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  • python class attribute

    - by chnet
    Hi, i have a question about class attribute in python. class base : def __init__ (self): pass derived_val = 1 t1 = base() t2 = base () t2.derived_val +=1 t2.__class__.derived_val +=2 print t2.derived_val # its value is 2 print t2.__class__.derived_val # its value is 3 The results are different. I also use id() function to find t2.derived_val and t2.class.derived_val have different memory address. My problem is derived_val is class attribute. Why it is different in above example? Is it because the instance of class copy its own derived_val beside the class attribute?

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  • Redirect application's graphical output in Windows Vista/7 (with DWM)

    - by puri
    I want to create a desktop manager that takes informations of all running applications including states and screenshots to display and manipulate them in my virtual space (probably in 3D). It can be considered as another layer of abstraction on top of Windows itself. Because many native Windows Vista/7 features like Flip 3D and Live Thumbnails are able to show each window's activities in real-time e.g. video keeps playing in taskbar's thumbnail, I think DWM allows an application to redirect its output to somewhere else or some special processes are able to collect other applications' graphical outputs (maybe of child processes only). Has Microsoft released a set of public APIs to do so? If not, is it technically possible? And is it easier if I limit my scope to just .NET applications with WPF?

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  • Save VM properties with EF code first

    - by Julien
    I thought this would be simple but can't find any good examples. public Class BookVm : ImplementsPropertyChanged { public int BookId {get;set;} private bool _favorite; public bool Favorite { get { return _favorite; } set { _favorite = value; OnPropertyChanged("Favorite"); MyDbContext.SaveChanges() // this does not work } } Then in my XAML bound to Book <CheckBox Content="Favorite" IsChecked="{Binding Favorite}" /> How and when do I call SaveChanges() on my DatabaseContext? I don't want to implement a save button. If I intercept the PropertyChange event and call SaveChanges, nothing seems to happen. My object is modified in memory but the database does not see a change. My BookVm class is created on application startup like so: foreach (var book in MyDbContext.Books) Books.Add(book); Where Books is an ObservableCollection<Book> in my MainWindowVm

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  • How does multiple implementing multiple COM interfaces work in C++?

    - by Martin
    I am trying to understand this example code regarding Browser Helper Objects. Inside, the author implements a single class which exposes multiple interfaces (IObjectWithSite, IDispatch). His QueryInterface function performs the following: if(riid == IID_IUnknown) *ppv = static_cast<BHO*>(this); else if(riid == IID_IObjectWithSite) *ppv = static_cast<IObjectWithSite*>(this); else if (riid == IID_IDispatch) *ppv = static_cast<IDispatch*>(this); I have learned that from a C perspective, interface pointers are just pointers to VTables. So I take it to mean that C++ is capable of returning the VTable of any implemented interface using static_cast. Does this mean that a class constructed in this way has a bunch of VTables in memory (IObjectWithSite, IDispatch, etc)? What does C++ do with the name collisions on the different interfaces (they each have a QueryInterface, AddRef and Release function), can I implement different methods for each of these?

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  • MySQL ALTER TABLE on very large table - is it safe to run it?

    - by Timothy Mifsud
    I have a MySQL database with one particular MyISAM table of above 4 million rows. I update this table about once a week with about 2000 new rows. After updating, I then perform the following statement: ALTER TABLE x ORDER BY PK DESC i.e. I order the table in question by the primary key field in descending order. This has not given me any problems on my development machine (Windows with 3GB memory), but, even though 3 times I have tried it successfully on the production Linux server (with 512MB RAM - and achieving the resulted sorted table in about 6 minutes each time), the last time I tried it I had to stop the query after about 30 minutes and rebuild the database from a backup. I have started to wonder whether a 512MB server can cope with that statement (on such a large table) as I have read that a temporary table is created to perform the ALTER TABLE command?! And, if it can be safely run, what should be the expected time for the alteration of the table? Thanks in advance, Tim

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  • Elapsed time of running a C program

