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Manifesto for Integrated Development Environments

- by Hugo S Ferreira

Have you recently take a peek at Coda, or Espresso, or Textmate? Or even Google Chrome's Developer Tools? They are well designed, intuitive, interface rich, and extensible. But Coda, Espresso or Textmate, among several, are text editors, not IDEs. On the other side, VIM and Emacs live in the last century, and Eclipse is an overbloated platform. This is more like an outcry for a decent, common infrastructure for REAL IDEs. But there's some questions attached: (i) what features are needed for such a product and (ii) what products are out there that could fullfil this need, and what are they missing. So here's my draft for a manifesto: Manifesto for Integrated Development Environments: We favor interactivity and productivity over syntax and tools. We favor inline, contextual documentation over man and html files. We favor high-definition, graphic-capable color screens over 80x25 character terminals. We favor the use of advanced input schemas over unintuitive keyboard shortcuts. We favor a common, extensible and customizable infrastructure over unmaintained chaintools. We know the difference between search&replace and refactoring. We know the difference between integrated debugging support over a terminal window. We know the difference between semantic-aware code-completion over dumb textual templates. We favor the usage of standards like (E)BNF.

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Access values of a group of select boxes in php from post

- by 2Real

Hi, I'm new to PHP, and I can't figure this out. I'm trying to figure out how to access the data of a group of select boxes I have defined in my HTML code. I tried grouping them as a class, but that doesn't seem to work... maybe I was doing it wrong. This is the following HTML code. <form action="" method="post"> <select class="foo"> <option> 1.....100</option> </select> <select class="foo"> <option> 1.... 500></option> </select> <input type="submit" value="Submit" name="submit"/> </form> I essentially want to group all my select boxes and access all the values in my PHP code. Thanks

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How to test jQuery Ajax with php?

- by vladv

I tried to just send some information to a php file using Jquery Ajax. I wanted to send some info to the php file every time a click is made. <script> $(document).ready(function() { $('#checkbox').click(function() { $.ajax({type : "POST", url : "test.php", data : "ffs=somedata&ffs2=somedata2", succes : function() { alert("something"); } }); }); }); </script> <body> <input type = "checkbox" name = "checkbox" id = "checkbox"> </body> The php file looks like this: <?php echo $_POST['ffs']; ?> Now, I see the POST going, (using firebug). I get no errors, but nothing happens in the php file. Also success is never reached, so no alert is triggered. What should I do in the php file so that I can trigger success and also see the sent info?

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[IceFaces] Why are validators of unchanged components called?

- by bitschnau

I have a IceFaces-form and several input fields. Let's say I have this: <ice:selectOneMenu id="accountMenu" value="#{accountController.account.aId}" validator="#{accountController.validateAccount}"> <f:selectItems id="accountItems" value="#{accountController.accountItems}" /> </ice:selectOneMenu> and this: <ice:selectOneMenu id="costumerMenu" value="#{customerController.customer.cId}" validator="#{customerController.validateCustomer"> <f:selectItems id="customerItems" value="#{customerController.customerItems}" /> </ice:selectOneMenu> If I change one value, the respective validator is called, what is fine. But also the other validator is called, which is not fine, because the user get's an irritating message to insert a value to a field he maybe was just going to pay attention to. It's like poking the user with a stick to "Hurry up now!". BAD! I thought the attribute "partialSubmit" is controlling this behaviour, so only the one DOM-part is submitted, which is affected by the user interaction, but if I declare the both components to be partially submitted, nothing changes. Still both validators are called if one component value is changed. How can I prevent the whole form from being validated until it is submitted completely?

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Why can't I handle a KeyboardInterrupt in python?

- by Josh

I'm writing python 2.6.6 code on windows that looks like this: try: dostuff() except KeyboardInterrupt: print "Interrupted!" except: print "Some other exception?" finally: print "cleaning up...." print "done." dostuff() is a function that loops forever, reading a line at a time from an input stream and acting on it. I want to be able to stop it and clean up when I hit ctrl-c. What's happening instead is that the code under except KeyboardInterrupt: isn't running at all. The only thing that gets printed is "cleaning up...", and then a traceback is printed that looks like this: Traceback (most recent call last): File "filename.py", line 119, in <module> print 'cleaning up...' KeyboardInterrupt So, exception handling code is NOT running, and the traceback claims that a KeyboardInterrupt occurred during the finally clause, which doesn't make sense because hitting ctrl-c is what caused that part to run in the first place! Even the generic except: clause isn't running. EDIT: Based on the comments, I replaced the contents of the try: block with sys.stdin.read(). The problem still occurs exactly as described, with the first line of the finally: block running and then printing the same traceback.

