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  • Double Buffering for Game objects, what's a nice clean generic C++ way?

    - by Gary
    This is in C++. So, I'm starting from scratch writing a game engine for fun and learning from the ground up. One of the ideas I want to implement is to have game object state (a struct) be double-buffered. For instance, I can have subsystems updating the new game object data while a render thread is rendering from the old data by guaranteeing there is a consistent state stored within the game object (the data from last time). After rendering of old and updating of new is finished, I can swap buffers and do it again. Question is, what's a good forward-looking and generic OOP way to expose this to my classes while trying to hide implementation details as much as possible? Would like to know your thoughts and considerations. I was thinking operator overloading could be used, but how do I overload assign for a templated class's member within my buffer class? for instance, I think this is an example of what I want: doublebuffer<Vector3> data; data.x=5; //would write to the member x within the new buffer int a=data.x; //would read from the old buffer's x member data.x+=1; //I guess this shouldn't be allowed If this is possible, I could choose to enable or disable double-buffering structs without changing much code. This is what I was considering: template <class T> class doublebuffer{ T T1; T T2; T * current=T1; T * old=T2; public: doublebuffer(); ~doublebuffer(); void swap(); operator=()?... }; and a game object would be like this: struct MyObjectData{ int x; float afloat; } class MyObject: public Node { doublebuffer<MyObjectData> data; functions... } What I have right now is functions that return pointers to the old and new buffer, and I guess any classes that use them have to be aware of this. Is there a better way?

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  • Why don't stacks grow upwards (for security)?

    - by AshleysBrain
    This is related to the question 'Why do stacks typically grow downwards?', but more from a security point of view. I'm generally referring to x86. It strikes me as odd that the stack would grow downwards, when buffers are usually written to upwards in memory. For example a typical C++ string has its end at a higher memory address than the beginning. This means that if there's a buffer overflow you're overwriting further up the call stack, which I understand is a security risk, since it opens the possibility of changing return addresses and local variable contents. If the stack grew upwards in memory, wouldn't buffer overflows simply run in to dead memory? Would this improve security? If so, why hasn't it been done? What about x64, do those stacks grow upwards and if not why not?

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  • How do I step through and debug a Scheme program using Dr. Racket?

    - by Thomas Owens
    I'm using the Dr. Racket development environment and the language definition #lang scheme to do work for a course. However, I'm not sure how to best use this tool for debugging. I would like to be able to execute a function and step through it, observing the values of different functions at various points in execution. Is this possible? If not, what is the typical method of stepping through the execution of a Scheme program and debugging it?

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  • How can I merge properties of two JavaScript objects dynamically?

    - by JC Grubbs
    I need to be able to merge two (very simple) JavaScript objects at runtime. For example I'd like to: var obj1 = { food: 'pizza', car: 'ford' } var obj2 = { animal: 'dog' } obj1.merge(obj2); //obj1 now has three properties: food, car, and animal Does anyone have a script for this or know of a built in way to do this? I do not need recursion, and I do not need to merge functions, just methods on flat objects.

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  • Are .dll files loaded once for every program or once for all programs?

    - by Nilbert
    I have a simple small question which someone who knows will be able to answer easily, I searched google but couldn't find the answer. There are many programs running at once on a computer, and my question is: when a program loads a DLL, does it actually load the DLL file or does it find the memory in which the DLL is already loaded? For example, is ws2_32.dll (winsock 2) loaded for every program that uses winsock, or is it loaded once and all programs that use it use the same memory addresses to call the functions?

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  • How closely related is music composition to coding?

    - by ehsanul
    It seems to me as if there are a higher proportion of musicians in the programming field than in the general public. Maybe it's just an illusion caused by the fact that I'm an amateur guitarist myself, so I tend to notice coding musicians (or musical coders?) more. But I wonder if there really is some connection. Perhaps a shared set of skills or an innate quality that makes it more likely for someone who enjoys programming to also enjoy playing and composing music. How closely related is music composition to coding? I'd especially like to hear from the musicians around here.

