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• Is it poor design to create objects that only execute code during the constructor?

  - by Curtix

  In my design I am using objects that evaluate a data record. The constructor is called with the data record and type of evaluation as parameters and then the constructor calls all of the object's code necessary to evaluate the record. This includes using the type of evaluation to find additional parameter-like data in a text file. There are in the neighborhood of 250 unique evaluation types that use the same or similar code and unique parameters coming from the text file. Some of these evaluations use different code so I benefit a lot from this model because I can use inheritance and polymorphism. Once the object is created there isn't any need to execute additional code on the object (at least for now) and it is used more like a struct; its kept on a list and 3 properties are used later. I think this design is the easiest to understand, code, and read. A logical alternative I guess would be using functions that return score structs, but you can't inherit from methods so it would make it kind of sloppy imo. I am using vb.net and these classes will be used in an asp.net web app as well as in a distributed app. thanks for your input

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• Get XML-RPC (Andorid - PHP) web service different params type

  - by Jovan

  Hi, I want to create XML-RPC web service for Andorid (client) - PHP (Server) communication I create XML-RPC PHP web service server using this tutorial: http://articles.sitepoint.com/article/own-web-service-php-xml-rpc/5 For andorid client web service I use this project: http://code.google.com/p/android-xmlrpc/ server and client communication is OK, but I have problem with getting params from andorid client to php server. From andorid client I send two params (first integer and second float number) Object[] params = { 3, 3.6f, }; method.call(params); , but I don't know how to handle this parameters in php server?? in php server there is some function , but with only one param ($news_id): function news_viewNewsItem ( $news_id ) { /* Define the query to fetch the news item */ $query = "SELECT * FROM kd_xmlrpc_news WHERE news_id = '" . $news_id . "'"; $sql = mysql_query ( $query ); if ( $result = mysql_fetch_array ( $sql ) ) { /* Extract the variables for sending in our server response */ $news_item['news_id'] = $result['news_id']; $news_item['date'] = XMLRPC_convert_timestamp_to_iso8601( mysql_datetime_to_timestamp( $result['date'] ) ); $news_item['title'] = $result['title']; $news_item['full_desc'] = $result['full_desc']; $news_item['author'] = $result['author']; /* Respond to the client with the news item */ XMLRPC_response(XMLRPC_prepare($news_item), KD_XMLRPC_USERAGENT); } else { /* If there was an error, respond with a fault code instead */ XMLRPC_error("1", "news_viewNewsItem() error: Unable to read news:" . mysql_error(), KD_XMLRPC_USERAGENT); } } In server.py file there is functions for every method but I dont know how to write in php server: def add(self, x, y): print print "input x=%s, y=%s" % (str(x), str(y)) sum = x + y print "output", sum print return sum Can some one help me with code , and tell me how to handle various types from client to server?? Thanks and Happy New Year

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• Sending a JSON object to an ASP.NET web service using JQUERY ajax function

  - by uzay95

  I want to create object on the client side of aspx page. And i want to add functions to these javascript classes to make easier the life. Actually i can get and use the objects (derived from the server side classes) which returns from the services. When i wanted to send objects from the client by jquery ajax methods, i couldn't do it :) This is my javascript object: function ClassAndMark(_mark, _lesson){ this.Lesson = _lesson; this.Mark = _mark; } function Student(_name, _surname, _classAndMark){ this.Name = _name; this.SurName = _surname; this.ClassAndMark = _classAndMark; } JSClass.prototype.fSaveToDB(){ $.ajax({ type: "POST", contentType: "application/json; charset=utf-8", url: "/WS/SaveObject.asmx/fSaveToDB"), data: ????????????, dataType: "json" }); } Actually i don't know what should be definition of classes and methods on the Server side but i think: class ClassAndMark{ public string Lesson ; public string Mark ; } class Student{ public string Name ; public string SurName ; public ClassAndMark ClassAndMark ; } Web service is below but again i couldn't get what should be instead of the ???? : [WebMethod()] public void fSaveToDB(???? _obj) { // How can i convert input parameter/parameters // of method in the server side object? }

