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  • C++ initializing constants and inheritance

    - by pingvinus
    I want to initialize constant in child-class, instead of base class. And use it to get rid of dynamic memory allocation (I know array sizes already, and there will be a few child-classes with different constants). So I try: class A { public: const int x; A() : x(0) {} A(int x) : x(x) {} void f() { double y[this->x]; } }; class B : A { B() : A(2) {} }; Pretty simple, but compiler says: error C2057: expected constant expression How can I say to compiler, that it is really a constant?

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  • Using Timer only once

    - by zaidwaqi
    Hi, I want to use a timer only once, at 1 second after the initialization of my main form. I thought the following would have a message box saying "Hello World" just once, but actually a new message box says "Hello World" every one second. Why so? I had put t.Stop() in the tick event. Also, do I need to dispose the timer somehow to avoid memory leakage? Timer t = new Timer(); t.Interval = 1000; t.Tick += delegate(System.Object o, System.EventArgs e) { MessageBox.Show("Hello World"); t.Stop(); }; t.Start(); Please help and show if there is a better way of doing this? Thanks.

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  • How to initialize an std::string using ""?

    - by Mohsin
    I'm facing problems with initializing a std::string variable using "" (i.e. an empty string). It's causing strange behavior in code that was previously working. Is the following statement wrong? std::string operationalReason = ""; When I use the following code everything works fine: std::string operationalReason; operationalReason.clear(); I believe that string literals are stored in a separate memory location that is compiler-dependent. Could the problem I'm seeing actually be indicating a corruption of that storage? If so, it would get hidden by my usage of the clear() function. Thanks.

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  • How to implement arrays in an interpreter?

    - by Ray
    I have managed to write several interpreters including Tokenizing Parsing, including more complicated expressions such as ((x+y)*z)/2 Building bytecode from syntax trees Actual bytecode execution What I didn't manage: Implementation of dictionaries/lists/arrays. I always got stuck with getting multiple values into one variable. My value structure (used for all values passed around, including variables) looks like this, for example: class Value { public: ValueType type; int integerValue; string stringValue; } Works fine with integers and strings, but how could I implement arrays? (From now on with array I mean arrays in my experimental language, not in C++) How can I fit the array concept into the Value class above? Is it possible? How should I make arrays able to be passed around just as you could pass around integers and strings in my language, using the class above? Accessing array elements or memory allocation wouldn't be the problem, I just don't know how to store them.

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  • Finding unique elements in an string array in C

    - by LuckySlevin
    Hi, C bothers me with its handling of strings. I have a pseudocode like this in my mind: char *data[20]; char *tmp; int i,j; for(i=0;i<20;i++) { tmp = data[i]; for(j=1;j<20;j++) { if(strcmp(tmp,data[j]))//then except the uniqueness, store them in elsewhere. } } But when i coded this the results were bad.(I handled all the memory stuff,little things etc.) The problem is in the second loop obviously :D. But i cannot think any solution. How do i find unique strings in an array. Example input : abc def abe abc def deg entered unique ones : abc def abe deg should be found.

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  • Why MSSQL keeps throwing me Exceptions?

    - by Augusto Càzares
    I have my project in .NET that uses a db in MSSQL Server,i'm using LINQ , sometimes when the projec throws me an exception (Constraint) in a part of the project this same error keeps showing in other part of the project when i do another thing with the db, like when i do an insertion and i had before an exception on delete the insertion throws me the delete exeption, and it remainds this way until i close and open again the project, my major problem is when this happen in my online project, this error in my project causes me problems in the project i'm testing online (i use the same db). I don't know if this exception is on the memory or something but its have been causing me a lot of headechs.

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  • Difference between static const char* and const char*.

    - by Will MacDonagh
    Could someone please explain the difference in how the 2 snippets of code are handled below? They definitely compile to different assembly code, but I'm trying to understand how the code might act differently. I understand that string literals are thrown into read only memory and are effectively static, but how does that differ from the explicit static below? struct Obj1 { void Foo() { const char* str( "hello" ); } }; and struct Obj2 { void Bar() { static const char* str( "hello" ); } };

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  • Direct video card access

    - by icemanind
    Guys, I am trying to write a class in C# that can be used as a direct replacement for the C# Bitmap class. What I want to do instead though is perform all graphic functions done on the bitmap using the power of the video card. From what I understand, functions such as DrawLine or DrawArc or DrawText are primitive functions that use simple cpu math algorithms to perform the job. I, instead, want to use the graphics card cpu and memory to do these and other advanced functions, such as skinning a bitmap (applying a texture) and true transparancy. My problem is, in C#, how do I access direct video functions? Is there a library or something I need?