    - by yCalleecharan
    Hi, I would like to know what lines of C code to add to a program so that it tells me the total time that the program takes to run. I guess there should be counter initialization near the beginning of main and one after the main function ends. Is the right header clock.h? Thanks a lot... Update I have a Win Xp machine. Is it just adding clock() at the beginning and another clock() at the end of the program? Then I can estimate the time difference. Yes, you're right it's time.h. Here's my code: #include <stdio.h> #include <stdlib.h> #include <math.h> #include <share.h> #include <time.h> void f(long double fb[], long double fA, long double fB); int main() { clock_t start, end; start = clock(); const int ARRAY_SIZE = 11; long double* z = (long double*) malloc(sizeof (long double) * ARRAY_SIZE); int i; long double A, B; if (z == NULL) { printf("Out of memory\n"); exit(-1); } A = 0.5; B = 2; for (i = 0; i < ARRAY_SIZE; i++) { z[i] = 0; } z[1] = 5; f(z, A, B); for (i = 0; i < ARRAY_SIZE; i++) printf("z is %.16Le\n", z[i]); free(z); z = NULL; end = clock(); printf("Took %ld ticks\n", end-start); printf("Took %f seconds\n", (double)(end-start)/CLOCKS_PER_SEC); return 0; } void f(long double fb[], long double fA, long double fB) { fb[0] = fb[1]* fA; fb[1] = fb[1] - 1; return; } Some errors with MVS2008: testim.c(16) : error C2143: syntax error : missing ';' before 'const' testim.c(18) :error C2143: syntax error : missing ';' before 'type' testim.c(20) :error C2143: syntax error : missing ';' before 'type' testim.c(21) :error C2143: syntax error : missing ';' before 'type' testim.c(23) :error C2065: 'z' : undeclared identifier testim.c(23) :warning C4047: '==' : 'int' differs in levels of indirection from 'void *' testim.c(28) : error C2065: 'A' : undeclared identifier testim.c(28) : warning C4244: '=' : conversion from 'double' to 'int', possible loss of data and it goes to 28 errors. Note that I don't have any errors/warnings without your clock codes. LATEST NEWS: I unfortunately didn't get a good reply here. But after a search on Google, the code is working. Here it is: #include <stdio.h> #include <stdlib.h> #include <math.h> #include <share.h> #include <time.h> void f(long double fb[], long double fA, long double fB); int main() { clock_t start = clock(); const int ARRAY_SIZE = 11; long double* z = (long double*) malloc(sizeof (long double) * ARRAY_SIZE); int i; long double A, B; if (z == NULL) { printf("Out of memory\n"); exit(-1); } A = 0.5; B = 2; for (i = 0; i < ARRAY_SIZE; i++) { z[i] = 0; } z[1] = 5; f(z, A, B); for (i = 0; i < ARRAY_SIZE; i++) printf("z is %.16Le\n", z[i]); free(z); z = NULL; printf("Took %f seconds\n", ((double)clock()-start)/CLOCKS_PER_SEC); return 0; } void f(long double fb[], long double fA, long double fB) { fb[0] = fb[1]* fA; fb[1] = fb[1] - 1; return; } Cheers

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  • Issue with Visual C++ 2010 (Express) External Tools command

    - by espais
    I posted this on SuperUser...but I was hoping the pros here at SO might have a good idea about how to fix this as well.... Normally we develop in VS 2005 Pro, but I wanted to give VS 2010 a spin. We have custom build tools based off of GNU make tools that are called when creating an executable. This is the error that I see whenever I call my external tool: ...\gnu\make.exe): * couldn't commit memory for cygwin heap, Win32 error 487 The caveat is that it still works perfectly fine in VS2005, as well as being called straight from the command line. Also, my external tool is setup exactly the same as in VS 2005. Is there some setting somewhere that could cause this error to be thrown?

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  • Sqlite3 Database versus populating Arrays

    - by Kenoy
    hi, I am working on a program that requires me to input values for 12 objects, each with 4 arrays, each with 100 values. (4800) values. The 4 arrays represent possible outcomes based on 2 boolean values... i.e. YY, YN, NN, NY and the 100 values to the array are what I want to extract based on another inputted variable. I previously have all possible outcomes in a csv file, and have imported these into sqlite where I can query then for the value using sql. However, It has been suggested to me that sqlite database is not the way to go, and instead I should populate using arrays hardcoded. Which would be better during run time and for memory management?

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  • Why might different computers calculate different arithmetic results in VB.NET?