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• QObject::connect not connecting signal to slot

  - by user1662800

  I am using C++ and Qt in my project and my problem is QObject::connect function doesn't connect signal to a slot. I have the following classes: class AddCommentDialog : public QDialog { Q_OBJECT public: ...some functions signals: void snippetAdded(); private slots: void on_buttonEkle_clicked(); private: Ui::AddCommentDialog *ui; QString snippet; }; A part of my Main window: class MainWindow : public QMainWindow { Q_OBJECT public: explicit MainWindow(QWidget *parent = 0); ~MainWindow(); private slots: void commentAddedSlot(); void variableAddedSlot(); ... private: AddCommentDialog *addCommentDialog; ... }; Ant the last dialog; class AddDegiskenDialog : public QDialog { Q_OBJECT public: ... signals: void variableAdded(); private slots: void on_buttonEkle_clicked(); private: Ui::AddDegiskenDialog *ui; ... }; In the main window constructor i connect signals and slots: addCommentDialog=new AddCommentDialog(); addDegiskenDialog=new AddDegiskenDialog(); connect(addDegiskenDialog, SIGNAL(variableAdded()), this, SLOT(variableAddedSlot())); connect(addCommentDialog, SIGNAL(snippetAdded()), this, SLOT(commentAddedSlot())); The point is my commentAddedSlot is connected to it's signal successfully, but commentAddedSlot is failed. There is the Q_OBJECT macros, no warning such as about no x slot. In addition to this, receivers(SIGNAL(snippetAdded())) gives me 1 but receivers(SIGNAL(variableAdded())) gives me 0 and i used commands qmake -project; qmake and make to fully compile. What am i missing?

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• Cross-platform general purpose C++ RPC library

  - by iUm

  Here's the task: Imagine, we have an applications and a plug-in for it (dynamic library). Interface between the application and the plug-in is completely defined. Now I need to run the application and the plug-in on different computers. I wrote a stub for the plug-in on a computer where the real applications is running. And the application loads it and calls its functions like if it were a native plug-in. On the other computer there's a stub instead of the real application, which loads the native plug-in. Now I need to organize RPCs between my stubs over the network, regardless the very transport. Usually, it's not difficult. But there're some restrictions: Application-plug-in interaction can be reenterable (e.g. application calls f1() from plug-in, in f1() plug-in calls g1() from application, in g1() application calls f2() from plug-in and so on...) Any such reenteration should be executed exactly by the same thread, which started the sequence Where can I find a cross-platform C++ RPC library with such features?

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• Enumeration trouble: redeclared as different kind of symbol

  - by Matt

  Hello all. I am writing a program that is supposed to help me learn about enumeration data types in C++. The current trouble is that the compiler doesn't like my enum usage when trying to use the new data type as I would other data types. I am getting the error "redeclared as different kind of symbol" when compiling my trangleShape function. Take a look at the relevant code. Any insight is appreciated! Thanks! (All functions are their own .cpp files.) header file #ifndef HEADER_H_INCLUDED #define HEADER_H_INCLUDED #include <iostream> #include <iomanip> using namespace std; enum triangleType {noTriangle, scalene, isoceles, equilateral}; //prototypes void extern input(float&, float&, float&); triangleType extern triangleShape(float, float, float); /*void extern output (float, float, float);*/ void extern myLabel(const char *, const char *); #endif // HEADER_H_INCLUDED main function //8.1 main // this progam... #include "header.h" int main() { float sideLength1, sideLength2, sideLength3; char response; do //main loop { input (sideLength1, sideLength2, sideLength3); triangleShape (sideLength1, sideLength2, sideLength3); //output (sideLength1, sideLength2, sideLength3); cout << "\nAny more triangles to analyze? (y,n) "; cin >> response; } while (response == 'Y' || response == 'y'); myLabel ("8.1", "2/11/2011"); return 0; } triangleShape shape # include "header.h" triangleType triangleShape(sideLenght1, sideLength2, sideLength3) { triangleType triangle; return triangle; }

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• How can i mock or test my deferred execution functionality?

