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  • How to tell where I am in an array with pointer arythmetic?

    - by klez
    In C, I have declared a memory area like this: int cells = 512; int* memory = (int*) malloc ((sizeof (int)) * cells); And I place myself more or less in the middle int* current_cell = memory + ((cells / 2) * sizeof (int)); My question is, while I increment *current_cell, how do I know if I reached the end of the allocated memory area?

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  • Const_cast on a this pointer - would I get told off by other C++ coders for doing this?

    - by BeeBand
    I have a class Game e.g. class Game { public: InitObjects(); ... }; And I have another class Grid, that needs to be initialised with a non-const reference to that Game object. ( A Grid object needs to call functions that can update a Game object ). class Grid { public: Grid(Game & g): game(g){} ... private: Game & game; ... }; The Game object is responsible for initialising the Grid. I did this: void Game::InitObjects() { grid = new Grid(*(const_cast<Game*>(this)) ); } grid is not a member of a Game - it's a global ( argh - i know... I don't mind making it a member, but I have the same problem right? ). Can some seasoned C++ folk tell me if this odd looking const_cast is acceptable?

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  • How to wrap a C function whose parameters are pointer to structs, so that it can be called from Lua?

    - by pierr
    I have the follwing C function. How should I wrap it so it can be called from a Lua script? typedef struct tagT{ int a ; int b ; } type_t; int lib_a_f_4(type_t *t) { return t->a * t->b ; } I know how to wrapr it if the function parameter type were int or char *. Should I use table type for a C structure? EDIT: I am using SWIG for the wraping , according to this doc, It seems that I should automatically have this funtion new_type_t(2,3) , but it is not the case. If you wrap a C structure, it is also mapped to a Lua userdata. By adding a metatable to the userdata, this provides a very natural interface. For example, struct Point{ int x,y; }; is used as follows: p=example.new_Point() p.x=3 p.y=5 print(p.x,p.y) 3 5 Similar access is provided for unions and the data members of C++ classes. C structures are created using a function new_Point(), but for C++ classes are created using just the name Point().

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  • pointers to member functions in an event dispatcher

    - by derivative
    For the past few days I've been trying to come up with a robust event handling system for the game (using a component based entity system, C++, OpenGL) I've been toying with. class EventDispatcher { typedef void (*CallbackFunction)(Event* event); typedef std::unordered_map<TypeInfo, std::list<CallbackFunction>, hash_TypeInfo > TypeCallbacksMap; EventQueue* global_queue_; TypeCallbacksMap callbacks_; ... } global_queue_ is a pointer to a wrapper EventQueue of std::queue<Event*> where Event is a pure virtual class. For every type of event I want to handle, I create a new derived class of Event, e.g. SetPositionEvent. TypeInfo is a wrapper on type_info. When I initialize my data, I bind functions to events in an unordered_map using TypeInfo(typeid(Event)) as the key that corresponds to a std::list of function pointers. When an event is dispatched, I iterate over the list calling the functions on that event. Those functions then static_cast the event pointer to the actual event type, so the event dispatcher needs to know very little. The actual functions that are being bound are functions for my component managers. For instance, SetPositionEvent would be handled by void PositionManager::HandleSetPositionEvent(Event* event) { SetPositionEvent* s_p_event = static_cast<SetPositionEvent*>(event); ... } The problem I'm running into is that to store a pointer to this function, it has to be static (or so everything leads me to believe.) In a perfect world, I want to store pointers member functions of a component manager that is defined in a script or whatever. It looks like I can store the instance of the component manager as well, but the typedef for this function is no longer simple and I can't find an example of how to do it. Is there a way to store a pointer to a member function of a class (along with a class instance, or, I guess a pointer to a class instance)? Is there an easier way to address this problem?

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  • Disable touchpad tap to click on Oneiric ocelot

    - by AWE
    You've heard this a million times but the "tap to click" is a pain in the behind and I want to disable it. There is no touchpad in gpointing-device-settings and neither in mouse and touchpad in system settings. I've tried some commands in terminal but it's all crap. Dconf-editor doesn't react. How about solving this once and for all? xinput list: ? Virtual core pointer id=2 [master pointer (3)] ? ? Virtual core XTEST pointer id=4 [slave pointer (2)] ? ? PS/2 Generic Mouse id=13 [slave pointer (2)] ? Virtual core keyboard id=3 [master keyboard (2)] ? Virtual core XTEST keyboard id=5 [slave keyboard (3)] ? Power Button id=6 [slave keyboard (3)] ? Video Bus id=7 [slave keyboard (3)] ? Video Bus id=8 [slave keyboard (3)] ? Power Button id=9 [slave keyboard (3)] ? Sleep Button id=10 [slave keyboard (3)] ? Laptop_Integrated_Webcam_HD id=11 [slave keyboard (3)] ? AT Translated Set 2 keyboard id=12 [slave keyboard (3)] ? Dell WMI hotkeys id=14 [slave keyboard (3)]

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  • Generic that takes only numeric types (int double etc)?

