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  • Whats the best to way convert a set of Java objects to another set of objects?

    - by HDave
    Basic Java question here from a real newbie. I have a set of Java objects (of class "MyClass") that implement a certain interface (Interface "MyIfc"). I have a set of these objects stored in a private variable in my class that is declared as follows: protected Set<MyClass> stuff = new HashSet<MyClass>(); I need to provide a public method that returns this set as a collection of objects of type "MyIfc". public Collection<MyIfc> getMyStuff() {...} How do I do the conversion? The following line gives me an error that it can't do the conversion. I would have guessed the compiler knew that objects of class MyClass implemented MyIfc and therefore would have handled it. Collection<MyIfc> newstuff = stuff; Any enlightenment is appreciated.

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  • C pointer initialization and dereferencing, what's wrong here?

    - by randombits
    This should be super simple, but I'm not sure why the compiler is complaining here. #include <stdio.h> #include <stdlib.h> int main(int argc, char *argv[]) { int *n = 5; printf ("n: %d", *n); exit(0); } Getting the following complaints: foo.c: In function ‘main’: foo.c:6: warning: initialization makes pointer from integer without a cast I just want to print the value that the pointer n references. I'm dereferencing it in the printf() statement and I get a segmentation fault. Compiling this with gcc -o foo foo.c.

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  • How do XAML files associate with cs files?

    - by LLS
    It seems that XAML files should have corresponding .cs files in a C# project. I know Visual Studio does all the things for us. I'm just curious how they are linked together? I mean, are they specified in the project file, or just because they have the same names? And also, App.xaml file specifies the startup file, but how does the compiler know? Is it possible to appoint another file other than App.xaml to do the same things as App.xaml does?

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  • how to access child instances in a vector in c++

    - by tsubasa
    I have a parent class and child class (inherited from parent). In the child class, I have a member function named function_blah(); I used vector<parent*> A to store 5 parent instances, 3 child instances. So the total number of elements in the vector is 8. I can easily access to member functions of element A[0] to A[4], which are parent instances. But whenever I try to have access to member functions of element A[5] to A[7], the compiler complains that class parent has no member named 'function_blah' The way I access to elements is using index. e.x A[i] with i = 0..7. Is it correct? if not, how?

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  • Writing a jquery plugin in coffeescript - how to get "(function($)" and "(jQuery)"?

    - by PandaWood
    I am writing a jquery plugin in coffeescript but am not sure how to get the function wrapper part right. My coffeescript starts with this line: $.fn.extend({ Which creates the javascript with a function wrapper: (function() { $.fn.extend({ but I want a '$' passed in like this: (function($) { $.fn.extend({ Similar for the ending I have... nothing in particular in coffeescript. I get this in javascript: })(); But would like this: })(jQuery); Does anyone know how to achieve this with the coffeescript compiler? Or what is the best way to get this done within coffeescript?

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  • "Find all tiles connected to this one" project

    - by Omega
    Remember MS Paint? The bucket tool? If you used it and clicked on a pixel, all pixels connected to this pixel that are the same are affected. The theory is, I suppose, to check if there is any pixel adjacent to the selected one. If such pixel is the same type as the selected one, check for more adjacent pixels in this one, and so on. I want to implement something similar in VB.NET. Basically I have a 2D array map which represents the map. Let's assume there are only two types of tile: 0 and 1. Now, I got pretty much everything ready: I got my 2d map and I can tell which tile is clicked and tell what array indexes are the ones that represent such tile. Now for the "painting" process. Whenever I think about it, I can't figure a convenient way to execute such iteration. Can someone help me choosing a correct design/way/tip to achieve this?

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  • How would one call std::forward on all arguments in a variadic function?

    - by Noah Roberts
    I was just writing a generic object factory and using the boost preprocessor meta-library to make a variadic template (using 2010 and it doesn't support them). My function uses rval references and std::forward to do perfect forwarding and it got me thinking...when C++0X comes out and I had a standard compiler I would do this with real variadic templates. How though, would I call std::forward on the arguments? template < typename ... Params void f(Params ... params) // how do I say these are rvalue reference? { y(std::forward(...params)); //? - I doubt this would work. } Only way I can think of would require manual unpacking of ...params and I'm not quite there yet either. Is there a quicker syntax that would work?

