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  • Passing objects by reference or not in C#

    - by Piku
    Suppose I have a class like this: public class ThingManager { List<SomeClass> ItemList; public void AddToList (SomeClass Item) { ItemList.Add(Item); } public void ProcessListItems() { // go through list one item at a time, get item from list, // modify item according to class' purpose } } Assume "SomeClass" is a fairly large class containing methods and members that are quite complex (List<s and arrays, for example) and that there may be a large quantity of them, so not copying vast amounts of data around the program is important. Should the "AddToList" method have "ref" in it or not? And why? It's like trying to learn pointers in C all over again ;-) (which is probably why I am getting confused, I'm trying to relate these to pointers. In C it'd be "SomeClass *Item" and a list of "SomeClass *" variables)

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  • How to reduce redundant code when adding new c++0x rvalue reference operator overloads

    - by Inverse
    I am adding new operator overloads to take advantage of c++0x rvalue references, and I feel like I'm producing a lot of redundant code. I have a class, tree, that holds a tree of algebraic operations on double values. Here is an example use case: tree x = 1.23; tree y = 8.19; tree z = (x + y)/67.31 - 3.15*y; ... std::cout << z; // prints "(1.23 + 8.19)/67.31 - 3.15*8.19" For each binary operation (like plus), each side can be either an lvalue tree, rvalue tree, or double. This results in 8 overloads for each binary operation: // core rvalue overloads for plus: tree operator +(const tree& a, const tree& b); tree operator +(const tree& a, tree&& b); tree operator +(tree&& a, const tree& b); tree operator +(tree&& a, tree&& b); // cast and forward cases: tree operator +(const tree& a, double b) { return a + tree(b); } tree operator +(double a, const tree& b) { return tree(a) + b; } tree operator +(tree&& a, double b) { return std::move(a) + tree(b); } tree operator +(double a, tree&& b) { return tree(a) + std::move(b); } // 8 more overloads for minus // 8 more overloads for multiply // 8 more overloads for divide // etc which also has to be repeated in a way for each binary operation (minus, multiply, divide, etc). As you can see, there are really only 4 functions I actually need to write; the other 4 can cast and forward to the core cases. Do you have any suggestions for reducing the size of this code? PS: The class is actually more complex than just a tree of doubles. Reducing copies does dramatically improve performance of my project. So, the rvalue overloads are worthwhile for me, even with the extra code. I have a suspicion that there might be a way to template away the "cast and forward" cases above, but I can't seem to think of anything.

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  • Modifying reference member from const member function in C++

    - by Philipp
    I am working on const-correctness of my code and just wondered why this code compiles: class X { int x; int& y; public: X(int& _y):y(_y) { } void f(int& newY) const { //x = 3; would not work, that's fine y = newY; //does compile. Why? } }; int main(int argc, char **argv) { int i1=0, i2=0; X myX(i1); myX.f(i2); ... } As far as I understand, f() is changing the object myX, although it says to be const. How can I ensure my compiler complains when I do assign to y? (Visual C++ 2008) Thank a lot!

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  • Boost singleton and undefined reference

    - by Ockonal
    Hello, I globally use singleton pattern in my project. To make it easier - boost::singleton. Current project uses Ogre3d library for rendering. Here is some class: class GraphicSystem : public singleton<GraphicSystem> { private: Ogre::RenderWindow *mWindow; public: Ogre::RenderWindow *getWindow() const { return mWindow; } }; In GraphicSystem constructor I fill the mWindow value: mWindow = mRoot->createRenderWindow(...); I cheked it, everything makes normally. So, now I have to use handler for the window in input system (to get window handle). Somewhere else in another class: Ogre::RenderWindow *temp = GraphicSystem::get_mutable_instance().getWindow(); GraphicSystem::get_mutable_instance().getWindow()->getCustomAttribute("WINDOW", &mWindowHandle); temp is 0x00, and there is segfault at last line (getting custon attribute). I can't understand, why does singleton returns undefined pointer for the window. All another singleton-based classes work well.

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  • Reference Object calling function in Javascript

    - by Louis
    I have a makeshift events system in JS and the attacher looks like this: events.attach(events.NEW_TASK,this.update); Where this.update is a callback/handler/function. The problem is, when the dispatcher tries to call this handler, it loses it's original context. How can I bind the handler with the context of the object that calls the attach function without passing this as an argument and using that?

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  • What should happen when a reference is deleted?

    - by Apeksha
    I have a vb.net 3.5 application which references a dll (abc.dll, also in .net 3.5) This dll is accessed by the application from time to time. If at anytime during execution, if I delete the dll, I expect the application to throw an error the next time it tries to use a class from the dll. But, this is not the behaviour I see. If I delete the dll before startup, the application throws an error at startup. But not when the dll is deleted after startup. Is this the standard behaviour, or am I doing something wrong? Can I get the app to throw an error if the dll is not found when it tries to use its classes? Thanks in advance.