  - by cottsak

  I have what could be seen as a bizarre hybrid of IQueryable<T> and IList<T> collections of domain objects passed up my application stack. I'm trying to maintain as much of the 'late querying' or 'lazy loading' as possible. I do this in two ways: By using a LinqToSql data layer and passing IQueryable<T>s through by repositories and to my app layer. Then after my app layer passing IList<T>s but where certain elements in the object/aggregate graph are 'chained' with delegates so as to defer their loading. Sometimes even the delegate contents rely on IQueryable<T> sources and the DataContext are injected. This works for me so far. What is blindingly difficult is proving that this design actually works. Ie. If i defeat the 'lazy' part somewhere and my execution happens early then the whole thing is a waste of time. I'd like to be able to TDD this somehow. I don't know a lot about delegates or thread safety as it applies to delegates acting on the same source. I'd like to be able to mock the DataContext and somehow trace both methods of deferring (IQueryable<T>'s SQL and the delegates) the loading so that i can have tests that prove that both functions are working at different levels/layers of the app/stack. As it's crucial that the deferring works for the design to be of any value, i'd like to see tests fail when i break the design at a given level (separate from the live implementation). Is this possible?

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• Javascript Closures, Callbacks, This and That

  - by nazbot

  I am having some trouble getting a callback function to work. Here is my code: SomeObject.prototype.refreshData = function() { var read_obj = new SomeAjaxCall("read_some_data", { }, this.readSuccess, this.readFail); } SomeObject.prototype.readSuccess = function(response) { this.data = response; this.someList = []; for (var i = 0; i < this.data.length; i++) { var systemData = this.data[i]; var system = new SomeSystem(systemData); this.someList.push(system); } this.refreshList(); } Basically SomeAjaxCall is making an ajax request for data. If it works we use the callback 'this.readSuccess' and if it fails 'this.readFail'. I have figured out that 'this' in the SomeObject.readSuccess is the global this (aka the window object) because my callbacks are being called as functions and not member methods. My understanding is that I need to use closures to keep the 'this' around, however, I have not been able to get this to work. If someone is able show me what I should be doing I would appreciate it greatly. I am still wrapping my head around how closures work and specifically how they would work in this situation. Thanks!

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• remove duplicated array values in a function PHP

  - by Deividas Juškevicius

  I read all topics related to this question in stackoverflow and whole internet and cant find working sollution... Each owner has his item and when someone buy his item, owner gets an confirmation email, but when in cart is few same owner items, he gets several same email letters, so I need to remove dublicated array entries. I have tried to use DISTINCT and array_uniques functions but no luck. Any advices? I have an array and function to send mail.. function email($mail_array) { foreach(array_unique($mail_array) as $field => $value) { $result = mysql_query("select email from users where $field='$value'"); $row = mysql_fetch_array($result); $maail = mysql_real_escape_string($row['email']); $email_to = "".$maail.""; // rest of mail formatting code // create email headers $headers = 'From: '.$email_from."\r\n" . 'Reply-To: '.$email_from."\r\n" . 'X-Mailer: PHP/' . phpversion(); @mail($email_to, $email_subject, $email_message, $headers); } for ($i = 0; $i < $max; $i++) { $pid = $_SESSION['cart'][$i]['productid']; $owner = get_owner($pid); $mail_array = array( 'name' => $owner ); email($mail_array) //call function to send mail }

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• Strange Effect with Overridden Properties and Reflection

  - by naacal

  I've come across a strange behaviour in .NET/Reflection and cannot find any solution/explanation for this: Class A { public string TestString { get; set; } } Class B : A { public override string TestString { get { return "x"; } } } Since properties are just pairs of functions (get_PropName(), set_PropName()) overriding only the "get" part should leave the "set" part as it is in the base class. And this is just what happens if you try to instanciate class B and assign a value to TestString, it uses the implementation of class A. But what happens if I look at the instantiated object of class B in reflection is this: PropertyInfo propInfo = b.GetType().GetProperty("TestString"); propInfo.CanRead ---> true propInfo.CanWrite ---> false(!) And if I try to invoke the setter from reflection with: propInfo.SetValue("test", b, null); I'll even get an ArgumentException with the following message: Property set method not found. Is this as expected? Because I don't seem to find a combination of BindingFlags for the GetProperty() method that returns me the property with a working get/set pair from reflection.

