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  • Using TXMLDocument to serialize form settings to XML and database.

    - by LukLed
    I have an interface: type IXMLSerializable = interface function SaveToXML : DOMString; function SaveToXMLDocument : IXMLDocument; procedure LoadFromXML(AXML : DOMString); end; It is used to serialize some settings of forms or frames to xml. Simple implementation: SaveToXMLDocument: function TSomething.SaveToXMLDocument: IXMLDocument; begin Result := TXMLDocument.Create(nil); with Result do begin Active := True; with AddChild(Self.Name) do begin AddChild(edSomeTextBox.Name).Attributes['Text'] := edSomeTextBox.Text; end; end; Result := XMLDoc; end; LoadFromXML: procedure TSomething.LoadFromXML(AXML: DOMString); var XMLDoc : IXMLDocument; I : Integer; begin XMLDoc := TXMLDocument.Create(nil); with XMLDoc do begin LoadFromXML(AXML); Active := True; with ChildNodes[0] do begin for I := 0 to ChildNodes.Count-1 do begin If ChildNodes[I].NodeName = 'edSomeTextBox' then edSomeTextBox.Text := ChildNodes[I].Attributes['Text']; end; end; end; end; SaveToXML: function TSomething.SaveToXML: DOMString; begin SaveToXMLDocument.SaveToXML(Result); end; DOMString result of SaveToXML is saved to database to blob field. I had some encoding issues with other implementations and this one works fine (right now). Do you see any dangers in this code? Can I have issues with different settings on various machines and systems?

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  • Help me find article on Multi-threading and Event Handling in Java

    - by JDR
    I once read an article on how to properly write event handlers for multi-threading in Java, but I can't for the life of me find it anymore. It described the pitfalls and potentials for deadlocks that can occur when firing events (not Swing events mind you, but general events like model update notifications). To clarify, the situation would be as such: // let's say this is code from an MVC model somewhere public void setSomeProperty(String myProperty){ if(!this.myProperty.equals(myProperty)){ this.myProperty = myProperty; fireMyPropertyChangedEvent(...); } } The article described how passing control to arbitrary external listener code was a potential cause for deadlock. I now find myself in a situation where I need to fire such events in a multithreaded environment and I would very much like to read the article again to see what it has to say before I continue. Does anyone know the article I'm referring to? I believe it came as a (fairly short) PDF. It started off with an initial naive implementation and incrementally pointed out flaws and improved upon it. It ended with a sort of final proper-way-to-fire-multithreaded-events. I've searched endlessly in my browse history and on google, but all I could find were endless amounts topics on Swing event dispatch threads. Thank you.

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  • Global name not defined error in Django/Python trying to set foreignkey

    - by Mark
    Summary: I define a method createPage within a file called PageTree.py that takes a Source model object and a string. The method tries to generate a Page model object. It tries to set the Page model object's foreignkey to refer to the Source model object which was passed in. This throws a NameError exception! I'm trying to represent a website which is structured like a tree. I define the Django models Page and Source, Page representing a node on the tree and Source representing the contents of the page. (You can probably skip over these, this is a basic tree implementation using doubly linked nodes). class Page(models.Model): name = models.CharField(max_length=50) parent = models.ForeignKey("self", related_name="children", null=True); firstChild = models.ForeignKey("self", related_name="origin", null=True); nextSibling = models.ForeignKey("self", related_name="prevSibling", null=True); previousSibling = models.ForeignKey("self", related_name="nxtSibling", null=True); source = models.ForeignKey("Source"); class Source(models.Model): #A source that is non dynamic will be refered to as a static source #Dynamic sources contain locations that are names of functions #Static sources contain locations that are places on disk name = models.CharField(primary_key=True, max_length=50) isDynamic = models.BooleanField() location = models.CharField(max_length=100); I've coded a python program called PageTree.py which allows me to request nodes from the database and manipulate the structure of the tree. Here is the trouble making method: def createPage(pageSource, pageName): page = Page() page.source = pageSource page.name = pageName page.save() return page I'm running this program in a shell through manage.py in Windows 7 manage.py shell from mysite.PageManager.models import Page, Source from mysite.PageManager.PageTree import * ... create someSource = Source(), populate the fields, and save it ... createPage(someSource, "test") ... NameError: global name 'source' is not defined When I type in the function definition for createPage into the shell by hand, the call works without error. This is driving me bonkers and help is appreciated.

