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  • Sorted sets and comparators

    - by Jack
    Hello, I'm working with a TreeSetthat is meant to store pathfind locations used during the execution of a A* algorithm. Basically until there are "open" elements (still to be exhaustively visited) the neighbours of every open element are taken into consideration and added to a SortedSetthat keeps them ordered by their cost and heuristic cost. This means that I have a class like: public class PathTileInfo implements Comparable<PathTileInfo> { int cost; int hCost; final int x, y; @Override public int compareTo(PathTileInfo t2) { int c = cost + hCost; int c2 = t2.cost + t2.hCost; int costComp = c < c2 ? -1 : (c > c2 ? 1: 0); return costComp != 0 ? costComp : (x < t2.x || y < t2.y ? -1 : (x > t2.x || y > t2.y ? 1 : 0)); } @Override public boolean equals(Object o2) { if (o2 instanceof PathTileInfo) { PathTileInfo i = (PathTileInfo)o2; return i.cost + i.hCost == cost + hCost && x == i.x && y == i.y; } return false; } } In this way first the total cost is considered, then, since a total ordering is needed (consistency with equals) a ordering according to the x,y coordinate is taken into account. This should work but simply it doesn't, if I iterate over the TreeSet during the algorithm execution like in for (PathTileInfo t : openSet) System.out.print("("+t.x+","+t.y+","+(t.cost+t.hCost)+") "); I get results in which the right ordering is not kept, eg: (7,7,6) (7,6,7) (6,8,6) (6,6,7) (5,8,7) (5,7,7) (6,7,6) (6,6,7) (6,5,7) (5,7,7) (5,5,8) (4,7,7) (4,6,8) (4,5,8) is there something subtle I am missing? Thanks!

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  • Is there a way to send tracking info to Google Analytics from PHP ?

    - by seatoskyhk
    I have a PHP code that will return a image. the link is given to 3rd party. so, i need to keep track where the php request coming from. Because the PHP only return the image, I cannot use the Javascript code for Google analytics. I know that I can get the information from the access.log, but i think I can't dump the access.log to GA for analyzing, right? so, is there a way that I can do in PHP (e.g. sending a CURL ), send somethig to Google Analytics for tracking?

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  • How to add default value on django save form?

    - by Ignacio
    I have an object Task and a form that saves it. I want to automatically asign created_by field to the currently logged in user. So, my view is this: def new_task(request, task_id=None): message = None if task_id is not None: task = Task.objects.get(pk=task_id) message = 'TaskOK' submit = 'Update' else: task = Task(created_by = GPUser(user=request.user)) submit = 'Create' if request.method == 'POST': # If the form has been submitted... form = TaskForm(request.POST, instance=task) if form.is_valid(): task = form.save(commit=False); task.created_by = GPUser(user=request.user) task.save() if message == None: message = 'taskOK' return tasks(request, message) else: form = TaskForm(instance=task) return custom_render('user/new_task.html', {'form': form, 'submit': submit, 'task_id':task.id}, request) The problem is, you guessed, the created_by field doesn't get saved. Any ideas? Thanks

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  • Operator Overloading with C# Extension Methods

    - by Blinky
    I'm attempting to use extension methods to add an operater overload to the C# StringBuilder class. Specifically, given StringBuilder sb, I'd like sb += "text" to become equivalent to sb.Append("text"); Here's the syntax for creating an extension method for StringBuilder: public static class sbExtensions { public static StringBuilder blah(this StringBuilder sb) { return sb; } } It successfully adds the "blah" extension method to the StringBuilder. Unfortunately, operator overloading does not seem to work: public static class sbExtensions { public static StringBuilder operator +(this StringBuilder sb, string s) { return sb.Append(s); } } Among other issues, the keyword 'this' is not allowed in this context. Are adding operator overloads via extension methods possible? If so, what's the proper way to go about it?

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  • Disable link with the prototype observe method...

    - by enyo
    I want to create a link like this: <a href="http://example.com">text</a> and replace the behavior so that the link downloads the content with Ajax instead when clicking. It is important for me not to replace the href attribute (so copying the link still works). One solution would be to do: $('link').onclick = function() { return false; }; but I would like to use the .observe method. But this doesn't work: $('link').observe('click', function() { return false; }); (which is quite logical). Any ideas on how I could achieve this? Thanks.

