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  • When is Googling it wrong?

    - by Drahcir
    I've been going through Stack Overflow for quite a bit now and noticed certain people (usually experienced programmers) frown upon Googling (researching) certain problems. Since I myself tend to use Google quite a bit to solve certain programming related issues I found certain comments rather demoralising. Now some of you may have come here trigger happy to delete this post but I needed some clarification. I usually Google things that usually syntax related that I would have never figured out on my own. For example I once wondered how to access the properties of a class that I didn't have a direct relationship to. So after a bit of research I discovered reflection and got what I wanted. Now in another scenario is learning a new language, in my case Silverlight were it differs in certain aspects of .NET compared to say ASP.NET. A few weeks ago I had no idea how to load another Silverlight page (usercontrol) and had to Google my way to the solution which I found wasn't as simple as I had imagined. In scenario three is were I myself frown up, that is just stealing a huge chunk of code to avoid doing the work yourself, for example paging a HTML table using JavaScript, where one just copies and pastes the JavasSript code without as much as trying to understand how it works. I do admit I have done this once or twice before for trivial tasks that had very little time limit and weren't all that important but most of the time still have to throw away what I found because it took too much time to adapt it and get what I wanted out of it. In the last scenario, I sometimes have a piece of code that I would be really unhappy about, as in I find it sloppy or too overcomplicated and try to look on the Internet to see other ways to tackle the same problem, let's say filtering through a table. With the knowledge I acquire I learned new coding practices that help me work more efficiently like "Do not repeat yourself" and such. Now in your opinion when do you find it wrong to use Google (or any other researching tool) to find a solution to your problem?

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  • Packages name conflicting with getters and setters?

    - by MrKishi
    Hello, folks. So, I've came across this compilation error a while ago.. As there's an easy fix and I didn't find anything relevant at the time, I eventually let it go. I just remembered it and I'm now wondering if this is really part of the language grammar (which I highly doubt) or if it's a compiler bug. I'm being purely curious about this -- it doesn't really affect development, but it would be nice to see if any of you have seen this already. package view { import flash.display.Sprite; public class Main extends Sprite { private var _view:Sprite = new Sprite(); public function Main() { this.test(); } private function test():void { trace(this.view.x, this.view.y); //1178: Attempted access of inaccessible property x through a reference with static type view:Main. //1178: Attempted access of inaccessible property y through a reference with static type view:Main. //Note that I got this due to the package name. //It runs just fine if I rename the package or getter. } public function get view():Sprite { return this._view; } } }

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  • Getting tree construction with ANTLR

    - by prosseek
    As asked and answered in http://stackoverflow.com/questions/2999755/removing-left-recursion-in-antlr , I could remove the left recursion E - E + T|T T - T * F|F F - INT | ( E ) After left recursion removal, I get the following one E - TE' E' - null | + TE' T - FT' T' - null | * FT' Then, how to make the tree construction with the modified grammar? With the input 1+2, I want to have a tree ^('+' ^(INT 1) ^(INT 2)). Or similar. grammar T; options { output=AST; language=Python; ASTLabelType=CommonTree; } start : e - e ; e : t ep - ??? ; ep : | '+' t ep - ??? ; t : f tp - ??? ; tp : | '*' f tp - ??? ; f : INT | '(' e ')' - e ; INT : '0'..'9'+ ; WS: (' '|'\n'|'\r')+ {$channel=HIDDEN;} ;

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  • CSS with Java Script

    - by Field
    I have been at this for a long time. I have a css div that is center on page. It floats on bottom. When I add content to div #menu i can not get it to shift right. I want to add full menu that float on the page. It have a live chat button coded. It just does not seem to work right #menu { background: url("grid2.gif") repeat scroll 0 0 transparent; margin:0 auto; border: 0px solid #888888; color: #FFFFFF; display: block; font-weight: bold; padding: 0px; position: fixed; align: right; bottom: 30px; width: 970px; } * html #menu { position: absolute; } #menu a:visited, #menu a { color: #000000; display: block; height: 20px; line-height: 20px; margin: 0 auto; text-align: center; text-decoration: none; } <div id="menu"><script language="JavaScript" src="/livehelp/js/status_image.php?base_url=/livehelp&l=adminlive&x=1&deptid=1&"></a></script></div>

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  • Easy way to "organize"/"render"/"generate" HTML?

