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  • Why is C# statically typed?

    - by terrani
    I am a PHP web programmer who is trying to learn C#. I would like to know why C# requires me to specify the data type when creating a variable. Class classInstance = new Class(); Why do we need to know the data type before a class instance?

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  • Core Data produces Analyzer warnings

    - by RickiG
    Hi I am doing the final touch ups on an app and I am getting rid of every compiler/analyzer warning. I have a bunch of Class methods that wrap my apps access to Core Data entities. This is "provoking" the analyzer. + (CDProductEntity*) newProductEntity { return (CDProductEntity*)[NSEntityDescription insertNewObjectForEntityForName:@"CDProductEntity" inManagedObjectContext:[self context]]; } Which results in an Analyzer warning: Object with +0 retain counts returned to caller where a +1 (owning) retain count is expected In the method that calls the above Class Method I have this: CDProductEntity *newEntity = [self newProductEntity]; Which results in an Analyzer warning: Method returns an Objective-C object with a +1 retain count (owning reference) Explicitly releasing or autoreleasing a Core Data entity is usually very very bad, but is that what it is asking me to do here? First it tells me it has a +0 retain count and that is bad, then it tells me it has a +1 which is also bad. What can I do to ensure that I am either dealing with a Analyzer hiccup or that I release correctly? Thanks in advance

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  • Gimpel's PC-lint and Flexelint; Anyone used them?

    - by samoz
    So I've read a few magazine articles and the website for Gimpel's PC-lint and Flexelint C/C++ compiler. It's really expensive (at least for me), but it seems like it might have some merit to warrant the cost. So I'm wondering if anyone else has used/bought them and can provide their opinions?

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  • Typed metaprogramming languages

    - by Jacques Carette
    I want to do some metaprogramming in a statically typed language, where both my programs and my meta-programs will be typed. I mean this in a strong sense: if my program generator compiles, I want the type system to be strong enough that only type-correct programs can be generated. As far as I know, only metaocaml can do this. (No, neither Template Haskell nor C++ templates fit the bill -- see this paper).

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  • Why do we have reinterpret_cast in C++ when two chained static_cast can do it's job?

    - by Nawaz
    Say I want to cast A* to char* and vice-versa, we have two choices (I mean, many of us think we've two choices, because both seems to work! Hence the confusion!): struct A { int age; char name[128]; }; A a; char *buffer = static_cast<char*>(static_cast<void*>(&a)); //choice 1 char *buffer = reinterpret_cast<char*>(&a); //choice 2 Both work fine. //convert back A *pA = static_cast<A*>(static_cast<void*>(buffer)); //choice 1 A *pA = reinterpret_cast<A*>(buffer); //choice 2 Even this works fine! So why do we have reinterpret_cast in C++ when two chained static_cast can do it's job? Some of you might think this topic is a duplicate of the previous topics such as listed at the bottom of this post, but it's not. Those topics discuss only theoretically, but none of them gives even a single example demonstrating why reintepret_cast is really needed, and two static_cast would surely fail. I agree, one static_cast would fail. But how about two? If the syntax of two chained static_cast looks cumbersome, then we can write a function template to make it more programmer-friendly: template<class To, class From> To any_cast(From v) { return static_cast<To>(static_cast<void*>(v)); } And then we can use this, as: char *buffer = any_cast<char*>(&a); //choice 1 char *buffer = reinterpret_cast<char*>(&a); //choice 2 //convert back A *pA = any_cast<A*>(buffer); //choice 1 A *pA = reinterpret_cast<A*>(buffer); //choice 2 Also, see this situation where any_cast can be useful: Proper casting for fstream read and write member functions. So my question basically is, Why do we have reinterpret_cast in C++? Please show me even a single example where two chained static_cast would surely fail to do the same job? Which cast to use; static_cast or reinterpret_cast? Cast from Void* to TYPE* : static_cast or reinterpret_cast

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  • CDN for Images in ASP.NET

    - by Chris
    I am in the process of moving all of the images in my web application over to a CDN but I want to easily be able to switch the CDN on or off without having to hard code the path to the images. My first thought was to add an HttpHandler for image extensions that depending whether a variable in the web.config (something like ) will serve the image from the server or from the CDN. But after giving this a little though I think I've essentially ruled this out as it will cause ASP.NET to handle the request for every single image, thus adding overhead, and it might actually completely mitigate the benefits of using a CDN. An alternative approach is, since all of my pages inherit from a base page class, I could create a function in the base class that determines what path to serve the files from based off the web.config variable. I would then do something like this in the markup: <img src='<%= GetImagePath()/image.png' /> I think this is probably what I'll have to end up doing, but it seems a little clunky to me. I also envision problems with the old .NET error of not being able to modify the control collection because of the "<%=" though the "<%#" solution will probably work. Any thoughts or ideas on how to implement this?