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• Model class for NSDictionary information with Lazy Loading

  - by samfu_1

  My application utilizes approx. 50+ .plists that are used as NSDictionaries. Several of my view controllers need access to the properties of the dictionaries, so instead of writing duplicate code to retrieve the .plist, convert the values to a dictionary, etc, each time I need the info, I thought a model class to hold the data and supply information would be appropriate. The application isn't very large, but it does handle a good deal of data. I'm not as skilled in writing model classes that conform to the MVC paradigm, and I'm looking for some strategies for this implementation that also supports lazy loading.. This model class should serve to supply data to any view controller that needs it and perform operations on the data (such as adding entries to dictionaries) when requested by the controller functions currently planned: returning the count on any dictionary adding one or more dictionaries together Currently, I have this method for supporting the count lookup for any dictionary. Would this be an example of lazy loading? -(NSInteger)countForDictionary: (NSString *)nameOfDictionary { NSBundle *bundle = [NSBundle mainBundle]; NSString *plistPath = [bundle pathForResource: nameOfDictionary ofType: @"plist"]; //load plist into dictionary NSMutableDictionary *dictionary = [[NSMutableDictionary alloc] initWithContentsOfFile: plistPath]; NSInteger count = [dictionary count] [dictionary release]; [return count] }

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• setting the openCV configuration in an openGL project produce several errors

  - by GolSa

  I have a win32 solution which is set for openGL; it works well; but I want to write a function which use functions of openCV; I set the configuration for openCV for both X86 and X64;;I commented the openCV function and just to test the correctness of configuration, I run it; but when I want to run it on X64 I faced with the error below: Error 1 error C2065: 'GWL_HINSTANCE' : undeclared identifier D:\matrix\matrixProjection\src\ControllerMain.cpp 35 1 matrixProjection Error 2 error C2664: 'CreateDialogParamW' : cannot convert parameter 4 from 'BOOL (__cdecl *)(HWND,UINT,WPARAM,LPARAM)' to 'DLGPROC' D:\matrix\matrixProjection\src\DialogWindow.cpp 47 1 matrixProjection Error 2 points to this line of code: HWND DialogWindow::create() { /*-->this line*/ handle = ::CreateDialogParam(instance, MAKEINTRESOURCE(id), parentHandle, Win::dialogProcedure, (LPARAM)controller); return handle; } but on Debug Win32 configure, it runs; I used openGL32 in my project; is there any probability to be the cause? is there any X64 version for openGL? I know that there is something needed in X64 mode which my solution can not handle it; I googled a lot about it but I did not find any solution; How can I solve that?

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• C++ polymorphism, function calls

  - by moai

  Okay, I'm pretty inexperienced as a programmer, let alone in C++, so bear with me here. What I wanted to do was to have a container class hold a parent class pointer and then use polymorphism to store a child class object. The thing is that I want to call one of the child class's functions through the parent class pointer. Here's a sort of example of what I mean in code: class SuperClass { public: int x; } class SubClass : public SuperClass { public: void function1() { x += 1; } } class Container { public: SuperClass * alpha; Container(SuperClass& beta) { alpha = beta; } } int main() { Container cont = new Container(new SubClass); } (I'm not sure that's right, I'm still really shaky on pointers. I hope it gets the point across, at least.) So, I'm not entirely sure whether I can do this or not. I have a sneaking suspicion the answer is no, but I want to be sure. If someone has another way to accomplish this sort of thing, I'd be glad to hear it.

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• Easiest way to remove Keys from a 2D Array?

