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• How to find all clusters of forest on map?

  - by Damir

  How to find all clusters of forest on map ? I have simple class cell like (Type is enum {RIVER, FOREST,GRASS,HILL} class Cell{ public: Type type; int x; int y }; and map like vector<Cell> grid. Can anyone suggest me algorithm to create list<list<Cell>> clusters where list contains FOREST cells in same cluster (cluster are set of connected cells - connection can be in eight direction:up,down,left,right,up_right,up_left,down_left,down_right)? I need to find all clusters of forest on map and put every single cluster in list<Cell>.

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• Why can't I store a float value - it's always zero!

  - by just_another_coder

  I have a view controller that is created by the app delegate - it's the first one shown in the app. In its interface I declare float lengthOfTime; I also set it as a property: @property (nonatomic) float lengthOfTime; And in it's implemetation: @synthesize lengthOfTime; In the class viewDidLoad method, I set the value: self.lengthOfTime = 3.0f; However, after this, the value is always zero. No errors, no compile warnings, nothing. Just zero. The class is instantiated, it is showing in the view, so I'm pretty sure it's not a nil reference. I've searched all over Google and can't figure it out. What's going on?!? :(

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• Java: implementation of simple commands

  - by HH

  I have created a pkg for my regular simple commands. They are non-static, to be more extensible, but somewhat more time-consuming to use because of creating object to use one. My other classes use them. $ ls *.java CpF.java IsBinary.java RmLn.java Tools.java F2S.java IsRoot.java SaveToDisk.java WordCount.java Filters.java ModRelativePaths.java SetWord.java WordNumber.java Find.java powerTools.java Sort.java Which option would you choose to use them easier? to develop a small interface like 'powerTools.java' for the pkg. to create a class with static methods for them. to add a static method to each class to stop overusing 'creating too many files' and centralising some? sthing else?

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• How to determine whether a .NET exception is being handled?

  - by romkyns

  We're investigating a coding pattern in C# in which we'd like to use a "using" clause with a special class, whose Dispose() method does different things depending on whether the "using" body was exited normally or with an exception. To the best of my understanding, the CLR keeps track of the current exception being handled until it's been consumed by a "catch" handler. However it's not entirely clear whether this information is exposed in any way for the code to access. Do you know whether it is, and if so, how to access it? For example: using (var x = new MyObject()) { x.DoSomething(); x.DoMoreThings(); } class MyObject : IDisposable { public void Dispose() { if (ExceptionIsBeingHandled) Rollback(); else Commit(); } } This looks almost like System.Transactions.TransactionScope, except that success/failure is not determined by a call to x.Complete(), but rather based on whether the using body was exited normally.

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• Find if id of a link equals id of parent container

  - by Robert Lawson

  Hi guys needing a bit of help. I am creating a one page personal site. Each section has a menu in it to jump to another section, however i want to have a class added to menu for the current section: i.e. if you are in about the about link would have a class 'current'. This is how it looks. <section id="about"> <nav> <li><a href="#" id ="about">About</a></li> <li><a href="#" id ="contact">About</a></li> <li><a href="#" id ="blog">About</a></li> </nav> New to jquery so i am struggling to find out how to do this. Any help will be greatly appreciated. Thanks

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• python iterators and thread-safety

  - by Igor

  I have a class which is being operated on by two functions. One function creates a list of widgets and writes it into the class: def updateWidgets(self): widgets = self.generateWidgetList() self.widgets = widgets the other function deals with the widgets in some way: def workOnWidgets(self): for widget in self.widgets: self.workOnWidget(widget) each of these functions runs in it's own thread. the question is, what happens if the updateWidgets() thread executes while the workOnWidgets() thread is running? I am assuming that the iterator created as part of the for...in loop will keep some kind of reference to the old self.widgets object? So I will finish iterating over the old list... but I'd love to know for sure.

