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  • runtime/compile time polymorphism

    - by dmadhavaraj
    Hi , In the below code , why b1.subtract() fails . Please explain me the reason ie., what happens in JVM while invoking that method . class Base { public void add() { System.out.println("Base ADD"); } } class Child extends Base { public void add(){ System.out.println("Child ADD"); } public void subtract() { System.out.println("Child Subtract"); } } class MainClass { public static void main(String args[]) { Base b1 = new Base(); Base b2 = new Child(); Child b3 = new Child(); b1.add(); b1.subtract(); // ?????????** b2.add(); b3.subtract(); } }

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  • Seeking free ODBC database optimization tool for non-experts

    - by mawg
    I'm a database n00b and am reading as many books as I can. I have been given responsibility for an ODBC tool where the databases were designed by a hardware engineer with some VB experience - which made him a s/w guru in the small firm at that time. Things are running slowly and I suspect that the db could have been designed better. I hope to learn enough to use Explain/Describe, etc maybe add some indices, but, in the meantime, is there any free for commercial use tool which can examine an ODBC database and suggest improvements. I'm just talking about db schema here, but maybe I should also be looking at optimizing Selects with Joins? Is there a tool for that? ODBC compliant.

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  • Infinite recursion trying to check all elements of a TreeCtrl

    - by mavnn
    I have a TreeCtrl in which more than one Item can be assigned the same object as PyData. When the object is updated, I want to update all of the items in the tree which have that object as their PyData. I thought the following code would solve the problem quite neatly, but for some reason the logical test (current != self.GetFirstVisibleItem()) always returns true leading to infinite recursion. Can anyone explain why? def RefreshNodes(self, obj, current=None): print "Entered refresh" current = current or self.GetFirstVisibleItem() if current.IsOk(): print self.GetPyData(current).name if self.GetPyData(current) == obj: self.RefreshNode(current) current = self.GetNextVisible(current) if current != self.GetFirstVisibleItem(): self.RefreshNodes(obj, current) Edit: the above is obviously part of a class based on wx.TreeCtrl

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  • How to update a table in database using LINQ in F#?

    - by sudaly
    I have seen plenty of examples on how to query the database but nothing on how to update records. Below is the simple code that I wrote to retrieve a table, but can someone explain me how can I modify a field, say lastActiveDate, and update the table on the database Thank you, suday open System open Microsoft.FSharp.Linq let connString = "Server=localhost;Database=myDb;Trusted_Connection=True;" let db = new MyDb(connString) db.Log <- System.Console.Out let res = Query.query <@ seq { for users in db.userAccounts do yield users } @> |> List.ofSeq printfn "Totla users: %d" res.Length

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  • [JS] How to manipulate a PHP Array in javascript?

    - by rasouza
    I have an Array in PHP which contains data from database. And it prints out also as a table in the same page which has an AJAX delete function. Trying to explain better The array contains debt sums related to many people, it is the application's main function. In the same page, there is a table containing every debt record related to the array, which can be deleted or edited using AJAX. I have coded the part of deleting the record and removing the TR entry, but it's not enough: I'd like to change also the debt sum using AJAX which is an PHP Array. What I have I have the JS function which removes the TR when the delete button is clicked // TR Fading when deleted $('.delete') .click(function() { $.ajax({ type: 'GET', url: 'history/delete/id/'+$(this).attr('id') }); $(this).parent().parent().fadeOut(); return false; }); and I have the PHP array (image)

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  • Understanding "this" keyword

    - by Raffaele
    In this commit there is a change I cannot explain deferred.done.apply( deferred, arguments ).fail.apply( deferred, arguments ); becomes deferred.done( arguments ).fail( arguments ); AFAIK, when you invoke a function as a member of some object like obj.func(), inside the function this is bound to obj, so there would be no use invoking a function through apply() just to bound this to obj. Instead, according to the comments, this was required because of some preceding $.Callbacks.add implementation. My doubt is not about jQuery, but about the Javascript language itself: when you invoke a function like obj.func(), how can it be that inside func() the this keyword is not bound to obj?

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  • How to synchronize two DataBase Schemas Oracle 10G?