  - by dbemerlin

  Hi, I have an Array that looks like this: array( 0 => array( 'key1' => 'a', 'key2' => 'b', 'key3' => 'c' ), 1 => array( 'key1' => 'c', 'key2' => 'b', 'key3' => 'a' ), ... ) I need a function to get an array containing just a (variable) number of keys, i.e. reduce_array(array('key1', 'key3')); should return: array( 0 => array( 'key1' => 'a', 'key3' => 'c' ), 1 => array( 'key1' => 'c', 'key3' => 'a' ), ... ) What is the easiest way to do this? If possible without any additional helper function like array_filter or array_map as my coworkers already complain about me using too many functions. The source array will always have the given keys so it's not required to check for existance. Bonus points if the values are unique (the keys will always be related to each other, meaning that if key1 has value a then the other key(s) will always have value b). My current solution which works but is quite clumsy (even the name is horrible but can't find a better one): function get_unique_values_from_array_by_keys(array $array, array $keys) { $result = array(); $found = array(); if (count($keys) > 0) { foreach ($array as $item) { if (in_array($item[$keys[0]], $found)) continue; array_push($found, $item[$keys[0]]); $result_item = array(); foreach ($keys as $key) { $result_item[$key] = $item[$key]; } array_push($result, $result_item); } } return $result; } Addition: PHP Version is 5.1.6.

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• Common "truisms" needing correction the most

  - by Charles Bretana

  In addition to "I never met a man I didn't like", Will Rogers had another great little ditty I've always remembered. It went: "It's not what you don't know that'll hurt you, it's what you do know that ain't so." We all know or subscribe to many IT "truisms" that mostly have a strong basis in fact, in something in our professional careers, something we learned from others, lessons learned the hard way by ourselves, or by others who came before us. Unfortuntely, as these truisms spread throughout the community, the details—why they came about and the caveats that affect when they apply—tend to not spread along with them. We all have a tendency to look for, and latch on to, small "rules" or principles that we can use to avoid doing a complete exhaustive analysis for every decision. But even though they are correct much of the time, when we sometimes misapply them, we pay a penalty that could be avoided by understooding the details behind them. For example, when user-defined functions were first introduced in SQL Server it became "common knowledge" within a year or so that they had extremely bad performance (because it required a re-compilation for each use) and should be avoided. This "trusim" still increases many database developers' aversion to using UDFs, even though Microsoft's introduction of InLine UDFs, which do not suffer from this issue at all, mitigates this issue substantially. In recent years I have run into numerous DBAs who still believe you should "never" use UDFs, because of this. What other common not-so-"trusims" do you know, which many developers believe, that are not quite as universally true as is commonly understood, and which the developer community would benefit from being better educated about? Please include why it was "true" to start off with, and under what circumstances it's not true. Limit responses to issues that are technical, where the "common" application of a "rule or principle" is in fact correct most of the time, or was correct back when it was first elucidated, but—in the edge cases, or because of not understanding the principle thoroughly, because technology has changed since it first spread, or applying the rule today without understanding the details behind the rule—can easily backfire or cause the opposite of the intended effect.

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• Testing When Correctness is Poorly Defined?

  - by dsimcha

  I generally try to use unit tests for any code that has easily defined correct behavior given some reasonably small, well-defined set of inputs. This works quite well for catching bugs, and I do it all the time in my personal library of generic functions. However, a lot of the code I write is data mining code that basically looks for significant patterns in large datasets. Correct behavior in this case is often not well defined and depends on a lot of different inputs in ways that are not easy for a human to predict (i.e. the math can't reasonably be done by hand, which is why I'm using a computer to solve the problem in the first place). These inputs can be very complex, to the point where coming up with a reasonable test case is near impossible. Identifying the edge cases that are worth testing is extremely difficult. Sometimes the algorithm isn't even deterministic. Usually, I do the best I can by using asserts for sanity checks and creating a small toy test case with a known pattern and informally seeing if the answer at least "looks reasonable", without it necessarily being objectively correct. Is there any better way to test these kinds of cases?

