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• Email server; Is this method spam-safe?

  - by Camran

  I have a classifieds website, and on each classified there is a tip-form where users may tip a friend about the classified. The tip-forms' action is set to a php-page, which mails the email after sanitizing etc... I have to filter away spam etc so that my email-server don't get blacklisted or anything... I have my own server (VPS, Linux) and have thought about a solution... How does this sound to you: 1- Install a mail-server 2- Configure Firewall to ONLY allow connections to the mail-server from my website 3- Configure the mail-server so that a maximum of 'x' emails may be sent every 5 minutes or so 4- Create a php filter before sending the mail, which checks for 'bad' words. 5- If necessary, as last resort, ask the user a question (ex 5+5) before submitting form I would rather preferr if I didn't have to implement the 5th implementation above... What do you think? Also, another q I have that you may answer is: If an email-server gets blacklisted, is there any way to un-blacklist it? Or whats the solution if this happens? Thanks

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• Why do I have memory problems?

  - by Tattat

  I got this error from XCode: objc[8422]: FREED(id): message release sent to freed object=0x3b120c0 I googled and find that is related to the memory. But I don't know which line of code I go wrong, any ideas? After I launch my app in simulator, it prompts a second, than, no other error except the error above. @implementation MyAppDelegate @synthesize window; @synthesize viewController; - (void)applicationDidFinishLaunching:(UIApplication *)application { // Override point for customization after app launch [window addSubview:viewController.view]; [window makeKeyAndVisible]; [self changeScene:[MainGameMenuScene class]]; } - (void)dealloc { [viewController release]; [window release]; [super dealloc]; } - (void) changeScene: (Class) scene { BOOL animateTransition = true; if(animateTransition){ [UIView beginAnimations:nil context:NULL]; [UIView setAnimationDuration:0.5]; [UIView setAnimationTransition:UIViewAnimationTransitionFlipFromLeft forView:window cache:YES]; //does nothing without this line. } if( viewController.view != nil ) { [viewController.view removeFromSuperview]; //remove view from window's subviews. [viewController.view release]; //release gamestate } viewController.view = [[scene alloc] initWithFrame:CGRectMake(0, 0, IPHONE_WIDTH, IPHONE_HEIGHT) andManager:self]; //now set our view as visible [window addSubview:viewController.view]; [window makeKeyAndVisible]; if(animateTransition){ [UIView commitAnimations]; } }

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• getting active records to display as a plist

  - by phil swenson

  I'm trying to get a list of active record results to display as a plist for being consumed by the iphone. I'm using the plist gem v 3.0. My model is called Post. And I want Post.all (or any array or Posts) to display correctly as a Plist. I have it working fine for one Post instance: [http://pastie.org/580902][1] that is correct, what I would expect. To get that behavior I had to do this: class Post < ActiveRecord::Base def to_plist attributes.to_plist end end However, when I do a Post.all, I can't get it to display what I want. Here is what happens: http://pastie.org/580909 I get marshalling. I want output more like this: [http://pastie.org/580914][2] I suppose I could just iterate the result set and append the plist strings. But seems ugly, I'm sure there is a more elegant way to do this. I am rusty on Ruby right now, so the elegant way isn't obvious to me. Seems like I should be able to override ActiveRecord and make result-sets that pull back more than one record take the ActiveRecord::Base to_plist and make another to_plist implementation. In rails, this would go in environment.rb, right?

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• How can a B-tree node be represented?