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• django m2m how can i get m2m table elements in a view

  - by dana

  i have a model using m2m feature: class Classroom(models.Model): user = models.ForeignKey(User, related_name = 'classroom_creator') classname = models.CharField(max_length=140, unique = True) date = models.DateTimeField(auto_now=True) open_class = models.BooleanField(default=True) members = models.ManyToManyField(User,related_name="list of invited members", through = 'Membership') and i want to take all members of one class in a view and display them using the template system. In the view, i'm trying to take all the members from a classroom like that: def inside_classroom(request,classname): try: theclass = Classroom.objects.get(classname = classname) members = Members.objects.all() etc but it doesn't work,(though the db_table is named Classroom_Members) i guess i have to use another query for getting all the members from the classroom classname. also, i want to verify if the request.user is a member using (if request.user in members) how can i het those members? Thanks in advance!

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• Django says the "id may not be NULL" but why is it?

  - by Oli

  I'm going crazy today. I just tried to insert a new record and it threw back a "post_blogpost.id may not be NULL" error. Here's my model: class BlogPost(models.Model): title = models.CharField(max_length=100) slug = models.SlugField(max_length=100) who = models.ForeignKey(User, default=1) when = models.DateTimeField() intro = models.TextField(blank=True, null=True) content = models.TextField(blank=True, null=True) counter = models.PositiveIntegerField(default=0) published = models.BooleanField(default=False) css = models.TextField(blank=True, null=True) class Meta: ordering = ('-when', 'id') There are a number of functions beneath the model too but I won't include them in full here. Their names are: content_cache_key, clear_cache, __unicode__, reads, read, processed_content. I'm adding through the admin... And I'm running out of hair.

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• Multiple classes in a Python module

  - by ralphL

  I'm very new to Python (I'm coming from a JAVA background) and I'm wondering if anyone could help me with some of the Python standards. Is it a normal or "proper" practice to put multiple class in a module? I have been working with Django and started with the tutorials and they place their database model classes in the same module. Is this something that is normally done or should I stick with 1 class per module? Is their a reason I would do one over the other? Hope I'm being clear and not to generic. Thanks to everyone in advance!

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• How to access private static target field in aspect in AspectJ?

  - by LihO

  I have a simple class Main with private static int x and an aspect that should output the old value of x before it is reassigned: public class Main { private static int x; public static void main(String[] args) { foo(7); } public static void foo(int y) { x = y; } } and MonitorX.aj: public aspect MonitorX { before() : set(static int Main.x){ System.out.println(Main.x); } } which doesn't work since I can't access private x using Main.x. I've also tried: before(int t) : set(static int Main.x) && target(t){ System.out.println(t); } which doesn't work either (nothing is outputted, if I try to output string, it seems that the aspect isn't invoked at all). However printing out the new value that is being assigned works: before(int newVal) : set(static int Main.x) && args(newVal){ System.out.println(newVal); } What am I missing?

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• Beginner having a problem with classes

  - by David

  I'm working through O'Reilly's "Learning Python" and having a problem with classes. I think I understand the concept, but in practice have stumbled upon this problem. Fron page 88-89: >>> class Worker: def __innit__(self, name, pay): self.name=name self.pay=pay def lastName(self): return self.name.split()[-1] def giveRaise(self, percent): self.pay*=(1.0+percent) Then the book says "Calling the class like a function generates instances of a new type ...etc" and gives this example. bob = Worker('Bob Smith', 50000) This gives me this error: TypeError: this constructor takes no arguments. And then I start muttering profanities. So what am I doing wrong here? Thanks for the help.

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• Unable to create unmanaged object using new keyword in managed C++

  - by chair79

  Hi all, I've created a class with a boost::unordered_map as a member, Linkage.h #ifndef LINKAGE_H #define LINKAGE_H #include <boost/unordered_map.hpp> class Linkage { private: boost::unordered_map<int, int> m_IOMap; public: .... }; Linkage.cpp #include "stdafx.h" ... // methods and in the managed side of C++, I try to create the pointer of the obj: private: System::Void Form1_Load(System::Object^ sender, System::EventArgs^ e) { Linkage* m_pLink = new Linkage(); ..... } However this produces errors: Error 4 error LNK2005: "private: static unsigned int const boost::detail::type_with_alignment_imp<4>::found" (?found@?$type_with_alignment_imp@$03@detail@boost@@$$Q0IB) already defined in Proj_Test.obj Linkage.obj ..... Error 7 fatal error LNK1169: one or more multiply defined symbols found Could anyone explain to me pls? Thanks.

