaken, creating a function in python works like this def my_func(param1, param2): /*stuff*/ However, you don't actually give the types of those parameters. Also, if I remember, python is a strongly typed language, as such, it seams like python shouldn't let you pass in a parameter of a different type then the function creator expected. However, how does python know that the user of the function is passing in the proper types? Or will the program just die if it's the wrong type, assuming the function actually uses the parameter? Or do you have to specify the type/I'm missing something? Thank you.

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  • Constructing an object and calling a method without assignment in VB.Net

    - by mdryden
    I'm not entirely sure what to call what C# does, so I haven't had any luck searching for the VB.Net equivalent syntax (if it exists, which I suspect it probably doesn't). In c#, you can do this: public void DoSomething() { new MyHelper().DoIt(); // works just fine } But as far as I can tell, in VB.Net, you must assign the helper object to a local variable or you just get a syntax error: Public Sub DoSomething() New MyHelper().DoIt() ' won't compile End Sub Just one of those curiosity things I run into from day to day working on mixed language projects - often there is a VB.Net equivalent which uses less than obvious syntax. Anyone?

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  • Server Side Javascript

    - by XGreen
    Hi all, I can't help to see in many sites I visit the enthusiasm about server side javascript and the appealing look of a single language governing all tiers of the site. Mozilla Rhino, Aptana Jaxer and various John Resig's articles are some of the highlights of my search. I wanted to ask for some input from you guys on SO. your opinions and preferably experience in this. I do most of the data access and business logic currently either with asp.net or php depending on the hosting package of the client. Is anyone among you who's gave up these for ssjs?

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  • linux locale unset

    - by naugtur
    I have a ARM based machine with ubuntu distro on it and it often feeds me with this while running various commands: Please check that your locale settings: LANGUAGE = (unset), LC_ALL = (unset), LANG = "pl_PL.UTF-8" This is output of the locale command locale: Cannot set LC_CTYPE to default locale: No such file or directory locale: Cannot set LC_MESSAGES to default locale: No such file or directory locale: Cannot set LC_ALL to default locale: No such file or directory LANG=pl_PL.UTF-8 LC_CTYPE="pl_PL.UTF-8" LC_NUMERIC="pl_PL.UTF-8" LC_TIME="pl_PL.UTF-8" LC_COLLATE="pl_PL.UTF-8" LC_MONETARY="pl_PL.UTF-8" LC_MESSAGES="pl_PL.UTF-8" LC_PAPER="pl_PL.UTF-8" LC_NAME="pl_PL.UTF-8" LC_ADDRESS="pl_PL.UTF-8" LC_TELEPHONE="pl_PL.UTF-8" LC_MEASUREMENT="pl_PL.UTF-8" LC_IDENTIFICATION="pl_PL.UTF-8" LC_ALL= What should I do to stop it from popping now and then and configure it properly for the aescznól [important characters of mine]?

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  • A Simple PHP Array Manipulation

    - by Ygam
    Hi guys! how would you turn this array: array( 0 => Title1, 1 => Title2, 3 => Address1, 4 => Address2, ) to this array: array ( 0 => array( 'title' => 'Title1' 'address' =>'Address1' ), 1 => array( 'title' => 'Title2', 'address' => 'Address2' ) ); when you were initially given $_POST['title'] = array('Title1', 'Title2); $_POST['address'] = array('Address1', 'Address2'); which when merged would give you the first array I have given I was able to solve this via a high level Arr:Rotate function in Kohana framework, along with Arr::merge function but I can't quite understand the implementation. Please help

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  • Readline, the Input Record Separator and Ruby

    - by JustSmith
    In Ruby I'm looking to read data until I reach a delimiter or end of file. I found this is possible by redefining $/ or the $INPUT_RECORD_SEPARATOR to my delimiter. However with all the "features" in the Ruby language it seems hokey to change the value of a global to do this. Also, readline used to consume the delimiter while not it is included in what is returned. Is there any other way to "read until" while consuming the delimiter that doesn't involve getting the values char by char in a loop?