  - by chronodekar

  We're learning B-trees in class and have been asked to implement them in code. The teacher has left choice of programming language to us and I want to try and do it in C#. My problem is that the following structure is illegal in C#, unsafe struct BtreeNode { int key_num; // The number of keys in a node int[] key; // Array of keys bool leaf; // Is it a leaf node or not? BtreeNode*[] c; // Pointers to next nodes } Specifically, one is not allowed to create a pointer to point to the structure itself. Is there some work-around or alternate approach I could use? I'm fairly certain that there MUST be a way to do this within the managed code, but I can't figure it out. EDIT: Eric's answer pointed me in the right direction. Here's what I ended up using, class BtreeNode { public List<BtreeNode> children; // The child nodes public static int MinDeg; // The Minimum Degree of the tree public bool IsLeaf { get; set; } // Is the current node a leaf or not? public List<int> key; // The list of keys ... }

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• Need help in javascript

  - by raja

  Hi: I am getting the error for the below code. Please help me out. <html><head> <title>(Type a title for your page here)</title> <script language=JavaScript> function check_length(my_formm,fieldName) { alert(fieldName); alert(document.my_formm.fieldName.value); } </script> </head> <body> <form name=my_form method=post> <input type="text" onKeyPress=checkCompanyName(); onChange=check_length("my_form","my_text"); name=my_text rows=4 cols=30 value=""> <br> <input size=1 value=50 name=text_num> Characters Left </form> </body> </html>

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• Sockets and COBOL

  - by kati

  I have received a job at a hospital which still uses COBOL for all organizational work, the whole (now 20 Terabyte) database (Which was a homebrew in, guess what, COBOL) is filled with the data of every patient since the last 45 (or so) years. So that was my story. Now to my question: Currently, all sockets were (from what I've seen) implemented by COBOL programs writing their data into files. These files then were read out by C++ programs (That was an additional module added in the late 1980s) and using C++ sockets sent to the database. Now this solution has stopped working as they are moving the database from COBOL to COBOL, yes - they didn't use MySQL or so - they implemented a new database - again in COBOL. I asked the guy that worked there before me (hes around 70 now) why the hell someone would do that and he told me that he is so good at COBOL that he doesn't want to write it in any other language. So far so good now my question: How can I implement socket connections in COBOL? I need to create an interface to the external COBOL database located at, for example, 192.168.1.23:283.

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• How would I sort files to directories based on filenames?

  - by gnomed

  I have a huge number of files to sort all named in some terrible convention. Here are some examples: (4)_mr__mcloughlin____.txt 12__sir_john_farr____.txt (b)mr__chope____.txt dame_elaine_kellett-bowman____.txt dr__blackburn______.txt These names are supposed to be a different person (speaker) each. Someone in another IT department produced these from a ton of XML files using some script but the naming is unfathomably stupid as you can see. I need to sort literally tens of thousands of these files with multiple files of text for each person; each with something stupid making the filename different, be it more underscores or some random number. They need to be sorted by speaker. This would be easier with a script to do most of the work then I could just go back and merge folders that should be under the same name or whatever. There are a number of ways I was thinking about doing this. parse the names from each file and sort them into folders for each unique name. get a list of all the unique names from the filenames, then look through this simplified list of unique names for similar ones and ask me whether they are the same, and once it has determined this it will sort them all accordingly. I plan on using Perl, but I can try a new language if it's worth it. I'm not sure how to go about reading in each filename in a directory one at a time into a string for parsing into an actual name. I'm not completely sure how to parse with regex in perl either, but that might be googleable. For the sorting, I was just gonna use the shell command: `cp filename.txt /example/destination/filename.txt` but just cause that's all I know so it's easiest. I dont even have a pseudocode idea of what im going to do either so if someone knows the best sequence of actions, im all ears. I guess I am looking for a lot of help, I am open to any suggestions. Many many many thanks to anyone who can help. B.

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• C++ : Declaring the array size with a non-constant variable

  - by Jérôme

  I always thought that when declaring an array in C++, the size has to be a constant integer value. For instance : int MyArray[5]; // correct or const int ARRAY_SIZE = 6; int MyArray[ARRAY_SIZE]; // correct but int ArraySize = 5; int MyArray[ArraySize]; // incorrect Here is also what is explained in The C++ Programming Language, by Bjarne Stroustrup : The number of elements of the array, the array bound, must be a constant expression (§C.5). If you need variable bounds, use a vector(§3.7.1, §16.3). For example: void f(int i) { int v1[i]; // error : array size not a constant expression vector<int> v2[i]; // ok } But to my big surprise, the code above does compile fine on my system ! Here is what I tried to compile : void f(int i) { int v2[i]; } int main() { int i = 3; int v1[i]; f(5); } I got no error ! I'm using GCC v4.4.0. Is there something I'm missing ?