    - by brandon
    In a program I'm working on, I need to write a function to take any numeric type (int, short, long etc) and shove it in to a byte array at a specific offset. There exists a Bitconverter.GetBytes() method that takes the numeric type and returns it as a byte array, and this method only takes numeric types. So far I have: private void AddToByteArray<T>(byte[] destination, int offset, T toAdd) where T : struct { Buffer.BlockCopy(BitConverter.GetBytes(toAdd), 0, destination, offset, sizeof(toAdd)); } So basically my goal is that, for example, a call to AddToByteArray(array, 3, (short)10) would take 10 and store it in the 4th slot of array. The explicit cast exists because I know exactly how many bytes I want it to take up. There are cases where I would want a number that is small enough to be a short to really take up 4 bytes. On the flip side, there are times when I want an int to be crunched down to just a single byte. I'm doing this to create a custom network packet, if that makes any ideas pop in to your heads. If the where clause of a generic supported something like "where T : int || long || etc" I would be ok. (And no need to explain why they don't support that, the reason is fairly obvious) Any help would be greatly appreciated! Edit: I realize that I could just do a bunch of overloads, one for each type I want to support... but I'm asking this question because I want to avoid precisely that :)

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  • CUDA 4.1 Update

    - by N0xus
    I'm currently working on porting a particle system to update on the GPU via the use of CUDA. With CUDA, I've already passed over the required data I need to the GPU and allocated and copied the date via the host. When I build the project, it all runs fine, but when I run it, the project says I need to allocate my h_position pointer. This pointer is my host pointer and is meant to hold the data. I know I need to pass in the current particle position to the required cudaMemcpy call and they are currently stored in a list with a for loop being created and interated for each particle calling the following line of code: m_particleList[i].positionY = m_particleList[i].positionY - (m_particleList[i].velocity * frameTime * 0.001f); My current host side cuda code looks like this: float* h_position; // Your host pointer. This holds the data (I assume it's already filled with the data.) float* d_position; // Your device pointer, we will allocate and fill this float* d_velocity; float* d_time; int threads_per_block = 128; // You should play with this value int blocks = m_maxParticles/threads_per_block + ( (m_maxParticles%threads_per_block)?1:0 ); const int N = 10; size_t size = N * sizeof(float); cudaMalloc( (void**)&d_position, m_maxParticles * sizeof(float) ); cudaMemcpy( d_position, h_position, m_maxParticles * sizeof(float), cudaMemcpyHostToDevice); Both of which were / can be found inside my UpdateParticle() method. I had originally thought it would be a simple case of changing the h_position variable in the cudaMemcpy to m_particleList[i] but then I get the following error: no suitable conversion function from "ParticleSystemClass::ParticleType" to "const void *" exists I've probably messed up somewhere, but could someone please help fix the issues I'm facing. Everything else seems to running fine, it's just when I try to run the program that certain things hit the fan.

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  • ALPS touchpad on DELL Inspiron I15RN-3647BK with Ubuntu 11.10 x64

    - by Miguel
    I can't make work the multitouch of the ALPS touchpad in my Dell Inspiron I15RN-3647BK with Ubuntu 11.10 x64, kernel 3.0.0-17-generic... I have tried with this driver but it doesn't work http://people.canonical.com/~sforshee/alps-touchpad/psmouse-alps-0.10/psmouse-alps-dkms_0.10_all.deb. This is the result from the following command: user@laptop:~$ xinput list ? Virtual core pointer id=2 [master pointer (3)] ? ? Virtual core XTEST pointer id=4 [slave pointer (2)] ? ? PS/2 Generic Mouse id=12 [slave pointer (2)] ? Virtual core keyboard id=3 [master keyboard (2)] ? Virtual core XTEST keyboard id=5 [slave keyboard (3)] ? Power Button id=6 [slave keyboard (3)] ? Video Bus id=7 [slave keyboard (3)] ? Power Button id=8 [slave keyboard (3)] ? Sleep Button id=9 [slave keyboard (3)] ? Laptop_Integrated_Webcam_HD id=10 [slave keyboard (3)] ? AT Translated Set 2 keyboard id=11 [slave keyboard (3)] ? Dell WMI hotkeys That came with or without the alps driver from canonical repository and the touchpad just works like a PS2 generic mouse... Any ideas? Thanks in advance...

