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  • Java static method parameters

    - by Blitzkr1eg
    Why does the following code return 100 100 1 1 1 and not 100 1 1 1 1 ? public class Hotel { private int roomNr; public Hotel(int roomNr) { this.roomNr = roomNr; } public int getRoomNr() { return this.roomNr; } static Hotel doStuff(Hotel hotel) { hotel = new Hotel(1); return hotel; } public static void main(String args[]) { Hotel h1 = new Hotel(100); System.out.print(h1.getRoomNr() + " "); Hotel h2 = doStuff(h1); System.out.print(h1.getRoomNr() + " "); System.out.print(h2.getRoomNr() + " "); h1 = doStuff(h2); System.out.print(h1.getRoomNr() + " "); System.out.print(h2.getRoomNr() + " "); } } Why does it appear to pass Hotel by-value to doStuff() ?

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  • Difference of function argument as (const int &) and (int & a) in C++

    - by Narek
    I know that if you write void function_name(int& a), then function will not do local copy of your variable passed as argument. Also have met in literature that you should write void function_name(const int & a) in order to say compiler, that I dont want the variable passed as argument to be copied. So my question: what is the difference with this two cases (except that "const" enshures that the variable passes will not be changed by function!!!)???

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  • Problem with "moveable-only types" in VC++ 2010

    - by Luc Touraille
    I recently installed Visual Studio 2010 Professional RC to try it out and test the few C++0x features that are implemented in VC++ 2010. I instantiated a std::vector of std::unique_ptr, without any problems. However, when I try to populate it by passing temporaries to push_back, the compiler complains that the copy constructor of unique_ptr is private. I tried inserting an lvalue by moving it, and it works just fine. #include <utility> #include <vector> int main() { typedef std::unique_ptr<int> int_ptr; int_ptr pi(new int(1)); std::vector<int_ptr> vec; vec.push_back(std::move(pi)); // OK vec.push_back(int_ptr(new int(2)); // compiler error } As it turns out, the problem is neither unique_ptr nor vector::push_back but the way VC++ resolves overloads when dealing with rvalues, as demonstrated by the following code: struct MoveOnly { MoveOnly() {} MoveOnly(MoveOnly && other) {} private: MoveOnly(const MoveOnly & other); }; void acceptRValue(MoveOnly && mo) {} int main() { acceptRValue(MoveOnly()); // Compiler error } The compiler complains that the copy constructor is not accessible. If I make it public, the program compiles (even though the copy constructor is not defined). Did I misunderstand something about rvalue references, or is it a (possibly known) bug in VC++ 2010 implementation of this feature?

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  • C# XNA: What can cause SpriteBatch.End() to throw a NRE?

    - by Rosarch
    I don't understand what I'm doing wrong here: public void Draw(GameTime gameTime) // in ScreenManager { SpriteBatch.Begin(SpriteBlendMode.AlphaBlend); for (int i = 0; i < Screens.Count; i++) { if (Screens[i].State == Screen.ScreenState.HIDDEN) continue; Screens[i].Draw(gameTime); } SpriteBatch.End(); // null ref exception } SpriteBatch itself is not null. Some more context: public class MasterEngine : Microsoft.Xna.Framework.Game { public MasterEngine() { graphicsDeviceManager = new GraphicsDeviceManager(this); Components.Add(new GamerServicesComponent(this)); // ... spriteBatch = new SpriteBatch(graphicsDeviceManager.GraphicsDevice); screenManager = new ScreenManager(assets, gameEngine, graphicsDeviceManager.GraphicsDevice, spriteBatch); } //... protected override void Draw(GameTime gameTime) { screenManager.Draw(gameTime); // calls the problematic method base.Draw(gameTime); } } Am I failing to initialize something properly? UPDATE: As an experiment, I tried this to the constructor of MasterEngine: spriteBatch = new SpriteBatch(graphicsDeviceManager.GraphicsDevice); spriteBatch.Begin(); spriteBatch.DrawString(assets.GetAsset<SpriteFont>("calibri"), "ftw", new Vector2(), Color.White); spriteBatch.End(); This does not cause a NRE. hmm.... UPDATE 2: This does cause an NRE: protected override void Draw(GameTime gameTime) { spriteBatch.Begin(); spriteBatch.End(); // boned here //screenManager.Draw(gameTime); base.Draw(gameTime); }

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  • Does a HashSet make an internal copy of added Objects?

    - by praks5432
    Let's say I have a function that is recursive and is like this public void someRecur(List<Integer>someList){ if(someBreakCondition) Set.add(someList); for(int i = 0; i < someLen ; i++){ someList.add(someInt); someRecur(someList); someList.remove(someInt); } } Does the remove affect the list that has been put into the set? What should I do to give the set an actual copy of the list?