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  • How to use Festival Text To Speech C/C++ API

    - by Peeyush
    I want to use Festival TTS with my C++ programme. So i have downloaded all files form http://www.cstr.ed.ac.uk/downloads/festival/2.0.95/ then i start reading manual(http://www.cstr.ed.ac.uk/projects/festival/manual/festival_28.html) for C++ API but in manual they says that: In order to use Festival you must include festival/src/include/festival.h' which in turn will include the necessary other include files infestival/src/include' and speech_tools/include' you should ensure these are included in the include path for you your program. Also you will need to link your program withfestival/src/lib/libFestival.a', speech_tools/lib/libestools.a',speech_tools/lib/libestbase.a' and `speech_tools/lib/libeststring.a' as well as any other optional libraries such as net audio. " I am using UBUNTU 10.04(festival package is by default installed and i can use it form terminal by festival command) and GCC 4.4.3 but the problem is that i am new to GCC and i am not understanding which files i have to include in order to run my C++ code and i also don't know how to link libraries with my c++ code. So please tell me exactly which files i have to include and how to link with libraries if anyone already use festival tts with c++ then please post your code Thanks

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  • Is Win32_PerfFormattedData_PerfDisk_PhysicalDisk missing from WMI in Vista?

    - by Martin
    From what I understand, the following script should work in Windows XP and higher, but it doesn't work for me in Vista Business 32-bit Service Pack 2. Thus far I have been very unsuccessful googling for information about this performance class. strComputer = "." Set objWMIService = GetObject("winmgmts:\\" & strComputer & "\root\cimv2") Set colApps = objWMIService.ExecQuery("Select * from Win32_PerfFormattedData_PerfDisk_PhysicalDisk") For Each objApp in colApps Wscript.Echo objApp.Caption Next Does this WMI class simply not exist in Vista? If it is just me, is there a way to fix WMI? I have already tried running winmgmt /resetrepository and winmgmt /resyncperf and neither helps.

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  • Mixing JQuery Ajax with ASP.NET : is there any security risk

    - by Sayem Ahmed
    I am using jQuery with ASP.NET in a project. Instead of using ASP.NET Ajax, I am using jquery's ajax functions. Is there any security risk if I do that? I mean, since I am using jquery's ajax calls, no view state information will be passed to the server so that it can verify the page's authenticity (though it saves a lot of bandwidth..). I would also like to know what is the best/good practice here.

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  • READING WEBSITE CONTENTS JAVA

    - by Sahil Manchanda
    IM DEVELOPING AN ANDROID APPLICATION WHERE in a website i PROGRAMMATICALLY submit data into search box and retrieve results by JAVA. i get the data by using URLConnect JAVA. i get the source code ie html code...... Urlconnection a = .connect to host getinputstream read data i use these functions now if the site has content like: sahil 3/5 patel chowk 965955 since these details will be inside html tags i want to extract this information . any idea

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  • An interesting case of delete and destructor (C++)

    - by Viet
    I have a piece of code where I can call destructor multiple times and access member functions even the destructor was called with member variables' values preserved. I was still able to access member functions after I called delete but the member variables were nullified (all to 0). And I can't double delete. Please kindly explain this. Thanks. #include <iostream> using namespace std; template <typename T> void destroy(T* ptr) { ptr->~T(); } class Testing { public: Testing() : test(20) { } ~Testing() { printf("Testing is being killed!\n"); } int getTest() const { return test; } private: int test; }; int main() { Testing *t = new Testing(); cout << "t->getTest() = " << t->getTest() << endl; destroy(t); cout << "t->getTest() = " << t->getTest() << endl; t->~Testing(); cout << "t->getTest() = " << t->getTest() << endl; delete t; cout << "t->getTest() = " << t->getTest() << endl; destroy(t); cout << "t->getTest() = " << t->getTest() << endl; t->~Testing(); cout << "t->getTest() = " << t->getTest() << endl; //delete t; // <======== Don't do it! Double free/delete! cout << "t->getTest() = " << t->getTest() << endl; return 0; }

