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• How to learn proper C++?

  - by Chris

  While reading a long series of really, really interesting threads, I've come to a realization: I don't think I really know C++. I know C, I know classes, I know inheritance, I know templates (& the STL) and I know exceptions. Not C++. To clarify, I've been writing "C++" for more than 5 years now. I know C, and I know that C and C++ share a common subset. What I've begun to realize, though, is that more times than not, I wind up treating C++ something vaguely like "C with classes," although I do practice RAII. I've never used Boost, and have only read up on TR1 and C++0x - I haven't used any of these features in practice. I don't use namespaces. I see a list of #defines, and I think - "Gracious, that's horrible! Very un-C++-like," only to go and mindlessly write class wrappers for the sake of it, and I wind up with large numbers (maybe a few per class) of static methods, and for some reason, that just doesn't seem right lately. The professional in me yells "just get the job done," the academic yells "you should write proper C++ when writing C++" and I feel like the point of balance is somewhere in between. I'd like to note that I don't want to program "pure" C++ just for the sake of it. I know several languages. I have a good feel for what "Pythonic" is. I know what clean and clear PHP is. Good C code I can read and write better than English. The issue is that I learned C by example, and picked up C++ as a "series of modifications" to C. And a lot of my early C++ work was creating class wrappers for C libraries. I feel like my own personal C-heavy background while learning C++ has sort of... clouded my acceptance of C++ in it's own right, as it's own language. Do the weathered C++ lags here have any advice for me? Good examples of clean, sharp C++ to learn from? What habits of C does my inner-C++ really need to break from? My goal here is not to go forth and trumpet "good" C++ paradigm from rooftops for the sake of it. C and C++ are two different languages, and I want to start treating them that way. How? Where to start? Thanks in advance! Cheers, -Chris

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• Passing Variables Along in a Function

  - by John

  Hello, In the function show_commentbox() below, I would like to pass along the variables $_SESSION['loginid'], $submissionid, $submission, $url, $submittor, $submissiondate, $countcomments, $dispurl. With the setup below, it's not working. How could I change it to make show_commentbox() pass the variables along? Thanks in advance, John index.php: <?php $submission = $_GET['submission']; require_once "header.php"; include "login.php"; include "comments.php"; include "commentformonoff.php"; ?> In header.php: require_once ("function.inc.php"); In comments.php: $uid = $_SESSION['loginid']; $submissiondate = mysql_real_escape_string($_GET['submissiondate']); $submittor = mysql_real_escape_string($_GET['submittor']); $countcomments = mysql_real_escape_string($_GET['countcomments']); $dispurl = mysql_real_escape_string($_GET['dispurl']); $url = mysql_real_escape_string($_GET['url']); $submission = mysql_real_escape_string($_GET['submission']); $submissionid = mysql_real_escape_string($_GET['submissionid']); commentformonoff.php: <?php if (!isLoggedIn()) { if (isset($_POST['cmdlogin'])) { if (checkLogin($_POST['username'], $_POST['password'])) { show_commentbox(); } else { echo "Login to comment"; } } else { echo "Login to comment"; } } else { show_commentbox(); } ?> In display.functions.inc.php: function show_commentbox() { echo '<form action="http://www...com/sandbox/comments/comments2.php" method="post"> <input type="hidden" value="'.$_SESSION['loginid'].'" name="uid"> <input type="hidden" value="'.$submissionid.'" name="submissionid"> <input type="hidden" value="'.$submission.'" name="submission"> <input type="hidden" value="'.$url.'" name="url"> <input type="hidden" value="'.$submittor.'" name="submittor"> <input type="hidden" value="'.$submissiondate.'" name="submissiondate"> <input type="hidden" value="'.$countcomments.'" name="countcomments"> <input type="hidden" value="'.$dispurl.'" name="dispurl"> <label class="addacomment" for="title">Add a comment:</label> <textarea class="commentsubfield" name="comment" type="comment" id="comment" maxlength="1000"></textarea> <div class="commentsubbutton"><input name="submit" type="submit" value="Submit"></div> </form> '; }

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• What is the advantage of using static methods in Python?

  - by Curious2learn

  I ran into unbound method error in python with the code class Sample(object): '''This class defines various methods related to the sample''' def drawSample(samplesize,List): sample=random.sample(List,samplesize) return sample Choices=range(100) print Sample.drawSample(5,Choices) After reading many helpful posts here, I figured how I could add @staticmethod above to get the code working. I am python newbie. Can someone please explain why one would want to define static methods? Or, why are not all methods defined as static methods. Thanks in advance.