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  • why am i getting a null pointer when converting string to int array?

    - by Sackling
    My main method: public static void main(String[] args) { Scanner input = new Scanner(System.in); String string1; string1 = input.next(); LargeInteger firstInt = new LargeInteger(string1); System.out.printf("First integer: %s \n", firstInt.display()); } LargeInteger class: public class LargeInteger { private int[] intArray; //convert the strings to array public LargeInteger(String s) { for (int i = 0; i < s.length(); i++) { intArray[i] = Character.digit(s.charAt(i), 10); // in base 10 } } //display the strings public String display() { String result = ""; for (int i = 0; i < intArray.length; i++) { result += intArray[i]; } return result.toString(); } }

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  • Looking for feedback on design pattern for simple 2D environment

    - by Le Mot Juiced
    I'm working in iOS. I am trying to make a very simple 2D environment where there are some basic shapes you can drag around with your finger. These shapes should interact in various ways when dropped on each other, or when single-tapped versus double-tapped, etc. I don't know the name for the design pattern I'm thinking of. Basically, you have a bunch of arrays named after attributes, such as "double-tappable" or "draggable" or "stackable". You assign these attributes to the shapes by putting the shapes in the arrays. So, if there's a double-tap event, the code gets the location of it, then iterates through the "double-tappable" array to see if any of its members are in that location. And so on: every interactive event causes a scan through the appropriate array or arrays. It seems like that should work, but I'm wondering if there's a better pattern for the purpose.

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  • Is it safe to take the address of std::wstring's internal pointer?

    - by LCC
    I have an interface which is used like the following: if (SUCCEEDED(pInterface->GetSize(&size)) { wchar_t tmp = new wchar_t[size]; if (SUCCEEDED(pInterface->GetValue(tmp, size))) { std::wstring str = tmp; // do some work which doesn't throw } delete[] tmp; } Is it safe and portable to do this instead? if (SUCCEEDED(pInterface->GetSize(&size)) { std::wstring str; str.resize(size); if (SUCCEEDED(pInterface->GetValue(&str[0], size))) { // do some work } } Now, obviously this works (doesn't crash/corrupt memory) or I wouldn't have asked, but I'm mostly wanting to know if there's a compelling reason not to do this.

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  • Problem with C function of type char pointer, can someone explain?

    - by JJ
    Find the errors from following C function : char* f(int i) { int i; char buffer[20]; switch ( i ) { 1: strcpy( buffer, "string1"); 2: strcpy( buffer, "string2"); 3: strcpy( buffer, "string3"); default: strcpy(buffer, "defaultstring"); } return buffer; } this is c funtion not C++, I think it has to do with type conversion my compiler give warning that declaration of int i shadows a parameter.

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  • Why does casting to double using "String * 1" fail? Will CDbl(String) work on all systems?

    - by Jamie Bull
    I have an application which contains the line below to assign a parsed XML value to a variant array. V(2) = latNode.Text * 1 This works fine on my system (Windows 7, Excel 2010) but doesn't work on some other system or systems - and I've not been able to get a response from the user who reported the problem. I've switched out the offending line for: V(2) = CDbl(latNode.Text) This still works on my system, but then I had no problem in the first place. The question is on what systems does the first approach fail and why, and will the second method always work? I'm sure I've used the "Stying * 1" trick elsewhere before and would like to know how concerned I should be about tracking down other occurrences. Thanks.

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  • How can I configure the touchpad and keyboard settings on a Dell Inspiron 5110?