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• Looking for a book which teaches how to write applications (as opposed to writng code)

  - by rumtscho

  I am not a developer. I have coded for fun and for university projects in several languages, and during an internship, I have written code which is still in use by a department of Fortune Global 500 company. I also have extensive theoretical knowledge of software engineering - process models, architecture, project management, UI construction using Lauesen's virtual windows... you get the picture. But I am not involved with software development in my job. I recently decided to start coding for fun again, and now I have some free days to do it. But this time, I want to do it right. I want to write a real, useful application, install it on my devices and use it myself. Also I want to publish it for others to use, should they want to do so. I am vaguely aware that there is more to writing an application than to writing code. There is stuff like version control software, decision for the right IDE, having a suite of unit tests, producing an installation package - and probably lots of other things I never thought of but which must be taken care of in a proper application, as opposed to a bunch of classes I am running from my IDE. All this is stuff I should know before I start, but I have not learned it. Coding books touch on some of the subjects like IDE choice, but don't go into detail, and are not exhaustive. Theoretical software engineering textbooks are even less helpful. So is there a book which teaches exactly that? I know that I can find information on each of these topics on the Internet, but I'd rather have a systematic book exhaustively listing all the things I should take care of if I want to create a good application, and offering the currently accepted solutions for them. In the best case, it will be language- and platform independent, but if you know of a good book focusing on a specific platform, I would like to know about it too. I know I want a lot, but given how important such knowledge is and how many people need it, surely somebody must have written such a book?

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• Should I be backing up a webapp's data to another host continuously ?

  - by user196289

  I have webapp in development. I need to plan for what happens if the host goes down. I will lose some very recent session status (which I can live with) and everything else should be persistently stored in the database. If I am starting up again after an outage, can I expect a good host to reconstruct the database to within minutes of where I was up to ? Or seconds ? Or should I build in a background process to continually mirror the database elsewhere ? What is normal / sensible ? Obviously a good host will have RAID and other redundancy so the likelihood of total loss should be low, and if they have periodic backups I should lose only very recent stuff but this is presumably likely to be designed with almost static web content in mind, and my site is transactional with new data being filed continuously (with a customer expectation that I don't ever lose it). Any suggestions / advice ? Are there off the shelf frameworks for doing this ? (I'm primarily working in Java) And should I just plan to save the data or should I plan to have an alternative usable host implementation ready to launch in case the host doesn't come back up in a suitable timeframe ?

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• Server side method not getting called

  - by Rangel Fernandes

  From the below javascript code i am trying to call a serverside method, but serververside method is not getting called. I am using jquery, ajax <script type="text/javascript" src="JquryLib.js"></script> <script type="text/javascript" language="javascript"> function fnPopulateCities() { debugger; var State = $("#ddlState").val(); GetCities(State); return false; } function GetCities(StateId) { debugger; var v1 = 'StateId: ' + StateId; $.ajax( { type: "POST", url: 'DropDownList_Cascade.aspx/PopulateCities', data: '{' + v1 + '}', contentType: "application/json; charset=utf-8", dataType: "json", success: function (result) { if (result.status === "OK") { alert('Success!!'); } else { fnDisplayCities(result); } }, error: function (req, status, error) { alert("Sorry! Not able to retrieve cities"); } }); } </script> This is my serverside method which i need to call. private static ArrayList PopulateCities(int StateId) { //this code returns Cities ArrayList from database. } It is giving me the following error: 500 (Internal Server Error) I cannot figure out what is wrong. please help! Stack Trace: [ArgumentException: Unknown web method PopulateCities.Parameter name: methodName]