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  • Argument type deduction, references and rvalues

    - by uj2
    Consider the situation where a function template needs to forward an argument while keeping it's lvalue-ness in case it's a non-const lvalue, but is itself agnostic to what the argument actually is, as in: template <typename T> void target(T&) { cout << "non-const lvalue"; } template <typename T> void target(const T&) { cout << "const lvalue or rvalue"; } template <typename T> void forward(T& x) { target(x); } When x is an rvalue, instead of T being deduced to a constant type, it gives an error: int x = 0; const int y = 0; forward(x); // T = int forward(y); // T = const int forward(0); // Hopefully, T = const int, but actually an error forward<const int>(0); // Works, T = const int It seems that for forward to handle rvalues (without calling for explicit template arguments) there needs to be an forward(const T&) overload, even though it's body would be an exact duplicate. Is there any way to avoid this duplication?

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  • How to hash and check for equality of objects with circular references

    - by mfya
    I have a cyclic graph-like structure that is represented by Node objects. A Node is either a scalar value (leaf) or a list of n=1 Nodes (inner node). Because of the possible circular references, I cannot simply use a recursive HashCode() function, that combines the HashCode() of all child nodes: It would end up in an infinite recursion. While the HashCode() part seems at least to be doable by flagging and ignoring already visited nodes, I'm having some troubles to think of a working and efficient algorithm for Equals(). To my surprise I did not find any useful information about this, but I'm sure many smart people have thought about good ways to solve these problems...right? Example (python): A = [ 1, 2, None ]; A[2] = A B = [ 1, 2, None ]; B[2] = B A is equal to B, because it represents exactly the same graph. BTW. This question is not targeted to any specific language, but implementing hashCode() and equals() for the described Node object in Java would be a good practical example.

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  • perl: added hash entry in a subroutine is lost

    - by hansi
    Why is the hash empty on the second call of printHash? my %hash = (); addToHash(\%hash); printHash(\%hash); sub addToHash { my %hash = %{$_[0]}; $hash{"test"} = "test"; printHash(\%hash); } sub printHash { print "printHash: \n"; my %hash = %{$_[0]}; foreach my $key (keys %hash) { print "key: $key, value: $hash{$key}\n"; } } Output: printHash: key: test, value: test printHash:

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  • Is there any way to pass an anonymous array as an argument in C++?

    - by Jeremy Friesner
    Hi all, I'd like to be able to declare an array as a function argument in C++, as shown in the example code below (which doesn't compile). Is there any way to do this (other than declaring the array separately beforehand)? #include <stdio.h> static void PrintArray(int arrayLen, const int * array) { for (int i=0; i<arrayLen; i++) printf("%i -> %i\n", i, array[i]); } int main(int, char **) { PrintArray(5, {5,6,7,8,9} ); // doesn't compile return 0; }

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  • Pointing class property to another class with vectors

    - by jmclem
    I've got a simple class, and another class that has a property that points to the first class: #include <iostream> #include <vector> using namespace std; class first{ public: int var1; }; class second{ public: first* classvar; }; Then, i've got a void that's supposed to point "classvar" to the intended iteration of the class "first". void fill(vector<second>& sec, vector<first>& fir){ sec[0].classvar = &fir[0]; } Finally the main(). Create and fill a vector of class "first", create "second" vector, and run the fill function. int main(){ vector<first> a(1); a[0].var1 = 1000; vector<second> b(1); fill(b, a); cout << b[0].classvar.var1 << '\n'; system("PAUSE"); return 0; } This gives me the following error: 1>c:\...\main.cpp(29) : error C2228: left of '.var1' must have class/struct/union 1> type is 'first *' And I can't figure out why it reads the "classvar" as the whole vector instead of just the single instance. Should I do this cout << b[0].classvar[0].var1 << '\n'; it reads perfectly. Can anyone figure out the problem? Thanks in advance

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  • .click() callback references local variable from the calling method instead of copying by value

    - by Eric Freese
    The following jQuery Javascript code is included on an otherwise empty page. $(function() { for (var i = 0; i < 10; i++) { element = $('<div>' + i + '</div>'); element.click(function() { alert(i); }); $('body').append(element); } }); The desired behavior is that this code should generate 10 div elements numbered from 0 to 9. When you click on a div element, an alert popup will show the number of the div element you clicked on (i.e. if a user clicks on the div element labeled '4', the alert popup should show the number 4). The alert popup instead shows the number 10 regardless of which div element is clicked on. How can I modify this code to make it behave in the desired way?

