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  • Find all paths from root to leaves of tree in Scheme

    - by grifaton
    Given a tree, I want to find the paths from the root to each leaf. So, for this tree: D / B / \ A E \ C-F-G has the following paths from root (A) to leaves (D, E, G): (A B D), (A B E), (A C F G) If I represent the tree above as (A (B D E) (C (F G))) then the function g does the trick: (define (g tree) (cond ((empty? tree) '()) ((pair? tree) (map (lambda (path) (if (pair? path) (cons (car tree) path) (cons (car tree) (list path)))) (map2 g (cdr tree)))) (else (list tree)))) (define (map2 fn lst) (if (empty? lst) '() (append (fn (car lst)) (map2 fn (cdr lst))))) But this looks all wrong. I've not had to do this kind of thinking for a while, but I feel there should be a neater way of doing it. Any ideas for a better solution (in any language) would be appreciated.

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  • Overriding constructors

    - by demas
    Here is sample code: class One def initialize(*args) case args.size when 0 puts "one initialize" when 1 puts "one initialize #{args[0]}" end end end class Two def initialize(*args) if args.size == 2 then puts "two initialize #{args[0]} and #{args[1]}" else super(args) end end end one = One.new one = One.new("thing") two = Two.new("some", "other") two = Two.new("some") Now I'm launching the code and getting the error message: [[email protected]][~/temp]% ruby test2.rb one initialize one initialize thing two initialize some and other test2.rb:17:in `initialize': wrong number of arguments(1 for 0) (ArgumentError) from test2.rb:17:in `initialize' from test2.rb:26:in `new' from test2.rb:26:in `<main>' How can I call parent's constructor from class Two ?

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  • Java generics: Illegal forward reference

    - by Arian
    Given a generic interface interface Foo<A, B> { } I want to write an implementation that requires A to be a subclass of B. So I want to do class Bar<A, B super A> implements Foo<A, B> { } // --> Syntax error or class Bar<A extends B, B> implements Foo<A, B> { } // --> illegal forward reference But the only solution that seems to work is this: class Bar<B, A extends B> implements Foo<A, B> { } which is kind of ugly, because it reverses the order of the generic parameters. Are there any solutions or workarounds to this problem?

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  • (C++) Linking with namespaces causes duplicate symbol error

    - by user577072
    Hello. For the past few days, I have been trying to figure out how to link the files for a CLI gaming project I have been working on. There are two halves of the project, the Client and the Server code. The client needs two libraries I've made. The first is a general purpose game board. This is split between GameEngine.h and GameEngine.cpp. The header file looks something like this namespace gfdGaming { // struct sqr_size { // Index x; // Index y; // }; typedef struct { Index x, y; } sqr_size; const sqr_size sPos = {1, 1}; sqr_size sqr(Index x, Index y); sqr_size ePos; class board { // Prototypes / declarations for the class } } And the CPP file is just giving everything content #include "GameEngine.h" type gfdGaming::board::functions The client also has game-specific code (in this case, TicTacToe) split into declarations and definitions (TTT.h, Client.cpp). TTT.h is basically #include "GameEngine.h" #define TTTtar "localhost" #define TTTport 2886 using namespace gfdGaming; void* turnHandler(void*); namespace nsTicTacToe { GFDCON gfd; const char X = 'X'; const char O = 'O'; string MPhostname, mySID; board TTTboard; bool PlayerIsX = true, isMyTurn; char Player = X, Player2 = O; int recon(string* datHolder = NULL, bool force = false); void initMP(bool create = false, string hn = TTTtar); void init(); bool isTie(); int turnPlayer(Index loc, char lSym = Player); bool checkWin(char sym = Player); int mainloop(); int mainloopMP(); }; // NS I made the decision to put this in a namespace to group it instead of a class because there are some parts that would not work well in OOP, and it's much easier to implement later on. I have had trouble linking the client in the past, but this setup seems to work. My server is also split into two files, Server.h and Server.cpp. Server.h contains exactly: #include "../TicTacToe/TTT.h" // Server needs a full copy of TicTacToe code class TTTserv; struct TTTachievement_requirement { Index id; Index loc; bool inUse; }; struct TTTachievement_t { Index id; bool achieved; bool AND, inSameGame; bool inUse; bool (*lHandler)(TTTserv*); char mustBeSym; int mustBePlayer; string name, description; TTTachievement_requirement steps[safearray(8*8)]; }; class achievement_core_t : public GfdOogleTech { public: // May be shifted to private TTTachievement_t list[safearray(8*8)]; public: achievement_core_t(); int insert(string name, string d, bool samegame, bool lAnd, int lSteps[8*8], int mbP=0, char mbS=0); }; struct TTTplayer_t { Index id; bool inUse; string ip, sessionID; char sym; int desc; TTTachievement_t Ding[8*8]; }; struct TTTgame_t { TTTplayer_t Player[safearray(2)]; TTTplayer_t Spectator; achievement_core_t achievement_core; Index cTurn, players; port_t roomLoc; bool inGame, Xused, Oused, newEvent; }; class TTTserv : public gSserver { TTTgame_t Game; TTTplayer_t *cPlayer; port_t conPort; public: achievement_core_t *achiev; thread threads[8]; int parseit(string tDat, string tsIP); Index conCount; int parseit(string tDat, int tlUser, TTTplayer_t** retval); private: int parseProto(string dat, string sIP); int parseProto(string dat, int lUser); int cycleTurn(); void setup(port_t lPort = 0, bool complete = false); public: int newEvent; TTTserv(port_t tlPort = TTTport, bool tcomplete = true); TTTplayer_t* userDC(Index id, Index force = false); int sendToPlayers(string dat, bool asMSG = false); int mainLoop(volatile bool *play); }; // Other void* userHandler(void*); void* handleUser(void*); And in the CPP file I include Server.h and provide main() and the contents of all functions previously declared. Now to the problem at hand I am having issues when linking my server. More specifically, I get a duplicate symbol error for every variable in nsTicTacToe (and possibly in gfdGaming as well). Since I need the TicTacToe functions, I link Client.cpp ( without main() ) when building the server ld: duplicate symbol nsTicTacToe::PlayerIsX in Client.o and Server.o collect2: ld returned 1 exit status Command /Developer/usr/bin/g++-4.2 failed with exit code 1 It stops once a problem is encountered, but if PlayerIsX is removed / changed temporarily than another variable causes an error Essentially, I am looking for any advice on how to better organize my code to hopefully fix these errors. Disclaimers: -I apologize in advance if I provided too much or too little information, as it is my first time posting -I have tried using static and extern to fix these problems, but apparently those are not what I need Thank you to anyone who takes the time to read all of this and respond =)