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  • Windows API Programming

    - by Chris
    I found this site, http://www.apitalk.com/document.php?id=1184207999_1 and I'm not sure if this site is using ATL, STL, MFC, or just calling API functions directly. I have done console programming with C++ and graphics programmign with C++ in Borland, but I've have never done Win32 C++ programming and I'm curious if anyone knows of a good site to start with? Does anyone know of any good sites to recommend about getting up and going fast with Win32 API C++?

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  • Which Workflow Engine do you recommend?

    - by Glenn
    I am kicking around the idea of using a workflow engine on this upcoming project. We know that there is a lot of caveats with using a workflow engine and we have a lot of development experience in many platforms so we would be willing to let the choice of workflow engine take precedence over our favorite toolset or developer IDE. We are more interested in internal workflow (i.e. petri net for easily changeable ERP purposes without involving additional coder time) than external workflow (i.e. aggregating SOAP calls into a transaction aware, higher level SOA). Which workflow engine would you recommend? We have superficially looked at offerings by Oracle, Microsoft, and some open source stuff too. It's all very overwhelming so please respond only if you have real life experience with implementing internal workflow.

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  • Invoke Python modules from Java

    - by user36813
    I have a Python interface of a graph library written in C - igraph (the name of library). My need is to invoke the python modules pertaining to this graph library from Java code. It goes like this, the core of library is in c. This core has been imported into Python and interfaces to the functions embedded in core are available in Python. My project's rest of the code is in Java and hence I would like to call the graph functions by Java as well. Jython - which lets you invoke python modules with in Java was an option.I went on trying Jython to discover that it will not work in my case as the core code is in C and Jython wont support anything that is imported as a c dll in python code.I also thought of opting for the approach of calling graph routines directly in c. That is without passing through Python code. I am assuming there must be something which lets you call c code from Java, how ever I am not good in C hence I did not go for it. My last resort seems to execute Python interpreter from command line using Java. But that is a dirty and shameless. Also to deal with the results produced by Python code I will have to write the results in a file and read it back in java. Again dirty way. Is there something that any one can suggest me? Thanks to every one giving time. Thanks Igal for answering. I had a look at it. At first glance it appears as if it is simply calling the python script. Jep jep = new Jep(false, SCRIPT_PATH, cl); jep.set("query", query); jep.runScript(SCRIPT_PATH + file); jep.close(); Isnt it very similar to what we would do if called the python interpreter from command line through a Java code. Runtime runtime = Runtime.getRuntime(); Process proc = runtime.exec("python test.py"); Concern is how do I use the results generated by Python script. The naive way is to write them to file and read it back in Java. I am searching for a smarter approach.Thanks for suggestion anyway.

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  • is versus as pl/sql

    - by sqlgrasshopper5
    I thought that oracle treats both "is" and "as" same for functions and procedures.I tried googling with "pl/sql is vs as" and got the following link which says both are the same. http://stackoverflow.com/questions/2338408/is-vs-as-keywords-for-pl-sql-oracle-function-or-procedure-creation But I found http://www.adp-gmbh.ch/ora/plsql/coll/declaration.html#index_by which seems to indicate there is a difference. Could somebody (list/point me to a link) the other contexts where using "is/as" makes a difference?. Thanks.