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  • Asp.net Mvc - Kigg: Maintain User object in HttpContext.Items between requests.

    - by Pickels
    Hallo, first I want to say that I hope this doesn't look like I am lazy but I have some trouble understanding a piece of code from the following project. http://kigg.codeplex.com/ I was going through the source code and I noticed something that would be usefull for my own little project I am making. In their BaseController they have the following code: private static readonly Type CurrentUserKey = typeof(IUser); public IUser CurrentUser { get { if (!string.IsNullOrEmpty(CurrentUserName)) { IUser user = HttpContext.Items[CurrentUserKey] as IUser; if (user == null) { user = AccountRepository.FindByClaim(CurrentUserName); if (user != null) { HttpContext.Items[CurrentUserKey] = user; } } return user; } return null; } } This isn't an exact copy of the code I adjusted it a little to my needs. This part of the code I still understand. They store their IUser in HttpContext.Items. I guess they do it so that they don't have to call the database eachtime they need the User object. The part that I don't understand is how they maintain this object in between requests. If I understand correctly the HttpContext.Items is a per request cache storage. So after some more digging I found the following code. internal static IDictionary<UnityPerWebRequestLifetimeManager, object> GetInstances(HttpContextBase httpContext) { IDictionary<UnityPerWebRequestLifetimeManager, object> instances; if (httpContext.Items.Contains(Key)) { instances = (IDictionary<UnityPerWebRequestLifetimeManager, object>) httpContext.Items[Key]; } else { lock (httpContext.Items) { if (httpContext.Items.Contains(Key)) { instances = (IDictionary<UnityPerWebRequestLifetimeManager, object>) httpContext.Items[Key]; } else { instances = new Dictionary<UnityPerWebRequestLifetimeManager, object>(); httpContext.Items.Add(Key, instances); } } } return instances; } This is the part where some magic happens that I don't understand. I think they use Unity to do some dependency injection on each request? In my project I am using Ninject and I am wondering how I can get the same result. I guess InRequestScope in Ninject is the same as UnityPerWebRequestLifetimeManager? I am also wondering which class/method they are binding to which interface? Since the HttpContext.Items get destroyed each request how do they prevent losing their user object? Anyway it's kinda a long question so I am gradefull for any push in the right direction. Kind regards, Pickels

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  • C# / Entity Framework / Linq question regarding calling a method when a class is accessed...

    - by Daniel
    So this is probably really basic, but I'm fairly new to all this. I am using Entity Framework with POCO entities. I want to call a method when a class property is set. I am trying to build an advertisement platform. I have a Customer class, a Venue class and an Advertisement class. I have my indexes set up in such a way that I can call customer.venue. However, I want to be able to call Customer.Venue.CurrentAdvertisement and have it execute a method (if CurrentAdvertisement is null) and return the current advertisement. I know I can explicitly set it every time, but I want to be able to override my classes so that whenever the CurrentAdvertisement property is accessed via LINQ it runs that method to return an ad. In order to do this I need to pass the Venue class a variable (venue name).

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  • KeyError this says that key(partner) is not in dict ?

    - by Ansh Jain
    I am trying to make an chat application using python and django. I almost complete it and its working fine for 8-10 minutes when two persons are chatting after that certain time it shows an error. here is the traceback : - Traceback (most recent call last): File "\Django_chat\django_chat\chat\views.py", line 55, in receive message = chatSession.getMessage(request.session['partner'],request.session['uid'],afterTime) File "C:\Python26\lib\site-packages\django\contrib\sessions\backends\base.py", line 47, in __getitem__ return self._session[key] KeyError: 'partner' here is the receive module :- def receive(request): message received by this user chatSession = chat() data = request.POST afterTime = data['lastMsgTime'] try: message = chatSession.getMessage(request.session['partner'],request.session['uid'],afterTime) except: #partnerId = virtual_users.objects.get(id=request.session['uid']).partner print('there is an error in receive request') traceback.print_exc(file=open("/myapp.log","a")) msg = serializers.serialize("json", message) return HttpResponse(msg) Please Help me :( thanks Ansh J

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  • Django models & Python class attributes

    - by Geo
    The tutorial on the django website shows this code for the models: from django.db import models class Poll(models.Model): question = models.CharField(max_length=200) pub_date = models.DateTimeField('date published') class Choice(models.Model): poll = models.ForeignKey(Poll) choice = models.CharField(max_length=200) votes = models.IntegerField() Now, each of those attribute, is a class attribute, right? So, the same attribute should be shared by all instances of the class. A bit later, they present this code: class Poll(models.Model): # ... def __unicode__(self): return self.question class Choice(models.Model): # ... def __unicode__(self): return self.choice How did they turn from class attributes into instance attributes? Did I get class attributes wrong?