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• Generate Javadoc for interfaces only using Ant script?

  - by ipkiss

  Hi all, I am using Apache Ant to generate Javadoc for my program which has many projects(or modules). However, I just want to generate Javadoc for Interfaces ONLY and I do not know how to check if a file is a class or interface in Ant. Someone suggested me that I should use and specify a list of files to exclude or include. However, there are hundreds of files in my program and specifying a list of class files to exclude is impossible. Does anyone have some ideas, please?

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• what is this 'map' mean..in django

  - by zjm1126

  this is the code: def create(request, form_class=MapForm, template_name="maps/create.html"): map_form = form_class(request.POST or None) if map_form.is_valid(): map = map_form.save(commit=False) and the map_form is : class MapForm(forms.ModelForm): slug = forms.SlugField(max_length=20, help_text = _("a short version of the name consisting only of letters, numbers, underscores and hyphens."), #error_message = _("This value must contain only letters, numbers, underscores and hyphens.")) ) def clean_slug(self): if Map.objects.filter(slug__iexact=self.cleaned_data["slug"]).count() > 0: raise forms.ValidationError(_("A Map already exists with that slug.")) return self.cleaned_data["slug"].lower() def clean_name(self): if Map.objects.filter(name__iexact=self.cleaned_data["name"]).count() > 0: raise forms.ValidationError(_("A Map already exists with that name.")) return self.cleaned_data["name"] class Meta: model = Map fields = ('name', 'slug', 'description')

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• How can I specify my own Rhino context in Java?

  - by Dan Howard

  I'm trying to ensure that my Rhino scripts (running under Java 6) are strict so that if a script developer misspells an expression I want an exception to be thrown. Currently what happens is the expression simply evaluates to "undefined". Now according to Mozilla org https://developer.mozilla.org/en/New_in_Rhino_1.6R6 there are features to enable strict checking in the context. I cannot find a working example of this. What I did so far was write a class to extend ContextFactory and then override the hasFeature method. public class ScriptContextFactory extends ContextFactory { protected boolean hasFeature(Context context, int featureIndex) { switch (featureIndex) { case Context.FEATURE_STRICT_EVAL: return true; case Context.FEATURE_STRICT_VARS: return true; } return super.hasFeature(context, featureIndex); } } Then in the Main I set mine to the default. ContextFactory.initGlobal(new ScriptContextFactory()); and I get an illegal state exception. :( Any ideas or samples on how this works? TIA

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• 'Why' and 'Where' Generics is actually used?

  - by NLV

  Hi all I know that generics are used to achieve type safety and i frequently read that they are largely used in custom collections. But why actually do we need to have it generic? For example, Why cant i use string[] instead of List<string> Lets consider i declare generic class and it has a property X T x; If i provide a method for the class which does x = x + 1; what does it mean actually? I dono what T is actually going to be and i dono what x = x + 1 going to perform actually? If i'm not able to do my own manipulations in my methods how the generics are going to be help me anyway? I've already studied lot of bookish answers. It would be much appreciated if any one can provide some clear insights in this. Regards NLV

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• WIndows xp embedded file-based write filter

  - by Nima Rikhtegar

  does any body know any .net wrapper class for windows xp embedded file-based write filter (FBWF)?

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• Storing a reference to an object in C#

  - by Jack

  I was wondering how one could store a reference to an object in .net. That is, I would like something like the following code (note, of course, that the following code may be way off from how to actually do it): class Test { private /*reference to*/ Object a; public Test(ref int a) { this.a = a; this.a = ((int)this.a) + 1; } public Object getA() { return this.a; } } /* * ... */ static void Main(string[] args) { int a; a=3; Test t = new Test(ref a); Console.WriteLine(a); Console.WriteLine(t.getA()); Console.ReadKey(); } To produce the following output: 4 4 Ideally, I would like to do this without writing a wrapper class around the integer. In other words, I think I want pointers in .Net.