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Ajax: strange behaviour while checking a textfield

- by ilnur777

I have a registration form with checking the available name for username field through ajax. Inputing a username into username field and pushing the "Check!" button, the script sends value to php script. Then php script replaces the username field with the username field + style like this: <input type="text" name="login" value="'.$_GET["user"].'" style="width:205; height:22; border-width:1; border-color:red; border-style:solid; background-color:rgb(255,232,230);"> So when replacing the username field in the form with its equivalent from php script and then submitting a form, it is then get to script on the page that checks whether the username field is empty or not. And it returns an error that it is empty, though after checking through ajax the username field it has value. I don't understand why it gets to empty field checking script, having the same field name and having value?

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Open source real life license examples: yours or others

- by donpal

I'm aware of the usual list of open source licenses, so I'm not even going to list it here. What I'd like to ask is about your open source projects (whether out or planned for the future), and why you're planning to choose a certain license over the other. Basically say I went for X license because I wanted Y and that other license didn't provide it for me. I understand that the language itself can make a difference in the choice of license: interpreted languages like PHP vs. compiled languages like Java. I'm mostly interested in hearing about PHP projects, but of course additional insights are welcome. You may even have chosen that particular language for a licensing reason. Ideally I want to hear answers from people who were involved in the actual project (i.e. your own project), because that usually means you've put some thought into the license yourself and understand the implications of that license. But examples of existing projects that aren't your own are OK. Please just say why you think that license was good/bad for them. But first-hand experience is preferred. Looking forward to hearing some informative input.

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XSLT for-each from query results

- by Ben Record

I've been on a hunt for a while trying to find a solution to this but I cannot find anywhere that addresses this problem. I'm running a SQL query through XSLT which will return three rows. Here is the query: <query name="OrderedProductNames" rowElementName ="OrderedItem"> <sql> <![CDATA[ select OrderedProductName, Quantity from Orders_ShoppingCart where OrderNumber = 101689 // Hard coded order number for testing purposes. ]]> </sql> </query> Ideally, I would like to iterate through each row returned and do a choose when which is tested on a variable from the current row being inspected in the for-each loop, but I am not entirely sure thhis is possible. My secondary thought would be to use the for-each loop as a way to inject hidden HTML input elements with the values I would need, then I could write a javascript function to complete what I'm trying to do. Any suggestion on how I would go about completing either task would be greatly appreciated.

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On Disk Substring index

- by emeryc

I have a file (fasta file to be specific) that I would like to index, so that I can quickly locate any substring within the file and then find the location within the original fasta file. This would be easy to do in many cases, using a Trie or substring array, unfortunately the strings I need to index are 800+ MBs which means that doing them in memory in unacceptable, so I'm looking for a reasonable way to create this index on disk, with minimal memory usage. (edit for clarification) I am only interested in the headers of proteins, so for the largest database I'm interested in, this is about 800 MBs of text. I would like to be able to find an exact substring within O(N) time based on the input string. This must be useable on 32 bit machines as it will be shipped to random people, who are not expected to have 64 bit machines. I want to be able to index against any word break within a line, to the end of the line (though lines can be several MBs long). Hopefully this clarifies what is needed and why the current solutions given are not illuminating. I should also add that this needs to be done from within java, and must be done on client computers on various operating systems, so I can't use any OS Specific solution, and it must be a programatic solution.

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Communication between lexer and parser

- by FredOverflow

Every time I write a simple lexer and parser, I stumble upon the same question: how should the lexer and the parser communicate? I see four different approaches: The lexer eagerly converts the entire input string into a vector of tokens. Once this is done, the vector is fed to the parser which converts it into a tree. This is by far the simplest solution to implement, but since all tokens are stored in memory, it wastes a lot of space. Each time the lexer finds a token, it invokes a function on the parser, passing the current token. In my experience, this only works if the parser can naturally be implemented as a state machine like LALR parsers. By contrast, I don't think it would work at all for recursive descent parsers. Each time the parser needs a token, it asks the lexer for the next one. This is very easy to implement in C# due to the yield keyword, but quite hard in C++ which doesn't have it. The lexer and parser communicate through an asynchronous queue. This is commonly known under the title "producer/consumer", and it should simplify the communication between the lexer and the parser a lot. Does it also outperform the other solutions on multicores? Or is lexing too trivial? Is my analysis sound? Are there other approaches I haven't thought of? What is used in real-world compilers? It would be really cool if compiler writers like Eric Lippert could shed some light on this issue.

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Best Way to View Generated Source of Webpage?