    - by Rockmaninoff
    Hi all, I'm a relative newbie to web development. I know my HTML and CSS, and am getting involved with Ruby on Rails for some other projects, which has been daunting but very rewarding. Basically I'm wondering if there's a language/backbone/program/solution to eliminate the copypasta trivialities of HTML, with some caveats. Currently my website is hosted on a school server and unfortunately can't use Rails. Being a newbie I also don't really know what other technologies are available to me (or even what those technologies might be). I'm essentially looking for a way to auto-insert all of my header/sidebar/footer/menu information, and when those need to be updated, the rest of the pages get updated. Right now, I have a sidebar that is a tree of all of the pages on my website. When I add a page, not only do I need to update the sidebar, I have to update it for every page in my domain. This is really inefficient and I'm wondering if there is a better way. I imagine this is a pretty widespread problem, but searching Google turns up too many irrelevant links (design template websites, tutorials, etc.). I'd appreciate any help. Oh, and I've heard of HAML as a way to render HTML; how would it be used in this situation?

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  • why create CLSID_CaptureGraphBuilder2 instance always failed in a machine

    - by Yigang Wu
    It's a real strange issue, the machine information below is from DXDiag. There is no error reported, but create CLSID_CaptureGraphBuilder2 instance always failed in the machine. It's okay to create CLSID_FilterGraph. Before create CLSID_CaptureGraphBuilder2, I have called CoInitialize and created CLSID_FilterGraph. Only this machine has the error, what dll related with this interface or any function needed to call before to make it work? Thanks in advance. System Information Time of this report: 4/24/2010, 09:46:58 Machine name: TURION Operating System: Windows XP Home Edition (5.1, Build 2600) Service Pack 3 (2600.xpsp_sp3_qfe.100216-1510) Language: Japanese (Regional Setting: Japanese) System Manufacturer: To Be Filled By O.E.M. System Model: MS-7145 BIOS: Default System BIOS Processor: AMD Turion(tm) 64 Mobile Technology MT-30, MMX, 3DNow, ~1.6GHz Memory: 768MB RAM Page File: 376MB used, 1401MB available Windows Dir: C:\WINDOWS DirectX Version: DirectX 9.0c (4.09.0000.0904) DX Setup Parameters: Not found DxDiag Version: 5.03.2600.5512 32bit Unicode DxDiag Notes DirectX Files Tab: No problems found. Display Tab 1: No problems found. Sound Tab 1: No problems found. Sound Tab 2: No problems found. Music Tab: No problems found. Input Tab: No problems found. Network Tab: No problems found.

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  • 3D and AI basics. The foundation before the coding.

    - by Allan
    Hi, everyone. (If you have the time and patience:) I've recently made the decision to study programming seriously and I'm about to order TAOCP and Concrete Mathematics to begin my studies (please don't get caught up on this). I'm very much interested in learning and understanding how 3D works but I'm aware that if I plan to do it right there's still a long walk before I get to actually play with 3D coding. Now to the question.. (tl;dr) Excluding programming itself, what disciplines do I have to be familiar with to code 3D? What kinds of mathematics? Physics? What else? What books do you recommend on such subjects? Now read it all again but replacing "3D" with "AI". Please don't recommend computer-specific books. The question is about the foundation to be learned before using the machine. Also, if possible, please keep the list brief; I plan to order one book on each subject but no more than that for now. Excuse me for any English mistakes, it's not my first language. Thank you.