    - by gnash-85
    Hi Masters, Good Day, I am new and very naive to Oracle DB. I am using Oracle 10G. Let me explain to you. I have one source database named ( DB1) and Target Database named (DB2). I have 2 schema's named dbs1 and dbs2 in the source database (DB1). I have exported both the database schemas in Source Database (DB1) and imported it successfully into the Target Database (DB2). Now I face a challenge in synchronizing these database schemas every time from Source DB (DB1) to Target DB (DB2). Can anyone please help in letting me know how can achieve this synchronization? It would a great help. Thanks Nash

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  • Can C++ Constructors be templates?

    - by Gokul
    Hi, I have non-template class with a templatized constructor. This code compiles for me. But i remember that somewhere i have referred that constructors cannot be templates. Can someone explain whether this is a valid usage? typedef double Vector; //enum Method {A, B, C, D, E, F}; struct A {}; class Butcher { public: template <class Method> Butcher(Method); private: Vector a, b, c; }; template <> Butcher::Butcher(struct A) : a(2), b(4), c(2) { // a = 0.5, 1; // b = -1, 1, 3, 2; // c = 0, 1; } Thanks, Gokul.

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  • How to convince a colleague that code duplication is bad?

    - by vitaut
    A colleague of mine was implementing a new feature in a project we work on together and he did it by taking a file containing the implementation of a similar feature from the same project, creating a copy of it renaming all the global declarations and slightly modifying the implementation. So we ended up with two large files that are almost identical apart from renaming. I tried to explain that it makes our project more difficult to maintain but he doesn't want to change anything saying that it is easier for him to program in such way and that there is no reason to fix the code if it "ain't broke". How can I convince him that such code duplication is a bad thing? It is related to this questions, but I am more interested in the answers targeted to a technical person (another programmer), for example a reference to an authoritative source like a book would be great. I have already tried simple arguments and haven't succeeded.

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  • Why does PHP 5.2 disallow abstract static class methods?

    - by Artem Russakovskii
    After enabling strict warnings in PHP 5.2, I saw a load of strict standards warnings from a project that was originally written without strict warnings: Strict Standards: Static function Program::getSelectSQL() should not be abstract in Program.class.inc The function in question belongs to an abstract parent class Program and is declared abstract static because it should be implemented in its child classes, such as TVProgram. I did find references to this change here: Dropped abstract static class functions. Due to an oversight, PHP 5.0.x and 5.1.x allowed abstract static functions in classes. As of PHP 5.2.x, only interfaces can have them. My question is: can someone explain in a clear way why there shouldn't be an abstract static function in PHP?

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  • How to understand the functional programming code for converting IP string to a number?

    - by zfz
    In a python discusion, I saw a way to convert IP string to a integer in functional progamming way. Here is the Link . The function is implemented in a single line. def ipnumber(ip): return reduce(lambda sum, chunk: sum <<8 | chunk, map(int, ip.split("."))) However, I have few ideas of funcional programming. Could anybody explain the function in detail? I've some knowledg of "map" and "reduce". But I don't konw what "|" and "chunk" mean here? Thanks.

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  • how to use NtCreateMutant(Zw) to create a mutex in C++

    - by Simon
    Hey i want to create a mutex with the kernel function NtCreateMutant. I did it like this: Handle hMutex; NTSTATUS ntMutex = NtOpenMutant(&hMutex,MUTEX_ALL_ACCESS,false); the NTSTATUS value that is returned: C0000024 STATUS_OBJECT_TYPE_MISMATCH hope someone can help me with calling NtOpenMutant the right way. With the windows API OpenMutex(..) its working just fine.. HANDLE hMutex; hMutex = OpenMutex(MUTEX_ALL_ACCESS, FALSE, "Name"); Hope someone can explain me how to use the nativ function :)

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  • Django template tag basic question

    - by ninja123
    It looks like this template tag works like a charm for most people: http://blog.localkinegrinds.com/2007/09/06/digg-style-pagination-in-django/ For some reason I get this error: Caught an exception while rendering: 'is_paginated' I use this template tag in my template like so: {% load digg_paginator %} {% digg_paginator %} Where digg_paginator.py is in my app/templatetags folder and the included template context digg_paginator.html is in my app/templates folder. The queryset that needs pagination is called 'destinations'. If i just specify {% digg_paginator %}, how does it know what variable to paginate?? I feel I am missing something important here or just plain stupid :P Someone please help, or explain to me how this should be done. Thanks

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  • CSS Sprites : Mysterious Concept Explored ?