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• Application lifecycle. How to run something only when application starts

  - by David

  I have a dialog popup to indicate how long I want an activity to run. Seems simple enough, but its difficult to determine when the activity is really starting. If the user opens the keyboard on a G1 and thereby goes into landscape, that reruns the activities onCreate method. I can't have a static for the class or even create an application class, because I can't determine when the 'application' goes away. Even after destroying the only activity, the application is apparently still alive. Is there a way to determine that onCreate has been called because of the keyboard being extended or landscape mode invoked? Thanks

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• net c# lock statement in data access layer

  - by Pedro Rivera

  I saw a code where they have the data access layer like this: public class CustomerDA{ private static readonly object _sync = new object(); private static readonly CustomerDA _mutex = new CustomerDA(); private CustomerDA(){ } public CustomerDA GetInstance(){ lock(_sync){ return _mutex; } } public DataSet GetCustomers(){ //database SELECT //return a DataSet } public int UpdateCustomer(some parameters){ //update some user } } public class CustomerBO{ public DataSet GetCustomers(){ //some bussiness logic return CustomerDA.GetInstance().GetCustomers(); } } I was using it, but start thinking... "and what if had to build a facebook like application where there are hundreds of thousands of concurrent users? would I be blocking each user from doing his things until the previous user ends his database stuff? and for the Update method, is it useful to LOCK THREADS in the app when database engines already manage concurrency at database server level?" Then I started to think about moving the lock to the GetCustomers and UpdateCustomer methods, but think again: "is it useful at all?"

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• Placement of service methods

  - by mhp

  Let's assume I have two service classes with the following methods: GroupService createGroup() deleteGroup() updateGroup() findGroup() UserService createUser() deleteUser() updateUser() findUser() Now, I am thinking about the aesthetics of theses classes. Imagine we want to implement a method which search for all user of a specific group. Which service class is responsible for such a method? I mean, the return value is a user (or maybe a collection of users) but the parameter (which means the name of the group) is a group. So which service class is the better place to put this method in?

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• Problem in databinding a dictionary in ListView combo-box column.

  - by Ashish Ashu

  I have a listview of which itemsource is set to my custom collection, let's say MyCollection. The code below is not full code , it's just a code snippets to explain the problem. class Item : INotifyPropertyChanged { Options _options; public Options OptionProp { get { return _options; } set { _options = value; OnPropertyChanged ("OptionProp");} } string _Name; public string NameProp { get { return _Name; } set { _Name = value; OnPropertyChanged ("NameProp");} } } class Options : Dictionary<string,string> { public Options() { this.Clear(); this.Add("One" , "1" ); this.Add("Two" , "2" ); this.Add("Three" , "3" ); } } MyCollection in my viewModel class viewModel { ObservableCollection<Item> **MyCollection**; KeyValuePair<sting,string> **SelectedOption**; } The listview Item Source is set to my MyCollection. <ListView ItemSource = MyCollectoin> I Listview contains two columns of which I have defined a datatemplats in the listview. First column is a combo-box of which Itemsource is set to Options ( defined above ) Second column is a simple textblock to display Name. Problem 1. I have defined a datatemplate for first column in which I have a combo box , I have set the Itemsource =**MyCollection** and SelectedItem = SelectedOption of the combo-box. User can perform following operations in the listview: Add ( Add the row in the listview ) Move Up ( Move row up in the listview ) Move Down ( Move down the item in the listview ) .Now when I add the row in the listview , the combo-box selected index is always comes to -1 (first column). However the combo box contains options One, Two and Three. Also, I have initialized the SelectedOption to contain the first item, i:e One. problem 2. . Let suppose, I have added a single row in a listview and I have selected Option "one" in the combo box manually. Now when I perform Move Up or Move Down operations the selected index of a combo box is again set to -1. In the Move Up or Move Down operation , I am calling MoveUp and MoveDown methods of the Observable collection. Probelm 3 How to serialize the entire collection in XML. Since I can't serialize the Dictionary and KeyValue Pair. I have to restore the state of the listview.

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• iPhone SDK:How do you play video inside a view? Rather than fullscreen.

