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  • Can I use memcpy in C++ to copy classes that have no pointers or virtual functions

    - by Shane MacLaughlin
    Say I have a class, something like the following; class MyClass { public: MyClass(); int a,b,c; double x,y,z; }; #define PageSize 1000000 MyClass Array1[PageSize],Array2[PageSize]; If my class has not pointers or virtual methods, is it safe to use the following? memcpy(Array1,Array2,PageSize*sizeof(MyClass)); The reason I ask, is that I'm dealing with very large collections of paged data, as decribed here, where performance is critical, and memcpy offers significant performance advantages over iterative assignment. I suspect it should be ok, as the 'this' pointer is an implicit parameter rather than anything stored, but are there any other hidden nasties I should be aware of?

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  • How to make a file with .pt extension, with xml syntax highlighting and vim's plugin snipmate load p

    - by Somebody still uses you MS-DOS
    I have the following in my .vimrc: au BufNewFile,BufRead *.pt set filetype=xml This is needed because although I'm editing a file with *.pt extension, it's indeed a valid xml file: setting the filetype like this I can have syntax highlighting. I'm using vim's snipmate plugin, and tried to create pt.snippets to specific needs since these files are Zope Page Templates (ZPT with TAL). Now, I have a problem: I don't want to create these snippets in xml.snippets, since they aren't really generic xml snippets, but my *.pt files are set to xml, so when I define my pt snippets they aren't loaded unless I run :set filetype=pt on my pt file on vim - but then I lose syntax highlighting. I would like to be able to have a pt file, with xml syntax highlighting, to be able to load a pt.snippets file from snipmate. How can I do it? (I would like to avoid putting my snippets in a generic snippet file, I would like it to be present only in pt.snippets to be easier to maintain.)

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  • C++ (g++) Compile Error, Expected "="/etc. Before 'MyWindow" (my class name)

    - by Ell
    Hi all, I have a very strange problem and the following code wont compile: #ifndef MYWINDOW_HPP_INCLUDED #define MYWINDOW_HPP_INCLUDED class MyWindow{ private: WNDCLASSEX window_class; HWND window_handle; HDC device_context_handle; HGLRC open_gl_render_context; MSG message; BOOL quit; public: Window(int height=416, int width=544, WindowStyle window_style=WINDOWED); void Show(); void Close(); ~Window(); }; #endif // MYWINDOW_HPP_INCLUDED I get the following error: error: expected '=', ',', ';', 'asm' or 'attribute' before 'MyWindow' I can't see any syntax errors here, although I coukd be wrong as I am very (very) new in c++. Thanks in advance, ell.

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  • Data-only static libraries with GCC

    - by regularfry
    How can I make static libraries with only binary data, that is without any object code, and make that data available to a C program? Here's the build process and simplified code I'm trying to make work: ./datafile: abcdefghij Makefile: libdatafile.a: ar [magic] datafile main: libdatafile.a gcc main.c libdatafile.a -o main main.c: #define TEXTPTR [more magic] int main(){ char mystring[11]; memset(mystring, '\0', 11); memcpy(TEXTPTR, mystring, 10); puts(mystring); puts(mystring); return 0; } The output I'm expecting from running main is, of course: abcdefghijabcdefghij My question is: what should [magic] and [more magic] be?

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  • mapping list of different types implementing same function?

    - by sisif
    I want to apply a function to every element in a list (map) but the elements may have different types but all implement the same function (here "putOut") like an interface. However I cannot create a list of this "interface" type (here "Outputable"). How do I map a list of different types implementing the same function? main :: IO () main = do map putOut lst putStrLn "end" where lst :: [Outputable] -- ERROR: Class "Outputable" used as a type lst = [(Out1 1),(Out2 1 2)] class Outputable a where putOut :: a -> IO () -- user defined: data Out1 = Out1 Int deriving (Show) data Out2 = Out2 Int deriving (Show) instance Outputable Out1 where putOut out1 = putStrLn $ show out1 instance Outputable Out2 where putOut out2 = putStrLn $ show out2 I cannot define it this way: data Out = Out1 Int | Out2 Int Int putOut Out1 = ... putOut Out2 = ... because this is a library and users should be able to extend Out with their own types

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  • Expected Class-name before { token