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  • boost variant static_visitor problem picking correct function

    - by Steve
    I'm sure I'm having a problem with template resolution here, but I'm not sure why I'm having the problem. I have a static visitor I'm passing to boost variant where i've had to do template specialization for certain cases. The case for everything except for MyClass should throw in the static_visitor below. Unfortunately, when the visitor is applied to pull a MyClass out, it selects the most generic case rather than the exact match. I would type each case explicitly, but that will be rather long. So, why is the compiler resolving the most generic case over the exact match, and is there anyway to fix it template<> class CastVisitor<MyClass>:public boost::static_visitor<MyClass> { public: template<typename U> MyClass operator()(const U & i) const { throw std::exception("Unable to cast"); } MyClass operator()(const MyClass& i) { return i; } };

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  • STL: how to overload operator= for <vector> ?

    - by MBes
    There's simple example: #include <vector> int main() { vector<int> veci; vector<double> vecd; for(int i = 0;i<10;++i){ veci.push_back(i); vecd.push_back(i); } vecd = veci; // <- THE PROBLEM } The thing I need to know is how to overload operator = so that I could make assignment like this: vector<double> = vector<int>; I've just tried a lot of ways, but always compiler has been returning errors... Is there any option to make this code work without changing it? I can write some additional lines, but can't edit or delete the existing ones. Ty.

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  • typedef fixed length array

    - by Rajorshi
    Hi, I have to define a 24-bit data type.I am using char[3] to represent the type. Can I typedef char[3] to type24? I tried it in a code sample. I put typedef char[3] type42; in my header file. The compiler did not complain about it. But when I defined a function void foo(type24 val) {} in my C file, it did complain. I would like to be able to define functions like type24_to_int32(type24 val) instead of type24_to_int32(char value[3]).

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  • Pass an event into a constructor

    - by Vaccano
    I have a class that I want to be able the handle the mouse up event for a grid. I tried to create it with a static method call like this: MyDataBinding.BindObjectsToDataGrid(ListOfObjectsToBind, myGrid.MouseUp); The end goal being that in the method I would assign a delegate to the MouseUp PassedInMouseUp += myMethodThatWillHandleTheMouseUp; Looks good here (to me) but the compiler chokes on the first line. It says that I can only use MouseUp with a += or a -=. Clearly I am going about this the wrong way. How can I get a different class to handle the mouse up with out having to: Pass in the whole grid Expose the method that will be handling the mouse up as a public method. Or, is this just a limitation and I will have to do one of the above?

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  • C++ volatile required when spinning on boost::shared_ptr operator bool()?

    - by JaredC
    I have two threads referencing the same boost::shared_ptr: boost::shared_ptr<Widget> shared; On thread is spinning, waiting for the other thread to reset the boost::shared_ptr: while(shared) boost::thread::yield(); And at some point the other thread will call: shared.reset(); My question is whether or not I need to declare the shared pointer as volatile to prevent the compiler from optimizing the call to shared.operator bool() out of the loop and never detecting the change? I know that if I were simply looping on a variable, waiting for it to reach 0 I would need volatile, but I'm not sure if boost::shared_ptr is implemented in such a way that it is not necessary here.

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  • Why do I have to give an identifier?

    - by Knowing me knowing you
    In code: try { System.out.print(fromClient.readLine()); } catch(IOException )//LINE 1 { System.err.println("Error while trying to read from Client"); } In code line marked as LINE 1 compiler forces me to give an identifier even though I'm not using it. Why this unnatural constrain? And then if I type an identifier I'm getting warning that identifier isn't used. It just doesn't make sense to me, forcing a programmer to do something unnecesarry and surplus. And after me someone will revise this code and will be wondering if I didn't use this variable on purpouse or I just forgot. So in order to avoid that I have to write additional comment explaining why I do not use variable which is unnecessary in my code. Thanks

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  • Can Visual Studio (should it be able to) compute a diff between any two changesets associated with a

    - by Hamish Grubijan
    Here is my use case: I start on a project XYZ, for which I create a work item, and I make frequent check-ins, easily 10-20 in total. ALL of the code changes will be code-read and code-reviewed. The change sets are not consecutive - other people check-in in-between my changes, although they are very unlikely to touch the exact same files. So ... at the en of the project I am interested in a "total diff" - as if there was a single check-in by me to complete the entire project. In theory this is computable. From the list of change sets associated with the work item, you get the list of all files that were affected. Then, the algorithm can aggregate individual diffs over each file and combine them into one. It is possible that a pure total diff is uncomputable due to the fact that someone else renamed files, or changed stuff around very closely, or in the same functions as me. I that case ... I suppose a total diff can include those changes by non-me as well, and warn me about the fact. I would find this very useful, but I do not know how to do t in practice. Can Visual Studio 2008/2010 (and/or TFS server) do it? Are there other source control systems capable of doing this? Thanks.