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  • jQuery draggable removing without changing position of other elements

    - by Yurish
    Hi! I am building a page layout configuration system on jQuery. So everyone, who is using my website can make it personal by moving elements on webpage. But, I have a problem. Every element on my page is a draggable div with option to be removed from page if necessary. When user wants to remove an element, he clicks on inner div and the following function is called: <script language="javascript"> $(function() { $('.close').click(function(){ $(this).parent().hide(); }); }); </script> <div class="main"><div class="close"></div></div> When user wants to add an element on page, he clicks on link and followinf function is called: function addNewWidget(page_name, size){ var page = $('#'+page_name); var closeDiv = $(document.createElement("div")).attr("class", "close").html('X'); closeDiv.click(function(){ $(this).parent().hide(); }); var div = $(document.createElement("div")) div.attr("class", "drag"); div.appendTo(page); closeDiv.appendTo(div); div.draggable({ containment: "#page", scroll: false, grid: [200, 200] }); div.css("top:0; left:0"); div.addClass(size); div.addClass('widget'); } Everything works fine, but when element is removed, other elements, which were on page are moving up. It is because of element positioning in the code. These divs in the code are before div, which was removed, and their absolute top is changed by -heghtOfRemovedElement Is there any way to prevent other elements from moving up?

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  • java array pass by reference does not work?

    - by stdnoit
    guys i thought almost all language including java pass array into function as reference (modifiable) but somehow it does not work here. and the testArray is still 1,2,3 with size of 3 strange enough, when if i change result[i] = 2 to a[1] =2; it work . it did pass by reference what is wrong with this code? at the end, i had a = result; (which update the a). did result get removed from stack. that is why a still get to the original a ? i am confused. thanks class Test { public static void main(String[] args) { int[] testArray = {1,2,3}; equalize(testArray, 6); System.out.println("test Array size :" + testArray.length); for(int i = 0; i < testArray.length; i++) System.out.println(testArray[i]); } public static void equalize(int[] a, int biggerSize) { if(a.length > biggerSize) throw new Error("Array size bigger than biggerSize"); int[] result = new int[biggerSize]; // System.arraycopy(a, 0, result, 0, a.length); // int array default value should be 0 for(int i = 0; i < biggerSize; i++) result[i] = 2; a = result; } }

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  • How to have table span the entire height?

    - by Yogendra
    Hi All, I have a html table and I am trying to have it span the entire page height. For some reason I am not able to get this to work. I have set the html, body and table height to be 100%, but the table still does not occupy the entire 100%. Heres the code. It is very basic because I am just trying to have the table occupy the entire height. <%@ Page Language="C#" AutoEventWireup="true" CodeBehind="WebForm1.aspx.cs" Inherits="WebApplication1.WebForm1" %> <style type="text/css"> body,html { margin:0; padding:0; height:100%; } </style> <table border="2" cellpadding="0" cellspacing="0" style="height:100%; width:100%" > <tr> <td>ABCD</td> </tr> </table> </form> I tried for couple of hours and I could not get it to work. Any help is really appreciated.

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  • move jQuery code to a function

    - by GSTAR
    I have the following jQuery code: $('.show-additional-link').click(function(){ $(this).parent().next().slideDown(); $(this).hide(); return false; }); HTML: <div class="row"> <label for="native_language">Select</label> <select name="native_language" id="native_language"> <option value="">Any</option> <option value="1">English</option> </select> <a class="show-additional-link" href="#">Select Additional Languages</a> </div> <div id="additional-languages" style="display: none;"> <a class="hide-additional-link" href="#">[hide]</a> <div class="row"> <!-- additional language checkboxes --> </div> </div> I would like to move the contents of my jQuery code (within the 'click' function) in to a separate function, as I will need to call it again on page load (after the form is submitted, so that the DIV is shown again automatically). I'm having trouble with this - can anyone help?

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  • Is it getting to be time for C# to support compile-time macros?