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• Redirect after refreshing update panel

  - by teebot.be

  Hello, Do you think it's possible to refresh an update panel and immediately after redirecting the response (for instance a download) ? I tried this: an invisible button - as an asyncpostbacktrigger a download button - when it is clicked the onclientclick clicks the invisible button the click event on the invisible button refreshes the update panel then the download button click event launches the download (normal postback which launches the download) However for some reason when the invisible button is clicked by the download button client script, it doesn't refresh the update panel.. Do you have an idea why it doesn't work? Or do you have other and cleaner techniques? Here's how the elements are declared: <asp:Button runat="server" ID="ButtonInvisible" Text="" Click="RefreshDisplay" /> <asp:Button runat="server" ID="ButtonDownload" Text="Download" OnClientClick="clickInvisible(this.id)" Click="Download" /><Triggers> <asp:AsyncPostBackTrigger ControlID="ButtonInvisible" /></Triggers> //the javascript <script type="text/javascript" language="javascript"> function clickInvisible(idButton) { document.getElementById('ButtonInvisible').click(); }</script> ' //the methods Download(object source, EventArgs e){Response.Redirect("test.txt")} RefreshDisplay(object source, EventArgs e){ ButtonCancel.Enabled = false;}

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• Custom stream wrappers, what could they be useful for in web applications?

  - by michael

  I suppose the concept is language agnostic, but I don't know what it's called in other languages. In PHP they're Stream Wrappers. In short, a wrapper class that allows manipulation of a streamable resource (resource that can be read to/written to/seek into, such as a file, a db, an url). For example, in a template engine (a view), upon including a template file such as: include "view.wrapper://path/to/my/template/file.phtml"; my custom wrapper, declared elsewhere and associated with "view.wrapper", would first intercepts the file to replace such things as short tags (<?=) with a more verbose counterpart (<?php echo). This allows developers to use short tags in views, even if the server isn't set to allow it. It can also be applied to the preprocessing of views pseudo syntax such as {@myVar} (e.g. replacing it with $this->myVar). This is only one application of custom stream wrappers, but the feature seems powerful enough to make me think that there are others that could make life a lot simpler for developers. What have you built, or thought about building, custom stream wrappers for? where have you seen some interesting implementations? I'm particularly interested in their applications in web development.

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• I can't seem to figure out type variables mixed with classes.

  - by onmach

  I pretty much understand 3/4 the rest of the language, but every time I dip my feet into using classes in a meaningful way in my code I get permantently entrenched. Why doesn't this extremely simple code work? data Room n = Room n n deriving Show class HasArea a where width :: (Num n) => a -> n instance (Num n) => HasArea (Room n) where width (Room w h) = w So, room width is denoted by ints or maybe floats, I don't want to restrict it at this point. Both the class and the instance restrict the n type to Nums, but it still doesn't like it and I get this error: Couldn't match expected type `n1' against inferred type `n' `n1' is a rigid type variable bound by the type signature for `width' at Dungeon.hs:11:16 `n' is a rigid type variable bound by the instance declaration at Dungeon.hs:13:14 In the expression: w In the definition of `width': width (Room w h) = w In the instance declaration for `HasArea (Room n)' So it tells me the types doesn't match, but it doesn't tell me what types it thinks they are, which would be really helpful. As a side note, is there any easy way to debug an error like this? The only way I know to do it is to randomly change stuff until it works.