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  • Microsoft chart images are not loaded from MOSS server

    - by hd
    hi, i have webpage in which a webpart contains a Chart control. the problem is chart control is rendered perfectly when i login as central admin. but when i login as another user with contribute permisson following problems occur. when i change webconfig as --- add key="ChartImageHandler" value="storage=file;timeout=20;dir=c:\TempImageFiles\;"--- page is not at all loaded. i get error like YOU ARE NOT AUTHORIZED TO VIEW THIS PAGE. when i change the wbconfig as --- add key="ChartImageHandler" value="storage=memory;timeout=20;URL=/_layouts/Images/MicrosoftChartControls/" --- the page loads fine but image is not rendered. A red mark appears in place of image. I tried all optins got by googling.. any more suggestions/help will be welcomed

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  • efficient way to detect if an image is empty

    - by Jos
    Hi, I need a very fast method to detect if an image is empty. Im my case then all pixels are white and transparant. The images are png's. My current method is to load them in a memory bitmap and check each pixel value, but this is way to slow. Is there a more efficient way? This is my current code: 'Lock the bitmap bits. Dim bmpData As System.Drawing.Imaging.BitmapData = bmp.LockBits(rectBmp, _ Drawing.Imaging.ImageLockMode.ReadOnly, bmp.PixelFormat) Try Dim x As Integer Dim y As Integer For y = 0 To bmpData.Height - 1 For x = 0 To bmpData.Width - 1 If System.Runtime.InteropServices.Marshal.ReadByte(bmpData.Scan0, (bmpData.Stride * y) + (4 * x) + 3) <> 0 Then Return True Exit For End If Next Next Finally bmp.UnlockBits(bmpData) End Try

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  • How do I do a join in ActiveRecord after records have been returned?

    - by Russ Bradberry
    I am using ActiveRecord in Rails 3 to pull data from two different tables in two different databases. These databases can not join on each other, but I have the need to do a simple join after-the-fact. I would like to preserve the relation so that I can chain it down the line. here is a simplified version of what I am doing browsers = Browser.all # <-- this is fairly small and can reside in memory events = Event.where(:row_date=>Date.today).select(:name, :browser_id) So as you can see, I want to join browsers in on the events relation, where browser_id should equal browsers.name. events is a relation and I can still add clauses to it down the line, so I dont want to run the query on the db just yet. How would I accomplish this?

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  • In C, would !~b ever be faster than b == 0xff ?

    - by James Morris
    From a long time ago I have a memory which has stuck with me that says comparisons against zero are faster than any other value (ahem Z80). In some C code I'm writing I want to skip values which have all their bits set. Currently the type of these values is char but may change. I have two different alternatives to perform the test: if (!~b) /* skip */ and if (b == 0xff) /* skip */ Apart from the latter making the assumption that b is an 8bit char whereas the former does not, would the former ever be faster due to the old compare to zero optimization trick, or are the CPUs of today way beyond this kind of thing?

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  • CPU Usage relative to number of users? - ASP.Net Application

    - by soldieraman
    My Asp.net application uses 25-30% of the CPU on a test server which has 600 MB Ram on it. I can see the asp_wb process taking that much percentage of CPU. This is when I am testing using one user. How many users can the server afford then without falling over? Is there a relationship between the CPU Usage and number of user aka if there are 2 users my application will sky rocket to 60% of memory usage? Or does/Should/How does the server handle this?

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  • storing an integral value in a pointer variable while declaration

    - by benjamin button
    int main() { int *d=0; printf("%d\n",*d); return 0; } this works fine. >cc legal.c > ./a.out 0 if i change the statement int *d=0; to int *d=1; i see the error. cc: "legal.c", line 6: error 1522: Cannot initialize a pointer with an integer constant other than zero. so its obvious that it will allow only zero.i want to know what happens inside the memory when we do this int *d=0 which is making it valid syntax. I am just asking this out of curiosity!

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  • Remove from a std::set<shared_ptr<T>> by T*

    - by Autopulated
    I have a set of shared pointers: std::set<boost::shared_ptr<T>> set; And a pointer: T* p; I would like to efficiently remove the element of set equal to p, but I can't do this with any of the members of set, or any of the standard algorithms, since T* is a completely different type to boost::shared_ptr<T>. A few approaches I can think of are: somehow constructing a new shared_ptr from the pointer that won't take ownership of the pointed to memory (ideal solution, but I can't see how to do this) wrapping / re-implementing shared_ptr so that I can do the above just doing my own binary search over the set Help!

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  • #define vs enum in an embedded environment (How do they compile?)

    - by Alexander Kondratskiy
    This question has been done to death, and I would agree that enums are the way to go. However, I am curious as to how enums compile in the final code- #defines are just string replacements, but do enums add anything to the compiled binary? Or are they both equivalent at that stage. When writing firmware and memory is very limited, is there any advantage, no matter how small, to using #defines? Thanks! EDIT: As requested by the comment below, by embedded, I mean a digital camera. Thanks for the answers! I am all for enums!

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  • Expert system for writing programs?

    - by aaa
    I am brainstorming an idea of developing a high level software to manipulate matrix algebra equations, tensor manipulations to be exact, to produce optimized C++ code using several criteria such as sizes of dimensions, available memory on the system, etc. Something which is similar in spirit to tensor contraction engine, TCE, but specifically oriented towards producing optimized rather than general code. The end result desired is software which is expert in producing parallel program in my domain. Does this sort of development fall on the category of expert systems? What other projects out there work in the same area of producing code given the constraints?