    - by Robik
    I am using ubuntu 11.10. I want the following 3 things: I have dell inspiron 5110 laptop. There is button at the top right corner of laptop which can be used for turning the screen off. It works in windows but it does not work in ubuntu 11.10. Even in the manual of the laptop, it the button is supported only in windows. Is there a way to activate it in ubuntu 11.10? Some of the keys like: "break" etc. are missing. Can I use other keys (or combinations of other keys) to function as those missing keys? In the program, "mouse and touchpad", there is no tab for touchpad. I want to enable vertical and horizontal scrolling. How do I do that? The command: xinput list shows Virtual core pointer id=2 [master pointer (3)] ? ? Virtual core XTEST pointer id=4 [slave pointer (2)] ? ? PS/2 Generic Mouse id=13 [slave pointer (2)] ? Virtual core keyboard id=3 [master keyboard (2)] ? Virtual core XTEST keyboard id=5 [slave keyboard (3)] ? Power Button id=6 [slave keyboard (3)] ? Video Bus id=7 [slave keyboard (3)] ? Video Bus id=8 [slave keyboard (3)] ? Power Button id=9 [slave keyboard (3)] ? Sleep Button id=10 [slave keyboard (3)] ? Laptop_Integrated_Webcam_HD id=11 [slave keyboard (3)] ? AT Translated Set 2 keyboard id=12 [slave keyboard (3)] ? Dell WMI hotkeys Please help!!

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  • Can I make a pointer to the code, and pass to the next instruction?

    - by drigoSkalWalker
    Like this link http://gcc.gnu.org/onlinedocs/gcc-3.3.1/gcc/Labels-as-Values.html I can get the memory address of an label, so if I declare a label, get your address, and add your address, i will pass to next instruction? some ilustration int main () { void *ptr; label: instruction 1; instruction 2; ptr = &&label; // So if I do it... ptr = ptr + 1; // I will get the instruction 2 correct?? Thanks for all answers.

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  • How to avoid double construction of proxy with DynamicProxy::CreateClassProxyWithTarget?

    - by Belvasis
    I am decorating an existing object using the CreateClassProxyWithTarget method. However, the constructor and therefore, initialization code, is being called twice. I already have a "constructed" instance (the target). I understand why this happens, but is there a way to avoid it, other than using an empty constructor? Edit: Here is some code: First the proxy creation: public static T Create<T>(T i_pEntity) where T : class { object pResult = m_pGenerator.CreateClassProxyWithTarget(typeof(T), new[] { typeof(IEditableObject), typeof(INotifyPropertyChanged) , typeof(IMarkerInterface), typeof(IDataErrorInfo) }, i_pEntity, ProxyGenerationOptions.Default, new BindingEntityInterceptor<T>(i_pEntity)); return (T)pResult; } I use this for example with an object of the following class: public class KatalogBase : AuditableBaseEntity { public KatalogBase() { Values = new HashedSet<Values>(); Attributes = new HashedSet<Attributes>(); } ... } If i now call BindingFactory.Create(someKatalogBaseObject); the Values and Attributes properties are beeing initialized again.

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  • PHP Curl Not formatting quotes properly; producing weird character set for single/double quotes

    - by user595052
    I wrote a html scraper to scrape my various social identites, so I can make a real time 'biography' website. However after using php curl_exec, I find that texts that I have quoted, end up being formatted in a weird character set. ex: "I love dogs" gets formatted to ’I love dogs ’ "I hate cheese" gets formatted to “I hate cheese� How do I either scrub these characters, or set curl not to format quotes like this. Also, I have turned off magic_quotes.

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  • Interesting fact #123423

    - by Tim Dexter
    Question from a customer on an internal mailing list this, succintly answered by RTF Template God, Hok-Min Q: Whats the upper limit for a sum calculation in terms of the largest number BIP can handle? A: Internally, XSL-T processor uses double precession.  Therefore the upper limit and precision will be same as double (IEEE 754 double-precision binary floating-point format, binary64). Approximately 16 significant decimal digits, max is 1.7976931348623157 x 10308 . So, now you know :)

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  • Do double forward slashes direct IE to use specific css?

    - by kjh
    I have just found something very weird while developing a website. While trying to get a div element to display across the top of the screen, I noticed that I wasn't achieving a desired result in any browser except for old versions of IE. In order to test some different code, instead of deleting the faulty line, I used '//' to comment it out (I'm not really even sure if that works in css) but what happened was, the compatible browsers used the uncommented code, while IE used the code marked by '//'. here is the code: #ban-menu-div{ position:fixed;top:0; //position:relative; //<-- IE keeps the banner with rel pos while the other display:block; // browsers used fixed margin:auto; padding:0px; width:100%; text-align:center; background:black; } so basically, it seems as though // can be used to instruct newer browsers to ignore specific lines of code, and instruct older versions of IE to use it? If this is common practice someone please let me know. it sure makes developing for older browsers a hell of a lot easier

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