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  • JNA Passing Structure By Reference Help

    - by tyeh26
    Hi all, I'm trying to use JNA to talk over a USB device plugged into the computer. Using Java and a .dll that was provided to me. I am having trouble with the Write function: C code: typedef struct { unsigned int id; unsigned int timestamp; unsigned char flags; unsigned char len; unsigned char data[16]; } CANMsg; CAN_STATUS canplus_Write( CANHANDLE handle, //long CANMsg *msg ); Java Equivalent: public class CANMsg extends Structure{ public int id = 0; public int timestamp = 0; public byte flags = 0; public byte len = 8; public byte data[] = new byte[16]; } int canplus_Write(NativeLong handle, CANMsg msg); I have confirmed that I can open and close the device. The close requires the NativeLong handle, so i am assuming that the CANMsg msg is the issue here. I have also confirmed that the device works when tested with C only code. I have read the the JNA documentation thoroughly... I think. Any pointers. Thanks all.

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  • C++ get method - returning by value or by reference

    - by HardCoder1986
    Hello! I've go a very simple question, but unfortunately I can't figure the answer myself. Suppose I've got some data structure that holds settings and acts like a settings map. I have a GetValue(const std::string& name) method, that returns the corresponding value. Now I'm trying to figure out - what kind of return-value approach would be better. The obvious one means making my method act like std::string GetValue(const std::string& name) and return a copy of the object and rely on RVO in performance meanings. The other one would mean making two methods std::string& GetValue(...) const std::string& GetValue(...) const which generally means duplicating code or using some evil constant casts to use one of these routines twice. #Q What would be your choice in this kind of situation and why?

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  • How to pass function reference into arguments

    - by Ockonal
    Hi, I'm using boost::function for making function-references: typedef boost::function<void (SomeClass &handle)> Ref; someFunc(Ref &pointer) {/*...*/} void Foo(SomeClass &handle) {/*...*/} What is the best way to pass Foo into the someFunc? I tried something like: someFunc(Ref(Foo));

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  • Real world examples of Ecmascript functions returning a Reference?

    - by Bergi
    Read the EcmaScript specification, section 8.7 The Reference Specification Type: The Reference type is used to explain the behaviour of such operators as delete, typeof, and the assignment operators. […] A Reference is a resolved name binding. Function calls are permitted to return references. This possibility is admitted purely for the sake of host objects. No built-in ECMAScript function defined by this specification returns a reference and there is no provision for a user-defined function to return a reference. Those last two sentences impressed me. With this, you could do things like coolHostFn() = value (valid syntax, btw). So my question is: Are there any EcmaScript implementations that define host function objects which result in Reference values?

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  • a design to avoid circular reference in this scenario

    - by BDotA
    Here is our dependency tree: BigApp - Child Apps - Libraries ALL of our components are HEAVILY using one of the Libraries as above ( LibA). But it has a ‘few’ public methods that require classes from ‘higher-level’ assemblies and we want to avoid CIRCULAR references. What do you propose as a good design for this?

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  • C++ reference variables

    - by avd
    I have these two functions (with Point2D & LineVector (has 2 Point2D member variables) classes and SQUARE macro predefined) inline float distance(const Point2D &p1,const Point2D &p2) { return sqrt(SQUARE(p2.getX()-p1.getX())+SQUARE(p2.getY()-p1.getY())); } inline float maxDistance(const LineVector &lv1,const LineVector &lv2) { return max(distance(lv1.p1,lv2.p2),distance(lv1.p2,lv2.p1)); } but it gives compilation error in maxDistance() function (line 238) saying: /usr/lib/gcc/i686-pc-cygwin/3.4.4/include/c++/bits/stl_iterator_base_types.h: In instantiation of `std::iterator_traits<Point2D>': quadrilateral.cpp:238: instantiated from here /usr/lib/gcc/i686-pc-cygwin/3.4.4/include/c++/bits/stl_iterator_base_types.h:129: error: no type named `iterator_category' in `class Point2D' /usr/lib/gcc/i686-pc-cygwin/3.4.4/include/c++/bits/stl_iterator_base_types.h:130: error: no type named `value_type' in `class Point2D ' /usr/lib/gcc/i686-pc-cygwin/3.4.4/include/c++/bits/stl_iterator_base_types.h:131: error: no type named `difference_type' in `class Point2D' /usr/lib/gcc/i686-pc-cygwin/3.4.4/include/c++/bits/stl_iterator_base_types.h:132: error: no type named `pointer' in `class Point2D' /usr/lib/gcc/i686-pc-cygwin/3.4.4/include/c++/bits/stl_iterator_base_types.h:133: error: no type named `reference' in `class Point2D' Please suggest what is the error?