    - by Robert Rossney
    Thus far, Microsoft's C# team has resisted adding formal compile-time macro capabilities to the language. There are aspects of programming with WPF that seem (to me, at least) to be creating some compelling use cases for macros. Dependency properties, for instance. It would be so nice to just be able to do something like this: [DependencyProperty] public string Foo { get; set; } and have the body of the Foo property and the static FooProperty property be generated automatically at compile time. Or, for another example an attribute like this: [NotifyPropertyChanged] public string Foo { get; set; } that would make the currently-nonexistent preprocessor produce this: private string _Foo; public string Foo { get { return _Foo; } set { _Foo = value; OnPropertyChanged("Foo"); } } You can implement change notification with PostSharp, and really, maybe PostSharp is a better answer to the question. I really don't know. Assuming that you've thought about this more than I have, which if you've thought about it at all you probably have, what do you think? (This is clearly a community wiki question and I've marked it accordingly.)

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  • What Are The Ways to Devide Text in Multi-Column? Need an Overview of Possibilities.

    - by Sam
    Hi folks, From source1 and source2 i gather that IE9 will NOT support multi-column css3!! Since it is still the most popular browser (another thing i cannot understand), i am left but no other choice than to use Programming Power to make multi-columns work. Now, I use three divs that float to left, and which are manually filled with text. Please don't laugh i know its stupid! But I would wish to not to have to worry about the columns and just have a one piece of (un-interrupted) text which all goes into only 1 div, and then have a program smart enough to split it up into X equally wide columns. Question: before i start reinvent the wheel, what methods of programming power have you known that tackle this elegantly? Please suggest your best working multi-column layout sources so I can evaluate which option is the best (I will update the below table). Exploring all possibilities 2011 and further, to enable multi column text user experience: Language Author SourceCodeUsage WorksOnAllMajorBrowser? ================================================================================= html manual labour put text manually in separate left-floating divs "Y" // Upside: control! Downside: few changes necessitates to reflow 3 divs manually! CSS3 w3c css3.info/preview/multi-column-layout/ "N" // {-moz-column-count: 3; -webkit-column-count: 3; } Thats all! javascript a list apart will add url soon ? // php ? ? ? //

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  • Generating a python file

    - by fema
    Hi! I'm havin issues with python (imo python itself is an issue). I have a txt file, it contains a custom language and I have to translate it to a working python code. The input: import sys n = int(sys.argv[1]) ;;print "Beginning of the program!" LOOP i in range(1,n) {print "The number:";;print i} BRANCH n < 5 {print n ;;print "less than 5"} The wanted output looks exactly like this: import sys n = int(sys.argv[1]) print "Beginning of the program!" for i in range(1,n) : print "The number:" print i if n < 5 : print n print "less than 5" The name of the input file is read from parameter. The out file is out.py. In case of a wrong parameter, it gives an error message. The ;; means a new line. When I tried to do it, I made an array, I read all the lines into it, split by " ". Then I wanted to strip it from the marks I don't need. I made 2 loops, one for the lines, one for the words. So then I started to replace the things. Everything went fine until it came to the } mark. It finds it, but it can not replace or strip it. I have no more idea what to do. Could someone help me, please? Thanks in advance!

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  • Centralizing Messagebox handling for application

    - by DRapp
    I'm wondering how others deal with trying to centralize MessageBox function calling. Instead of having long text embedded all over the place in code, in the past (non .net language), I would put system and application base "messagebox" type of messages into a database file which would be "burned" into the executable, much like a resource file in .Net. When a prompting condition would arise, I would just do call something like MBAnswer = MyApplication.CallMsgBox( IDUserCantDoThat ) then check the MBAnswer upon return, such as a yes/no/cancel or whatever. In the database table, I would have things like what the messagebox title would be, the buttons that would be shown, the actual message, a special flag that automatically tacked on a subsequent standard comment like "Please contact help desk if this happens.". The function would call the messagebox with all applicable settings and just return back the answer. The big benefits of this was, one location to have all the "context" of messages, and via constants, easier to read what message was going to be presented to the user. Does anyone have a similar system in .Net to do a similar approach, or is this just a bad idea in the .Net environment.