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  • An old flaw in X Window System. How does it work?

    - by Legend
    I was going through an article today when it mentioned the following: "We've found many errors over the years. One of the absolute best was the following in the X Window System: if(getuid() != 0 && geteuid == 0) { ErrorF("Only root"); exit(1); } It allowed any local user to get root access. (The tautological check geteuid == 0 was intended to be geteuid() == 0. In its current form, it compress the address of geteuid to 0; given that the function exists, its address is never 0)." The article explained what was wrong with the code but I would like to know what it means to say that "It allowed any local user to get root access". I am not an expert in C but can someone give me an exact context in which this exploit would work? Specifically, what I mean is, lets say I am the local user, how would I get root access if we assume this code to be present somewhere?

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  • Boost Test dynamically or statically linked?

    - by Halt
    We use Boost statically linked with our app but now I wan't to use Boost Test with an external test runner and that requires the tests themselves to link dynamically with Boost.Test through the use of the required BOOST_TEST_DYN_LINK define. Is this going to be a problem or is the way Boost Test links completely unrelated to the way the other Boost libraries are linked? Thx.

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  • Is the scope of what Xcode's "Build and Analyze" will catch as a leak supposed to be this limited?

    - by Ranking Stackingblocks
    It doesn't care about this: NSString* leaker() { return [[NSString alloc] init]; } I thought it would have been smart enough to check if any code paths could call that function without releasing its return value (I wouldn't normally code this way, I'm just testing the analyzer). It reports this as a leak: NSString* leaker() { NSString* s = [[NSString alloc] init]; [s retain]; return s; } but NOT this: NSString* leaker() { NSString* s = [[NSString alloc] init]; // [s retain]; return s; } which seems particularly weak to me. Does it only analyze within the local scope? If the tool can't pick up on things like this, how can I expect it to pick up on actual mistakes that I might make?

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  • Re-usable Obj-C classes with custom values: The right way

    - by Prairiedogg
    I'm trying to reuse a group of Obj-C clases between iPhone applications. The values that differ from app to app have been isolated and I'm trying to figure out the best way to apply these custom values to the classes on an app-to-app basis. Should I hold them in code? // I might have 10 customizable values for each class, that's a long signature! CarController *controller = [[CarController alloc] initWithFontName:@"Vroom" engine:@"Diesel" color:@"Red" number:11]; Should I store them in a big settings.plist? // Wasteful! I sometimes only use 2-3 of 50 settings! AllMyAppSettings *settings = [[AllMyAppSettings alloc] initFromDisk:@"settings.plist"]; MyCustomController *controller = [[MyCustomController alloc] initWithSettings:settings]; [settings release]; Should I have little, optional n_settings.plists for each class? // Sometimes I customize CarControllerSettings *carSettings = [[CarControllerSettings alloc] initFromDisk:@"car_settings.plist"]; CarController *controller = [[CarController alloc] initWithSettings:carSettings]; [carSettings release]; // Sometimes I don't, and CarController falls back to internally stored, reasonable defaults. CarController *controller = [[CarController alloc] initWithSettings:nil]; Or is there an OO solution that I'm not thinking of at all that would be better?

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  • Statically checking a Java app for link errors

    - by monorailkitty
    I have a scenario where I have code written against version 1 of a library but I want to ship version 2 of the library instead. The code has shipped and is therefore not changeable. I'm concerned that it might try to access classes or members of the library that existed in v1 but have been removed in v2. I figured it would be possible to write a tool to do a simple check to see if the code will link against the newer version of the library. I appreciate that the code may still be very broken even if the code links. I am thinking about this from the other side - if the code won't link then I can be sure there is a problem. As far as I can see, I need to run through the bytecode checking for references, method calls and field accesses to library classes then use reflection to check whether the class/member exists. I have three-fold question: (1) Does such a tool exist already? (2) I have a niggling feeling it is much more complicated that I imagine and that I have missed something major - is that the case? (3) Do you know of a handy library that would allow me to inspect the bytecode such that I can find the method calls, references etc.? Thanks!