    - by Eyal
    I have some software written in VB.NET that performs a lot of calculations, mostly extracting jpegs to bitmaps and computing calculations on the pixels like convolutions and matrix multiplication. Different computers are giving me different results despite having identical inputs. What might be the reason? Edit: I can't provide the algorithm because it's proprietary but I can provide all the relevant operations: ULong \ ULong (Turuncating division) Bitmap.Load("filename.bmp') (Load a bitmap into memory) Bitmap.GetPixel(Integer, Integer) (Get a pixel's brightness) Double + Double Double * Double Math.Sqrt(Double) Math.PI Math.Cos(Double) ULong - ULong ULong * ULong ULong << ULong List.OrderBy(Of Double)(Func) Hmm... Is it possible that OrderBy is using a non-stable QuickSort and that QuickSort is using a random pivot? Edit: Just tested, nope. The sort is stable.

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  • How should I deal with persisting an Android WebView if my activity gets destroyed while showing ano

    - by Shaun Crampton
    Hi, I'm building an Android application that's based around an enhanced WebView (based on PhoneGap). I've enhanced the WebView so that from JavaScript running inside you can invoke the native contact picker to choose a phone number (which may be supplied by Facebook for example). The problem I have is that the native contact picker runs in an activity in another process and the Android docs say that while another activity is open my activity may get destroyed due to memory constraints. I haven't actually seen this happen in my application but if it did then I'm guessing my WebView's state would be destroyed and the code that was waiting for the picked contact would be terminated. It seems a bit crazy that the activity requesting a contact could be destroyed while the contact picker is open. Does anyone know if that does indeed happen? Is there a way to persist the state of the WebView if it does? Thanks, -Shaun

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  • how come we need not close the handle returned by ShellExecute ?

    - by fred-hh
    On success, ShellExecute returns a handle. Do we need to close this handle, and if so, how ? According to examples published my Microsoft, we need not close this handle. But the doc of ShellExecute itself is mute on the subject. Can you confirm we indeed do not need to close this handle ? But then, how can a handle be valid and in no need of being closed ??? Which of the following statements is/are true: the handle is invalid and we can't do anything with it; the handle is never freed and there is a (Microsoft-sponsored) memory leak (until the caller program ends); the handle is automatically freed by the system at some time and never reused afterwards (- another kind of resource leak). Only on trying to use it can we know whether it still points to something. what else ?

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  • Is there any kind of standard for 8086 multiprocessing?

    - by Earlz
    Back when I made an 8086 emulator I noticed that there was the LOCK prefix intended for synchonization in a multiprocessor environment. Yet the only multitasking I know of for the x86 arch. involves use of the APIC which didn't come around until either the Pentiums or 486s. Was there any kind of standard for 8086 multitasking or was it done by some manufacturer specific extensions to the instruction set and/or special ports? By standard, I mean things like: How do you separate the 2 processors if they both use the same memory? This is impossible without some kind of way to make each processor execute a different piece of code. (or cause an interrupt on only one processor)

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  • HttpContext User value changing on its own?

    - by larryq
    Hi everyone, I'm working on an ASP.Net 2.0 application and am having a strange issue involving the HttpContext User. It appears to be changing on its own when I go to a particular page/directory. All of our pages inherit from a base page. In that base page's Page_Load() method we run an authorization check to see if the user can see the page they're going to. We retrieve the user to check against with this code: GenericPrincipal objPrincipal = (GenericPrincipal)Context.User; When I go to this unusual directory the User value isn't me, it's some other username I've never heard of. This username isn't authorized to see these pages, so authorization fails. This mysterious directory isn't a virtual web, just a regular directory in our website, however I've noticed it has its own Web.Config file. I'm guessing that's a cause of the trouble here. My question is, how can I investigate this further, in determining what's changing the User value when I go to this directory?

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  • Maven2 problem to access plugins repository !

    - by achraf
    Hi, i just come to install maven2, after configuring the settings.xml in ${user.home}/.m2 and fixing a proxy error. Now by executing the command : mvn -U archetype:create -DgroupId=maven-test -DartifactId=maven-test -DpackageName=net.ensode.maventest i get this error : [INFO] Scanning for projects... [INFO] Searching repository for plugin with prefix: 'archetype'. [INFO] org.apache.maven.plugins: checking for updates from central [WARNING] repository metadata for: 'org.apache.maven.plugins' could not be retri eved from repository: central due to an error: Authorization failed: Access deni ed to: http://repo2.maven.org/maven2/org/apache/maven/plugins/maven-metadata.xml [INFO] Repository 'central' will be blacklisted [INFO] ------------------------------------------------------------------------ [ERROR] BUILD ERROR [INFO] ------------------------------------------------------------------------ [INFO] The plugin 'org.apache.maven.plugins:maven-archetype-plugin' does not exi st or no valid version could be found [INFO] ------------------------------------------------------------------------ [INFO] For more information, run Maven with the -e switch [INFO] ------------------------------------------------------------------------ [INFO] Total time: < 1 second [INFO] Finished at: Thu Apr 29 16:05:40 CEST 2010 [INFO] Final Memory: 2M/247M [INFO] ------------------------------------------------------------------------ any idea of what could cause it ? thanks !