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• STLifying C++ classes

  - by shambulator

  I'm trying to write a class which contains several std::vectors as data members, and provides a subset of vector's interface to access them: class Mesh { public: private: std::vector<Vector3> positions; std::vector<Vector3> normals; // Several other members along the same lines }; The main thing you can do with a mesh is add positions, normals and other stuff to it. In order to allow an STL-like way of accessing a Mesh (add from arrays, other containers, etc.), I'm toying with the idea of adding methods like this: public: template<class InIter> void AddNormals(InIter first, InIter last); Problem is, from what I understand of templates, these methods will have to be defined in the header file (seems to make sense; without a concrete iterator type, the compiler doesn't know how to generate object code for the obvious implementation of this method). Is this actually a problem? My gut reaction is not to go around sticking huge chunks of code in header files, but my C++ is a little rusty with not much STL experience outside toy examples, and I'm not sure what "acceptable" C++ coding practice is on this. Is there a better way to expose this functionality while retaining an STL-like generic programming flavour? One way would be something like this: (end list) class RestrictedVector<T> { public: RestrictedVector(std::vector<T> wrapped) : wrapped(wrapped) {} template <class InIter> void Add(InIter first, InIter last) { std::copy(first, last, std::back_insert_iterator(wrapped)); } private: std::vector<T> wrapped; }; and then expose instances of these on Mesh instead, but that's starting to reek a little of overengineering :P Any advice is greatly appreciated!

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• redirecting _top page from asp:login control in iframe onloggedin

  - by jumpdart

  So yeah, Im building a little authenticated content(.NET app) to a large html site managed by another group. They are only comfortable with managing html so all my app content will be contained in iframes. Everything is working fine as far as navigation and calling services and whatnot but i cant bust out of the frame with my asp:login control. Im trying to register some JS on logged in but with no success. Thanks protected void login_LoggedIn(object sender, EventArgs e) { StringBuilder strScript = new StringBuilder(); strScript.Append("<script language='javascript'>"); string sHome = ConfigurationManager.AppSettings["AppHomePageURL"].ToString(); //strScript.AppendFormat("window.navigate('{0}');", sHome); //strScript.AppendFormat("parent.location.href='{0}';", sHome); //strScript.AppendFormat("window.open('{0}', '_top', '', false);", sHome); strScript.AppendFormat("top.location.href='{0}';", sHome); strScript.Append("WTF_let_me_outa_here();"); strScript.Append("</script>"); ClientScript.RegisterClientScriptBlock(typeof(Page), "LoginGO", strScript.ToString()); }

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• Filling in uninitialized array in java? (or workaround!)

  - by AlexRamallo

  Hello all, I'm currently in the process of creating an OBJ importer for an opengles android game. I'm relatively new to the language java, so I'm not exactly clear on a few things. I have an array which will hold the number of vertices in the model(along with a few other arrays as well): float vertices[]; The problem is that I don't know how many vertices there are in the model before I read the file using the inputstream given to me. Would I be able to fill it in as I need to like this?: vertices[95] = 5.004f; //vertices was defined like the example above or do I have to initialize it beforehand? if the latter is the case then what would be a good way to find out the number of vertices in the file? Once I read it using inputstreamreader.read() it goes to the next line until it reads the whole file. The only thing I can think of would be to read the whole file, count the number of vertices, then read it AGAIN the fill in the newly initialized array. Is there a way to dynamically allocate the data as is needed?

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• Is there command-line tool to extract typedef, structure, enumeration, variable, function from a C or C++ file?

  - by FooF

  I am desiring a command-line tool to extract a definition or declaration (typedef, structure, enumeration, variable, or function) from a C or C++ source file. Also a way to replace an existing definition/declaration would be handy (after transforming the extracted definition by a user-submitted script). Is there such generic tool available, or is some resonably close approximation of such a tool? Scriptability and ability to hook-up with user created scripts or programs is of importance here, although I am academically curious of GUI programs too. Open source solutions for Unix/Linux camp are preferred (although I am curious of Windows and OS X tools too). Primary language interests are C and C++ but more generic solution would be even better (I think we do not need super accurate parsing capabilities for finding, extracting and replacing a definition in a program source file). Sample Use Cases (extra - for the curious mind): Given deeply nested structs and variable (array) initializations of these types, suppose there is a need to change a struct definition by adding or reordering fields or rewriting the variable/array definitions in more readable format without introducing errors resulting from manual labor. This would work by extracting the old initializations, then using a script/program to write the new initializations to replace the old ones. For implementing a code browsing tool - extract a definition. Decorative code generation (e.g. logging function entries / returns). Scripted code structuring (e.g. extract this and that thing and put in different place without change - version control commit comment could document the command to perform this operation to make it evident and verifiable that nothing changed). Note about tags: More accurate tag than code-generation would be code-transformation but it does not exist.