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  • has_many association, nested models and callbacks

    - by fl00r
    Hi! I've got model A and model Attach. I'm editing my A form with nested attributes for :attaches. And when I am deleting all attaches from A via accepts_nested_attributes_for how can I get after_update/after_save callbacks for all of my nested models? Problem is that when I am executing callbacks in model A they are executed right AFTER model A is updated and BEFORE model Attach is updated, so I can't, for example, know if there is NO ANY attaches after I delete them all :). Look for example: my callback after_save :update_status won't work properly after I delete all of my attaches. model A after_save :update_status has_many :attaches accepts_nested_attributes_for :attaches, :reject_if => proc { |attributes| attributes['file'].blank? }, :allow_destroy => true def update_status print "\n\nOUPS! bag is empty!\n\n" if self.attaches.empty? end end model Attach belongs_to A end I am using rails 3 beta

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  • Django 1.5 custom User model error. "Manager isn't available; User has been swapped"

    - by bpetit
    I extend the django user model as described in the dev doc. I wan't to keep most of the original User model features so I extend the AbstractUser class. I've defined in settings.py: AUTH_USER_MODEL = 'myapp.CustomUser' My user class: class CustomUser(AbstractUser): custom_field = models.ForeignKey('OtherModel') objects = UserManager() Everything seems to work fine but when I try to make it managed by the admin site: admin.site.register(CustomUser, UserAdmin) I get this error on the admin CustomUser creation page (after validation of the password confirmation form): AttributeError: Manager isn't available; User has been swapped for 'myapp.CustomUser' The point is that I need this model managed by the admin site in order to have the same creation process as with the original User model (two step process with password validation). Thanks for any reply

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  • Android: Using MediaRecorder to crop an existing audio file?

    - by user141146
    Hi, I'd like to take an existing mp3 file located on an SD card and arbitrarily crop it (e.g. crop from 0:12 to 1:14 in a 3 minute song). The only class that I've seen that seems remotely relevant to do this is the MediaRecorder class. My 'hope' would be to "record" an existing file like this: MediaRecorder recorder = new MediaRecorder(); recorder.setAudioSource(###some magical way of specifying an existing file??###); But this obviously doesn't work (setAudioSource() takes an int and seems to default to the phone's microphone). Is there a class or an approach that can be used to crop audio on the phone itself? TKS!!