    - by Rachel
    I have 3 different images and now I want to create an sprite using css so that I am reducing HTTP Request. I am totally new to this concept and have not idea as to how to approach this. Can anyone suggest me what would be best bet for me ? Also I have seen there are some CSS Sprite generator engines where in you submit .zip folder containing your images and than they would combine it. I tried doing that but did not understood of what was happening and so any guidance regarding creating and using CSS sprites would be highly appreciated. Update: I have gone through the AList Part but it was not very clear to me. Can anyone explain the use case of CSS Sprites using an example ? Thanks.

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  • Unreachable, existing variable

    - by Oden
    I'm new at as3, maybe thats the reason why i don't understand, why the setInterval causes an error. <mx:Script> <![CDATA[ import flash.utils.setInterval; import mx.controls.Alert; [Bindable] public var MyInt:int = 500; setInterval(function():void{ ++MyInt; },1000); ]]> </mx:Script> I have a label where the value of MyInt gets visible, the bind works perfect, i've tested it several ways, and i i create a button it grows the number, but if i use the setInterval function i get an error: Access of undefined property myInt. Why? What does cause this? Please explain it, so I can avoid errors like this. Thanks

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  • C++ Pointers to functions.

    - by Andy Leman
    using namespace std; int addition (int a, int b) { return (a+b); } int subtraction (int a, int b) { return (a-b); } int operation (int x, int y, int (*functocall)(int,int)) { int g; g = (*functocall)(x,y); return(g); } int main() { int m,n; int (*minus)(int,int) = subtraction; m = operation (7,5,addition); n = operation (20,m,minus); cout << n; return 0; } Can anybody explain this line for me int (*minus)(int,int) = subtraction; Thanks a lot!

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  • Multiple user database design

    - by dieguitoweb
    I have to develop a basic social network for an academic purpose; but I need some tips for the users management.. The users are subdivided into 3 groups with different privilege: admins,analysts and standards users. For every user should be stored into the database the following information: name,lastname,e-mail,age,password. I'm not quite sure how I should design the database between theese two solutions: 1)one table called 'users' with the 'role' attribute that explain what a user can do and what can't do, and the permissions are managed via php 2)every application user is a database user created with the query 'CREATE ROLE' (It's a postgres database) and he has permissions on some tables granted with the 'GRANT' statement You should take into account that the project is for a database exam.. thanks

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  • Trouble using xib files in libraries

    - by flohei
    Hi there, I'm having some trouble working with libraries and included xib files. Let me explain my situation first. I've got a project that's running pretty good. Now I need a part of my project as a library for another customer who want's to use some of the functionality in his app. I've created a library with help of that highly recommended article. My customer should be able to initialize a main view controller like this: LibraryMainViewController *lmvc = [[LibraryMainViewController alloc] initWithNibName:@"LibraryMainViewController.xib" bundle:foo]; That for sure leads to an error when I try to present that view controller modally. I'm not sure what bundle I have to use here. I tried something like [NSBundle bundleForClass:[SomeClassInTheLibrary class]]; but that didn't solve the problem. I would be glad if someone could tell me how to actually use a xib file in that kind of situation. Thanks –f

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  • Need help in downloading file with header() function

    - by riccardo
    Hi. I'm trying to explain as best as I can, sorry for my English. I have a list of links, each linked to a php file with an id by parameters (ex. download.php?id=1 or ?id=2 and so on). This file create a new instance of a class witch return the correct header of the files so it displays the save dialog box of the browser. Now I need to check if the files is already downloaded in past (The first time you downloaded it I add a field on the mysql db). This checks go ahead if you haven't download the files, else return false. Here is the problem, when it returns false or something else the browser redirect me to the download.php file, so I get a blank page or what I'm echoing. I need that if the file is already download it show me a js alert for advice ppl. Hope you can understand what i mean. Thanks for help

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  • Initialising structs in C++

    - by Neil Butterworth
    As an addendum to this question, what is going on here: #include <string> using namespace std; struct A { string s; }; int main() { A a = {0}; } Obviously, you can't set a std::string to zero. Can someone provide an explanation (backed with references to the C++ Standard, please) about what is actually supposed to happen here? And then explain for example): int main() { A a = {42}; } Are either of these well-defined? Once again an embarrassing question for me - I always give my structs constructors, so the issue has never arisen before.