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• Would like some modelling tips for dependent values

  - by orjan

  I'm working on a model for a simple fishing competition and I have some issues with my design. The main class for the fishing game is Capture and it looks like this: public class Capture : Entity { public virtual int Weight { get; set; } public virtual int Length { get; set; } public virtual DateTime DateForCapture { get; set; } public virtual User CapturedBy { get; set; } public virtual Species Species { get; set; } } So far there´s no problem but I'm not really sure how to model the game. Every Species is connected to a reference weight that changes from year to year The number of point for a capture is its Weight divided by the current reference weight for the species. One way to solve the problem is to connect a capture to SpeciesReferenceWeight instead of Species public class SpeciesReferenceWeight : Entity { public virtual Species Species { get; set; } public virtual int ReferenceWeight { get; set; } public virtual int Year { get; set; } } But in that way that Capture is connected to the implementation details of the game and from my point of view a capture is still a capture even if it's not included in a game. The result I'm aiming for is like: http://hornalen.net/fishbonkern/2007/ that I wrote a couple of years ago with brute force sql and no domain model. I would be very happy for all kinds of feeback on this issue.

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• Custom class deallocated as soon as the app starts.

  - by Tangrs

  Heya, I've added a class object to the nib file. All connections are made. But for some reason, the object is deallocated as soon as it's created. Here's the code: control.h: #import <Foundation/Foundation.h> @interface control : NSObject { IBOutlet UILabel *PlayerScore; } -(IBAction) addPoint: sender; -(void) dealloc; @end control.m: #import "control.h" @implementation control -(IBAction)addPoint: sender { NSLog(@"Ohhai. Didn't crash."); //Doesn't even make it to this stage. int i = [PlayerScore.text intValue]; PlayerScore.text=[NSString stringWithFormat: @"%d",++i]; } -(void) dealloc { NSLog(@"ZOMGWTF?"); [super dealloc]; } @end Here is the console log: [Session started at 2010-06-09 19:47:57 +1000.] 2010-06-09 19:47:58.771 App[91100:207] ZOMGWTF? And after I click the button which messages addPoint, of course, it crashes. 2010-06-09 19:47:59.703 App[91100:207] * -[control] performSelector:withObject:withObject:]: message sent to deallocated instance 0x3843d80 Does anyone have any ideas?

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• FileInput Help/Advice

  - by user559142

  I have a fileinput class. It has a string parameter in the constructor to load the filename supplied. However it just exits if the file doesn't exist. I would like it to output a message if the file doesn't exist - but not sure how.... Here is the class: public class FileInput extends Input { /** * Construct <code>FileInput</code> object given a file name. */ public FileInput(final String fileName) { try { scanner = new Scanner(new FileInputStream(fileName)); } catch (FileNotFoundException e) { System.err.println("File " + fileName + " could not be found."); System.exit(1); } } /** * Construct <code>FileInput</code> object given a file name. */ public FileInput(final FileInputStream fileStream) { super(fileStream); } } And its implementation: private void loadFamilyTree() { out.print("Enter file name: "); String fileName = in.nextLine(); FileInput input = new FileInput(fileName); family.load(input); input.close(); }

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• Unable to `submit()` an html form after intercepting the submit with javascript.