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  • C# Reflection and Getting Properties

    - by Nathan
    I have the following dummy class structure and I am trying to find out how to get the properties from each instance of the class People in PeopleList. I know how to get the properties from a single instance of People but can't for the life of me figure out how to get it from PeopleList. I am sure this is really straightforward but can someone point me in the right direction? public class Example { public class People { private string _name; public string Name { get { return _name; } set { _name = value; } } private int _age; public int Age { get { return _age; } set { _age = value; } } public People() { } public People(string name, int age) { this._name = name; this._age = age; } } public class PeopleList : List<People> { public static void DoStuff() { PeopleList newList = new PeopleList(); // Do some stuff newList.Add(new People("Tim", 35)); } } }

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  • Convert the code from PHP to Ruby on rails

    - by theband
    public function getFtime() { $records=array(); $sql="SELECT * FROM `finishedtime`"; $result=mysql_query($sql); if(!$result){throw new Exception(mysql_error());} if(mysql_num_rows($result)==0){return $records;} while($row=mysql_fetch_assoc($result)){$records[]=$row;} return $records; } I am in the process of learning Ruby, can anyone convert this code into Ruby. This will make me construe on how to run a query and thrown the fetched result back.

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  • How to manually verify a user against the asp.net memberhip database

    - by Ekk
    I would like to know how I can verify a user's credential against an existing asp.net membership database. The short story is that we want provide single sign on access. So what I've done is to connect directly to the membership database and tried to run a sql query against the aspnet_Membership table: private bool CanLogin(string userName, string password) { // Check DB to see if the credential is correct try { string passwordHash = FormsAuthentication.HashPasswordForStoringInConfigFile(password, "SHA1"); string sql = string.Format("select 1 from aspnet_Users a inner join aspnet_Membership b on a.UserId = b.UserId and a.applicationid = b.applicationid where a.username = '{0}' and b.password='{1}'", userName.ToLowerInvariant(), passwordHash); using (SqlConnection sqlConn = new SqlConnection(ConfigurationManager.ConnectionStrings["LocalSqlServer"].ConnectionString)) using (SqlCommand sqlCmd = new SqlCommand(sql, sqlConn)) { sqlConn.Open(); int count = sqlCmd.ExecuteNonQuery(); sqlConn.Close(); return count == 1; } } catch (Exception ex) { return false; } } The problem is the password value, does anyone know how the password it is hashed?

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  • Height of a binary tree

    - by Programmer
    Consider the following code: public int heightOfBinaryTree(Node node) { if (node == null) { return 0; } else { return 1 + Math.max(heightOfBinaryTree(node.left), heightOfBinaryTree(node.right)); } } I want to know the logical reasoning behind this code. How did people come up with it? Does some have an inductive proof? Moreover, I thought of just doing a BFS with the root of the binary tree as the argument to get the height of the binary tree. Is the previous approach better than mine?Why?

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  • Mouse stops working after changing function