- by jeremy

I'm looking for a tool that will give me the proper generated source including DOM changes made by AJAX requests for input into W3's validator. I've tried the following methods: Web Developer Toolbar - Generates invalid source according to the doc-type (e.g. it removes the self closing portion of tags). Loses the doctype portion of the page. Firebug - Fixes potential flaws in the source (e.g. unclosed tags). Also loses doctype portion of tags and injects the console which itself is invalid HTML. IE Developer Toolbar - Generates invalid source according to the doc-type (e.g. it makes all tags uppercase, against XHTML spec). Highlight + View Selection Source - Frequently difficult to get the entire page, also excludes doc-type. Is there any program or add-on out there that will give me the exact current version of the source, without fixing or changing it in some way? So far, Firebug seems the best, but I worry it may fix some of my mistakes. Solution It turns out there is no exact solution to what I wanted as Justin explained. The best solution seems to be to validate the source inside of Firebug's console, even though it will contain some errors caused by Firebug. I'd also like to thank Forgotten Semicolon for explaining why "View Generated Source" doesn't match the actual source. If I could mark 2 best answers, I would.

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Real Time Progress Indicator

- by jignesh

I am trying to get the real time progress indicator. In the code snippet below,i am trying to set the width of DIV on the basis of the Number of Items retrieve from the Web Service Call Back Function. for (i = 0; i < data.length; i++) { table += '<tr>'; table += '<td>' + data[i].ItemId + '</td>'; table += '<td></td>'; table += '<td>' + data[i].Name + '</td>'; table += '<td>' + data[i].Unit + '</td>'; table += '<td><input type=text value=' + data[i].Quantity + '></td>'; table += '<td>' + data[i].Brands + '</td>'; table += '<td><img border=0 src=../images/Delete_icon.gif></td>'; table += '</tr>'; $('#divProgressIndicator').width((100 * (i / data.length)) + '%'); } As shown in the code above,after the for loop is executed i only see the divProgressIndicator filled with the background color and I am not able to see the progress. Can I achieve this in a for loop or i need to use some thing else. Regards

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Have Microsoft changed how ASP.NET MVC deals with duplicate action method names?

- by Jason Evans

I might be missing something here, but in ASP.NET MVC 4, I can't get the following to work. Given the following controller: public class HomeController : Controller { public ActionResult Index() { return View(); } [HttpPost] public ActionResult Index(string order1, string order2) { return null; } } and it's view: @{ ViewBag.Title = "Home"; } @using (Html.BeginForm()) { @Html.TextBox("order1")<br /> @Html.TextBox("order2") <input type="submit" value="Save"/> } When start the app, all I get is this: The current request for action 'Index' on controller type 'HomeController' is ambiguous between the following action methods: System.Web.Mvc.ActionResult Index() on type ViewData.Controllers.HomeController System.Web.Mvc.ActionResult Index(System.String, System.String) on type ViewData.Controllers.HomeController Now, in ASP.NET MVC 3 the above works fine, I just tried it, so what's changed in ASP.NET MVC 4 to break this? OK there could be a chance that I'm doing something silly here, and not noticing it. EDIT: I notice that in the MVC 4 app, the Global.asax.cs file did not contain this: public static void RegisterRoutes(RouteCollection routes) { routes.IgnoreRoute("{resource}.axd/{*pathInfo}"); routes.MapRoute( "Default", // Route name "{controller}/{action}/{id}", // URL with parameters new { controller = "Home", action = "Index", id = UrlParameter.Optional } // Parameter defaults ); } which the MVC 3 app does, by default. So I added the above to the MVC 4 app but it fails with the same error. Note that the MVC 3 app does work fine with the above route. I'm passing the "order" data via the Request.Form. EDIT: In the file RouteConfig.cs I can see RegisterRoutes is executed, with the following default route: routes.MapRoute( name: "Default", url: "{controller}/{action}/{id}", defaults: new { controller = "Home", action = "Index", id = UrlParameter.Optional }); I still get the original error, regards ambiguity between which Index() method to call.

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Looking for Go equivalent of scanf.