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  • How to find grid array in the browser ExtJs

    - by insanity
    Suppose if i have created a grid store like this var store = Ext.create('Ext.data.ArrayStore', { fields:['id','title', 'director', 'released', 'genre','tagline', 'price', 'available'], data: [ [ 1, "Office Space", "Mike Judge", "1999-02-19", 1, "Work Sucks", "19.95", 1 ], [ 3, "Super Troopers", "Jay Chandrasekhar", "2002-02-15", 1, "Altered State Police", "14.95", 1 ] ] }); when i run it on browser i could not see anything because it has already been saved in the browser's memory , we need to display it to the the grid to see those data. if i am editing the grid in the browser using editors plugin, so how can i see the changes made to the grid store? how to see it ?

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  • static library vs dynamic libraries

    - by user295030
    Can someone please explain in easy terms what is static library linking vs dynamic library linking other one has a larger memory map than the other or that the static library is used to compile/link with the program that will use it versus being loaded at runtime? I also need to create a static library of a program that I made in vs2008 and give one function interface to access the library. one of the requirements reads as such " * API should be in the form of static library. company xxx will link the library into a third party application to prevent any possible exposure of the code(dll)" how can they say both static and dll at the same time. I have never works with static library before. So please any help would be nice.

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  • dangling pointer, reason for value change after free()?

    - by Aman Jain
    In the following code segment, after free(x), why does y becomes 0? As per my understanding, the memory in the heap that was being pointed to by x, and is still being pointed by y, hasn't been allocated to someone else, so how can it change to 0? And moreover, I don't think it is free(x) that changed it to 0. Any comments? #include <stdio.h> int main ( int argc, char *argv[] ) { int *y = NULL; int *x = NULL; x = malloc(4); *x = 5; y = x; printf("[%d]\n", *y); //prints 5 free(x); printf("[%d]\n", *y); //why doesn't print 5?, prints 0 instead return 0; }

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  • Cannot Translate to SQL using Select(x => Func(x))

    - by Dan
    I'm slowly learning the ins and outs of LINQtoSQL, but this is confusing me. Here is the statement I have: IQueryable<IEvent> events = (from e in db.getEvents() select e).Select(x => SelectEvent(x, null)); What the SelectEvent does can be explained in this answer here. I am not using the .toList() function as I don't want potentially thousands of records brought into memory. public IEvent SelectEvent(SqlServer.Event ev, EventType? type) { // Create an object which implements IEvent // I don't have the code in front of me, so forgive the lack of code } My question is really for the Select() method. I get the "Cannot translate to SQL" error and the Select() is listed in the error message. Clueless on this one :-/.

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  • What is the best way to convince management that virtualization isn't always appropriate in producti

    - by uncle brad
    I work for a small company with a .NET product that was acquired by a medium sized company with "big iron" products. Recently, the medium-sized part of the company acquired another small company with a similar .NET product and management went to have a look at their technology. They make heavy use of virtualization in their production environment and it's been decided that we will too. Our product was not designed to be run in a virtual environment, but some accommodations can be made. For instance; there are times when we're resource bound due to customer initiated processes. This initiation is "bursty" by nature, but the processing can be made asynchronous and throttled. This is something that would need to be done for scalability anyway. But there is other processing that we do that isn't so easily modified because we're resource bound for extended periods of time. How do I convince management that heavy use of virtualization is probably not appropriate for us?