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• How to create a complete generic TreeView like data structure

  - by Nima Rikhtegar

  I want to create a completely generic treeview like structure. some thing like this: public class TreeView<T, K, L> { public T source; public K parent; public List<L> children; } as you can see in this class source, parent and also the children, all have a different generic data type. also i want my tree view to have unlimited number of levels (not just 3). this way when i want to work with my nodes in the code, all of them are going to be strongly typed. not just objects that i need to convert them to their original type. is it possible to create this kind of structure in c#, a treeview which all of its nodes are strongly typed? thanks

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• Ajax foreign key filter in Django admin interface

  - by Googol

  http://blog.philippmetzler.com/?p=52 Just tried django-ajax-filtered-fields and like it very much. I’m looking for a solution for this problem: My model looks like this: class Song(models.Model): Album = models.ForeignKey(Album) class Artist(models.Model): album = models.ForeignKey(Album) song = models.ForeignKey(Song, blank=True, null=True) So the user has to define a topic. He can also define a subtopic but doesn’t have to. The subtopic belongs to a topic. In the admin interface I’d like to limit the choices for subtopic based upon what he selects in topics. That should change dynamically with AJAX. I will have a closer look to django-ajax-filtered-fields but didn’t find a solution to that specific problem. Perhaps it’s another usecase for django-ajax-filtered-fields in general? Or do you know another solution to my specific requirements?

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• MonoTouch & SQLite - Cannot open database after previous successful connections

  - by Tanis Draven

  I am having difficulty in reading data from my SQLite database from MonoTouch. I can read and write without any difficulty for the first few screens and then suddenly I am unable to create any further connections with the error: Mono.Data.Sqlite.SqliteException: Unable to open the database file at Mono.Data.Sqlite.SQLite3.Open (System.String strFilename, SQLiteOpenFlagsEnum flags, Int32 maxPoolSize, Boolean usePool) [0x0007e] in /Developer/MonoTouch/Source/mono/mcs/class/Mono.Data.Sqlite/Mono.Data.Sqlite_2.0/SQLite3.cs:136 at Mono.Data.Sqlite.SqliteConnection.Open () [0x002aa] in /Developer/MonoTouch/Source/mono/mcs/class/Mono.Data.Sqlite/Mono.Data.Sqlite_2.0/SQLiteConnection.cs:888 I ensure that i dispose and close every connection each time i use it but still i have this problem. For example: var mySqlConn = new SqliteConnection(GlobalVars.connectionString); mySqlConn.Open(); SqliteCommand mySqlCommand = new SqliteCommand(SQL, mySqlConn); mySqlCommand.ExecuteNonQuery(); mySqlConn.Close(); mySqlCommand.Dispose(); mySqlConn.Dispose(); I'm guessing that I'm not closing the connections correctly. Any help would be greatly appreciated.

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• When to override OnError?

  - by Ek0nomik

  I'm looking into re-working and simplifying our error handling in an application I support. We currently have all of our pages inheriting from a base class we created, which in turn obviously inherits from System.Web.UI.Page. Within this base class, the OnError method is currently being overridden, and in turn calling MyBase.OnError, and then calling one of our custom logging methods. I don't see any benefit of overriding the OnError method, and I think it would be better to let the Application_Error method in the Global.asax take care of the unhandled exception (logging it) and then the customErrors section in the config would trigger a process to redirect the user. Looking online it looks like people override this method quite frequently, but I don't see a need to and this article from MSDN makes me think the same.

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• Session Logout in every two minutes.

  - by Pankaj Mishra

  I have Web Application in asp.net. Where I am maintaining Session for every User. And every Time I got logout in Approx 2 min. I tried to increase this time through web Config File upto 60 min but it is not working For me and I m getting same problem. I have created A class file For maintaining session.I am Using This Code. public static void createSession(System.Web.SessionState.HttpSessionState session) { Session = session; } This is my class file code. And I am calling this function in login Page load like this. BusinessClasses.SessionHandler.createSession(Page.Session); Then After I am Checking In everyPage. But this code is not working for me. Please Give Suggest me correct solution for this problem.

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• Split number and put each digit to separate html element

  - by Seven

  The problem is that I do not know how to break the loop for the first number and start again for the next one. Currently, one span.nNumber has a total digits of the two numbers (123456) and the next span.nNumber contains digits only from another number (456). Goal is to create sequence 123 and 456: <span class='nNumber'> <span>1</span> <span>2</span> <span>3</span> </span> and <span class='nNumber'> <span>4</span> <span>5</span> <span>6</span> </span> Example script: http://jsfiddle.net/PZ8Pt/2/

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• How does multiple implementing multiple COM interfaces work in C++?