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  • Flowcharting functional programming languages

    - by Sadface
    Flowcharting. This ancient old practice that's been in use for over 1000 years now, being forced upon us poor students, without any usefulness (or so do I think). It might work well with imperative, sequentially running languages, but what about my beloved functional programming? Sadly, I'm forced to create a flow chart for my programm (that is written in Haskell). I imagine it being easy for something like this: main :: IO () main = do someInput <- getLine let upped = map toUpper someInput putStrLn upped Which is just 3 sequenced steps, fetching data, uppercasing it, outputting it. Things look worse this time: main :: IO () main = do someInput <- fmap toUpper getLine putStrLn someInput Or like this: main :: IO () main = interact (map toUpper) Okay, that was IO, you can handle that like an imperative language. What about pure functions? An actual example: onlyMatching :: String -> [FilePath] -> [FilePath] onlyMatching ext = filter f where f name = lower ('.' : ext) == (lower . takeExtension $ name) lower = map toLower How would you flowchart that last one?

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  • PHP loop hanging/interspersed/threaded through HTML

    - by sandyv
    I can't figure out how to say what I'm talking about which is a big part of why I'm stuck. In PHP I often see code like this html <?php language construct that uses brackets { some code; ?> more html <?php some more code; } ?> rest of html Is there any name for this? Having seen this lead me to try it out so here is a concrete example whose behavior doesn't make sense to me <div id="content"> <ul id="nav"> <?php $path = 'content'; $dir = dir($path); while(false !== ($file = $dir->read())) { if(preg_match('/.+\.txt/i', $file)) { echo "<li>$file</li>"; ?> </ul> <?php echo file_get_contents($path . '/' . $file); } } ?> </div> Which outputs roughly <div><ul><li></li></ul><li></li>...</div> instead of <div><ul><li></li>...</ul></div> which is what I thought would happen and what I want to happen.

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  • How do I alias the scala setter method 'myvar_$eq(myval)' to something more pleasing when in java?

    - by feydr
    I've been converting some code from java to scala lately trying to teach myself the language. Suppose we have this scala class: class Person() { var name:String = "joebob" } Now I want to access it from java so I can't use dot-notation like I would if I was in scala. So I can get my var's contents by issuing: person = Person.new(); System.out.println(person.name()); and set it via: person = Person.new(); person.name_$eq("sallysue"); System.out.println(person.name()); This holds true cause our Person Class looks like this in javap: Compiled from "Person.scala" public class Person extends java.lang.Object implements scala.ScalaObject{ public Person(); public void name_$eq(java.lang.String); public java.lang.String name(); public int $tag() throws java.rmi.RemoteException; } Yes, I could write my own getters/setters but I hate filling classes up with that and it doesn't make a ton of sense considering I already have them -- I just want to alias the _$eq method better. (This actually gets worse when you are dealing with stuff like antlr because then you have to escape it and it ends up looking like person.name_\$eq("newname"); Note: I'd much rather have to put up with this rather than fill my classes with more setter methods. So what would you do in this situation?

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  • Question about CALL statement

    - by Bruce
    I have the following code in VC++ Func5(){ StackWalk(); } Func4{ Func5();} I am a Beginner in x86 Assembly Language. I am trying to find out the starting address of Func5(). I get the Func5()'s return address from its stack frame. Now before this return address there should be a CALL statement. So I extract out the bytes before the return address. Sometimes it's a near call like E8 ff ff ff d8. So for this statement I subtract the offset 0x28 from the function's return address to get Func5()'s base address (where it resides in memory). The problem is I don't know how to calculate this for a indirect NEAR call. I have been trying to find out how to do it for some time now. So I have extracted out the first 5 bytes before the return address and they are ff 75 08 ff d2 I think this stands for CALL ECX (ff d2) but I am not sure. I will be very grateful if someone can tell me what kind of CALL statement this is and how I can calculate the function's base address from this kind of call.