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  • Reference variable to an object instantiated/initialized in another class in Java

    - by Alex
    The reason I'm asking is because I'm getting NullPointerException. I now this is very easy but I'm pretty new programming and find this a bit confusing. So say I have initialized an object in a class and want to access that same object from another class. Like now for instance I'm working on a small Chess game, in my model Game class I have an instance of Board, an object. Board, in turn, has an array of Squares. Square[][]. Game has board, board has Square[][]. Now if I want to access the Square[][] through the object board (in Game) of type Board. Do I just declare a variable with the same name and type or do I have to initialize it again? Board board OR Board board = new Board(); Note, I have already initialized board in the class Game so if I do it again, won't they be two totally different Board objects?

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  • How to make a copy of a char and not a reference in C++

    - by Phenom
    If I declare a function like this: string hash (char* key) then any change I make to key will also change it's value when the function exits, correct? I want to make a copy of it in the function so that I can safely change it without changing the original value. I tried this, but it doesn't work. string temp = key; How can it be done?

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  • C++ Type error with Object versus Object reference

    - by muddybruin
    I have the following function (which worked in Visual Studio): bool Plane::contains(Vector& point){ return normalVector.dotProduct(point - position) < -doubleResolution; } When I compile it using g++ version 4.1.2 , I get the following error: Plane.cpp: In member function âvirtual bool Plane::contains(Vector&)â: Plane.cpp:36: error: no matching function for call to âVector::dotProduct(Vector)â Vector.h:19: note: candidates are: double Vector::dotProduct(Vector&) So as you can see, the compiler thinks (point-position) is a Vector but it's expecting Vector&. What's the best way to fix this? I verified that this works: Vector temp = point-position; return normalVector.dotProduct(temp) < -doubleResolution; But I was hoping for something a little bit cleaner. I heard a suggestion that adding a copy constructor might help. So I added a copy constructor to Vector (see below), but it didn't help. Vector.h: Vector(const Vector& other); Vector.cpp: Vector::Vector(const Vector& other) :x(other.x), y(other.y), z(other.z), homogenous(other.homogenous) { }

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  • pass variable by reference within class? in php

    - by user151841
    I'm working on a hex color class where you can change the color values of any hex code color. In my example, I haven't finished the hex math, but it's not completely relevant to what I'm explaining here. Naively, I wanted to start to do something that I don't think can be done. I wanted to pass object properties in a method call. Is this possible? class rgb { private $r; private $b; private $g; public function __construct( $hexRgb ) { $this->r = substr($hexRgb, 0, 2 ); $this->g = substr($hexRgb, 2, 2 ); $this->b = substr($hexRgb, 4, 2 ); } private function add( & $color, $amount ) { $color += amount; // $color should be a class property, $this->r, etc. } public function addRed( $amount ) { self::add( $this->r, $amount ); } public function addGreen( $amount ) { self::add( $this->g, $amount ); } public function addBlue( $amount ) { self::add( $this->b, $amount ); } } If this is not possible in PHP, what is this called and in what languages is it possible? I know I could do something like public function add( $var, $amount ) { if ( $var == "r" ) { $this->r += $amount } else if ( $var == "g" ) { $this->g += $amount } ... } But I want to do it this cool way.

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  • net.tcp Listener Adapter and net.tcp Port Sharing Service not starting on reboot

    - by Peter K.
    I am using the net.tcp protocol for various web services. When I reboot my Windows 7 Ultimate (64-bit) macbook pro, the service never restarts automatically, even though that is how they are set: The only relevant events I can see are in the System Event Log: Error 6/9/2011 19:47 Service Control Manager 7001 None The Net.Tcp Listener Adapter service depends on the Net.Tcp Port Sharing Service service which failed to start because of the following error: The service did not respond to the start or control request in a timely fashion." Error 6/9/2011 19:47 Service Control Manager 7000 None The Net.Tcp Port Sharing Service service failed to start due to the following error: The service did not respond to the start or control request in a timely fashion." Error 6/9/2011 19:47 Service Control Manager 7009 None A timeout was reached (30000 milliseconds) while waiting for the Net.Tcp Port Sharing Service service to connect. This post suggests that it's something else blocking the port (in the post it's SCCM 2007 R3 Client which I don't use). What else could be the problem? If it's something else blocking the port, how do I figure out what? When I manually start the services, they start correctly. Dependencies are: Net.Tcp Port Sharing Service Net.Tcp Listener Adapter Still no luck, but I think the problem might be that my network connection takes too long to come up. I put in a custom view of the event log, and found these items: The first in the series says: A timeout was reached (30000 milliseconds) while waiting for the Net.Tcp Port Sharing Service service to connect.