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  • How can I create a collection of references in C#

    - by Jonathan Kaufman
    Ok I am having a cross language hiccup. In C# with it's great collections like List and I have: a Map class with properties of: List<byte[]> Images; List<Tile> Tiles; a Tile Class of: byte[] ImageData; int X; int Y; Now I want to add an image to the Map class and have the ImageData property of the Tile Classes to "reference" it. I have discovered I can't just assign it Images[0]. You can't have a reference to an object of a List. My fix was to create a Dictionary. Is this the best way or can I somehow have a "pointer" to a collection of objects?

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  • Search resetting selection in tableview

    - by Jay
    I've got an NSTableView bound to an NSArrayController via content and selection indexes. All great so far - content displayed, etc. Now an NSSearchField is bound to the array controller via filterPredicate and the property of the array content instances that's to be searched. Searching/filtering the table view works great; table view showing only matching entries. However, searching resets the selection on the NSTableView if the existing selection isn't in the search results. Worse, not only during the search but after ending the search there's no selection on the table view. The NSArrayController is set up to Avoid Empty Selection. Any hints on how to properly configure bindings in this scenario to really prevent an empty selection much appreciated!

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  • Google App Engine python - Self is not defined

    - by sdasdas
    I have a request that maps to this class ChatMsg It takes in 3 get variables, username, roomname, and msg. But it fails on this last line here. class ChatMsg(webapp.RequestHandler): # this is line 239 def get(self): username = urllib.unquote(self.request.get('username')) roomname = urllib.unquote(self.request.get('roomname')) # this is line 242 When it tries to assign roomname, it tells me: <type 'exceptions.NameError'>: name 'self' is not defined Traceback (most recent call last): File "/base/data/home/apps/chatboxes/1.341998073649951735/chatroom.py", line 239, in <module> class ChatMsg(webapp.RequestHandler): File "/base/data/home/apps/chatboxes/1.341998073649951735/chatroom.py", line 242, in ChatMsg roomname = urllib.unquote(self.request.get('roomname')) what the hell is going on to make self not defined

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  • How to declare a generic constraint that is a generic type

    - by HackedByChinese
    I have a two generic abstract types: Entity and Association. Let's say Entity looks like this: public class Entity<TId> { //... } and Association looks like this: public class Association<TEntity, TEntity2> { //... } How do I constrain Association so they can be of any Entity? I can accomplish it by the following: public class Association<TEntity, TId, TEntity2, TId2> where TEntity : Entity<TId> where TEntity2: Entity<TId2> { //... } This gets very tedious as more types derive from Association, because I have to keep passing down TId and TId2. Is there a simpler way to do this, besides just removing the constraint?

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  • Anyone using ASP.NET MembershipProvider with Nhibernate?

    - by JLago
    Hi, I'm trying to implement Membership controls in a mvc 2 application and i'm having trouble dealing with the MembershipUser class. I have my own data store (in Postgresql) and I'm using Nhibernate to deal with it from C#. The thing is, I have my own user class, but I can't use it with any provider I found that implements Membership, because all the functions return the predefined MembershipUser class and cannot return my own. I'm losing my mind here, is there any way i can work with this, or should I implement everything myself? thanks in advance!

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  • Query multiple models with one value

    - by swoei
    I have multiple models which all have a FK to the same model. All I know is the FK how can I determine which of the models has the FK attached? Below an example to clearify: class ModelA(models.Model): title = models.CharField("title", max_length=80) class ModelB(models.Model): fk = models.ForeignKey(ModelA) class ModelC(models.Model): fk = models.ForeignKey(ModelA) How can I figure out without using a try/except on each model whether B or C has the FK? (The FK can only be in one of them, for the record in this case I only added two models but in the real world app there are multiple possible x amount of models which have the FK to modelA)

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  • Upsert - Efficient Update or Insert in VB.Net, SQL Server

    - by HK1
    I'm trying to understand how to streamline the process of inserting a record if none exists or updating a record if it already exists. I'm not using stored procedures, although maybe that would be the most efficient way of doing this. The actual scenario in which this is necessary is saving a user preference/setting to my SettingsUser table. In MS Access I would typically pull a DAO recordset looking for the specified setting. If the recordset comes back empty then I know I need to add a new record which I can do with the same recordset object. On the other hand, if it isn't empty, I can just update the setting's value right away. In theory, this is only two database operations. What is the recommended way of doing this in .NET?