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  • Is It Worth Using Bitwise Operators In Methods?

    - by user1626141
    I am very new to Java (and programming in general, my previous experience is with ActionScript 2.0 and some simple JavaScript), and I am working my way slowly and methodically through Java: A Beginner's Guide by Herbert Schildt. It is an incredible book. For one thing, I finally understand more-or-less what bitwise operators (which I first encountered in ActionScript 2.0) do, and that they are more efficient than other methods for certain sums. My question is, is it more efficient to use a method that uses, say, a shift right, to perform all your divisions/2 (or divisions/even) for you in a large program with many calculations (in this case, a sprawling RPG), or is it more efficient to simply use standard mathematical operations because the compiler will optimise it all for you? Or, am I asking the wrong question entirely?

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  • In C#: How to declare a generic Dictionary whose key and value types have a common constraint type?

    - by Marcel
    Hi all, I want to declare a dictionary that stores typed IEnumerable's of a specific type, with that exact type as key, like so: private IDictionary<T, IEnumerable<T>> _dataOfType where T: BaseClass; //does not compile! The concrete classes I want to store, all derive from BaseClass, therefore the idea to use it as constraint. The compiler complains that it expects a semicolon after the member name. If it would work, I would expect this would make the later retrieval from the dictionary simple like: IEnumerable<ConcreteData> concreteData; _sitesOfType.TryGetValue(typeof(ConcreteType), out concreteData); How to define such a dictionary?

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  • Operators vs Functions in C/C++

    - by user356106
    Someone recently asked me the difference between a C++ standard operator (e.g. new,delete,sizeof) and function (e.g. tan,delete, malloc). By "standard" I mean those provided by default by the compiler suite, and not user defined. Below were the answers I gave, though neither seemed satisfactory. (1) An operator doesn't need any headers to be included to use it : E.g. you can have a call to new without including any headers. However, a function (say free() ) does need headers included, compulsorily. (2) An operator is defined as such (ie as a class operator) somewhere in the standard headers. A function isn't. Can you critique these answers and give me a better idea of the difference?

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  • Aborted core dumped C++

    - by avd
    I have a large C++ function which uses OpenCV library and running on Windows with cygwin g++ compiler. At the end it gives Aborted(core dumped) but the function runs completely before that. I have also tried to put the print statement in the end of the function. That also gets printed. So I think there is no logical bug in code which will generate the fault. Please explain. I am also using assert statements.But the aborted error is not due to assert statement. It does not say that assertion failed. It comes at end only without any message. Also the file is a part of a large project so I cannot post the code also.

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  • Is `super` local variable?

    - by Michael
    // A : Parent @implementation A -(id) init { // change self here then return it } @end A A *a = [[A alloc] init]; a. Just wondering, if self is a local variable or global? If it's local then what is the point of self = [super init] in init? I can successfully define some local variable and use like this, why would I need to assign it to self. -(id) init { id tmp = [super init]; if(tmp != nil) { //do stuff } return tmp; } b. If [super init] returns some other object instance and I have to overwrite self then I will not be able to access A's methods any more, since it will be completely new object? Am I right? c. super and self pointing to the same memory and the major difference between them is method lookup order. Am I right? sorry, don't have Mac to try, learning theory as for now...

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  • Mysterious c debugging problem when trying to utilize printfs

    - by O_O
    Ok, folks. I've never encountered this before and it boggles the mind and is illogical. I have a somewhat complex loop and I want to try and see if everything is working by putting some printf statements. I look the intermediate products using printf and verify that the answer is ok. Then, when I comment out the printf to the intermediate products, the answer is WRONG. Has anyone ever encountered this? This is driving me insane and I don't see how the printfs could change an answer.... X_x If it helps, I am using a c/c++ compiler for a DSP. Thanks for any advice.. Here is a snippet... printf("splitBackground = %d, numWindowPoints = %d\n", splitBackground, numWindowPoints); splitBackground = splitBackground/numWindowPoints; printf("%d ", splitBackground); This is good but when I comment out the first line of code, it turns out to be hugely incorrect. :(

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  • how to databind a datalist's page index to a button's commandname?