- by Stephen Hsu

I'm looking for the Go equivalent of scanf(). I tried with following code: 1 package main 2 3 import ( 4 "scanner" 5 "os" 6 "fmt" 7 ) 8 9 func main() { 10 var s scanner.Scanner 11 s.Init(os.Stdin) 12 s.Mode = scanner.ScanInts 13 tok := s.Scan() 14 for tok != scanner.EOF { 15 fmt.Printf("%d ", tok) 16 tok = s.Scan() 17 } 18 fmt.Println() 19 } I run it with input from a text with a line of integers. But it always output -3 -3 ... And how to scan a line composed of a string and some integers? Changing the mode whenever encounter a new data type? The Package documentation: Package scanner A general-purpose scanner for UTF-8 encoded text. But it seems that the scanner is not for general use. Updated code: func main() { n := scanf() fmt.Println(n) fmt.Println(len(n)) } func scanf() []int { nums := new(vector.IntVector) reader := bufio.NewReader(os.Stdin) str, err := reader.ReadString('\n') for err != os.EOF { fields := strings.Fields(str) for _, f := range fields { i, _ := strconv.Atoi(f) nums.Push(i) } str, err = reader.ReadString('\n') } r := make([]int, nums.Len()) for i := 0; i < nums.Len(); i++ { r[i] = nums.At(i) } return r }

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Auto scale and rotate images

- by Dave Jarvis

Given: two images of the same subject matter; the images have the same resolution, colour depth, and file format; the images differ in size and rotation; and two lists of (x, y) co-ordinates that correlate the images. I would like to know: How do you transform the larger image so that it visually aligns to the second image? (Optional.) What are the minimum number of points needed to get an accurate transformation? (Optional.) How far apart do the points need to be to get an accurate transformation? The transformation would need to rotate, scale, and possibly shear the larger image. Essentially, I want to create (or find) a program that does the following: Input two images (e.g., TIFFs). Click several anchor points on the small image. Click the several corresponding anchor points on the large image. Transform the large image such that it maps to the small image by aligning the anchor points. This would help align pictures of the same stellar object. (For example, a hand-drawn picture from 1855 mapped to a photograph taken by Hubble in 2000.) Many thanks in advance for any algorithms (preferably Java or similar pseudo-code), ideas or links to related open-source software packages.

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DOMAIN REDIRECT PROBLEM WITH JQUERY / JAVASCRIPT

- by GiovanniDema

Hi guys, first time here. I got a strange problem. I have a fullscreen image scaler javascript (as GOTOCHINA website) that works very well on my website. Then, I purchased a domain redirect pointing on my website and when redirecting suddenly internet explorer 7 and internet explorer 8 give me this error Messagge: is not a valid argument. Line: 34 Char: 17 URI: http://*****/scaler.js The script is var db=document.body; var imag=document.getElementById('wallpaper'); var dbsize={}; var imgsrc=imag.src; var keyStop=function(e){ var e=window.event||e||{}; var tag=e.target.tagName.toLowerCase(); if(tag!='textarea'&&!(tag=='input'&&(e.target.type=='text'||e.target.type=='password'))){ if(e.keyCode==32||e.keyCode==39||e.keyCode==40){ if(e.preventDefault)e.preventDefault(); else e.returnValue=false; } } } if(this.addEventListener)window.addEventListener('keydown',keyStop,false); else window.attachEvent('onkeydown',keyStop); setInterval(function(){ window.scrollTo(0,0); if(imag.complete){ if(db.clientWidth!=dbsize.w||db.clientHeight!=dbsize.h||imag.src!=imgsrc){ imgsrc=imag.src; var dbsizew=db.clientWidth; var dbsizeh=db.clientHeight; var newwidth=Math.round(dbsizeh*(imag.offsetWidth/imag.offsetHeight)); var nextvar=dbsizewnewwidth?dbsizew:newwidth; imag.style.width=nextvar+'px'; } } },300); In other words when i open the official website everything's working correctly. When i open redirect domain pointing on official website... the previous error appears. The line is exactly this - imag.style.width=nextvar+'px'; Thanks in advance Giovanni

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How to convert between different currencies?

- by sil3nt

Hey there, this is part of a question i got in class, im at the final stretch but this has become a major problem. In it im given a certain value which is called the "gold value" and it is 40.5, this value changes in input. and i have these constants const int RUBIES_PER_DIAMOND = 5; // relative values. * const int EMERALDS_PER_RUBY = 2; const int GOLDS_PER_EMERALDS = 5; const int SILVERS_PER_GOLD = 4; const int COPPERS_PER_SILVER = 5; const int DIAMOND_VALUE = 50; // gold values. * const int RUBY_VALUE = 10; const int EMERALD_VALUE = 5; const float SILVER_VALUE = 0.25; const float COPPER_VALUE = 0.05; which means that basically for every diamond there are 5 rubies, and for every ruby there are 2 emeralds. So on and so forth. and the "gold value" for every diamond for example is 50 (diamond value = 50) this is how much one diamond is worth in golds. my problem is converting 40.5 into these diamonds and ruby values. I know the answer is 4rubies and 2silvers but how do i write the algorithm for this so that it gives the best estimate for every goldvalue that comes along?? please help!, im at my wits end

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How to customize the printing while using Window.print ?