  - by Martin

  I am trying to understand this example code regarding Browser Helper Objects. Inside, the author implements a single class which exposes multiple interfaces (IObjectWithSite, IDispatch). His QueryInterface function performs the following: if(riid == IID_IUnknown) *ppv = static_cast<BHO*>(this); else if(riid == IID_IObjectWithSite) *ppv = static_cast<IObjectWithSite*>(this); else if (riid == IID_IDispatch) *ppv = static_cast<IDispatch*>(this); I have learned that from a C perspective, interface pointers are just pointers to VTables. So I take it to mean that C++ is capable of returning the VTable of any implemented interface using static_cast. Does this mean that a class constructed in this way has a bunch of VTables in memory (IObjectWithSite, IDispatch, etc)? What does C++ do with the name collisions on the different interfaces (they each have a QueryInterface, AddRef and Release function), can I implement different methods for each of these?

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• How to get attribute of a model saved in instance variable

  - by Nazar

  I am writing a plugin, in which i define a new relation dynamically with in plugin. Sample code is given below module AttachDocumentsAs @as = nil def attach_documents_as(*attachment_as) attachment_as = attachment_as.to_a.flatten.compact.map(&:to_sym) @as = attachment_as.first class_inheritable_reader(@as) class_eval do has_many @as, :as => :attachable, :class_name=>"AttachDocuments::Models::AttachedDocument" accepts_nested_attributes_for @as end end end now in any model i used it as class Person < AtiveRecord::Base attach_documents_as :financial_documents end Now want to access want to access this attribute of the class in overloaded initialize method like this def initialize(*args) super(*args) "#{@as}".build end But it is not getting required attribute, can any one help me in it. I want to build this relation and set some initial values. Waiting for guidelines from all you guys.

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• custom list field with more than one row(image and text), and can be populated using a vector

  - by Jisson

  In my app I want show a list,and when user click in any list item ,some new items must be added to the same list.Now I use default ListField of bb and a vetcor to add or remove elements to or from it.Now I want the list to hold more than one row(an image and some text), i searched for it I got some good sample but it not suitable for me(http://stackoverflow.com/questions/1872160/how-to-customize-list-field-in-blackberry). I need a custom listfield which have atleast two rows and can be populated using a vector from the MainScreen class.I want only one object of custom class.If any one have idea please help.

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• Undefined reference to ...

  - by Patrick LaChance

  I keep getting this error message every time I try to compile, and I cannot find out what the problem is. any help would be greatly appreciated: C:\DOCUME~1\Patrick\LOCALS~1\Temp/ccL92mj9.o:main.cpp:(.txt+0x184): undefined reference to 'List::List()' C:\DOCUME~1\Patrick\LOCALS~1\Temp/ccL92mj9.o:main.cpp:(.txt+0x184): undefined reference to 'List::add(int)' collect2: ld returned 1 exit status code: //List.h #ifndef LIST_H #define LIST_H #include <exception> //brief Definition of linked list class class List { public: /** \brief Exception for operating on empty list */ class Empty : public std::exception { public: virtual const char* what() const throw(); }; /** \brief Exception for invalid operations other than operating on an empty list */ class InvalidOperation : public std::exception { public: virtual const char* what() const throw(); }; /** \brief Node within List */ class Node { public: /** data element stored in this node */ int element; /** next node in list */ Node* next; /** previous node in list */ Node* previous; Node (int element); ~Node(); void print() const; void printDebug() const; }; List(); ~List(); void add(int element); void remove(int element); int first()const; int last()const; int removeFirst(); int removeLast(); bool isEmpty()const; int size()const; void printForward() const; void printReverse() const; void printDebug() const; /** enables extra output for debugging purposes */ static bool traceOn; private: /** head of list */ Node* head; /** tail of list */ Node* tail; /** count of number of nodes */ int count; }; #endif //List.cpp I only included the parts of List.cpp that might be the issue #include "List.h" #include <iostream> #include <iomanip> using namespace std; List::List() { //List::size = NULL; head = NULL; tail = NULL; } List::~List() { Node* current; while(head != NULL) { current = head-> next; delete current->previous; if (current->next!=NULL) { head = current; } else { delete current; } } } void List::add(int element) { Node* newNode; Node* current; newNode->element = element; if(newNode->element > head->element) { current = head->next; } else { head->previous = newNode; newNode->next = head; newNode->previous = NULL; return; } while(newNode->element > current->element) { current = current->next; } if(newNode->element <= current->element) { newNode->previous = current->previous; newNode->next = current; } } //main.cpp #include "List.h" #include <iostream> #include <string> using namespace std; //void add(int element); int main (char** argv, int argc) { List* MyList = new List(); bool quit = false; string value; int element; while(quit==false) { cin>>value; if(value == "add") { cin>>element; MyList->add(element); } if(value=="quit") { quit = true; } } return 0; } I'm doing everything I think I'm suppose to be doing. main.cpp isn't complete yet, just trying to get the add function to work first. Any help will be greatly appreciated.