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  • Which is the event listener after doSave() in Symfony?

    - by fesja
    Hi, I've been looking at this event-listeners page http://www.doctrine-project.org/documentation/manual/1_1/pl/event-listeners and I'm not sure which is the listener I have to use to make a change after the doSave() method in the BaseModelForm.class.php. // PlaceForm.class.php protected function doSave ( $con = null ) { ... parent::doSave($con); .... // Only for new forms, insert place into the tree if($this->object->level == null){ $parent = Place::getPlace($this->getValue('parent'), Language::getLang()); ... $node = $this->object->getNode(); $method = ($node->isValidNode() ? 'move' : 'insert') . 'AsFirstChildOf'; $node->$method($parent); //calls $this->object->save internally } return; } What I want to do is to make a custom slug with the ancestors' name of that new place. So if I inserting "San Francisco", the slug would be "usa-california-san-francisco" public function postXXXXXX($event) { ... $event->getInvoker()->slug = $slug; } The problem is that I'm inserting a new object with no reference to its parent. After it's saved, I insert it to the tree. So I can't change the slug until then. I think a Transaction listener could work, but I'm use there is a better way I'm not seeing right now. thanks!

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  • How to pass variables to slot methods in QT?

    - by Neko
    Hi. I'm making a little chat messenger program, which needs a list of chat channels the user has joined. To represent this list graphically, I have made a list of QPushButtons, which all represent a different channel. These buttons are made with the following method, and that's where my problem kicks in: void Messenger::addToActivePanels(std::string& channel) { activePanelsContents = this->findChild<QWidget *>(QString("activePanelsContents")); pushButton = new QPushButton(activePanelsContents); pushButton->setObjectName("pushButton"); pushButton->setGeometry(QRect(0, 0, 60, 60)); pushButton->setText(""); pushButton->setToolTip(QString(channel.c_str())); pushButton->setCheckable(true); pushButton->setChecked(false); connect(pushButton, SIGNAL(clicked()), this, SLOT(switchTab(channel))); } (activePanelContents is a QWidget that holds the list.) The point is that each button should call the switchTab(string& tabname) method when clicked, including the specific channel's name as variable. This implementation doesn't work though, and I haven't been able to find out how to properly do this, even after reading several pages on it on the internet. Can anybody please tell me how to do this? It'd be greatly appreciated, as always. :)

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  • Adding new records in Access without wrecking the form

    - by Matt Parker
    I'm working on a simple Access 2003 application to keep track of things that need to be done for clients for some colleagues. Each colleague has a set of clients, and each client has a set of actions that need to be taken by a certain date. I've set up a form that consists of a combobox for client ID (indexed), a drop-down for the person who is handling that client's case, and a button for adding new clients (a standard Access-created Add Record button). The actions are listed in a subform below these three elements. The problem I've run into is that the first person I tested this on clicked the button to add a new record, then didn't fill it out and tried to select another client from the drop-down list. Access interprets this as an attempt to set the selected Client ID as the ID for the new record and rightfully throws an error for duplicate primary keys. I can think of a couple of ways around this problem, but I'd much rather hear your elegant solutions than kludge together some junk in a language I don't know. Let me know if you have any questions. Thank you.

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  • MVC design pattern in complex iPad app: is one fat controller acceptable?