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  • iPhone xcode - Best way to control audio from several view controllers

    - by Are Refsdal
    Hi, I am pretty new to iPhone programming. I have a navBar with three views. I need to control audio from all of the views. I only want one audio stream to play at a time. I was thinking that it would be smart to let my AppDelegate have an instance of my audioplaying class and let the three other views use that instance to control the audio. My problem is that I don´t know how my views can use the audioplaying class in my AppDelegate. Is this the best approach and if so, how? Is there a better way?

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  • How to load an external swf to the main stage from an instanced child class?

    - by RaamEE
    Hi, I am trying to get an instance of a class to the load an external swf and show it. So far I have the following: 1) I wrote a class that uses the Loader class to load an external swf "loadExtSWF". 2) I have a fla named "MainSWF.fla" that uses a document class "MainSWF.as". 3) I have the MainSWF.as file that instances "loadExtSWF" and calls loadExtSWF.startLoad to load the swf. This almost works. The instance of loadExtSWF loads the external swf, but the swf is not displayed. If I replace the fla's document class with loadExtSWF (this has an empty constructor) instead of MainSWF, and run loadExtSWF.startLoad, then the external swf is loaded and displayed. It seems that the way I initially do it, loads the swf to the wrong stage (?). Any ideas? Thanks for the help. Bye, RaamEE P.S. If you replace the document class for test_tsscreen from test_tsscreen.as to TSScreen.as, and remove the comment inside the test_tsscreen's constructor, the swf will be loaded. my code is: file test_as3.swf an external as3 swf file. file test_tsscreen.fla the fla is empty and references test_tsscreen.as as its document class. file test_tsscreen.as package { import flash.display.MovieClip; import TSScreen; public class test_tsscreen extends MovieClip{ var tsScreen1; public function test_tsscreen(){ // var tsScreen1:TSScreen = new TSScreen(10,10,100,100,0.5,0); var tsScreen1:TSScreen = new TSScreen(); tsScreen1.startLoad(this.stage); } } } file TSScreen.as package { import flash.display.MovieClip; import flash.display.*; import flash.net.URLRequest; import flash.system.ApplicationDomain; import flash.system.LoaderContext; import flash.display.Loader; import flash.events.Event; import flash.events.ProgressEvent; public class TSScreen extends MovieClip implements ITSScreenable{ public function TSScreen():void{ // startLoad(this); //Look important comment in above text } function startLoad(_this:Stage) { var mLoader:Loader = new Loader(); var mRequest:URLRequest = new URLRequest("test_as3.swf"); mLoader.contentLoaderInfo.addEventListener(Event.COMPLETE, onCompleteHandler); mLoader.contentLoaderInfo.addEventListener(ProgressEvent.PROGRESS, onProgressHandler); _this.parent.addChild(mLoader); mLoader.load(mRequest); trace(this.name); trace(_this.name); } function onCompleteHandler(loadEvent:Event) { addChild(loadEvent.currentTarget.content); } function onProgressHandler(mProgress:ProgressEvent) { var percent:Number = mProgress.bytesLoaded/mProgress.bytesTotal; trace(percent); } } }

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  • Possible to access all Movie clips on a layer, on timeline, through stage ?

    - by azislo
    I have a code ... var selection:Array = new Array(); var diplayObjCont:* = stage; // The rectangle that defines the selection in the containers coordinate space. // Loop throught the containers children. for(var a:int; a<diplayObjCont.numChildren; a++){ // Get the childs bounds in the containers coordinate space. var child:DisplayObject = diplayObjCont.getChildAt(a); selection.push(child); } trace(selection); that returns just [object MainTimeline] So, can I access layers on this MainTimeline to get all Movie Clips on this layer ? So I can do a simple operation "A_1_2.buttonMode = true;" to all my MC's (in an array for example) without writing every line (lot of MC's on layer and lot of lines).

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  • Project Reference added to one of the projects in the same solution appears broken in another solution

    - by CSharpLearner
    I have couple of solutions. In the first solution I have many projects. One of the project named 'A' has a project reference of another project 'B' of the same solution. In second solution, the project 'A' is added but not the project 'B'. Both the solutions build successfully. However, in second solution, reference of B added in the project A, appears broken. Why? Now, in first solution, instead of adding Project reference of B into A, i simply add a 'file reference' of B's DLL (which is copied at the common output directory created for all the projects) into A. Now the reference appears broken in both the solution even though both the solutions are built successfully. May I know what should I do when I have such a scenario?

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  • C# XNA: What can cause SpriteBatch.End() to throw a NPE?