    - by heyohletsgo
    I'm making a console board game on c++, and i've been able to make the mouse work in the first function, the menu one, however, when i get to the getmove function and need to click on a house, it simply doesn't work.. Can anyone help? This is the class with the mouse. #include <cstdlib> #include <iostream> #include <process.h> #include <windows.h> #include <time.h> #include <stdio.h> using namespace std; void Game(); int Chu(); int rato(int &row, int &col) { HANDLE hIn; hIn = GetStdHandle(STD_INPUT_HANDLE); bool Continue = TRUE; INPUT_RECORD InRec; DWORD NumRead; HWND window = GetConsoleWindow(); POINT cursorPos; RECT wpos; int x = 0; int y = 0; //cout << hIn << endl; FlushConsoleInputBuffer(hIn); while (Continue) { ReadConsoleInput(hIn, &InRec, 1, &NumRead); switch (InRec.EventType) { case MOUSE_EVENT: if (GetAsyncKeyState(VK_LBUTTON)) { cout << "RATO"<<endl; GetWindowRect(window, &wpos); GetCursorPos(&cursorPos); cursorPos.x -= wpos.left; cursorPos.y -= wpos.top; x = (cursorPos.x - 5) / 16; y = (cursorPos.y - 25) / 24; cout << x << " " << y << endl; row = x; col = y; return row; } else if (GetAsyncKeyState(VK_RBUTTON)){ GetWindowRect(window, &wpos); GetCursorPos(&cursorPos); cursorPos.x -= wpos.left; cursorPos.y -= wpos.top; x = (cursorPos.x - 5) / 16; y = (cursorPos.y - 25) / 24; cout << x << " " << y << endl; row = x; col = y; return row; } break; } } } int main() { cout << "\n\n\n click on the stars" << endl; cout << " \n\n\n *******" << endl; int z = 0; int x = 0; int y = 0; int xo = 0; switch (rato(x,y)) { case 1: Game(); break; case 2: Game(); break; case 3: Game(); break; case 4: rato(x, y); break; case 5: rato(x, y); break; case 6: Game(); break; case 7: Game(); break; case 8: Game(); break; case 9: Game(); break; default: cout << "click again"; break; } return 0; } void Game() { int x = 0; int y = 0; int i = 0; cout << "GAME" << endl; do{ i++; rato(x, y); } while (i <= 2); Chu(); } int Chu() { int x = 0; int y = 0; int a = 0; int b = 0; int xo = 0; int yo = 0; cout << "\ click on the stars" << endl; HANDLE hConsole; hConsole = GetStdHandle(STD_OUTPUT_HANDLE); do{ xo = rato(x, y); if (0 <= xo && xo <= 5) { a = 1;} else cout << "CLICK AGAIN" << endl; } while (xo!=0); cout << a; return a; system("PAUSE"); }

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  • Clicking the TableView leads you to the another View

    - by lakesh
    I am a newbie to iPhone development. I have already created an UITableView. I have wired everything up and included the delegate and datasource. However, instead of adding a detail view accessory by using UITableViewCellAccessoryDetailClosureButton, I would like to click the UITableViewCell and it should lead to another view with more details about the UITableViewCell. My view controller looks like this: ViewController.h #import <UIKit/UIKit.h> @interface ViewController : UIViewController<UITableViewDataSource,UITableViewDelegate>{ NSArray *tableItems; NSArray *images; } @property (nonatomic,retain) NSArray *tableItems; @property (nonatomic,retain) NSArray *images; @end ViewController.m #import "ViewController.h" #import <QuartzCore/QuartzCore.h> @interface ViewController () @end @implementation ViewController @synthesize tableItems,images; - (void)viewDidLoad { [super viewDidLoad]; tableItems = [[NSArray alloc] initWithObjects:@"Item1",@"Item2",@"Item3",nil]; images = [[NSArray alloc] initWithObjects:[UIImage imageNamed:@"clock.png"],[UIImage imageNamed:@"eye.png"],[UIImage imageNamed:@"target.png"],nil]; } - (void)didReceiveMemoryWarning { [super didReceiveMemoryWarning]; // Dispose of any resources that can be recreated. } - (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section{ return tableItems.count; } - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath{ //Step 1:Check whether if we can reuse a cell UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:@"cell"]; //If there are no new cells to reuse,create a new one if(cell == nil) { cell = [[UITableViewCell alloc] initWithStyle:(UITableViewCellStyleDefault) reuseIdentifier:@"cell"]; UIView *v = [[UIView alloc] init]; v.backgroundColor = [UIColor redColor]; cell.selectedBackgroundView = v; //changing the radius of the corners //cell.layer.cornerRadius = 10; } //Set the image in the row cell.imageView.image = [images objectAtIndex:indexPath.row]; //Step 3: Set the cell text content cell.textLabel.text = [tableItems objectAtIndex:indexPath.row]; //Step 4: Return the row return cell; } - (void)tableView:(UITableView *)tableView willDisplayCell:(UITableViewCell *)cell forRowAtIndexPath:(NSIndexPath *)indexPath{ cell.backgroundColor = [ UIColor greenColor]; } @end Need some guidance on this.. Thanks.. Please pardon me if this is a stupid question.