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  • Acts as Tree with Multiple Models

    - by Joe
    I've got several models that I'd like to relate together hierarchically. For simplicity's sake, let's say I've got these three: class Group < ActiveRecord::Base acts_as_tree has_many :users end class User < ActiveRecord::Base acts_as_tree belongs_to :group has_many :posts end class Post < ActiveRecord::Base acts_as_tree belongs_to :user end Under the current acts_as_tree, each node can individually can relate hierarchically to other nodes provided they are of the same type. What I'd like is to remove this restriction on type identity, so that SomePost.parent could have a User or a Post as its' parent, and that SomeUser.parent could have another user or a group as its parent. Any thoughts?

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  • Django json serialization problem

    - by codingJoe
    I am having difficulty serializing a django object. The problem is that there are foreign keys. I want the serialization to have data from the referenced object, not just the index. For example, I would like the sponsor data field to say "sponsor.last_name, sponsor.first_name" rather than "13". How can I fix my serialization? json data: {"totalCount":"2","activities":[{"pk": 1, "model": "app.activity", "fields": {"activity_date": "2010-12-20", "description": "my activity", "sponsor": 13, "location": 1, .... model code: class Activity(models.Model): activity_date = models.DateField() description = models.CharField(max_length=200) sponsor = models.ForeignKey(Sponsor) location = models.ForeignKey(Location) class Sponsor(models.Model): last_name = models.CharField(max_length=20) first_name= models.CharField(max_length=20) specialty = models.CharField(max_length=100) class Location(models.Model): location_num = models.IntegerField(primary_key=True) location_name = models.CharField(max_length=100) def activityJSON(request): activities = Activity.objects.all() total = activities.count() activities_json = serializers.serialize("json", activities) data = "{\"totalCount\":\"%s\",\"activities\":%s}" % (total, activities_json) return HttpResponse(data, mimetype="application/json")

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  • ADT will not allow creation of Android Activity

    - by NewShelbyWoo
    I installed the ADT bundle from http://developer.android.com/sdk/index.html yesterday, and I was following a basic Hello World tutorial. I created a new Android Application Project with a Blank Activity named MainActivity. The resulting project has an empty src folder and empty res\layout folder. There is a R.java file in the gen folder but it has no reference to MainActivity. This is what the SDK manager says I have installed Android SDK Tools v 22.6 Android SDK Platform-tools v 19.0.1 Android SDK Build-tools v 19 SDK Platform v 3 ARM EABI v7a System Image v 2 Android Support Library v 19.0.1 Google USB Driver v 9 I also tried manually creating an activity by right clicking the src folder and going to Android Activity, but when I hit Finish on the creation wizard, nothing happens. Does anyone have any clues as to what's going on? Did I miss a key component to install or something?

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  • How to load a configuration file at startup within tomcat

    - by Alex
    I want to be able to load my configuration for the webapp at startup of tomcat (apache commons configuration library) is this a possible way: public class MyAppCfg implements javax.servlet.ServletContextListener { private ServletContext context = null; @Override public void contextInitialized(ServletContextEvent event) { try{ this.context = event.getServletContext(); XMLConfiguration config = new XMLConfiguration("cfg.xml"); config.setReloadingStrategy(new FileChangedReloadingStrategy()); this.context.setAttribute("mycfg", config); } catch (Exception e) { e.printStackTrace(); } } @Override public void contextDestroyed(ServletContextEvent arg0) { this.context = null; } } web.xml <listener> <listener-class>mypackage.MyAppCfg</listener-class> </listener> and later acces them in the webapp via this.cfg = (XMLConfiguration) servletRequest.getAttribute("mycfg");

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  • JavaScript socket vs. Flash socket?

    - by Dr.Dredel
    Steve Jobs just posted this article on why Apple rejects Flash... http://www.apple.com/hotnews/thoughts-on-flash/ I agree that javascript and css can be used to replicate some of Flash's animation, though Flash does all sorts of scaling and tweening that is incredibly powerful, and I'm not sure that there's anything comparable in javascript, if there is, I certainly haven't seen it. However, my question is about the socket. Flash has an incredibly powerful openSocket class that allows you to connect to a server and have the server and the client talk back and forth to one another. As far as I know there is no equivalent class in Javascript. Am I mistaken? Is there some secret mystery Ajax class that replicates the openSocket? If not, then that feature alone makes Flash an invaluable tool. I'm interested in all answers though... and yes this IS a programming question! :)

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  • INotifyPropertyChange ~ PropertyChanged not firing when property is a collection and a new item is a