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  • Test Driven Development For Complex Methods involving external dependency

    - by bill_tx
    I am implementing a Service Contract for WCF Service. As per TDD I wrote a test case to just pass it using hardcoded values. After that I started to put real logic into my Service implementation. The actual logic relies on 3-4 external service and database. What should I do to my original test case that I wrote ? If i Keep it same in order to make test pass it will have to call several other external services. So I have question in general what should I do if I write a test case for a Business Facade first using TDD and later when I add real logic, if it involves external dependency.

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  • Error Creating RSS Feed XML file - Java

    - by GigaPr
    Hi, i am trying to create an RssFeed using java this is the class i use import com.rssFeed.domain.RSS; import com.rssFeed.domain.RSSItem; import java.io.FileOutputStream; import java.util.Iterator; import javax.xml.stream.XMLEventFactory; import javax.xml.stream.XMLEventWriter; import javax.xml.stream.XMLOutputFactory; import javax.xml.stream.XMLStreamException; import javax.xml.stream.events.Characters; import javax.xml.stream.events.EndElement; import javax.xml.stream.events.StartDocument; import javax.xml.stream.events.StartElement; import javax.xml.stream.events.XMLEvent; public class RssBuilder { private static String XML_BLOCK = "\n"; private static String XML_INDENT = "\t"; public static void BuildRss(RSS rss, String xmlfile) throws Exception { XMLOutputFactory output = XMLOutputFactory.newInstance(); XMLEventWriter writer = output.createXMLEventWriter(new FileOutputStream(xmlfile)); try { XMLEventFactory eventFactory = XMLEventFactory.newInstance(); XMLEvent endSection = eventFactory.createDTD(XML_BLOCK); StartDocument startDocument = eventFactory.createStartDocument(); writer.add(startDocument); writer.add(endSection); StartElement rssStart = eventFactory.createStartElement("", "", "rss"); writer.add(rssStart); writer.add(eventFactory.createAttribute("version", "2.0")); writer.add(endSection); writer.add(eventFactory.createStartElement("", "", "channel")); writer.add(endSection); createNode(writer, "title", rss.getTitle()); createNode(writer, "description", rss.getDescription()); createNode(writer, "link", rss.getLink()); createNode(writer, "dateCreated", rss.getDateCreated().toString()); createNode(writer, "language", rss.getLanguage()); createNode(writer, "pubDate", rss.getPubDate().toString()); createNode(writer, "dateModified", rss.getDateModified().toString()); createNode(writer, "dateModified", rss.getDateModified().toString()); createNode(writer, "pubDate", rss.getPubDate().toString()); createNode(writer, "lastBuildDate", rss.getLastBuildDate().toString()); createNode(writer, "language", rss.getLanguage().toString()); createNode(writer, "rating", rss.getRating().toString()); Iterator<RSSItem> iterator = rss.getRssItems().iterator(); while (iterator.hasNext()) { RSSItem entry = iterator.next(); writer.add(eventFactory.createStartElement("", "", "item")); writer.add(endSection); createNode(writer, "title", entry.getTitle()); createNode(writer, "description", entry.getDescription()); createNode(writer, "link", entry.getLink()); createNode(writer, "dateCreated", entry.getDateCreated().toString()); createNode(writer, "pubDate", entry.getDateModified().toString()); writer.add(eventFactory.createEndElement("", "", "item")); writer.add(endSection); } writer.add(endSection); writer.add(eventFactory.createEndElement("", "", "channel")); writer.add(endSection); writer.add(eventFactory.createEndElement("", "", "rss")); writer.add(endSection); writer.add(eventFactory.createEndDocument()); writer.close(); } catch(Exception e) { writer.close(); } } private static void createNode(XMLEventWriter eventWriter, String name, String value)throws XMLStreamException { XMLEventFactory eventFactory = XMLEventFactory.newInstance(); XMLEvent endSection = eventFactory.createDTD(XML_BLOCK); XMLEvent tabSection = eventFactory.createDTD(XML_INDENT); StartElement sElement = eventFactory.createStartElement("", "", name); eventWriter.add(tabSection); eventWriter.add(sElement); Characters characters = eventFactory.createCharacters(value); eventWriter.add(characters); EndElement eElement = eventFactory.createEndElement("", "", name); eventWriter.add(eElement); eventWriter.add(endSection); } } But i get the following error type Exception report message descriptionThe server encountered an internal error () that prevented it from fulfilling this request. exception org.springframework.web.util.NestedServletException: Request processing failed; nested exception is javax.xml.stream.XMLStreamException: Can not write DOCTYPE declaration (DTD) when not in prolog any more (state 2; start element(s) written) root cause javax.xml.stream.XMLStreamException: Can not write DOCTYPE declaration (DTD) when not in prolog any more (state 2; start element(s) written) what does it mean?