    - by nutsmuggler
    I am building a complex iPad application; think of it as a scrapbook. For the purpose of this question, let's consider a page with two images over it. My main view displays my doc data rendered as a single UIImage; this because I need to do some global manipulation over them. This is my DisplayView. When editing I need to instantiate an EditorView with my two images as subviews; this way I can interact with a single image, (rotate it, scale it, move it). When editing is triggered, I hide my DisplayView and show my EditorView. In a iPhone app, I'd associate each main view (that is, a view filling the screen) to a view controller. The problem is here there is just one view controller; I've considered passing the EditorView via a modal view controller, but it's not an option (there a complex layout with a mask covering everything and palettes over it; rebuilding it in the EditorView would create duplicate code). Presently the EditorView incorporates some logic (loads data from the model, invokes some subviews for fine editing, saves data back to the model); EditorView subviews also incorporate some logic (I manipulate images and pass them back to the main EditorView). I feel this logic belongs more to a controller. On the other hand, I am not sure making my only view controller so fat a good idea. What is the best, cocoa-ish implementation of such a class structure? Feel free to ask for clarifications. Cheers.

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  • What's the *right* way to handle a POST in FP?

    - by Malvolio
    I'm just getting started with FP and I'm using Scala, which may not be the best way, since I can always fall back to an imperative style if the going gets tough. I'd just rather not. I've got a very specific question that points to a broader lacuna in my understanding of FP. When a web application is processing a GET request, the user wants information that already exists on the web-site. The application only has to process and format the data in some way. The FB way is clear. When a web application is processing a POST request, the user wants change the information held on the site. True, the information is not typically held in application variables, it's in a database or a flat-file, but still, I get the feeling I'm not grokking FP properly. Is there a pattern for handling updates to static data in an FP language? My vague picture of this is that the application is handed the request and the then-current site state. The application does its thing and returns the new site-state. If the current site-state hasn't changed since the application started, the new state becomes the current state and the reply is sent back to the browser (this is my dim image of Clojure's style); if the current state has been changed (by another thread, well, something else happens ...

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  • C As Principal Class For Mac App

    - by CodaFi
    So, I've got a c file raring to go and be the main class behind an all-C mac-app, however, a combination of limiting factors are preventing the application from being launched. As it currently stands, the project is just a main.m and a class called AppDelegate.c, so I entered "AppDelegate" as the name of the principal class in the info.plist, and to my complete surprise, the log printed: Unable to find class: AppDelegate, exiting This would work perfectly well in iOS, because the main function accepts the name of a delegate class, and handles it automatically, but NSApplicationMain() takes no such argument. Now, I know this stems from the fact that there are no @interface/@implementation directives in C, and that's really what the OS seems to be looking for, so I wrote a simple NSApplication subclass and provided it as the Principal Class to the plist, and it launched perfectly well. My question is, how could one go about setting a c file as the principal class in a mac application and have it launch correctly? PS, don't ask what or why I'm doing this for, the foundation must be dug. For @millimoose's amusement, here be the AppDelegate.c file: #include <objc/runtime.h> #include <objc/message.h> struct AppDel { Class isa; id window; }; // This is a strong reference to the class of the AppDelegate // (same as [AppDelegate class]) Class AppDelClass; BOOL AppDel_didFinishLaunching(struct AppDel *self, SEL _cmd, void *application, void *options) { self->window = objc_msgSend(objc_getClass("NSWindow"), sel_getUid("alloc")); self->window = objc_msgSend(self->window, sel_getUid("init")); objc_msgSend(self->window, sel_getUid("makeKeyAndOrderFront:"), self); return YES; }

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  • Why is Excel's 'Evaluate' method a general expression evaluator?

    - by jtolle
    A few questions have come up recently involving the Application.Evaluate method callable from Excel VBA. The old XLM macro language also exposes an EVALUATE() function. Both can be quite useful. Does anyone know why the evaluator that is exposed can handle general expressions, though? My own hunch is that Excel needed to give people a way to get ranges from string addresses, and to get the value of named formulas, and just opening a portal to the expression evaluator was the easiest way. (The help for the VBA version does say its purpose it to "convert a Microsoft Excel name to an object or a value".) But of course you don't need the ability to evaluate arbitrary expressions just to do that. (That is, Excel could provide a Name.Evaluate method or something instead.) Application.Evaluate seems kind of...unfinished. It's full behavior isn't very well documented, and there are quite a few quirks and limitations (as described by Charles Williams here: http://www.decisionmodels.com/calcsecretsh.htm) with what is exposed. I suppose the answer could be simply "why not expose it?", but I'd be interested to know what design decisions led to this feature taking the form that it does. Failing that, I'd be interested to hear other hunches.