    - by ML
    Hi All, I am trying to figure out whey I get an error: expected class-name before { token Here is the relative source to the error: #pragma once #ifndef H_FXACTION #define H_FXACTION #include "CP_M_RefCounted.h" #include "FxTypes.h" #include "string" #include "FxString.h" #include "FxPixels.h" #include "CP_Rect.h" #include "FxStreamable.h" #include "FxPoint.h" #include "FxPtr.h" #include "FxImage.h" #include "FxSleekStreaming.h" typedef FxID FxActionType; typedef FxUInt32 FxActionID; FxActionID FrMakeUniqueActionID(void); class FxActionData; class FxActionData : public CP_M_RefCounted { public: FxActionData(); FxActionData(FxBool final) :mFinal(final) { } virtual ~FxActionData(); I get the error at this line: class FxActionData : public CP_M_RefCounted What I dont get is why the line: class FxActionData; is there when you are creating the class directly under it. Isn't this a forward declaration? What things could be going on here?

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  • Can I configure Eclipse / JBoss integration so it does not rely on deploying Jars to the "server/def

    - by kellyfj
    I am using MyEclipse 7.5 with JBoss 4.2.3 GA. When I define my local development JBoss server in MyEclipse it always wants to deploy jars, wars etc. to the "server/default/deploy" directory. Unfortunately our JBoss directory structure for production is "server/XYZ/deploy/abc" (driven by a third party). As a result our Dev JBoss instances are different from our QA/Staging/Production JBoss instances. Is there a way to configure Eclipse to use JBoss but deploy to that specific folder path "server/XYZ/deploy/abc" rather than the default one "server/default/deploy"?

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  • C Structure Pointer Problem

    - by Halo
    I have this struct; #define BUFSIZE 10 struct shared_data { pthread_mutex_t th_mutex_queue; int count; int data_buffer_allocation[BUFSIZE]; int data_buffers[BUFSIZE][100]; }; and I want to allocate one of the data_buffers for a process, for that purpose I execute the following function; int allocate_data_buffer(int pid) { int i; for (i = 0; i < BUFSIZE; i++) { if (sdata_ptr->data_buffer_allocation[i] == NULL) { sdata_ptr->data_buffer_allocation[i] = pid; return i; } } return -1; } but the compiler warns me that I'm comparing pointer to a value. When I put a & in front of sdata_ptr it calms down but I'm not sure if it will work. Isn't what I wrote above supposed to be true?

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  • technique for how to debug macros in C

    - by Dervin Thunk
    Hi. So I have the (mostly vilified) #define MAX( a, b ) ( ((a) > (b)) ? (a) : (b) ) somewhere in a program (yes, yes, I know). At some point in the code there is a comparison X>-1?, where X is (as far as I can tell) a (signed) integer. The line is j += MAX(bmGs[i], bmBc[(int)y[i + j]] - m + 1 + i);, where y here is a char*. Not necessarily surprisingly, I find that the macro is returning -1 as the larger number (I'm guessing too long a number for int or an unsigned issue, but I can't find it). I would like to know techniques you guys may have for finding these kinds of errors. Notice that I'm not asking for programming advice about whether or not to use that macro, I'm sure folks are dying to tell me I should refrain from things like that, but the question is going somewhere else. Thanks.

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  • how to diff / align Python lists using arbitrary matching function?

    - by James Tauber
    I'd like to align two lists in a similar way to what difflib.Differ would do except I want to be able to define a match function for comparing items, not just use string equality, and preferably a match function that can return a number between 0.0 and 1.0, not just a boolean. So, for example, say I had the two lists: L1 = [('A', 1), ('B', 3), ('C', 7)] L2 = ['A', 'b', 'C'] and I want to be able to write a match function like this: def match(item1, item2): if item1[0] == item2: return 1.0 elif item1[0].lower() == item2.lower(): return 0.5 else: return 0 and then do: d = Differ(match_func=match) d.compare(L1, L2) and have it diff using the match function. Like difflib, I'd rather the algorithm gave more intuitive Ratcliff-Obershelp type results rather than a purely minimal Levenshtein distance.

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  • Adding on touch event to images inside gridview

    - by Steve
    I have a gridview where each item has a image and a textview (an app), i added the onItemClick to the gridview in order to launch the app, i also removed the orange selection and made selector in xml so when pressed the text would change to grey and on release it would return to white. My problem is that i need the image to apply an alpha value when pressed and restore the previous alpha on release i tested a lot of ways and none did worked correctly. I came close with the updated answer from the autor of the question: How to set alpha value for drawable in a StateListDrawable?, but some how the state pressed never gets called, i don´t know if this is because i am using the onitemClick to launch the app or not. Also i since i can´t define the alpha on imageview xml i don´t know what else to do Any help will be appreciated

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  • static const double in c++

    - by Crystal
    Is this the proper way to use a static const variable? In my top level class (Shape) #ifndef SHAPE_H #define SHAPE_H class Shape { public: static const double pi; private: double originX; double originY; }; const double Shape::pi = 3.14159265; #endif And then later in a class that extends Shape, I use Shape::pi. I get a linker error. I moved the const double Shape::pi = 3.14... to the Shape.cpp file and my program then compiles. Why does that happen? thanks.