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  • Compiler error when casting to function pointer

    - by detly
    I'm writing a bootloader for the PIC32MX, using HiTech's PICC32 compiler (similar to C90). At some point I need to jump to the real main routine, so somewhere in the bootloader I have void (*user_main) (void); user_main = (void (*) (void)) 0x9D003000; user_main(); (Note that in the actual code, the function signature is typedef'd and the address is a macro.) I would rather calculate that (virtual) address from the physical address, and have something like: void (*user_main) (void); user_main = (void (*) (void)) (0x1D003000 | 0x80000000); user_main(); ...but when I try that I get a compiler error: Error #474: ; 0: no psect specified for function variable/argument allocation Have I tripped over some vagarity of C syntax here? This error doesn't reference any particular line, but if I comment out the user_main() call, it goes away. (This might be the compiler removing a redundant code branch, but the HiTech PICC32 isn't particularly smart in Lite mode, so maybe not.)

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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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  • Sharing user controls acrros multiple websites

    - by Jasper
    Hello, I am currently working on a project which involves three different websites with a lot of common functionality. At the moment the common functionality is placed in a different website full of user controls. The problem is sharing the user controls across the multiple websites. Looking around on SO and other websites, the only solution seems the be using virtual directories. As this is a workable solution (we us this at the moment) it doesn't seem as a "clean" solution. Which "best practices" exist on sharing common functionality (including the GUI/HTML) between different site? Is it (for example) possible to create a single Web Application project and deploy subdirectories (each with their own web.config) to different production environments?

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  • Add C pointer to NSMutableArray

    - by Georges Oates Larsen
    I am writing an Objective-C program that deals with low level image memory. I am using ANSI-C structs for my data storage -- Full blown objects seem overkill seeing as the data I am storing is 100% data, with no methods to operate on that data. Specifically, I am writing a customizable posterization algorithm which relies on an array of colors -- This is where things get tricky. I am storing my colors as structs of three floats, and an integer flag (related to the posterization algorithm specifically). Everyhting is going well, except for one thing... [actual question] I can't figure out how to add pointers to an NSMutableArray! I know how to add an object, but adding a pointer to a struct seems to be more difficult -- I do not want NSMutableArray dereferencing my pointer and treating the struct as some sort of strange object. I want NSMutableArray to add the pointer its self to its collection. How do I go about doing this? Thanks in advance, G

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  • SQLite Transaction fills a table BEFORE the transaction is commited

    - by user1500403
    Halo I have a code that creates a datatable (in memory) from a select SQL statement. However I realised that this datatable is filling during the procedure rather as a result of the transaction comit statment, it does the job but its slow. WHat amI doing wrong ? Inalready.Clear() 'clears a dictionary Using connection As New SQLite.SQLiteConnection(conectionString) connection.Open() Dim sqliteTran As SQLite.SQLiteTransaction = connection.BeginTransaction() Try oMainQueryR = "SELECT * FROM detailstable Where name= :name AND Breed= :Breed" Dim cmdSQLite As SQLite.SQLiteCommand = connection.CreateCommand() Dim oAdapter As New SQLite.SQLiteDataAdapter(cmdSQLite) With cmdSQLite .CommandType = CommandType.Text .CommandText = oMainQueryR .Parameters.Add(":name", SqlDbType.VarChar) .Parameters.Add(":Breed", SqlDbType.VarChar) End With Dim c As Long = 0 For Each row As DataRow In list.Rows 'this is the list with 500 names If Inalready.ContainsKey(row.Item("name")) Then Else c = c + 1 Form1.TextBox1.Text = " Fill .... " & c Application.DoEvents() Inalready.Add(row.Item("name"), row.Item("Breed")) cmdSQLite.Parameters(":name").Value = row.Item("name") cmdSQLite.Parameters(":Breed").Value = row.Item("Breed") oAdapter.Fill(newdetailstable) End If Next oAdapter.FillSchema(newdetailstable, SchemaType.Source) Dim z = newdetailstable.Rows.Count 'At this point the newdetailstable is already filled up and I havent even comited the transaction ' sqliteTran.Commit() Catch ex As Exception End Try End Using

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  • avoid preselection of a view when focus is gained android

    - by Sephy
    Hi all, I don't know if the title is very clear, but my issue is as follows : I have an activity with a listview, and on top of this listview, i have a searchfield (edittext). The issue is that when i try debugging on a phone, the virtual keyboard gets out straight after the screen displays the activity... And of course, it's hidding half of the list... So, is there an attribute or something I can use to prevent this from happening?(I still want to keybord to appear when i click the edittext though...) thank you

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