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  • Is this the best way to make an API request using PHP CURL?

    - by Abs
    Hello all, I have a site that has a simple API which can be used via http. I wish to make use of the API and submit data about 1000-1500 times at one time. Here is their API: http://api.jum.name/ I have constructed the URL to make a submission but now I am wondering what is the best way to make these 1000-1500 API GET requests? Here is the PHP CURL implementation I was thinking of: $add = 'http://www.mysite.com/3rdparty/API/api.php?fn=post&username=test&password=tester&url=http://google.com&category=21&title=story a&content=content text&tags=Season,news'; curl_setopt ($ch, CURLOPT_URL, "$add"); curl_setopt ($ch, CURLOPT_POST, 0); curl_setopt ($ch, CURLOPT_COOKIEFILE, 'files/cookie.txt'); curl_setopt ($ch, CURLOPT_FOLLOWLOCATION, 0); curl_setopt ($ch, CURLOPT_RETURNTRANSFER, TRUE); $postdata = curl_exec ($ch); Shall I close the CURL connection every time I make a submission? Can I re-write the above in a better way that will make these 1000-1500 submissions quicker? Thanks all

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  • Unit Testing Interfaces in Python

    - by Nicholas Mancuso
    I am currently learning python in preperation for a class over the summer and have gotten started by implementing different types of heaps and priority based data structures. I began to write a unit test suite for the project but ran into difficulties into creating a generic unit test that only tests the interface and is oblivious of the actual implementation. I am wondering if it is possible to do something like this.. suite = HeapTestSuite(BinaryHeap()) suite.run() suite = HeapTestSuite(BinomialHeap()) suite.run() What I am currently doing just feels... wrong (multiple inheritance? ACK!).. class TestHeap: def reset_heap(self): self.heap = None def test_insert(self): self.reset_heap() #test that insert doesnt throw an exception... for x in self.inseq: self.heap.insert(x) def test_delete(self): #assert we get the first value we put in self.reset_heap() self.heap.insert(5) self.assertEquals(5, self.heap.delete_min()) #harder test. put in sequence in and check that it comes out right self.reset_heap() for x in self.inseq: self.heap.insert(x) for x in xrange(len(self.inseq)): val = self.heap.delete_min() self.assertEquals(val, x) class BinaryHeapTest(TestHeap, unittest.TestCase): def setUp(self): self.inseq = range(99, -1, -1) self.heap = BinaryHeap() def reset_heap(self): self.heap = BinaryHeap() class BinomialHeapTest(TestHeap, unittest.TestCase): def setUp(self): self.inseq = range(99, -1, -1) self.heap = BinomialHeap() def reset_heap(self): self.heap = BinomialHeap() if __name__ == '__main__': unittest.main()

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  • How to format dates in Jahia 6 CMS?

    - by dpb
    I am helping a friend of mine put up a site for his business. I’ve read different posts and sites trying to find the ideal CMS tool, but people have different views of what is the best, so I finally just picked one of them at random. So I went for an evaluation of Jahia 6.0-CE. As you’ve probably guessed by now, I don’t have so much experience with CMS tools. I just want to setup the CMS, write the templates for the site and let my friend manage the content from there on. So I extracted the sources from SVN and went for a test drive. I managed to create some simple templates to get a hang of things but now I have an issue with a date format. In my definitions.cnd I declared the field like so: date myDateField (datetimepicker[format='dd.MM.yyyy']) This is formatted in the page and the selector also presents this in the dd.MM.yyyy format when inserting the content. But how about sites in other countries, countries that represent the date as MM.dd.yyyy for example? If I specify the format in the CND, hard coded, how can I change this later on so that it adapts based on the browser’s language? Do I extract the content from the repository and format it by hand in the JSP template based on a Locale, or is there a better way? Thank you.