  - by Jessica

  Hi, I am trying to play video inside a UIView, so my first step was to add a class for that view and start playing a movie in it using this code: - (IBAction)movie:(id)sender{ NSBundle *bundle = [NSBundle mainBundle]; NSString *moviePath = [bundle pathForResource:@"Movie" ofType:@"m4v"]; NSURL *movieURL = [[NSURL fileURLWithPath:moviePath] retain]; MPMoviePlayerController *theMovie = [[MPMoviePlayerController alloc] initWithContentURL:movieURL]; theMovie.scalingMode = MPMovieScalingModeAspectFill; [theMovie play]; } But this just crashes the app when using this method inside it's own class, but is fine elsewhere. Does anyone know how to play video inside a view? and avoid it being full screen?

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• How to hide a label for="x01" Checkbox using jQuery

  - by tonsils

  Hi, I am attempting to hide this checkbox, which is a check all checkbox in my table header, using jQuery but am not having much luck. The view source of the section I am trying to hide from the user is as follows: <th class="t12subheader" id="CHECK$01"><label for="x01" class="hideMe508">Check All</label><input type="checkbox" name="x02" value="1" onclick="checkAll(this)" /></th> I have tried both: $('#x01, label[for="x01"]').hide (); & $('#x01').hide (); to no avail. Any help using jQuery would be appreciated. Also, does it matter the positioning of hiding this chckbox? Thanks.

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• How to let users edit list<T> content?

  - by iTayb

  I'm making an aspx page that can edit books. A book is an complex class with lots of properties. I've made an edit page for most of them, however I'm having trouble with showing edit options for my Sellers Proprety. It is an list<Seller> object. Seller is as follows: public class Seller { private string sellerName; private double price; } How can I print a list to the screen, and let the clinet edit it, then load it back to the object? Thank you very much.

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• Nhibernate: mapping two different properties between the same 2 entities

  - by Carlos Decas

  I have a Class A: public class ClassA { public int ID {get; private set;} public string Code {get; private set;} public ClassB B {get; private set;} public IList<ClassB> ListB {get; private set;} } And a ClassB: public class ClassB { public int ID {get; private set;} public string Code {get; private set;} public ClassA A {get; private set;} //some other attributes... } And the Mappings: public ClassAMap() { Table("ClassA"); Id(classA => classA .ID, "ID").GeneratedBy.Identity(); Map(classA => classA.Code, "Code").Unique().Not.Nullable(); //HERE IS THE PROBLEM: -------- References(classA => classA.B,"IDClassB").Cascade.SaveUpdate(); //----- HasMany(classA => classA.ListB).Table("ClassB").KeyColumn("IDClassA").AsBag().Not.LazyLoad().Inverse().Cascade.AllDeleteOrphan(); } ClassB Mappings: public ClassBMap() { Table("ClassB"); Id(classB => classB.ID).GeneratedBy.Identity(); References(classB => classB.A, "IDClassA").ForeignKey("ID").Cascade.SaveUpdate(); } The mappings for ListB in classA worked ok, because at first the was only ListB property and not B, when i had to map B i tried this: References(classA => classA.B,"IDClassB"); The mapping test failed because B wasn't saved, so i did this: References(classA => classA.B,"IDClassB").Cascade.SaveUpdate(); This time B was saved, but by saving B, classA was inserted two times, by A.B and by B.A. How can i solve this problem? Why does it work for the ListB property and not for the B property? Thanks

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• Does std::multiset guarntee insertion order?

  - by Naveen

  I have a std::multiset which stores elements of class A. I have provided my own implementation of operator< for this class. My question is if I insert two equivalent objects into this multiset is their order guaranteed? For example, first I insert a object a1 into the set and then I insert an equivalent object a2 into this set. Can I expect the a1 to come before a2 when I iterate through the set? If no, is there any way to achieve this using multiset?