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  • Java stop MIDI playback

    - by user456268
    Hi I have java application which plays midi messages from sequence. I'm doing this using jfugue library. the problem is when I'm tryingto stop playback with stop button (which call sequencer.stop() and sequencer.close()) the last played note is sound all of rest time, and I can't stop it. So I'm asking about solution about stopping all audio and MIDI too! sound playback from java application. Notice: If you want propose just mute volume, you need to know that I want end-use will be able to press play button again and hear the sound again, so muting volumr will be not a solution, or explain please. Thank you!

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  • Inability to detect the Output from inside a SSIS script component

    - by Danaja
    In the script of the script components the Output buffer is not being detected as an existing component. I am trying to use the following piece of code Output0Buffer.AddRow(); within the public override void Input0_ProcessInputRow(Input0Buffer Row) method. I know it should be available within this method because at the moment I am copying and using a component from a previous project that has this code and it works. but when I create a new component and put the same code in it doesn't Can any one explain why this is happening?

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  • wcf net.tcp service fails to start when extra properties are set

    - by Pharabus
    i have a current project that runs fine with a self hosted net.tcp binding if I uses the following host.AddServiceEndpoint(typeof(IMonitorService), new NetTcpBinding() {PortSharingEnabled = false }, ""); host.AddServiceEndpoint(ServiceMetadataBehavior.MexContractName, MetadataExchangeBindings.CreateMexTcpBinding(), "mex"); however if I ammend to the below it fails to run with the message that there is already an endpoint on the port, can anyone explain why adding the extra properties causes it to fail? host.AddServiceEndpoint(typeof(IMonitorService), new NetTcpBinding() {PortSharingEnabled = false,ListenBacklog=1000,ReceiveTimeout=new TimeSpan(0,3,0) }, ""); host.AddServiceEndpoint(ServiceMetadataBehavior.MexContractName, MetadataExchangeBindings.CreateMexTcpBinding(), "mex"); Edit: testing confirms that the ReceiveTimeout property works Ok, as soon as I add the MaxConnections or ListenBacklog the service fails start Edit 2: this link seems to imply i ned portsharing is i want to modify these properies, not sure I am understanding it.

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  • How to retain a row which is foreign key in another table and remove other duplicate rows?

    - by Mithril
    I have two table: A: id code 1 A1 2 A1 3 B1 4 B1 5 C1 6 C1 ===================== B: id Aid 1 1 2 4 (B doesn't contain the Aid which link to code C1) Let me explain the overall flow: I want to make each row in table A have different code(by delete duplicate),and I want to retain the Aid which I can find in table B.If Aid which not be saved in table B,I retain the id bigger one. so I can not just do something as below: DELETE FROM A WHERE id NOT IN (SELECT MAX(id) FROM A GROUP BY code, ) I can get each duplicate_code_groups by below sql statement: SELECT code FROM A GROUP BY code HAVING COUNT(*) > 1 Is there some code in sql like for (var ids in duplicate_code_groups){ for (var id in ids) { if (id in B){ return id } } return max(ids) } and put the return id into a idtable?? I just don't know how to write such code in sql. then I can do DELETE FROM A WHERE id NOT IN idtable

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  • OPENGL Android getting the coordinates of my image

    - by Debopam
    I used the codes from the following the website. And it helped a lot to draw the required object on my screen. But the problem I am facing is getting the coordinates of my object. Let me explain. According to the code. You just need to add your graphic images in PNG format and refer it to the class here. What I am trying to achieve is a simple collision detection mechanism. I have added a maze (as PNG). And have a object (as PNG) to go through the blank path within the maze. In order to do this I need to know the blank spaces within the coordinates through which my object will move. Can any one tell me how to get the blank spaces as (x,y) coordinates through which I can take my object?

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