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  • How to get route "name" when in route controller

    - by Murph
    I'm using routing in asp.net to get nice URLs When I define routes in global.asax I create two distinct routes that use the same controller (c#): // Setup code for route a... routes.Add("routeb", routea); // Setup code for route b... routes.Add("routeb", routeb); (How) is it possible to determine from within the controller what the "key" value is that directed the user to this controller? Alternatively is the pattern of use wrong - it would be straightforward to subclass the Controller (again) to distinguish between the two and retain common code if that is a more appropriate solution.

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  • Programatically opening an xml file in MS Word

    - by Dan Revell
    I'm opening an xml file in Microsoft Word 2007 using C#. I'm using an xsl file to define the layout which worked up to the point that I needed to include an image. I used the typical src html tag and the image displays when the xml is viewed in ie but not when it's opened in Word. I get the image place holder so I can only assume Word simply can't find the image. It's sitting next to both the xml file and xsl file but that doesn't make any difference. To open the document I'm passing the filenames for both the xml and xsl. I would imagine that as the src is in the xsl it would just look relative to one of these files. Any suggestions would be much appreciated. [EDIT] Apologies I lost track of this one. I fixed it in the end. I'll check what my solution was tomorrow and update this.

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  • Java: Reflection against casting when you know superclass

    - by Ema
    I don't know exactly how to define my doubt so please be patient if the question has already been asked. Let's say I have to dinamically instantiate an object. This object will surely be instance of a subclass of a known, immutable class A. I can obtain dinamically the specific implementation class. Would it be better to use reflection exactly as if I didn't know anything about the target class, or would it be preferrable/possible to do something like: A obj = (Class.forName("com.package.Sub-A")) new A(); where Sub-A extends A ? The purpose would be to avoid reflection overhead times... Thank you in advance.

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  • Given an instance of a Ruby object, how do I get its metaclass?

    - by Stanislaus Wernstrom
    Normally, I might get the metaclass for a particular instance of a Ruby object with something like this: class C def metaclass class << self; self; end end end # This is this instance's metaclass. C.new.metaclass => #<Class:#<C:0x01234567>> # Successive invocations will have different metaclasses, # since they're different instances. C.new.metaclass => #<Class:#<C:0x01233...>> C.new.metaclass => #<Class:#<C:0x01232...>> C.new.metaclass => #<Class:#<C:0x01231...>> Let's say I just want to know the metaclass of an arbitrary object instance obj of an arbitrary class, and I don't want to define a metaclass (or similar) method on the class of obj. Is there a way to do that?

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  • Declaration for object for which creation is wrapped in macro

    - by learner
    The following macro is defined in our code: #define MSGMacro(obj, arg) MyPaymentClass obj(arg) Where MSGMacro is used to creates the object of type MyPaymentClass using code like MSGMacro(Card, 1); MSGMacro(Cash, 2); ---- ---- //removed unwanted things to keep question cleaner. All the above code is in one cpp file, Now the problem is how we can expose these two objects of MyPaymentClass to other units in my project? i.e. I want to use Card and Cash in other CPP files. Please suggest how I can give the declaration for the same in some header file?

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  • A way of allocating multidimensional arrays dynamically

    - by C77431
    salute.. I am learning dynamic allocations for multidimensional arrays in a book and I found some ways for that, And now haven't problem in it. But the author of the book shows us a way, but it doesn't work correctly. It is this: pbeans = new double [3][4]; // Allocate memory for a 3x4 array And this is the error: error C2440: '=' : cannot convert from 'int (*)[4]' to 'int *' how should i define pbeans ( if this type of coding is legal)? and what is the problem exactly? Regards.

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  • An exception to the "only one implementation" rule ?