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• Recognition source of event in PyQT

  - by xTrol

  Hi, I`m starting with PyQt4 and right now I have a problem with events. I have one main class let say MainWindow. MainWindow has a list of buttons of type ButtonX (inherence form QPushButton). I would like to achieve one of 2 solutions (depends which is easier). 1) After click one of the button from the list I would like to run a one method of MainWindow. I would like to be able to read a source of event there (recognize clicked button) 2) Second solution is to run a method defined in ButtonX class. What I tried is: QtCore.QObject.connect(self.getButton(0, 0), QtCore.SIGNAL("clicked()"), self.getButton(0, 0).buttonMethod()) QtCore.QObject.connect(self.getButton(0, 0), QtCore.SIGNAL("clicked()"), self.getButton(0, 0), QtCore.SLOT("incrementValue()")) and even this line occure suspend Python interpreter QtCore.QObject.connect(self.getButton(0, 0), QtCore.SIGNAL("clicked()"), self.getButton(0, 0), QtCore.SLOT("incrementValue"))

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• Yii problem in blog tutorial

  - by Kani

  When i login occurs following problem. PHP Error Description include(User.php) [<a href='function.include'>function.include</a>]: failed to open stream: No such file or directory Source File D:\Badrakh\xampp\htdocs\yii\framework\YiiBase.php(395) 00383: * @return boolean whether the class has been loaded successfully 00384: */ 00385: public static function autoload($className) 00386: { 00387: // use include so that the error PHP file may appear 00388: if(isset(self::$_coreClasses[$className])) 00389: include(YII_PATH.self::$_coreClasses[$className]); 00390: else if(isset(self::$classMap[$className])) 00391: include(self::$classMap[$className]); 00392: else 00393: { 00394: if(strpos($className,'\\')===false) 00395: include($className.'.php'); 00396: else // class name with namespace in PHP 5.3

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• Is Dynamic Casting Possible in Java

  - by Tom Tucker

  So I have a class of overloaded methods like this: class Foo { public void test(Object value) { ... } public void test(String value) { ... } } I need to pass a property value of a bean to one of these methods depending on its type, but I don't know the actual property type until the runtime. e.g. public void run(Object bean, String propertyName) { Foo foo = new Foo(); foo.test(PropertyUtils.getProperty(bean, propertyName)); } BTW, PropertyUtils.getProperty() is a helper method that returns a value of the specified property on a bean. PropertyUtils.getProperty() returns an Object, so that test(Object value) will be always called and the actual property type will be ignored. I can figure out the propery type in the runtime, even if its value is null. Is there such a thing as dynamic casting in Java? If not, is there a way to have an overloaded method with the correct parameter type called?

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• Select child of earlier clicked item in jQuery

  - by koko

  I have clicked on a div. In this div is an image: <div class="grid_2 shareContent" id="facebook_45"> <a href="#"><img class="facebook" src="http://roepingen.kk/skins/admin/default/images/social/facebook.png" alt="Facebook not shared" width="32px" height="32px" /></a> </div> How can I change the image in the div? I have the clicked item saved in the variable 'clicked'. If possible I'd like to delete the link around the image also.

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• How to share a variable between two classes?

  - by Altefquatre

  How would you share the same object between two other objects? For instance, I'd like something in that flavor: class A { private string foo_; // It could be any other class/struct too (Vector3, Matrix...) public A (string shared) { this.foo_ = shared; } public void Bar() { this.foo_ = "changed"; } } ... // inside main string str = "test"; A a = new A(str); Console.WriteLine(str); // "test" a.Bar(); Console.WriteLine(str); // I get "test" instead of "changed"... :( I read there is some ref/out stuff, but I couldn't get what I'm asking here. I could only apply some changes in the methods scope where I was using ref/out arguments... I also read we could use pointers, but is there no other way to do it?

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• How can I check if a value exists in a list using C#

  - by Samantha J

  I have the following code that gives me a list of id and names from the new ASP.NET MVC5 Identity: var identityStore = new IdentityStore(); var users = ( from user in identityStore.DbContext.Set<User>() select new { id = user.Id, name = user.UserName } ); How could I modify this so that it allows me to check if a UserName exists? Here's the user class: public class User : IUser { public User(); public User(string userName); [Key] public string Id { get; set; } public virtual ICollection<UserLogin> Logins { get; set; } public virtual UserManagement Management { get; set; } public virtual ICollection<UserRole> Roles { get; set; } public string UserName { get; set; } }

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