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• overwrite parameters passed by querystring

  - by opensas

  I have the following problem I have a web framework built with classic asp that saves the page state in hidden textboxes, and then issues a submit to itself. Before submitting, we have a javascript functions that saves the action in a hidden "action" input, and then performs the submit. The page loads the state from those hidden texts, reads the action issued, reads extra parameters, like the id of the record to edit, and then builds the page accordingly. I'd like to make a url link to automatically start the page with "edit" action on a "x" id. So I was thinking about building the following url, for example http://myapp/user?action=edit&id=23 the problem is that when the page auto-submits, que url string keeps the parameters. I'd like to achieve the following: when the user clicks on http://myapp/user?action=edit&id=23 my page should receive the posted values action=edit and id=23 but the url should be just http://myapp/user and both parameters should be kept in the hidden texts... (I wonder if I make myself clear...) thanks a lot saludos sas ps: I have a couple of ideas about how to solve it, but I'll post them as answers...

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• C++ compiler unable to find function (namespace related)

  - by CS student

  I'm working in Visual Studio 2008 on a C++ programming assignment. We were supplied with files that define the following namespace hierarchy (the names are just for the sake of this post, I know "namespace XYZ-NAMESPACE" is redundant): (MAIN-NAMESPACE){ a bunch of functions/classes I need to implement... (EXCEPTIONS-NAMESPACE){ a bunch of exceptions } (POINTER-COLLECTIONS-NAMESPACE){ Set and LinkedList classes, plus iterators } } The MAIN-NAMESPACE contents are split between a bunch of files, and for some reason which I don't understand the operator<< for both Set and LinkedList is entirely outside of the MAIN-NAMESPACE (but within Set and LinkedList's header file). Here's the Set version: template<typename T> std::ostream& operator<<(std::ostream& os, const MAIN-NAMESPACE::POINTER-COLLECTIONS-NAMESPACE::Set<T>& set) Now here's the problem: I have the following data structure: Set A Set B Set C double num It's defined to be in a class within MAIN-NAMESPACE. When I create an instance of the class, and try to print one of the sets, it tells me that: error C2679: binary '<<' : no operator found which takes a right-hand operand of type 'const MAIN-NAMESPACE::POINTER-COLLECTIONS-NAMESPACE::Set' (or there is no acceptable conversion) However, if I just write a main() function, and create Set A, fill it up, and use the operator- it works. Any idea what is the problem? (note: I tried any combination of using and include I could think of).

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• Django Aggregation Across Reverse Relationship

  - by Tom

  Given these two models: class Profile(models.Model): user = models.ForeignKey(User, unique=True, verbose_name=_('user')) about = models.TextField(_('about'), blank=True) zip = models.CharField(max_length=10, verbose_name='zip code', blank=True) website = models.URLField(_('website'), blank=True, verify_exists=False) class ProfileView(models.Model): profile = models.ForeignKey(Profile) viewer = models.ForeignKey(User, blank=True, null=True) created = models.DateTimeField(auto_now_add=True) I want to get all profiles sorted by total views. I can get a list of profile ids sorted by total views with: ProfileView.objects.values('profile').annotate(Count('profile')).order_by('-profile__count') But that's just a dictionary of profile ids, which means I then have to loop over it and put together a list of profile objects. Which is a number of additional queries and still doesn't result in a QuerySet. At that point, I might as well drop to raw SQL. Before I do, is there a way to do this from the Profile model? ProfileViews are related via a ForeignKey field, but it's not as though the Profile model knows that, so I'm not sure how to tie the two together. As an aside, I realize I could just store views as a property on the Profile model and that may turn out to be what I do here, but I'm still interested in learning how to better use the Aggregation functions.