    - by Rosarch
    I don't understand what I'm doing wrong here: public void Draw(GameTime gameTime) // in ScreenManager { SpriteBatch.Begin(SpriteBlendMode.AlphaBlend); for (int i = 0; i < Screens.Count; i++) { if (Screens[i].State == Screen.ScreenState.HIDDEN) continue; Screens[i].Draw(gameTime); } SpriteBatch.End(); // null ref exception } SpriteBatch itself is not null. Some more context: public class MasterEngine : Microsoft.Xna.Framework.Game { public MasterEngine() { graphicsDeviceManager = new GraphicsDeviceManager(this); Components.Add(new GamerServicesComponent(this)); // ... spriteBatch = new SpriteBatch(graphicsDeviceManager.GraphicsDevice); screenManager = new ScreenManager(assets, gameEngine, graphicsDeviceManager.GraphicsDevice, spriteBatch); } //... protected override void Draw(GameTime gameTime) { screenManager.Draw(gameTime); // calls the problematic method base.Draw(gameTime); } } Am I failing to initialize something properly? UPDATE: As an experiment, I tried this to the constructor of MasterEngine: spriteBatch = new SpriteBatch(graphicsDeviceManager.GraphicsDevice); spriteBatch.Begin(); spriteBatch.DrawString(assets.GetAsset<SpriteFont>("calibri"), "ftw", new Vector2(), Color.White); spriteBatch.End(); This does not cause a NRE. hmm....

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  • Referencing dlls built with older .Net versions

    - by stiank81
    In a project using .Net4 - should there be any issues referencing dlls built for older versions of .Net? We're talking 3rd Party dlls here. I'm asking this as a general question. Specifically I have a problem referencing FluentNHibernate.dll - built with .Net3.5. It worked justed fine before I updated my project from .Net3.5 to .Net4.

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  • Is this Leftist Tree piece of code from Wikipedia correct?

    - by they changed my name
    Link public Node merge(Node x, Node y) { if(x == null) return y; if(y == null) return x; // if this was a max height biased leftist tree, then the // next line would be: if(x.element < y.element) if(x.element.compareTo(y.element) > 0) { // x.element > y.element Node temp = x; x = y; y = temp; } x.rightChild = merge(x.rightChild, y); if(x.leftChild == null) { // left child doesn't exist, so move right child to the left side x.leftChild = x.rightChild; x.rightChild = null; x.s = 1; } else { // left child does exist, so compare s-values if(x.leftChild.s < x.rightChild.s) { Node temp = x.leftChild; x.leftChild = x.rightChild; x.rightChild = temp; } // since we know the right child has the lower s-value, we can just // add one to its s-value x.s = x.rightChild.s + 1; } return x; } What makes me ask this question is: if(x.element.compareTo(y.element) > 0) { // x.element > y.element Node temp = x; x = y; y = temp; } Isn't that just not gonna work, since the references are only switched inside the method?

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  • rails: self-referential association

    - by john
    hi, My needs are very simple: I have a Tip table to receive comments and have comments to receive comments, too. To retrieve each comment that is stored in the same table (comments), I created another key for the comments on comments: "inverse_comments". I tried to use one comments table by using self-referntial association. Some resources seem to bring more than one table into the piture which are diffent from my needs. So I came up whth the following modeling for comments: class Comment < ActiveRecord::Base belongs_to :tip belongs_to :user has_many :mycomments, :through => :inverse_comments, :source => :comment end Apparently something is missing here but I cannot figure it out. Could some one enlighten me on this: what changes I need to do to make the model work? thanks.

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  • Object still linked (referenced) after selecting it out of list?

    - by djerry
    Hey guys, I was wondering, and i'm not really sure, but help me out here. If you have a List items, and there's one object you need to change a property of it. Say myClass has a string property "status". I'm searching my list with a for-loop and i get my object so i do myClass item = items[i]; if i want to change the "status" property, i do this for example : item.Status = "new status"; My question/issue is this: is "item" still linked to the list item, so that if i execute the line above, it will be changed in the list as well without having to set this : items[i] = item; Hope this is clear. Thanks in advance.

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  • Javascript jQuery .click() callback references local variable from the calling method instead of cop

    - by Eric Freese
    The following jQuery Javascript code is included on an otherwise empty page. $(function() { for (var i = 0; i < 10; i++) { element = $('<div>' + i + '</div>'); element.click(function() { alert(i); }); $('body').append(element); } }); The desired behavior is that this code should generate 10 div elements numbered from 0 to 9. When you click on a div element, an alert popup will show the number of the div element you clicked on (i.e. if a user clicks on the div element labeled '4', the alert popup should show the number 4). The alert popup instead shows the number 10 regardless of which div element is clicked on. How can I modify this code to make it behave in the desired way?

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