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  • Need to devise a number crunching algorithm

    - by Ravi Gupta
    I stumbled upon this question: 7 power 7 is 823543. Which higher power of 7 ends with 823543 ? How should I go about it ? The one I came up with is very slow, it keeps on multiplying by 7 and checks last 6 digits of the result for a match. I tried with Lou's code: int x=1; for (int i=3;i<=100000000;i=i+4){ x=(x*7)%1000000; System.out.println("i="+ i+" x= "+x); if (x==823543){ System.out.println("Ans "+i);} } And CPU sounds like a pressure cooker but couldn't get the answer :(

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  • Combinations and Permutations in F#

    - by Noldorin
    I've recently written the following combinations and permutations functions for an F# project, but I'm quite aware they're far from optimised. /// Rotates a list by one place forward. let rotate lst = List.tail lst @ [List.head lst] /// Gets all rotations of a list. let getRotations lst = let rec getAll lst i = if i = 0 then [] else lst :: (getAll (rotate lst) (i - 1)) getAll lst (List.length lst) /// Gets all permutations (without repetition) of specified length from a list. let rec getPerms n lst = match n, lst with | 0, _ -> seq [[]] | _, [] -> seq [] | k, _ -> lst |> getRotations |> Seq.collect (fun r -> Seq.map ((@) [List.head r]) (getPerms (k - 1) (List.tail r))) /// Gets all permutations (with repetition) of specified length from a list. let rec getPermsWithRep n lst = match n, lst with | 0, _ -> seq [[]] | _, [] -> seq [] | k, _ -> lst |> Seq.collect (fun x -> Seq.map ((@) [x]) (getPermsWithRep (k - 1) lst)) // equivalent: | k, _ -> lst |> getRotations |> Seq.collect (fun r -> List.map ((@) [List.head r]) (getPermsWithRep (k - 1) r)) /// Gets all combinations (without repetition) of specified length from a list. let rec getCombs n lst = match n, lst with | 0, _ -> seq [[]] | _, [] -> seq [] | k, (x :: xs) -> Seq.append (Seq.map ((@) [x]) (getCombs (k - 1) xs)) (getCombs k xs) /// Gets all combinations (with repetition) of specified length from a list. let rec getCombsWithRep n lst = match n, lst with | 0, _ -> seq [[]] | _, [] -> seq [] | k, (x :: xs) -> Seq.append (Seq.map ((@) [x]) (getCombsWithRep (k - 1) lst)) (getCombsWithRep k xs) Does anyone have any suggestions for how these functions (algorithms) can be sped up? I'm particularly interested in how the permutation (with and without repetition) ones can be improved. The business involving rotations of lists doesn't look too efficient to me in retrospect. Update Here's my new implementation for the getPerms function, inspired by Tomas's answer. Unfortunately, it's not really any fast than the existing one. Suggestions? let getPerms n lst = let rec getPermsImpl acc n lst = seq { match n, lst with | k, x :: xs -> if k > 0 then for r in getRotations lst do yield! getPermsImpl (List.head r :: acc) (k - 1) (List.tail r) if k >= 0 then yield! getPermsImpl acc k [] | 0, [] -> yield acc | _, [] -> () } getPermsImpl List.empty n lst

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  • Visual Studio 2010 / ASP.NET MVC 2 / Publish Error

    - by SevenCentral
    I just did a clean install on Windows 7 x64 Professional with the final release of Visual Studio 2010 Premium. In order to duplicate what I'm experiencing do the following in: Create a new ASP.NET MVC 2 Web Application Right click the project and select Properties On the Web tab, select "Use Local IIS Web Server" Click on Create Virtual Directory Save all Unload the project Edit the project file Change MvcBuildViews to true Save all Reload project Right click the project and select Publish Choose the file system publish method Enter a target location Choose Delete all existing files Select Publish Right click the project Select Publish Each time I do the above I get the following errror: "It is an error to use a section registered as allowDefinition='MachineToApplication' beyond application level..." The error originates from obj\debug\package\packagetmp\web.config, relative to the project directory. I can repeat this all day long with any MVC 2 project I've built. In order to fix this problem, I need to set MvcBuildViews to false in the project file. That's not really an option. This wasn't a problem in Visual Studio 2008 and it seems to be an issue with the way the Publish command stages files beneath the project directory. Can anyone else duplicate this error? Is this a bug or by design? Is there a fix, workaround, etc...? Thanks.

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