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• friend declaration in C++

  - by Happy Mittal

  In Thinking in C++ by Bruce eckel, there is an example given regarding friend functions as // Declaration (incomplete type specification): struct X; struct Y { void f(X*); }; struct X { // Definition private: int i; public: friend void Y::f(X*); // Struct member friend }; void Y::f(X* x) { x->i = 47; } Now he explained this: Notice that Y::f(X*) takes the address of an X object. This is critical because the compiler always knows how to pass an address, which is of a fixed size regardless of the object being passed, even if it doesn’t have full information about the size of the type. If you try to pass the whole object, however, the compiler must see the entire structure definition of X, to know the size and how to pass it, before it allows you to declare a function such as Y::g(X). But when I tried void f(X); as declaration in struct Y, it shows no error. Please explain why?

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• Python: why does this code take forever (infinite loop?)

  - by Rosarch

  I'm developing an app in Google App Engine. One of my methods is taking never completing, which makes me think it's caught in an infinite loop. I've stared at it, but can't figure it out. Disclaimer: I'm using http://code.google.com/p/gaeunitlink text to run my tests. Perhaps it's acting oddly? This is the problematic function: def _traverseForwards(course, c_levels): ''' Looks forwards in the dependency graph ''' result = {'nodes': [], 'arcs': []} if c_levels == 0: return result model_arc_tails_with_course = set(_getListArcTailsWithCourse(course)) q_arc_heads = DependencyArcHead.all() for model_arc_head in q_arc_heads: for model_arc_tail in model_arc_tails_with_course: if model_arc_tail.key() in model_arc_head.tails: result['nodes'].append(model_arc_head.sink) result['arcs'].append(_makeArc(course, model_arc_head.sink)) # rec_result = _traverseForwards(model_arc_head.sink, c_levels - 1) # _extendResult(result, rec_result) return result Originally, I thought it might be a recursion error, but I commented out the recursion and the problem persists. If this function is called with c_levels = 0, it runs fine. The models it references: class Course(db.Model): dept_code = db.StringProperty() number = db.IntegerProperty() title = db.StringProperty() raw_pre_reqs = db.StringProperty(multiline=True) original_description = db.StringProperty() def getPreReqs(self): return pickle.loads(str(self.raw_pre_reqs)) def __repr__(self): return "%s %s: %s" % (self.dept_code, self.number, self.title) class DependencyArcTail(db.Model): ''' A list of courses that is a pre-req for something else ''' courses = db.ListProperty(db.Key) def equals(self, arcTail): for this_course in self.courses: if not (this_course in arcTail.courses): return False for other_course in arcTail.courses: if not (other_course in self.courses): return False return True class DependencyArcHead(db.Model): ''' Maintains a course, and a list of tails with that course as their sink ''' sink = db.ReferenceProperty() tails = db.ListProperty(db.Key) Utility functions it references: def _makeArc(source, sink): return {'source': source, 'sink': sink} def _getListArcTailsWithCourse(course): ''' returns a LIST, not SET there may be duplicate entries ''' q_arc_heads = DependencyArcHead.all() result = [] for arc_head in q_arc_heads: for key_arc_tail in arc_head.tails: model_arc_tail = db.get(key_arc_tail) if course.key() in model_arc_tail.courses: result.append(model_arc_tail) return result Am I missing something pretty obvious here, or is GAEUnit acting up?

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• C++ design related question

  - by Kotti

  Hi! Here is the question's plot: suppose I have some abstract classes for objects, let's call it Object. It's definition would include 2D position and dimensions. Let it also have some virtual void Render(Backend& backend) const = 0 method used for rendering. Now I specialize my inheritance tree and add Rectangle and Ellipse class. Guess they won't have their own properties, but they will have their own virtual void Render method. Let's say I implemented these methods, so that Render for Rectangle actually draws some rectangle, and the same for ellipse. Now, I add some object called Plane, which is defined as class Plane : public Rectangle and has a private member of std::vector<Object*> plane_objects; Right after that I add a method to add some object to my plane. And here comes the question. If I design this method as void AddObject(Object& object) I would face trouble like I won't be able to call virtual functions, because I would have to do something like plane_objects.push_back(new Object(object)); and this should be push_back(new Rectangle(object)) for rectangles and new Circle(...) for circles. If I implement this method as void AddObject(Object* object), it looks good, but then somewhere else this means making call like plane.AddObject(new Rectangle(params)); and this is generally a mess because then it's not clear which part of my program should free the allocated memory. ["when destroying the plane? why? are we sure that calls to AddObject were only done as AddObject(new something).] I guess the problems caused by using the second approach could be solved using smart pointers, but I am sure there have to be something better. Any ideas?