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  • Transparently surround a component with a link in Wicket

    - by Toni Menzel
    I want to be able to add links on certain items in an ListView. If an items is surrounded by the link or not is up to the code, so its not in the normal page markup. Say i have a markup like this: <div class="column" wicket:id="columnRepeater"> <span wicket:id="column"></span> </div> So essentially, while filling the repeater with a ListView i am able to find a custom renderer for the column component. (not my playingfield). What i want is to add a Link/Ajax Link around the column component. I learned using wicket:border lets you surround additional stuff. Now, the border markup looks like this: <wicket:border> <a wicket:id="link"><wicket:body/></a> </wicket:border> Now, i am a bit puzzled what the Border implementation looks like. Anyone there who can suggest a working java part? I have a couple of "work in progress" solutions but none works. Most questions have to do with usage of component ids. Is the border id = column ? Whats the id of the inner (border body) id then?

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  • creating an object within a function of a program

    - by user1066524
    could someone please tell me what I need to do in order to create an object in a function. I will try to explain by making up some sort of example... Let's say I have a program named TimeScheduler.cpp that implements the class Schedule.h (and I have the implementation in a separate file Schedule.cpp where we define the methods). In the declaration file we have declared two constructors Schedule(); //the default and Schedule(int, int, int);//accepts three arguments to get to the point--let's say in the main program file TimeScheduler.cpp we created our own functions in this program apart from the functions inherited from the class Schedule. so we have our prototypes listed at the top. /*prototypes*/ void makeSomeTime(); etc..... we have main(){ //etc etc... } we then define these program functions void makeSomeTime(){ //process } let's say that inside the function makeSomeTime(), we would like to create an array of Schedule objects like this Schedule ob[]={ summer(5,14, 49), fall(9,25,50) }; what do I have to do to the function makeSomeTime() in order for it to allow me to create this array of objects. The reason I ask is currently i'm having difficulty with my own program in that it WILL allow me to create this array of objects in main()....but NOT in a function like I just gave an example of. The strange thing is it will allow me to create a dynamic array of objects in the function..... like Schedule *ob = new Schedule[n+1]; ob[2]= Schedule(x,y,z); Why would it let me assign to a non-dynamic array in main(), but not let me do that in the function?

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  • Where should I put validation code?

    - by D Lawson
    I'm creating interfaces and abstract classes that represent a messaging framework for short text-based messages like SMS, email, twitter, xml, etc.. and I was wondering where I should put the message validation code. The thing is that I am only writing the superclasses and interfaces, so I'm not putting the actual implementation in, I'll just put the hooks in that allow others to validate the content of the messages. The way I see it, I could do it several ways: in the abstract superclass "Message", have an abstract method 'isValid'. A variation on this would be to have isValid be called when the Message constructor is called, throwing a MalformedMessageException if the message is formatted incorrectly. in the transport layer, immediately before sending, validate the message. I would have a send(Message) method that calls an isValid(Message) method immediately before it sends. have a singleton message validator with a static method isValid(Message) that is called at some point. I'm sure there are other options that I'm missing. Currently, I'm leaning towards the first one, but it doesn't feel right to me to have validation code in what should be a domain object.

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  • How can I make this simple C# generics factory work?

    - by Kevin Brassen
    I have this design: public interface IFactory<T> { T Create(); T CreateWithSensibleDefaults(); } public class AppleFactory : IFactory<Apple> { ... } public class BananaFactory : IFactory<Banana> { ... } // ... The fictitious Apple and Banana here do not necessarily share any common types (other than object, of course). I don't want clients to have to depend on specific factories, so instead, you can just ask a FactoryManager for a new type. It has a FactoryForType method: IFactory<T> FactoryForType<T>(); Now you can invoke the appropriate interface methods with something like FactoryForType<Apple>().Create(). So far, so good. But there's a problem at the implementation level: how do I store this mapping from types to IFactory<T>s? The naive answer is an IDictionary<Type, IFactory<T>>, but that doesn't work since there's no type covariance on the T (I'm using C# 3.5). Am I just stuck with an IDictionary<Type, object> and doing the casting manually?

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  • How can I implement a splay tree that performs the zig operation last, not first?