    - by korben
    i got this inside a button inside a datalist CommandName="<%# Container.ItemIndex %>" when i click the button, i'm expecting commandname to = 0, then 1, then 2, etc, as the datalist progresses, and i'm using that value in the button click's c# but i'm getting this error, i'm pretty sure i'm using this exact setup on another page and i have no problems, any idea what's going on? Server Error in '/' Application. Compilation Error Description: An error occurred during the compilation of a resource required to service this request. Please review the following specific error details and modify your source code appropriately. Compiler Error Message: CS0117: 'System.Web.UI.Control' does not contain a definition for 'ItemIndex'

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  • Rails: Duplicate functionality across controllers? A humble plea.

    - by Alex
    So I'm working with authlogic, and I'm trying to duplicate the login functionality to the welcome page, so that you can log in by restful url or by just going to the main page. No, I don't know if we'll keep that feature, but I want to test it out anyway. Here's the error message: RuntimeError in Welcome#index Called id for nil, which would mistakenly be 4 -- if you really wanted the id of nil, use object_id The code is below. Basically, what's happening is the index view (the first code snippet) is sending the information from the form to the create method of user_sessions controller. At this point, in theory, it create should just pick up, but it doesn't. PLEASE help. Please. I've been doing this for about 8 hours. I checked Google. I checked IRC. I checked every book I could find. You don't even have to answer, I can to the grunt work if you just point me in the right direction. <% form_for @user_session, :url => user_sessions_path do |f| %> <%= f.text_field :email %><br /> <%= f.password_field :password %> <%= submit_tag 'Login' %> <% end %> class ApplicationController < ActionController::Base helper :all # include all helpers, all the time protect_from_forgery # See ActionController::RequestForgeryProtection for details # Scrub sensitive parameters from your log # filter_parameter_logging :password helper_method :current_user_session, :current_user before_filter :new_session_object protected def new_session_object unless current_user @user_session = UserSession.new(params[:user_session]) end end private def current_user_session return @current_user_session if defined?(@current_user_session) @current_user_session = UserSession.find end def current_user return @current_user if defined?(@current_user) @current_user = current_user_session && current_user_session.record end end

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  • How do you specify a 64 bit unsigned int const 0x8000000000000000 in VS2008?

    - by Mark Franjione
    I read about the Microsoft specific suffix "i64" for integer constants. I want to do an UNsigned shift to a ULONGLONG. ULONGLONG bigNum64 = 0x800000000000000i64 >> myval; In normal C, I would use the suffix "U", e.g. the similar 32 bit operation would be ULONG bigNum32 = 0x80000000U >> myval; I do NOT want the 2's complement sign extension to propogate through the high bits. I want an UNSIGNED shift on a 64 bit const number. I think my first statement is going to do a SIGNED shift right. I tried 0x800000000000000i64U and 0x800000000000000u64 but got compiler errors.

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  • How to understand the programming of an operating system

    - by piemesons
    Hello, I want to learn the operating system. How it works. I don't want to make my own operating system. I just want to learn how it works. As I can find out source code of any open source OS. But how to start. Like starting from the first elementary kernel (whatever it is). Somebody suggested I try to implement Linux from scratch etc. Please guide me in a proper way. I want to know about the proper path to follow. I am ready to invest three to four years just to understand the basics. I have good fundamentals of C, C++, PHP, OOP and compiler design.

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  • F# function calling syntax confusion

    - by Daniel
    I have a piece of code: links |> Seq.map (fun x -> x.GetAttributeValue ("href", "no url")) Which I wanted to rewrite to: links |> Seq.map (fun x -> (x.GetAttributeValue "href" "no url")) But the F# compiler doesn't seem to like that. I was under the impression that these two function calls were interchangeable: f (a, b) (f a b) The error that I get is: The member or object constructor 'GetAttributeValue' taking 2 arguments are not accessible from this code location. All accessible versions of method 'GetAttributeValue' take 2 arguments. Which seems amusing, as it seems to indicate that it needs what I'm giving it. What am I missing here?

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