  - by Ross Rogers

  I'm trying to intercept the submission of a form in order to change the value of my keywords label. I have the following code: <HTML> <FORM name="searchForm" method="get" action="tmp.html" > <input type="label" name="keywords" /> <input type="button" name="submit" value="submit" onclick="formIntercept();"/> </FORM> <SCRIPT language="JavaScript"> document.searchForm.keywords.focus(); function formIntercept( ) { var f = document.forms['searchForm']; f.keywords.value = 'boo'; f.submit(); }; </SCRIPT> </HTML> When I run this in chrome and click the submit button the keywords label changes to boo, but the javascript console says: Uncaught TypeError: Property 'submit' of object <#an HtmlFormElement> is not a function. How can I submit the form with the manipulated keywords?

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• Would there be a market for this idea (cross platform VM for iPhone OS)

  - by Tzury Bar Yochay

  For a long time I wondered if the following idea worth a nickel or just a waste of time and energy. I am willing to start a project which will provide a kind of a VM for all iPxxx apps - so developed once for iPxxx can run on a Macbook, iMac, Linux, Android and windows (desktop and mobile). You get the idea, right? I want to do to the current iPhone SDK, the same as what Mono did to Microsoft .Net and perhaps a more complete set of implementation. I tend to believe that if overnight all apps on appstore become available on the android market as well that would be a mini revolution. Think about running iPad apps on every tablet that will come out to the market in the future. Wouldn't it be fantastic to all the developers, which from now on, can write once and sell everywhere? The main questions which I ask myself repeatedly is: "Is This Legal?" - I mean, say I have done this, would apple's lawyers will start sending me all kinds of nasty emails? I am willing to hear your opinion about this idea as well as if some of you willing and able to join forces and start this open source project.

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• guarantee child records either in one table or another, but not both?

  - by user151841

  I have a table with two child tables. For each record in the parent table, I want one and only one record in one of the child tables -- not one in each, not none. How to I define that? Here's the backstory. Feel free to criticize this implementation, but please answer the question above, because this isn't the only time I've encountered it: I have a database that holds data pertaining to user surveys. It was originally designed with one authentication method for starting a survey. Since then, requirements have changed, and now there are two different ways someone could sign on to start a survey. Originally I captured the authentication token in a column in the survey table. Since requirements changed, there are three other bits of data that I want to capture in authentication. So for each record in the survey table, I'm either going to have one token, or a set of three. All four of these are of different types, so my thought was, instead of having four columns where either one is going to be null, or three are going to be null ( or even worse, a bad mashup of either of those scenarios ), I would have two child tables, one for holding the single authentication token, the other for holding the three. Problem is, I don't know offhand how to define that in DDL. I'm using MySQL, so maybe there's a feature that MySQL doesn't implement that lets me do this.

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• Multiple locking task (threading)

  - by Archeg

  I need to implement the class that should perform locking mechanism in our framework. We have several threads and they are numbered 0,1,2,3.... We have a static class called ResourceHandler, that should lock these threads on given objects. The requirement is that n Lock() invokes should be realeased by m Release() invokes, where n = [0..] and m = [0..]. So no matter how many locks was performed on single object, only one Release call is enough to unlock all. Even further if o object is not locked, Release call should perform nothing. Also we need to know what objects are locked on what threads. I have this implementation: public class ResourceHandler { private readonly Dictionary<int, List<object>> _locks = new Dictionary<int, List<object>>(); public static ResourceHandler Instance {/* Singleton */} public virtual void Lock(int threadNumber, object obj) { Monitor.Enter(obj); if (!_locks.ContainsKey(threadNumber)) {_locks.Add(new List<object>());} _locks[threadNumber].Add(obj); } public virtual void Release(int threadNumber, object obj) { // Check whether we have threadN in _lock and skip if not var count = _locks[threadNumber].Count(x => x == obj); _locks[threadNumber].RemoveAll(x => x == obj); for (int i=0; i<count; i++) { Monitor.Exit(obj); } } // ..... } Actually what I am worried here about is thread-safety. I'm actually not sure, is it thread-safe or not, and it's a real pain to fix that. Am I doing the task correctly and how can I ensure that this is thread-safe?

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