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  • Cannot implicitly convert type ... to ... problem

    - by Younes
    I have this code: public static IEnumerable<dcCustomer> searchCustomer(string Companyname) { TestdbDataContext db = new TestdbDataContext(); IEnumerable<dcCustomer> myCustomerList = (from Customer res in db.Customers where res.CompanyName == Companyname select res); return myCustomerList; } And whatever i try i keep getting the convert error. Error 1 Cannot implicitly convert type 'System.Collections.Generic.IEnumerable<ConnectionWeb.Customer>' to 'System.Collections.Generic.IEnumerable<ConnectionWeb.DAL.dcCustomer>'. An explicit conversion exists (are you missing a cast?) \\srv01\home$\Z****\Visual Studio 2008\Projects\ConnectionWeb\ConnectionWeb\DAL\dcCustomer.cs 63 20 ConnectionWeb I want to try get myCustomerList to keep the values in an enumerator and return it.

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  • Form validation with optional File Upload field callback

    - by MotiveKyle
    I have a form with some input fields and a file upload field in the same form. I am trying to include a callback into the form validation to check for file upload errors. Here is the controller for adding and the callback: public function add() { if ($this->ion_auth->logged_in()): //validate form input $this->form_validation->set_rules('title', 'title', 'trim|required|max_length[66]|min_length[2]'); // link url $this->form_validation->set_rules('link', 'link', 'trim|required|max_length[255]|min_length[2]'); // optional content $this->form_validation->set_rules('content', 'content', 'trim|min_length[2]'); $this->form_validation->set_rules('userfile', 'image', 'callback_validate_upload'); $this->form_validation->set_error_delimiters('<small class="error">', '</small>'); // if form was submitted, process form if ($this->form_validation->run()) { // add pin $pin_id = $this->pin_model->create(); $slug = strtolower(url_title($this->input->post('title'), TRUE)); // path to pin folder $file_path = './uploads/' . $pin_id . '/'; // if folder doesn't exist, create it if (!is_dir($file_path)) { mkdir($file_path); } // file upload config variables $config['upload_path'] = $file_path; $config['allowed_types'] = 'jpg|png'; $config['max_size'] = '2048'; $config['max_width'] = '1920'; $config['max_height'] = '1080'; $config['encrypt_name'] = TRUE; $this->load->library('upload', $config); // upload image file if ($this->upload->do_upload()) { $this->load->model('file_model'); $image_id = $this->file_model->insert_image_to_db($pin_id); $this->file_model->add_image_id_to_pin($pin_id, $image_id); } } // build page else: // User not logged in redirect("login", 'refresh'); endif; } The callback: function validate_upload() { if ($_FILES AND $_FILES['userfile']['name']): if ($this->upload->do_upload()): return true; else: $this->form_validation->set_message('validate_upload', $this->upload->display_errors()); return false; endif; else: return true; endif; } I am getting the error Fatal error: Call to a member function do_upload() on a non-object on line 92 when I try to run this. Line 92 is the if ($this->upload->do_upload()): line in the validate_upload callback. Am I going about this the right way? What's triggering this error?

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  • Getting the date object to work in IE6 (w/ YYYY-MM-DD param)?

    - by J. LaRosee
    I just got IE6 sprung on me for a project that is going out into the wild soon, which means it's time to go back and comb through all of the CSS and JS. I've gotten hung up on the date object, however: $.validator.addMethod("dateRange", function() { var today = new Date(); var event_date_raw = $('#event_date').val(); var event_date_parts = event_date_raw.split("-"); var event_date = new Date( event_date_parts[2]+","+event_date_parts[1]+","+event_date_parts[0] ); if( event_date.getTime() >= today.getTime() ) return true; return false; }, "Please specify a correct date:"); event_date.getTime() is returning "NaN" in IE6 so the validation fails. The event_raw_date is in the YYYY-MM-DD format, which date doesn't seem to mind in every other browser... Thoughts?

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  • C++ method chaining including class constructor

    - by jena
    Hello, I'm trying to implement method chaining in C++, which turns out to be quite easy if the constructor call of a class is a separate statement, e.g: Foo foo; foo.bar().baz(); But as soon as the constructor call becomes part of the method chain, the compiler complains about expecting ";" in place of "." immediately after the constructor call: Foo foo().bar().baz(); I'm wondering now if this is actually possible in C++. Here is my test class: class Foo { public: Foo() { } Foo& bar() { return *this; } Foo& baz() { return *this; } }; I also found an example for "fluent interfaces" in C++ (http://en.wikipedia.org/wiki/Fluent_interface#C.2B.2B) which seems to be exactly what I'm searching for. However, I get the same compiler error for that code. Thanks in advance for any hint. Best, Jean

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  • How To Discover RSS Feeds for a given site.

