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  • Boost binding a function taking a reference

    - by Jamie Cook
    Hi all, I am having problems compiling the following snippet int temp; vector<int> origins; vector<string> originTokens = OTUtils::tokenize(buffer, ","); // buffer is a char[] array // original loop BOOST_FOREACH(string s, originTokens) { from_string(temp, s); origins.push_back(temp); } // I'd like to use this to replace the above loop std::transform(originTokens.begin(), originTokens.end(), origins.begin(), boost::bind<int>(&FromString<int>, boost::ref(temp), _1)); where the function in question is // the third parameter should be one of std::hex, std::dec or std::oct template <class T> bool FromString(T& t, const std::string& s, std::ios_base& (*f)(std::ios_base&) = std::dec) { std::istringstream iss(s); return !(iss >> f >> t).fail(); } the error I get is 1>Compiling with Intel(R) C++ 11.0.074 [IA-32]... (Intel C++ Environment) 1>C:\projects\svn\bdk\Source\deps\boost_1_42_0\boost/bind/bind.hpp(303): internal error: assertion failed: copy_default_arg_expr: rout NULL, no error (shared/edgcpfe/il.c, line 13919) 1> 1> return unwrapper<F>::unwrap(f, 0)(a[base_type::a1_], a[base_type::a2_]); 1> ^ 1> 1>icl: error #10298: problem during post processing of parallel object compilation Google is being unusually unhelpful so I hope that some one here can provide some insights.

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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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  • Pass temporary object to function that takes pointer

    - by Happy Mittal
    I tried following code : #include<iostream> #include<string> using namespace std; string f1(string s) { return s="f1 called"; } void f2(string *s) { cout<<*s<<endl; } int main() { string str; f2(&f1(str)); } But this code doesn't compile. What I think is : f1 returns by value so it creates temporary, of which I am taking address and passing to f2. Now Please explain me where I am thinking wrong?

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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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  • 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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  • 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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  • 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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  • 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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  • 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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  • 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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  • Redeclaration of parameters

    - by Scott
    While looking through the Selenium source code I noticed the following in the PageFactory: public static <T> T initElements(WebDriver driver, Class<T> pageClassToProxy) { T page = instantiatePage(driver, pageClassToProxy); initElements(driver, page); return page; } public static void initElements(WebDriver driver, Object page) { final WebDriver driverRef = driver; initElements(new DefaultElementLocatorFactory(driverRef), page); } What is the benefit of having the following line? final WebDriver driverRef = driver; Wouldn't it have made sense to just make the parameter final, and then passing that along to the next method without declaring the new reference?

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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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  • 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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  • Pass a parameter from one jsp to another using form.action

    - by Ntz
    I have an ID that I need in the next jsp once the user click a button. I am trying to do the following: FirstJSP.jsp: function getSecond() { var frm = document.getElementById("frm"); frm.action = "**second.jsp?id=myId;"** frm.submit(); } ... form id="frm" ..... input type="button" value="Next" onclick="getSecond()"/ ...... This code takes me to my second page, but if I tried to access the id, it gives me an error since the id is null. I access the id in the second page by: final Long passedId = Long.parseLong(request.getParameter("id")); I think I am not passing the parameter correctly, but I don't know how to do it. Any ideas? Thank you so much!

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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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  • 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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  • Speaking at PASS 2012… Exciting and Scary… As usual…

    - by drsql
    Edit: As I reread this, I felt I should clarify.. As usual refers mostly to the "Scary" part. I have a lot of stage fright that I have to work through. And it is always exciting to be picked. I have been selected this year at the PASS Summit 2012 to do two sessions, and they are both going to be interesting. Pre-Con: Relational Database Design Workshop - Abstract Triggers: Born Evil or Misunderstood? - Abstract The pre-con session entitled Relational Database Design Workshop will be (at least) the...(read more)

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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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