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  • jQuery Scrollable Dynamic

    - by Coron3r
    Hi, I am doing a site where I need to change dynamically the amount of items in one slide depending on the resolution. I'm using the Jquery Tools scrollable For better understanding, here is the basic markup <div class="scrollable"> <!-- root element for the items --> <div class="items"> <!-- 1-5 --> <div> <img src="http://farm1.static.flickr.com/143/321464099_a7cfcb95cf_t.jpg" /> <img src="http://farm4.static.flickr.com/3089/2796719087_c3ee89a730_t.jpg" /> <img src="http://farm1.static.flickr.com/79/244441862_08ec9b6b49_t.jpg" /> <img src="http://farm1.static.flickr.com/28/66523124_b468cf4978_t.jpg" /> <img src="http://farm1.static.flickr.com/164/399223606_b875ddf797_t.jpg" /> </div> <!-- 5-10 --> <div> <img src="http://farm1.static.flickr.com/163/399223609_db47d35b7c_t.jpg" /> <img src="http://farm1.static.flickr.com/135/321464104_c010dbf34c_t.jpg" /> <img src="http://farm1.static.flickr.com/40/117346184_9760f3aabc_t.jpg" /> <img src="http://farm1.static.flickr.com/153/399232237_6928a527c1_t.jpg" /> <img src="http://farm1.static.flickr.com/50/117346182_1fded507fa_t.jpg" /> </div> <!-- 10-15 --> <div> <img src="http://farm4.static.flickr.com/3629/3323896446_3b87a8bf75_t.jpg" /> <img src="http://farm4.static.flickr.com/3023/3323897466_e61624f6de_t.jpg" /> <img src="http://farm4.static.flickr.com/3650/3323058611_d35c894fab_t.jpg" /> <img src="http://farm4.static.flickr.com/3635/3323893254_3183671257_t.jpg" /> <img src="http://farm4.static.flickr.com/3624/3323893148_8318838fbd_t.jpg" /> </div> </div> </div> Ok and now I would like to set, that if I have a resolution bellow 1440, I would show only e.g. 3 images <div class="scrollable"> <!-- root element for the items --> <div class="items"> <!-- 1-3 --> <div> <img src="http://farm1.static.flickr.com/143/321464099_a7cfcb95cf_t.jpg" /> <img src="http://farm4.static.flickr.com/3089/2796719087_c3ee89a730_t.jpg" /> <img src="http://farm1.static.flickr.com/79/244441862_08ec9b6b49_t.jpg" /> </div> <!-- 3-6 --> <div> <img src="http://farm1.static.flickr.com/163/399223609_db47d35b7c_t.jpg" /> <img src="http://farm1.static.flickr.com/135/321464104_c010dbf34c_t.jpg" /> <img src="http://farm1.static.flickr.com/40/117346184_9760f3aabc_t.jpg" /> </div> ..etc </div> </div> I know that I should use the screen.width(); function but how to slice and parse it depending on the resolution? Thanks for your comments!

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  • How to use Node.js to build pages that are a mix between static and dynamic content?

    - by edt
    All pages on my 5 page site should be output using a Node.js server. Most of the page content is static. At the bottom of each page, there is a bit of dynamic content. My node.js code currently looks like: var http = require('http'); http.createServer(function (request, response) { console.log('request starting...'); response.writeHead(200, { 'Content-Type': 'text/html' }); var html = '<!DOCTYPE html><html><head><title>My Title</title></head><body>'; html += 'Some more static content'; html += 'Some more static content'; html += 'Some more static content'; html += 'Some dynamic content'; html += '</body></html>'; response.end(html, 'utf-8'); }).listen(38316); I'm sure there are numerous things wrong about this example. Please enlighten me! For example: How can I add static content to the page without storing it in a string as a variable value with += numerous times? What is the best practices way to build a small site in Node.js where all pages are a mix between static and dynamic content?

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  • How to handle javascript & css files across a site?

    - by Industrial
    Hi everybody, I have had some thoughts recently on how to handle shared javascript and css files across a web application. In a current web application that I am working on, I got quite a large number of different javascripts and css files that are placed in an folder on the server. Some of the files are reused, while others are not. In a production site, it's quite stupid to have a high number of HTTP requests and many kilobytes of unnecessary javascript and redundant css being loaded. The solution to that is of course to create one big bundled file per page that only contains the necessary information, which then is minimized and sent compressed (GZIP) to the client. There's no worries to create a bundle of javascript files and minimize them manually if you were going to do it once, but since the app is continuously maintained and things do change and develop, it quite soon becomes a headache to do this manually while pushing out new updates that features changes to javascripts and/or css files to production. What's a good approach to handle this? How do you handle this in your application?