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  • What's the right way to calculate derived data in a Flex AdvancedDataGrid using summaries?

    - by Chris R
    Here's the gist of the problem: I have a set of rows of data with (say) field1 to field4 in them. I'm using a GroupingCollection to group on field1 and field2. So, I have something like this: f1.1 f2.1 f3.1 f4.1 f3.2 f4.2 f2.2 f3.3 f4.3 f3.4 f4.4 f3.5 f4.5 f1.2 f2.1 f3.6 f4.6 f2.2 f3.7 f4.7 f3.8 f4.8 f3.9 f4.9 (or at least, I hope that's clear enough) I need to calculate some derived values for each leaf row, for example f3, that is the ratio of f3 to the average of all f3 in that particular part of the tree. So, for f3.7 I need to calculate f3.7 / avg(f3.7..f3.9) and fill that into the f3_index property on the row, displaying that in lieu of f3 itself. So, basically, what it looks like I have to do is add source field values in the summarizeFunction implementation. It seems to me that there must be a better way of doing this. Is there?

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  • Which is faster in Python: x**.5 or math.sqrt(x)?

    - by Casey
    I've been wondering this for some time. As the title say, which is faster, the actual function or simply raising to the half power? UPDATE This is not a matter of premature optimization. This is simply a question of how the underlying code actually works. What is the theory of how Python code works? I sent Guido van Rossum an email cause I really wanted to know the differences in these methods. My email: There are at least 3 ways to do a square root in Python: math.sqrt, the '**' operator and pow(x,.5). I'm just curious as to the differences in the implementation of each of these. When it comes to efficiency which is better? His response: pow and ** are equivalent; math.sqrt doesn't work for complex numbers, and links to the C sqrt() function. As to which one is faster, I have no idea...

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  • Objective-C @class / import best practice

    - by Winder
    I've noticed that a lot of Objective-C examples will forward declare classes with @class, then actually import the class in the .m file with an import. I understand that this is considered a best practice, as explained in answers to question: http://stackoverflow.com/questions/322597/objective-c-class-vs-import Coming from C++ this feels backwards. I would normally include all needed .h files in the new classes header file. This seems useful since it would make the compiler generate a warning when two classes include each other, at which point I can decide whether this is a bad thing or not then use the same Objective-C style and forward declare the class in the header and include it in the .cpp file. What is the benefit of forward declaring @class and importing in the implementation file? Should it be a best practice in C++ to forward declare classes rather than including the header file? Or is it wrong to think of Objective-C and C++ in these similar terms to begin with?

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  • DotnetNuke redirect

    - by X-Dev
    our client needs to shortcuts to particular pages We need to redirect non existent urls like http://site.com/promotion1 to the actual URL similar to http://site.com/promotions/promotion1/tabid/799/language/en-AU/Default.aspx ... I've sent a list of appropriate DNN modules to our client but it may take them forever to get back to me. In the mean time they still submitting requests to us to create redirects for them. if there's no cost involved then i wont have to wait for them to get back to me. so I'm looking for a Quick and free way to enable the clients to set these up on this own. I've looked at: http://www.snowcovered.com/snowcovered2/Default.aspx?tabid=242&PackageID=3302 http://www.ventrian.com/Resources/Projects/FriendlyUrls.aspx http://www.codeproject.com/kb/aspnet/dnn2url_rewrite.aspx But haven't had much luck in the small amount of time i have available. Has anyone got some suggestions on how to achieve our goal with either the above resources or maybe some additional resource i haven't found yet? (DNN v4.9)

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