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  • Computing, storing, and retrieving values to and from an N-Dimensional matrix

    - by Adam S
    This question is probably quite different from what you are used to reading here - I hope it can provide a fun challenge. Essentially I have an algorithm that uses 5(or more) variables to compute a single value, called outcome. Now I have to implement this algorithm on an embedded device which has no memory limitations, but has very harsh processing constraints. Because of this, I would like to run a calculation engine which computes outcome for, say, 20 different values of each variable and stores this information in a file. You may think of this as a 5(or more)-dimensional matrix or 5(or more)-dimensional array, each dimension being 20 entries long. In any modern language, filling this array is as simple as having 5(or more) nested for loops. The tricky part is that I need to dump these values into a file that can then be placed onto the embedded device so that the device can use it as a lookup table. The questions now, are: What format(s) might be acceptable for storing the data? What programs (MATLAB, C#, etc) might be best suited to compute the data? C# must be used to import the data on the device - is this possible given your answer to #1?

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  • Scroll table upwards or downwards using up and down button

    - by Psinyee
    I want to create a banner scrolling function for my homepage. I am not too sure of which programming language to use here. I want to code something similar to: http://www.squidfaceandthemeddler.com/. But I want the footer to remain at the same position while the user scroll the table. Is it possible to get that result? I have create a simple tables and 2 images for the user to click on here is my code for the tables: <div id="banner" style="height:750px; width:600px; overflow:scroll;" > <table width="750px" height="600px"> <tr> <td><a href="sale_1.php"><img src="banner1.png"/></a></td> </tr> </table> <table width="750px" height="600px"> <tr> <td><a href="sale_2.php"><img src="banner2.png"/></a></td> </tr> </table> <table width="750px" height="600px"> <tr> <td><a href="sale_3.php"><img src="banner3.png"/></a></td> </tr> </table> </div> and this is the upwards and downwards button for the scrolling: <table width="750px" height="30px"> <tr> <td align="right"><img src="images/up_arrow.png"/><img src="images/down_arrow.png"/></td> </tr> </table>

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  • How to perform a Depth First Search iteratively using async/parallel processing?

    - by Prabhu
    Here is a method that does a DFS search and returns a list of all items given a top level item id. How could I modify this to take advantage of parallel processing? Currently, the call to get the sub items is made one by one for each item in the stack. It would be nice if I could get the sub items for multiple items in the stack at the same time, and populate my return list faster. How could I do this (either using async/await or TPL, or anything else) in a thread safe manner? private async Task<IList<Item>> GetItemsAsync(string topItemId) { var items = new List<Item>(); var topItem = await GetItemAsync(topItemId); Stack<Item> stack = new Stack<Item>(); stack.Push(topItem); while (stack.Count > 0) { var item = stack.Pop(); items.Add(item); var subItems = await GetSubItemsAsync(item.SubId); foreach (var subItem in subItems) { stack.Push(subItem); } } return items; } EDIT: I was thinking of something along these lines, but it's not coming together: var tasks = stack.Select(async item => { items.Add(item); var subItems = await GetSubItemsAsync(item.SubId); foreach (var subItem in subItems) { stack.Push(subItem); } }).ToList(); if (tasks.Any()) await Task.WhenAll(tasks); UPDATE: If I wanted to chunk the tasks, would something like this work? foreach (var batch in items.BatchesOf(100)) { var tasks = batch.Select(async item => { await DoSomething(item); }).ToList(); if (tasks.Any()) { await Task.WhenAll(tasks); } } The language I'm using is C#.