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• Does the pointer to free() have to point to beginning of the memory block, or can it point to the interior?

  - by Lambert

  The question is in the title... I searched but couldn't find anything. Edit: I don't really see any need to explain this, but because people think that what I'm saying makes no sense (and that I'm asking the wrong questions), here's the problem: Since people seem to be very interested in the "root" cause of all the problem rather than the actual question asked (since that apparently helps things get solved better, let's see if it does), here's the problem: I'm trying to make a D runtime library based on NTDLL.dll, so that I can use that library for subsystems other than the Win32 subsystem. So that forces me to only link with NTDLL.dll. Yes, I'm aware that the functions are "undocumented" and could change at any time (even though I'd bet a hundred dollars that wcstombs will still do the same exact thing 20 years from now, if it still exists). Yes, I know people (especially Microsoft) don't like developers linking to that library, and that I'll probably get criticized for the right here. And yes, those two points above mean that programs like chkdsk and defragmenters that run before the Win32 subsystem aren't even supposed to be created in the first place, because it's literally impossible to link with anything like kernel32.dll or msvcrt.dll and still have NT-native executables, so we developers should just pretend that those stages are meant to be forever out of our reaches. But no, I doubt that anyone here would like me to paste a few thousand lines of code and help me look through them and try to figure out why memory allocations that aren't failing are being rejected by the source code I'm modifying. So that's why I asked about a different problem than the "root" cause, even though that's supposedly known to be the best practice by the community. If things still don't make sense, feel free to post comments below! :)

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• QListWidget drag and drop items disappearing from list

  - by ppalasek

  Hello, I'm having trouble implementing a QListWidget with custom items that can be reordered by dragging and dropping. The problem is when I make a fast double click (a very short drag&drop) on an item, the item sometimes disappears from the QListWidget. This is the constructor for my Widget: ListPopisiDragDrop::ListPopisiDragDrop(QWidget *parent) : QListWidget(parent) { setSelectionMode(QAbstractItemView::SingleSelection); setDragEnabled(true); viewport()->setAcceptDrops(true); setDefaultDropAction(Qt::MoveAction); setDropIndicatorShown(true); setDragDropMode(QAbstractItemView::InternalMove); } also the drop event: void ListPopisiDragDrop::dropEvent(QDropEvent *event){ int startRow=currentIndex().row(); QListWidget::dropEvent(event); int endRow=currentIndex().row(); //more code... } Custom items are made by implementing paint() and sizeHint() functions from QAbstractItemDelegate. When the problem with disappearing items happens, the dropEvent isn't even called. I really don't know what is happening and if I'm doing something wrong. Any help is appreciated. Thanks! Edit: I'm running the application on a Symbian S60 5th edition phone. Edit2: If I add this line to the constructor: setDragDropOverwriteMode(true); the item in the list still disappears, but an empty row stays in it's place.

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• How do I select dynamic ids in this format?

  - by sjsc

  I'm trying to select dynamic ids when a user types something into the input fields. My app spits out the input fields in the following format: <input id="student_1_first_name" /> <input id="student_1_last_name" /> <input id="student_2_first_name" /> <input id="student_2_last_name" /> <input id="student_3_first_name" /> <input id="student_3_last_name" /> etc. For example, I tried doing this to select the end of the id string: <script type="text/javascript"> $(document).ready( function (){ $("input[id$=_first_name]").bind("keyup", run_some_function_here); run_some_function_here(); $("input[id$=_last_name]").bind("keyup", run_some_function_here); run_some_function_here(); } ); </script> When I do that, Jquery can't seem to select the input ids, so the functions don't run. Do you have any ideas on how I can select the ids correctly?

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