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  • Make sure bad patterns don't come back after refactoring

    - by Let_Me_Be
    I'm refactoring an old C code. The code has absolutely no layered architecture (everything is being accessed by everything) and I'm trying to change that. I would like to cut direct access to structure members (at least write for now) and only allow access through access functions. Is there some tool (or perhaps directly the compiler) that could check this rule for me? I need this since I'm maintaining a fork and the upstream isn't very concerned with code quality.

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  • Another problem with decltype

    - by There is nothing we can do
    template<class IntT, IntT low = IntT(), IntT high = IntT()> struct X { static_assert(std::is_same<decltype(low),decltype(high)>::value,"Different types not allowed");//this should give error if types are different decltype(low) a; decltype(high) b; X():a(decltype(a)()),b(decltype(b)())//WHY THIS DOES NOT COMPILE? { cout << typeid(a).name() << '\n'; cout << typeid(b).name() << '\n'; } }; int _tmain(int argc, _TCHAR* argv[]) { X<char,1,'a'> x;//this according to static_assert shouldn't compile but it does return 0; } Using VS2010. Please see 3 comments in code above.

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  • Haskell type signature with multiple type somethings (predicates?, for example Eq a =>)

    - by Andrew
    I'm not sure if type predicates is the right term, in fact I've never learned the word for this, so an edit to correct would be helpful - I'm referring to when you give the tipe of function f :: a -> b and you want to say a is a Eq and you say f :: Eq a => a -> b, the name for Eq a => - this is the thing i called a type predicate. My question, though, is how to have multiple of these, so if A is an Eq and B is a Num, I could say either f :: Eq a => a -> b or f :: Num b => a -> b. So, how can I have Eq a => and Num b => at the same time? f :: Eq a => Num b => a -> b, f :: Eq a -> Num b => a -> b, and f :: Eq a, Num b => a -> b all didn't do what I wanted.

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  • how phpmyvisitors works?

    - by hd
    hi i have installed "phpmyvisitors" cms to get statistics of my sites visits. it is written in php and is open source. i gets many useful information like: -total visits -viewed pages -visitor browser informations -visitor distribution over the world -how visitors access to site -how much time they spend on sites and .... it is some think like Google Analytics.but fewer features. my question is: " how does it do all of them? "

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  • static_cast from Derived* to void* to Base*

    - by Roberto
    I would like to cast a pointer to a member of a derived class to void* and from there to a pointer of the base class, like in the example below: #include <iostream> class Base { public: void function1(){std::cout<<"1"<<std::endl;} virtual void function2()=0; }; class Derived : public Base { public: virtual void function2(){std::cout<<"2"<<std::endl;} }; int main() { Derived d; void ptr* = static_cast<void*>(&d); Base* baseptr=static_cast<Base*>(ptr); baseptr->function1(); baseptr->function2(); } This compiles and gives the desired result (prints 1 and 2 respectively), but is it guaranteed to work? The description of static_cast I found here: http://en.cppreference.com/w/cpp/language/static_cast only mentions conversion to void* and back to a pointer to the same class (point 10).

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  • Is there a good [and modern] reason to not have static HTML pages with AJAX content , rather than generate pages?

    - by user1725
    Assumptions: We don't care about IE6, and Noscript users. Lets pretend we have the following design concept: All your pages are HTML/CSS that create the ascetics, layout, colours, general design related things. Lets pretend this basic code below is that: <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> <html> <head> <link href="/example.css" rel="stylesheet" type="text/css"/> <script src="example.js" type="text/javascript"></script> <head> <body> <div class="left"> </div> <div class="mid"> </div> <div class="right"> </div> </body> </html> Which in theory should produce, with the right CSS, three vertical columns on the web page. Now, here's the root of the question, what are the serious advantages and/or disadvantages of loading the content of these columns (lets assume they are all indeed dynamic content, not static) via AJAX requests, or have the content pre-set with a scripting language? So for instance, we would have, in the AJAX example, lets asume jquery is used on-load: //Multiple http requests $("body > div.left").load("./script.php?content=news"); $("body > div.right").load("./script.php?content=blogs"); $("body > div.mid").load("./script.php?content=links"); OR--- //Single http request $.ajax({ url: './script.php?content=news|blogs|links', method: 'json', type: 'text', success: function (data) { $("body > div.left").html(data.news); $("body > div.right").html(data.blogs); $("body > div.mid").html(data.links); } }) Verses doing this: <body> <div class="left"> <?php echo function_returning_news(); ?> </div> <div class="mid"> <?php echo function_returning_blogs(); ?> </div> <div class="right"> <?php echo function_returning_links(); ?> </div> </body> I'm personally thinking right now that doing static HTML pages is a better method, my reasoning is: I've separated my data, logic, and presentation (ie, "MVC") code. I can make changes to one without others. Browser caches mean I'm just getting server load mostly for the content, not the presentation wrapped around it. I could turn my "script.php" into a more robust API for the website. But I'm not certain or clear that these are legitimately good reasons, and I'm not confidently aware of other issues that could happen, so I would like to know the pros-and-cons, so to speak.