    - by ereOn
    While I was reading the accepted answer of this question, I had the following question: Typically, methods are defined in header files (.hpp or whatever), and implementation in source files (.cpp or whatever). One of the main reasons it is bad practice to ever include a "source file" (#include <source_file.cpp>) is that its methods implementation would then be duplicated, resulting in linking errors. When one writes: #ifndef BRITNEYSPEARS_HPP #define BRITNEYSPEARS_HPP class BritneySpears { public: BritneySpears() {}; // Here the constructor has implementation. }; #endif /* BRITNEYSPEARS_HPP */ He is giving the implementation of the constructor (here an "empty" implementation, but still). But why then including this header file multiple times (aka. on different source files) will not generate a "duplicate definition" error at link time ?

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  • Mix and match class in C++/MFC

    - by Coder
    I'm trying to re-factor a code base, and there is some common functionality among unrelated classes that I'd love to unite. I would like to add that functionality in common base class, but I'm not sure if it's clean and good approach. Say I have CMyWnd class and CMyDialogEx class, both different, so they cannot inherit from one base class. I want to add a button to both classes and add the message handlers to both classes as well. So I'd like to do something like this: CMyWnd : public CWnd, public COnOkBtnFunctionality, public COnCancelBtnFunctionality CMyDialogEx: public CWnd, public COnOkBtnFunctionality Where COnOkBtnFunctionality would define CButton m_buttonOk, and all the afx_msg functions it should have. And so on. Is this approach doable/good? Or are there better patterns I should resort to?

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  • C++ context menu image at left side showing partially, no fully

    - by Samir
    In C++ #define BITMAP_MAIN 201 //in resource.h BITMAP_MAIN BITMAP "main.bmp" // in .rc file // showing icon in menu... HBITMAP imgMain = LoadBitmap( aHinstance, MAKEINTRESOURCE(BITMAP_MAIN) ); SetMenuItemBitmaps ( hSubmenu, uMenuIndex, MF_BYPOSITION, imgMain, imgMain); The problem is in non-English XP OS the main.bmp is showing partially in the context menu. In Vista, Window7 main.bmp is showing just fine. Also in English XP its ok. But why the image is not showing fully in non-English XP? How would I use .ico file here instead of .bmp? This is to make the image transparent.

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  • Keep a javascript variable after an ajax call

    - by Guillaume le Floch
    I'm new in javascript and jQuery. I'm using ajax calls to get data from my server. The fact is, I'm losing my javascript variables after the call .. Here is what I did : the variable is define outside any function and treat in an other function. var a = 0; function myfunction(url){ $.ajax({ url: url, timeout: 20000, success: function(data){ // Do some stuff // The a variable is now undefined }, error: function(){ // Do some stuff } }); } Everything is working fine, the only thing is that I need to keep my variables ... but it looks like it's gone .. Does anyone know why? Thanks

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  • NHibernate Many-to-many with a boolean flag on the association table

    - by Nigel
    Hi I am doing some work on an application that uses an existing schema that cannot be altered. Whilst writing my NHibernate mappings I encountered a strange many-to-many relationship. The relationship is defined in the standard way as in this question with the addition of a boolean flag on the association table that signifies if the relationship is legal. This seems somewhat redundant but as I say, cannot be changed. Is it possible to define this relationship in Nhibernate without resorting to using a third class to represent the association? Perhaps by applying a filter? Many thanks.

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  • Random access view in boost::multi_array

    - by linai
    Here is a boost example: typedef boost::multi_array<double, 1> array_type; typedef array_type::index index; array_type A(boost::extents[100]); for(index i = 0; i != A.size(); ++i) { A[i] = (double)i; } // creating view array_type::index_gen indices; typedef boost::multi_array_types::index_range range; array_type::array_view<1>::type myview = A[ indices[range(0,50)] ]; What this code does is creating a subarray or view mapping onto the original array. This view is continuous and covers from 0th to 50th elements of an original array. What if I need to explicitly define elements I'd like to see in the view? How can I create a view with indices like [1, 5, 35, 23] ? Any ideas?

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  • c++ when to put method out side the class

    - by user63898
    i saw that some times in c++ applications using only namespace declarations with header and source file like this : #ifndef _UT_ #define _UT_ #include <string> #include <windows.h> namespace UT { void setRootPath(char* program_path, char* file_path); char * ConvertStringToCharP(std::string str); }; #endif //and then in UT.cpp #include "UT.h" namespace UT { char * ConvertStringToCharP(std::string str) { char * writable = new char[str.size() + 1]; std::copy(str.begin(), str.end(), writable); writable[str.size()] = '\0'; return writable; } void setRootPath(char* program_path, char* file_path) { //... } } is it better then defining classic class with static methods? or just simple class ? dose this method has something better for the compiler linker ? the methods in this namespace are called allot of times .

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