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  • simple wordpress plugin with some html and javascript

    - by h_a86
    I have an html page which i have to convert to wordpress plugin. my code is simple html and javascript <html> <head> <title>Calculate</title> <script language="javascript"> function addNumbers() { var val1 = parseInt(document.getElementById("value1").value); var val2 = parseInt(document.getElementById("value2").value); var ansD = document.getElementById("answer"); ansD.value = val1 + val2; } </script> </head> <body> <input type="text" id="value1" name="value1" value="1"/> <input type="text" id="value2" name="value2" value="2"/> <input type="button" name="Sumbit" value="Click here" onclick="javascript:addNumbers()"/> <input type="text" id="answer" name="answer" value=""/> </body> </html> I know basic plugin writing skills such as <?php /* Plugin Name: Coding friends hello world Plugin URI: http://www.codingfriends.com/ Description: Outputs hello world Version: 0.1 Author: Genux Author URI: http://www.codingfriends.com License: GPL2 */ function codingfriends_helloworld() { //put you form here and javascript here } add_action('get_header', 'codingfriends_helloworld'); ?> Thanks in advance

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  • javascript not firing when asp.net user control loads

    - by Jawahar
    I am trying to fire a Javascript call when an ASP.net user control to an aspx page. The Web site allows users to add user controls to a page (similar to adding a widget etc to a page like google widgets). But when the control is added the javascript does not fire, only if the page is refreshed will it fire the javascript. IF the next time the website is accessd and the controlis still there the javascript fires too. Do I need to use the RegisterClientScript method to register the call (setAutoTimer()) on the control load or OnPreRender event. In the User control I have this at the start of the ascx file: <script language="javascript" type="text/javascript"> $(document).ready(function () { if ($("#alarmList").length) { setAutoTimer(); getData(); } }); function setAutoTimer() { setInterval(getData, 10000); } function getData() { $.ajax({ type: "POST", url: "Service.asmx/getListData data: "{'inverterid': '" + "1'}", contentType: "application/json; charset=utf-8", dataType: "json", success: function (msg) { AjaxSucceeded(msg); }, error: AjaxFailed }); } function AjaxSucceeded(result) { $("#alarmList").empty(); $("#alarmsListTemplate").tmpl(result.d) .appendTo("#alarmList"); } function AjaxFailed(result) { alert(result.status + ' ' + result.statusText); } </script>

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  • Immutability and shared references - how to reconcile?

    - by davetron5000
    Consider this simplified application domain: Criminal Investigative database Person is anyone involved in an investigation Report is a bit of info that is part of an investigation A Report references a primary Person (the subject of an investigation) A Report has accomplices who are secondarily related (and could certainly be primary in other investigations or reports These classes have ids that are used to store them in a database, since their info can change over time (e.g. we might find new aliases for a person, or add persons of interest to a report) If these are stored in some sort of database and I wish to use immutable objects, there seems to be an issue regarding state and referencing. Supposing that I change some meta-data about a Person. Since my Person objects immutable, I might have some code like: class Person( val id:UUID, val aliases:List[String], val reports:List[Report]) { def addAlias(name:String) = new Person(id,name :: aliases,reports) } So that my Person with a new alias becomes a new object, also immutable. If a Report refers to that person, but the alias was changed elsewhere in the system, my Report now refers to the "old" person, i.e. the person without the new alias. Similarly, I might have: class Report(val id:UUID, val content:String) { /** Adding more info to our report */ def updateContent(newContent:String) = new Report(id,newContent) } Since these objects don't know who refers to them, it's not clear to me how to let all the "referrers" know that there is a new object available representing the most recent state. This could be done by having all objects "refresh" from a central data store and all operations that create new, updated, objects store to the central data store, but this feels like a cheesy reimplementation of the underlying language's referencing. i.e. it would be more clear to just make these "secondary storable objects" mutable. So, if I add an alias to a Person, all referrers see the new value without doing anything. How is this dealt with when we want to avoid mutability, or is this a case where immutability is not helpful?

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