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  • How to access static members in a Velocity template?

    - by matt b
    I'm not sure if there is a way to do this in Velocity or not: I have a User POJO which a property named Status, which looks like an enum (but it is not, since I am stuck on Java 1.4), the definition looks something like this: public class User { // default status to User private Status status = Status.USER; public void setStatus(Status status) { this.status = status; } public Status getStatus() { return status; } And Status is a static inner class: public static final class Status { private String statusString; private Status(String statusString) { this.statusString = statusString; } public final static Status USER = new Status("user"); public final static Status ADMIN = new Status("admin"); public final static Status STATUS_X = new Status("blah"); //.equals() and .hashCode() implemented as well } With this pattern, a user status can easily be tested in a conditional such as if(User.Status.ADMIN.equals(user.getStatus())) ... ... without having to reference any constants for the status ID, any magic numbers, etc. However, I can't figure out how to test these conditionals in my Velocity template with VTL. I'd like to just print a simple string based upon the user's status, such as: Welcome <b>${user.name}</b>! <br/> <br/> #if($user.status == com.company.blah.User.Status.USER) You are a regular user #elseif($user.status == com.company.blah.User.Status.ADMIN) You are an administrator #etc... #end But this throws an Exception that looks like org.apache.velocity.exception.ParseErrorException: Encountered "User" at webpages/include/dashboard.inc[line 10, column 21] Was expecting one of: "[" ... From the VTL User Guide, there is no mention of accessing a Java class/static member directly in VTL, it appears that the right hand side (RHS) of a conditional can only be a number literal, string literal, property reference, or method reference. So is there any way that I can access static Java properties/references in a Velocity template? I'm aware that as a workaround, I could embed the status ID or some other identifier as a reference in my controller (this is a web MVC application using Velocity as the View technology), but I strongly do not want to embed any magic numbers or constants in the view layer.

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  • How to combine a Distance and Keyword SQL query?

    - by Jason
    Hi Folks, I have a tables in my database called "points" and "category". A user will input info into both a location input and a keyword input text box. Then I want to find points in my table where the keyword matches either the "title" field in the points table, or the "category" but are within a certain distance from the user's location. I want to order the results by distance. Here are the 2 queries which btoh work independently: $mysql = "SELECT *, ( 3959 * acos( cos( radians('$search_lat') ) * cos( radians( lat ) ) * cos( radians( longi ) - radians('$search_lng') ) + sin( radians('$search_lat') ) * sin( radians( lat ) ) ) ) AS distance FROM points HAVING distance < '$radius'"; $mysql2 = "SELECT * FROM `points` LEFT JOIN category USING ( category_id ) WHERE (point_title LIKE '%$esc_catsearch%' OR category.title LIKE '%$esc_catsearch%')"; Here is what I tried: $sql_search = sprintf("SELECT *,point_id FROM points WHERE point_title LIKE '%%%s%%' UNION SELECT *, ( 3959 * acos( cos( radians('%s') ) * cos( radians( lat ) ) * cos( radians( longi ) - radians('%s') ) + sin( radians('%s') ) * sin( radians( lat ) ) ) ) AS distance FROM points HAVING distance < '%s' ORDER BY distance LIMIT %d , %d", $esc_catsearch, mysql_real_escape_string($search_lat), mysql_real_escape_string($search_lng), mysql_real_escape_string($search_lat), mysql_real_escape_string($radius), $offset, $rowsPerPage); But it tells me there is no know column "distance". If I remove the "Order By" phrase then it works but I'm still not sure this is giving me the results I want. I also tried the query the other way around with the distance search first but that seems to ignore my keyword. Any thoughts would be much appreciated!

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