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  • 907 Invalid Jar Midlet Class is not public: autostartup

    - by vajapravin
    I am developing blackberry app. I use eclipse. When I run app from eclipse it runs well on device. But when I run it on manually installed - copy web and standard folders to my device memory and run jar file it gives me 907 invalid jar... my .cod file is Manifest-Version: 1.0 MIDlet-Jar-Size: 65712 MicroEdition-Configuration: CLDC-1.1 MIDlet-Version: 0.0.1 MIDlet-Name: app_blackberry_6 RIM-COD-Size: 61852 RIM-COD-URL-69: App1.cod RIM-COD-URL-68: App2.cod ...and I have also tried to change size of MIDlet-Jar-Size: 0 but is not working.

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  • CUDA driver installation on a laptop with nVidia NVS140M card

    - by stanigator
    I'm trying to first figure out if my computer contains a CUDA-enabled card. It has an nVidia NVS 140M card, but I can't seem to figure out if it is the 128 MB version or 256 MB version. On the laptop purchase receipt, I found out that I ordered the 128 MB version, but the control panel description of the card said otherwise as shown below: When I ran the CUDA driver from nVidia's site, it cannot find a hardware compatible with CUDA (even though the product series is CUDA-enabled, the card does not have 256 MB minimum of memory to do so). What would be your recommendations in this case with trying to use CUDA on this computer (I'm not sure if nothing can be done at this point)? Thanks in advance.

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  • just-in-time list

    - by intuited
    I'd like to know if there is a class available, either in the standard library or in pypi, that fits this description. The constructor would take an iterator. It would implement the container protocol (ie _getitem_, _len_, etc), so that slices, length, etc., would work. In doing so, it would iterate and retain just enough values from its constructor argument to provide whatever information was requested. So if jitlist[6] was requested, it would call self.source.next() 7 times, save those elements in its list, and return the last one. This would allow downstream code to use it as a list, but avoid unnecessarily instantiating a list for cases where list functionality was not needed, and avoid allocating memory for the entire list if only a few members ended up being requested. It seems like a pretty easy one to write, but it also seems useful enough that it's likely that someone would have already made it available in a module.

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  • Connecting Delphi to P/Invoke and .net

    - by lexdean
    The Delphi complier often uses a *.Dll when a special delivery of code info is required to the complier/editor:- example bourland.dll is the memory manager for the Delphi complier, as I remember. And their are many other *.dll's that Embarcoo keep secret that do other things. Is their anything you know that is public information on this subject .net's un managed code could be declared in a *.pas file as a decelerations but the only way to communicate it out is calling *.dll's like P/Invoke I have ilasm.exe and ildasm.exe and a decomplier into Delphi asm code now but still getting around to learn how to use them all yet. I do not have any reference material/editorials on P/invoke at all as I cannot find anything With that I will have a good concrete plan to make a good result I do not know what *.DLL's are in P/Invoke. Do you have any documentation. I do not have any reference material/editorials on ADO.net. The Dlls that are called and any referqance matrial I could use. Best regards, J Lex Dean.

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  • double fork using vfork

    - by Oren S
    HI I am writing a part of a server which should dispatch some other child processes. Because I want to wait on some of the processes, and dispatch others without waiting for completion, I use double fork for the second kind of processes (thus avoiding the zombie processes). Problem is, my server holds a lot of memory, so forking takes a long time (even the copy-on-write fork used in Linux which copies only the paging tables) I want to replace the fork() with vfork(), and it's easy for the second fork (as it only calls execve() in the child), but I couldn't find any way I can replace the first one. Does anyone know how I can do that? Thanks! The server is a linux (RH5U4), written in C++.

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  • Soundpool sample not ready

    - by SteD
    I have a .wav file that I'd like to use across my game, currently I am loading the sound in onCreate() of each activity in the game. soundCount = soundpool.load(this,R.raw.count, 1); The sound will be played once the activity starts. soundpool.play(soundCount, 0.9f, 0.9f, 1, -1, 1f); Problem is at times I will hit the error "sample x not ready". Is it possible to load the .wav file once upon starting the game and keep it in memory and use it later across the game? Or is it possible to wait for 1-2 seconds for the sound to load finish?

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  • Homemade fstat to get file size, always return 0 length.

    - by Fred
    Hello, I am trying to use my own function to get the file size from a file. I'll use this to allocate memory for a data structure to hold the information on the file. The file size function looks like this: long fileSize(FILE *fp){ long start; fflush(fp); rewind(fp); start = ftell(fp); return (fseek(fp, 0L, SEEK_END) - start); } Any ideas what I'm doing wrong here?

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  • [FreeBSD kernel ]How to maintain a linked list on kernel lever?

    - by Andy Leman
    The situation is: I will implement sets of new system calls. Each of them need to access (read or write) a linked list. So, that means I will have several C programs. So, how can I maintain a linked list in memory and let several programs access it? Or,this is wrong....I should save it as a file? (but I hardly think this is a good idea).. A lot of confused questions here...Need help. Thank you indeed!

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