    - by ktolis
    The quest is, given a site url (say http://stackoverflow.com/ ) to return the list of all the feeds available on the site. Methods acceptable: a) use a 3rd party service (google?, yahoo?, ...) programmatically b) using a crawler/spider (and some tips on how to configure the spider to return the rss/xml feeds only) c) programmatically using c/c++/php (any language/library) The task here is not to get the feeds contained on the page returned by the url but ALL the feeds that are available on the server at any depth... in any cases please provide a simple usage example.

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  • Javascript recursive data structure definition

    - by Matt Bierner
    I need to define a data structure recursively in Javascript. Here is a simple example of a circular linked list: // List a very simplified example of what the actual (non list) code does. function List(f, r) { return function(){ return [f, r]; }; } var head = List('a', List('b', List('c', head))); When this is executed, head in List 'c' is resolved to undefined, not List 'a' as I need. List is an example function that returns a function (It is not an Javascript list that I can append to). I tried to wrap the definition of head is a self executing named function, but that blew the stack when head was resolved. What is the Javascript style solution that I am overlooking?

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  • Objective-C++ Memory Problem

    - by Stephen Furlani
    Hello, I'm having memory woes. I've got a C++ Library (Equalizer from Eyescale) and they use the Traversal Visitor Pattern to allow you to add new functionality to their classes. I've finally figured out how it works, and I've got a Visitor that just returns the properties from one of the objects. (since I don't know how they're allocated). so. My little code does this: VisitorResult AGLContextVisitor::visit( Channel* channel ) { // Search through Nodes, Pipes until we get to the right window. // Add some code to make sure we find the right one? // Not executing the following code as C++ in gdb? eq::Window* w = channel->getWindow(); OSWindow* osw = w->getOSWindow(); AGLWindow* aw = (AGLWindow *)osw; AGLContext agl_ctx = aw->getAGLContext(); this->setContext(agl_ctx); return TRAVERSE_PRUNE; } So here's the problem. eq::Window* w = channel->getWindow(); (gdb) print w 0x0 BUT If I do this: (gdb) set objc-non-blocking-mode off (gdb) print w=channel->getWindow() 0x300effb9 // an honest memory location, and sets w as verified in the Debugger window of XCode. It does the same thing for osw. I don't get it. Why would something work in (gdb) but not in the code? The file is completely a cpp file, but it seems to be running in objc++, since I need to turn blocking off. Help!? I feel like I'm missing some memory-management basic thing here, either with C++ or Obj-C. [edit] channel-getWindow() is supposed to do this: /** @return the parent window. @version 1.0 */ Window* getWindow() { return _window; } The code also executes fine if I run it from a C++-only application. [edit] No... I tried creating a simple stand-alone program since I was tired of running it as a plugin. Messy to debug. And no, it doesn't run in the C++ program either. So I'm really at a loss as to what I'm doing wrong. Thanks, -- Stephen Furlani

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  • Lambda expressions and nullable types

    - by Mathew
    I have two samples of code. One works and returns the correct result, one throws a null reference exception. What's the difference? I know there's some magic happening with capturing variables for the lambda expression but I don't understand what's going on behind the scenes here. int? x = null; bool isXNull = !x.HasValue; // this works var result = from p in data.Program where (isXNull) select p; return result.Tolist(); // this doesn't var result2 = from p in data.Program where (!x.HasValue) select p; return result2.ToList();

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  • Checking lazy loaded properties have been instantiated

    - by PaulG
    In a class which has a lazy loaded property, such as: private Collection<int> someInts; public Collection<int> SomeInts { get { if (this.someInts == null) this.someInts = new Collection<int>(); return this.someInts; } } Is it worth also having a property such as: public bool SomeIntsExist { get { return (this.someInts != null && this.someInts.Count > 0); } } And then using that property.. eg: if (thatClass.SomeIntsExist) { // do something with thatClass.SomeInts collection } or is this premature optimisation. Its certainly easier to roll with something like below, but it will instantiate the collection needlessly: if (thatClass.SomeInts.Count > 0) { // do something with thatClass.SomeInts collection } Is the compiler smart enough to figure things like this out? Is there a better way?

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