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• Dynamic dispatch and inheritance in python

  - by Bill Zimmerman

  Hi, I'm trying to modify Guido's multimethod (dynamic dispatch code): http://www.artima.com/weblogs/viewpost.jsp?thread=101605 to handle inheritance and possibly out of order arguments. e.g. (inheritance problem) class A(object): pass class B(A): pass @multimethod(A,A) def foo(arg1,arg2): print 'works' foo(A(),A()) #works foo(A(),B()) #fails Is there a better way than iteratively checking for the super() of each item until one is found? e.g. (argument ordering problem) I was thinking of this from a collision detection standpoint. e.g. foo(Car(),Truck()) and foo(Truck(), Car()) and should both trigger foo(Car,Truck) # Note: @multimethod(Truck,Car) will throw an exception if @multimethod(Car,Truck) was registered first? I'm looking specifically for an 'elegant' solution. I know that I could just brute force my way through all the possibilities, but I'm trying to avoid that. I just wanted to get some input/ideas before sitting down and pounding out a solution. Thanks

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• C++ Virtual Constructor, without clone()

  - by Julien L.

  I want to perform "deep copies" of an STL container of pointers to polymorphic classes. I know about the Prototype design pattern, implemented by means of the Virtual Ctor Idiom, as explained in the C++ FAQ Lite, Item 20.8. It is simple and straightforward: struct ABC // Abstract Base Class { virtual ~ABC() {} virtual ABC * clone() = 0; }; struct D1 : public ABC { virtual D1 * clone() { return new D1( *this ); } // Covariant Return Type }; A deep copy is then: for( i = 0; i < oldVector.size(); ++i ) newVector.push_back( oldVector[i]->clone() ); Drawbacks As Andrei Alexandrescu states it: The clone() implementation must follow the same pattern in all derived classes; in spite of its repetitive structure, there is no reasonable way to automate defining the clone() member function (beyond macros, that is). Moreover, clients of ABC can possibly do something bad. (I mean, nothing prevents clients to do something bad, so, it will happen.) Better design? My question is: is there another way to make an abstract base class clonable without requiring derived classes to write clone-related code? (Helper class? Templates?) Following is my context. Hopefully, it will help understanding my question. I am designing a class hierarchy to perform operations on a class Image: struct ImgOp { virtual ~ImgOp() {} bool run( Image & ) = 0; }; Image operations are user-defined: clients of the class hierarchy will implement their own classes derived from ImgOp: struct CheckImageSize : public ImgOp { std::size_t w, h; bool run( Image &i ) { return w==i.width() && h==i.height(); } }; struct CheckImageResolution; struct RotateImage; ... Multiple operations can be performed sequentially on an image: bool do_operations( std::vector< ImgOp* > v, Image &i ) { std::for_each( v.begin(), v.end(), /* bind2nd(mem_fun(&ImgOp::run), i ...) don't remember syntax */ ); } int main( ... ) { std::vector< ImgOp* > v; v.push_back( new CheckImageSize ); v.push_back( new CheckImageResolution ); v.push_back( new RotateImage ); Image i; do_operations( v, i ); } If there are multiple images, the set can be split and shared over several threads. To ensure "thread-safety", each thread must have its own copy of all operation objects contained in v -- v becomes a prototype to be deep copied in each thread.

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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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• is there a way to get a "subtree" from hclust ? (R)

  - by Tal Galili

  Hello all, I wish to create a "subtree" from an hclust object. For example, let's say I have the following object: a <- list() # initialize empty object a$merge <- matrix(c(-1, -2, -3, -4, 1, 2, -5,-6, 3,4), nc=2, byrow=TRUE ) a$height <- c(1, 1.5, 3,4,4.5) # define merge heights a$order <- 1:6 # order of leaves(trivial if hand-entered) a$labels <- 1:6# LETTERS[1:4] # labels of leaves class(a) <- "hclust" # make it an hclust object plot(a) # look at the result Now I wish the extract from it the following subtree: a <- list() # initialize empty object a$merge <- matrix(c(-1, -2, -3, -4, 1, 2 ), nc=2, byrow=TRUE ) a$height <- c(1, 1.5, 3) # define merge heights a$order <- 1:4 # order of leaves(trivial if hand-entered) a$labels <- 1:4# LETTERS[1:4] # labels of leaves class(a) <- "hclust" # make it an hclust object plot(a) # look at the result How could I access it? (I know that cutree could get me the objects of the sub tree, but not create an actual hclust object) Thanks for any help, Tal

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