    - by Jakob
    For my Algorithms & Data Structures class, I've been tasked with implementing a splay tree in Haskell. My algorithm for the splay operation is as follows: If the node to be splayed is the root, the unaltered tree is returned. If the node to be splayed is one level from the root, a zig operation is performed and the resulting tree is returned. If the node to be splayed is two or more levels from the root, a zig-zig or zig-zag operation is performed on the result of splaying the subtree starting at that node, and the resulting tree is returned. This is valid according to my teacher. However, the Wikipedia description of a splay tree says the zig step "will be done only as the last step in a splay operation" whereas in my algorithm it is the first step in a splay operation. I want to implement a splay tree that performs the zig operation last instead of first, but I'm not sure how it would best be done. It seems to me that such an algorithm would become more complex, seeing as how one needs to find the node to be splayed before it can be determined whether a zig operation should be performed or not. How can I implement this in Haskell (or some other functional language)?

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  • Within a DLL, how is the function table structured?

    - by Willi Ballenthin
    I've been looking into the implementation of a device library that doesn't explicitly support my operating system. In particular, I have a disassembled DLL, and a fair amount of supporting source code. Now, how is the function table/export table structured? My understanding is that the first structure of the .data section is a table of VRAs. Next is a table of strings linked by index to that first address table. This makes sense to me, as a linker could translate between symbols and addresses. How do functions referenced by ordinals fit into this picture? How does one know which function has such and such ordinal number, and how does the linker resolve this? In other words, given that some other DLL imports SOME_LIBRARY_ordinal_7, how does the linker know which function to work with? Thanks, all! edit More information... Im working with the FTDI libraries, and would like to resolve which function is being invoked. In particular, I see something like: extern FTD2XX_Ordinal_28: near how might I go about determining which function is being referenced, and how does the linker do this?

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  • Why is T() = T() allowed?

    - by Rimo
    I believe the expression T() creates an rvalue (by the Standard). However, the following code compiles (at least on gcc4.0): class T {}; int main() { T() = T(); } I know technically this is possible because member functions can be invoked on temporaries and the above is just invoking the operator= on the rvalue temporary created from the first T(). But conceptually this is like assigning a new value to an rvalue. Is there a good reason why this is allowed? Edit: The reason I find this odd is it's strictly forbidden on built-in types yet allowed on user-defined types. For example, int(2) = int(3) won't compile because that is an "invalid lvalue in assignment". So I guess the real question is, was this somewhat inconsistent behavior built into the language for a reason? Or is it there for some historical reason? (E.g it would be conceptually more sound to allow only const member functions to be invoked on rvalue expressions, but that cannot be done because that might break some existing code.)

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  • VB app to web service

    - by brandon
    I know very little about web service but I assumed it would be the solution I was looking for. Basically I made an application in VB that I want to be ubiquitous for a lack of a better word. I need it to receive requests from multiple users and respond all at once. I was told "technically if you write a webservice you can provide as many results back to users as are connected." Maybe there is another solution for me that will give me the results I want. Here is an example of what I'm trying to do. Lets say I make an application in VB that does math. I now make a website. My website allows for a person to input 1 + 1 they click submit and my website then connects to my VB application running on my server listening for a request. It accepts the request from my website, and then it solves the math problem and returns the answer back to the website "1 + 1 = 2" That is only an example of the type of thing I need. My problem is that I can't have multiple people visiting my website all connecting to that same application running on my server so somehow I need the application to be where it can be accessed by multiple users. I was told a web service would be the answer but if there is another solution I'd like to know. If the only solution is a web service, then how can I manage to either convert the VB app to a web service? Can I have to convert the app to asp.net or some other language? Is there an easier option?

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  • dynamically insert new rows in the table (JavaScript) ?