    - by eponymous23
    I have a class that implements the INotifyPropertyChanged interface. Some of the properties of the class are of type List. For example: public List<string> Answers { get { return _answers; } set { _answers = value; onPropertyChanged("Answers") } } ... private void onPropertyChanged(string propertyName) { if(this.PropertyChanged != null) this.PropertyChanged(this, new PropertyChangedEventArgs(propertyName)); } If I assign a new List<string> to Answer, then the PropertyChanged event fires as expected; but if I add a string string to the Answer list using the List Add method, then PropertyChanged event doesn't fire. I was considering adding an AddAnswer() method to my class, which would handle calling the lists's Add method and would call onPropertyChanged() from there, but is that the right way to do it? Is there a more elegant way of doing it? Cheers, KT

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  • Using Interfaces in an action signature of ASP.NET MVC controller

    - by Dmitry Borovsky
    Hello, I want to use interface in Action signature. So I've tried make own ModelBinder by deriving DefaultModelBinder: public class InterfaceBinder<T> : DefaultModelBinder where T: new() { protected override object CreateModel(ControllerContext controllerContext, ModelBindingContext bindingContext, Type modelType) { return base.CreateModel(controllerContext, bindingContext, typeof(T)); } } public interface IFoo { string Data { get; set; } } public class Foo: IFoo /*other interfaces*/ { /* a lot of other methods and properties*/ public Bar Data{get;set;} string IFoo.Data { get{return Data.ToString()}; set{Data = new Bar(value)}; } } public class MegaController: Controller { public ActionResult Process([ModelBinder(typeof(InterfaceBinder<Foo>))]IFoo foo){/*bla-bla-bla*/} } But it doesn't work. Does anybody have idea how release this behaviour? And yes, I know that I can make my own implementation of IModelBinder, but I'm looking for easier way.

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  • Conversion of Linq expressions

    - by Arnis L.
    I'm not sure how exactly argument what I'm trying to achieve, therefore - wrote some code: public class Foo{ public Bar Bar{get;set;} } public class Bar{ public string Fizz{get;set;} } public class Facts{ [Fact] public void fact(){ Assert.Equal(expectedExp(),barToFoo(barExp())); } private Expression<Func<Foo,bool>> expectedExp(){ return f=>f.Bar.Fizz=="fizz"; } private Expression<Func<Bar,bool>> barExp(){ return b=>b.Fizz=="fizz"; } private Expression<Func<Foo,bool>> barToFoo (Expression<Func<Bar,bool>> barExp){ return Voodoo(barExp); //<-------------------------------------------??? } } Is this even possible?

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  • Generic extension method returning IEnumerable<T> without using reflection

    - by roosteronacid
    Consider this snippet of code: public static class MatchCollectionExtensions { public static IEnumerable<T> AsEnumerable<T>(this MatchCollection mc) { return new T[mc.Count]; } } And this class: public class Ingredient { public String Name { get; set; } } Is there any way to magically transform a MatchCollection object to a collection of Ingredient? The use-case would look something like this: var matches = new Regex("([a-z])+,?").Matches("tomato,potato,carrot"); var ingredients = matches.AsEnumerable<Ingredient>();

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  • ActionScript: Determine wether superclass implements a particular interface?

    - by David Wolever
    Is there any non-hacky way to determine wether a class' superclass implements a particular interface? For example, assume I've got: class A extends EventDispatcher implements StuffHolder { private var myStuff = someKindOfStuff; public function getStuff():Array { if (super is StuffHolder) // <<< this doesn't work return super['getStuff']().concat([myStuf]); return [myStuff]; } class B extends A { private var myStuff = anotherKindOfStuff; } How could I perform that super is StuffHolder test in a way that, well, works? In this case, it always returns true.

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  • Android alarm not working

    - by erdomester
    I've been struggling with this for hours. I've also checked the documentation and several topics. I found this code in two topics, both guys said the code was working perfectly, but not on my computer. The first Toast appears, but the second one never. What is wrong? public class HelloAndroid2 extends Activity { @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); Intent intent = new Intent(this, AlarmReceiver.class); PendingIntent pendingIntent = PendingIntent.getBroadcast(this, 0, intent, PendingIntent.FLAG_ONE_SHOT); AlarmManager alarmManager = (AlarmManager) getSystemService(ALARM_SERVICE); alarmManager.set(AlarmManager.RTC_WAKEUP, System.currentTimeMillis() + (10 * 1000), pendingIntent); Toast.makeText(this, "Alarm set", Toast.LENGTH_LONG).show(); } public final class AlarmReceiver extends BroadcastReceiver { @Override public void onReceive(Context context, Intent intent) { Toast.makeText(context, "Alarm worked.", Toast.LENGTH_LONG).show(); } } }

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