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  • "SC.EXE config" and dollar sign in service name

    - by Joe Schmoe
    Say I want to make Windows Service startup dependent on SQL Server. In my case service name for SQL Server is MSSQL$SQL11 (SQL11 is SQL Server instance name) However, when I issue this command: SC.EXE config MyService depend= MSSQL$SQL11 everything after the dollar sign is ignored. When I go to "Dependencies" tab in "Services" SQL Server is not listed. When I check matching registry key it becomes clear why: it only has MSSQL. At this point I have to edit registry by hand to change MSSQL to MSSQL$SQL11 and then everything works as expected. Putting quotes around MSSQL$SQL11 doesn't help. Is there a way to specify $ in the middle of the SC.EXE argument string?

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  • printable PHP manual - 'all but the Function Reference section'

    - by JW01
    My Motivation I find it easier to learn things by reading 'offline'. I'd like to lean back and read the narrative part of a paper version of the official php manual. My Scuppered Plan My plan was to download the manual, print all but the Function Reference section and then read it. I have downloaded the "Single HTML file" version of the manual from the php.net download page. (That version did not contain any images, so I patched-in the ones from the Many HTML files version with no problem.) My plan was to open that "Single HTML file" in an HTML editor, delete the Function Reference section then print it out. Unfortunately, although I have tried three different editors, I have not been able to successfully load-up that massive html file to be able to edit it. Its about (~40MB). I started to look into the phpdoc framework with a view to rendering my own html docs from the source...but that's a steep learning curve for a newby..and is a last resort. I would use a file splitter, but they tend to split files crudely with no regard for html/xml/xhtml sematics. So the question is... Does anyone know know where you can download the php manual in a version that is a kind of half-way house between the 'Single HTML file' and the 'Many HTML files'? Ideally with the docs split into 3 parts: File 1 - stuff before the function reference File 2 - function reference File 3 - stuff after the function reference Or Can you suggest any editors/tools will enable me to split up this file myself?

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  • Nant COM Reference [migrated]

    - by user29286
    I'm trying to find the Nant syntax for including a COM reference. The current Nant script with the normal dll reference looks like .. <references> <include name="${external-lib}/System.Interop.AppName.dll" /> The COM reference in the .csproj file looks like this ... <COMReference Include="System.Interop.AppName"> <Guid>{00020813-0000-0000-C000-000000000046}</Guid> <VersionMajor>1</VersionMajor> <VersionMinor>7</VersionMinor> <Lcid>0</Lcid> <WrapperTool>primary</WrapperTool> <Isolated>False</Isolated> </COMReference> What syntax should I use in Nant to swap to the COM reference to do the build ?

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  • Deleting windows.edb and unchecking Indexing service lead to hard drive file records swapping

    - by linni
    I followed the instructions listed here:http://www.mydigitallife.info/2007/09/18/turn-off-and-disable-search-indexing-service-in-windows-xp/ to free up space on hard drive by deleting the windows.edb indexing file... I also stopped windows search service as mentioned in the comments following the article. In addition to unchecking the "Allow Indexing Service to index this disk for fast file searching" check box on the properties dialog for the C:\ drive, I did the same for two usb connected hard drives (J:\ and I:\ ). I'm not sure why I did that, thought it might shrink the windows.edb file so I wouldn't have to delete it (which sounded a bit risky in my ears at the time). The file of course didn't shrink so I ended up deleting it and freeing up over 3 GB of space, yeehaw. However, as soon as I had done this I could not access the usb connected hard drives anymore. The error I got was "I:\photos is not accessible" "The file or directory is corrupted and unreadable" when I tried to open the photos directory on I:\ Here is where I enter the twilight zone... I try disconnecting I:\ usb hard drive. But XP shows me that instead J:\ drive has disconnected and I:\ is still there. So I disconnect both drives and restart the computer. I then connect one drive, but it lists up the contents of the other drive on root level. I tried connecting the drives vice versa and the same thing happens. I try taking one of the hard drives to another computer and when I connect it there it lists up not its own contents but the contents of the other hard drive and gives the same error as above when I try and access any of the folders (even folders on the root that have the same name as folders on the other drive (e.g. J:\photos and I:\photos)??? And no, this is not a me mixing up my drive letters. Computer Manager - Disk management shows the same result as explorer: The drive size is correct (one is 500GB, the other is 640GB) but the drive name is of the opposite drive, as long as the contents. Also, one drive was full of data and the other almost empty but they incorrectly show their free space status of the other drive. Somehow the usb drives seem to have switched file tables, file records, boot records or something, extremely weird! Even weirder, if I try and create a text file or folder on this drive, it works fine, accessing them, saving, whatever, all good, but accessing any other data on the drive gives me an error. Does anyone have a clue what is going on and more importantly, how I can restore the correct folder listings to access my family photos ??? cheers, linni

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