    - by Karandeep Singh
    <script type="text/javascript" language="javascript"> function addNewRow() { var table = document.getElementById("table1"); var tr = table.insertRow(); var td = tr.insertCell(); td.innerHTML= "a"; td = tr.insertCell(); td.innerHTML= "b"; td = tr.insertCell(); td.innerHTML= "c"; td = tr.insertCell(); td.innerHTML= "d"; td = tr.insertCell(); td.innerHTML= "e"; } </script> <body> <table id="table1" border="1" cellpadding="0" cellspacing="0" width="100%"> <tr id="row1"> <td>1</td> <td>2</td> <td>3</td> <td>4</td> <td>5</td> </tr> </table> <input type="button" onClick="addNewRow()" value="Add New"/> </body> This example is for dynamically insert new row and cells in the table. But its behavior is different in all browsers. Internet Explorer = It add row in the last and new added cells are starts from first. Chrome/Safari = It add new row in the first and new added cells are starts from end. Mozilla Firefox = It is not working. Sir, I want new added row in the last and new added cells starts from first like(Interner Explorer) in all browsers. If you have any solution for same behavior please tell me. Thanks,

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  • Number of characters recommended for a statement

    - by liaK
    Hi, I have been using Qt 4.5 and so do C++. I have been told that it's a standard practice to maintain the length of each statement in the application to 80 characters. Even in Qt creator we can make a right border visible so that we can know whether we are crossing the 80 characters limit. But my question is, Is it really a standard being followed? Because in my application, I use indenting and all, so it's quite common that I cross the boundary. Other cases include, there might be a error statement which will be a bit explanatory one and which is in an inner block of code, so it too will cross the boundary. Usually my variable names look bit lengthier so as to make the names meaningful. When I call the functions of the variable names, again I will cross. Function names will not be in fewer characters either. I agree a horizontal scroll bar shows up and it's quite annoying to move back and forth. So, for function calls including multiple arguments, when the boundary is reached I will make the forth coming arguments in the new line. But besides that, for a single statement (for e.g a very long error message which is in double quotes " " or like longfun1()->longfun2()->...) if I use an \ and split into multiple lines, the readability becomes very poor. So is it a good practice to have those statement length restrictions? If this restriction in statement has to be followed? I don't think it depends on a specific language anyway. I added C++ and Qt tags since if it might. Any pointers regarding this are welcome.

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  • Rapid Opening and Closing System.IO.StreamWriter in C#

    - by ccomet
    Suppose you have a file that you are programmatically logging information into with regards to a process. Kinda like your typical debug Console.WriteLine, but due to the nature of the code you're testing, you don't have a console to write onto so you have to write it somewhere like a file. My current program uses System.IO.StreamWriter for this task. My question is about the approach to using the StreamWriter. Is it better to open just one StreamWriter instance, do all of the writes, and close it when the entire process is done? Or is it a better idea to open a new StreamWriter instance to write a line into the file, then immediately close it, and do this for every time something needs to be written in? In the latter approach, this would probably be facilitated by a method that would do just that for a given message, rather than bloating the main process code with excessive amounts of lines. But having a method to aid in that implementation doesn't necessarily make it the better choice. Are there significant advantages to picking one approach or the other? Or are they functionally equivalent, leaving the choice on the shoulders of the programmer?

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  • When is it possible to override top-level bindings in (R7RS) scheme?

    - by Marc
    I have read the current draft of the forthcoming R7RS scheme standard (small language), but I don't understand under which conditions it is not an error to redefine top-level bindings. I guess that it is possible to define or set! a binding that has been introduced at the top-level of a program a second time. But what about imported bindings from an external library? Is it possible to override these bindings by the standard? On page 26/27 of the report, it says: The top level of a program may also include import declarations. In a library declaration, it is an error to import the same identifier more than once with different bindings, or to redefine or mutate an imported binding with define, define-syntax or set!. However, a REPL should permit these actions. Does it mean that redefining is only an error when it does happen in libraries for imported bindings? I understand that it prohibits optimisations by compilers if the compiler does not know whether, say + still means the built-in addition or is any other user-specified error. But from this perspective, it does not make sense to restrict forbidding to rebind on the library level, when it would also make sense (at least) for imported bindings in programs. P.S.: As this is all about the environment of a scheme program: am I right in saying that environments are not first class citizens because one cannot get hold of the current environment? (Which, in turn, allows a compiled program to forget about the chosen names of the bindings.)

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