- by Holicreature

i want to print a invoice and i use a print.css by media=print and when i change the current stylesheet to print.css i could able to view what i should be printing without the titles and content left aligned. But still while i'm printing there is space in the top and left and its taking up whole a4 sheet and also the whole width of the page.. But i've defined a body width of just 550 px. While i view to print preview, it takes the whole width instead of taking up 1/3 of the width.. My print.css is body { width:550px; height:450px; color:#000000; margin:0; padding:0; word-spacing:1.1pt; font-family : "Times New Roman", Times, serif; font-size : 10px; text-align:left; } a { visibility :hidden; display : none; } input{ display : none; } table { margin: 1px; text-align:left; } #list,#head,#cont,#fotter,#oth,#links,#name,li,ul,ol { display : none; } I'm printing through browser using window.print, so is there any special configuration i need to do...?

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reading newlines with FORMAT statement

- by peter.murray.rust

I'm writing a preprocessor and postprocessor for Fortran input and output using FORMAT-like statements (there are reasons not to use a FORTRAN library). I want to treat the new line ("/") character correctly. I don't have a Fortran compiler immediately to hand. Is there a simple algorithm for working out how many newlines are written or consumed (This post just gives reading examples) [Please assume a FORTRAN77-like mentality in the FORTRAN code and correct any FORTRAN syntax on my part] UPDATE: no comments yet so I am reduced to finding a compiler and running it myself. I'll post the answers if I'm not beaten to it. No-one commented I had the format syntax wrong. I've changed it but there may still be errors Assume datafile 1 a b c d etc... (a) does the READ command always consume a newline? does READ(1, '(A)') A READ(1, '(A)') B give A='a' and B='b' (b) what does READ(1,'(A,/)') A READ(1,'(A)') B give for B? (I would assume 'c') (c) what does READ(1, '(/)') READ(1, '(A)') A give for A (is it 'b' or 'c') (d) what does READ(1,'(A,/,A)') A, B READ(1,'(A)') C give for A and B and C(can I assume 'a' and 'b' and 'c') (e) what does READ(1,'(A,/,/,A)') A, B READ(1,'(A)') C give for A and B and C(can I assume 'a' and 'c' and 'd')? Are there any cases in which the '/' is redundant?

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Firefox add-on development: Register global dynamic custom keyboard shortcuts

- by dezwart

I have been tasked with developing a Firefox add-on that is capable of registering global keyboard shortcuts (ones that will work throughout all areas of Firefox) that will open up the side-bar and execute an XMLRPC request based on previously recorded input. The idea here is that there will be many potential XMLRPC requests that the user will want to execute via a keyboard shortcut. Currently, the add-on is capable of handling pre-defined static keyboard shortcuts via the Firefox overlay. What I would like to achieve, is to allow the user to register their own dynamic custom keyboard shortcut. There is an add-on that currently has some of this functionality, called Keyconfig. I'm not keen on having to ask users to install a second add-on to define their own shortcuts. It also seems that using the dynamic keyboard shortcut registration method in Keyconfig would require the user to close all Firefox windows before the dynamic shortcut is made available. What I would like to know is: Is an XPCOM component the best way to register dynamic keyboard shortcuts from within a Firefox add-on? Is there a way to register the keyboard shortcut so that it is immediately available to all Firefox windows, without having to close the windows beforehand?

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Validating JSP's and HTML Forms, Server-side or Client-side, or both?

- by CitadelCSAlum

I am aware that I can Google "HTML Form Validation" and would get a billion tutorials. I am well aware that I can use simple JavaScript to validate form input, but I have been told that this is not necessarily an efficient method. I have also heard that it is a best practice to validate both client and server-side code. OK! Well, What exactly does this mean besides writing code on both? Does it mean I do some with JavaScript and other with Servlet's or does it mean that I write identical validation methods on both? My real question is can anybody give me insight and direction as how to go about validation my HTML forms. I am using JSP's and Servlet's and I have tons of form validation to do. I have already done minor form validation with regex in Java, but want to figure out if Im heading in the right track before I write any more code. Only productive answers please, If I wanted negative feedback on how inexperienced I was, I would have gone to Reddit. Thanks!

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What characters are NOT escaped with a mysqli prepared statement?

- by barfoon

Hey everyone, I'm trying to harden some of my PHP code and use mysqli prepared statements to better validate user input and prevent injection attacks. I switched away from mysqli_real_escape_string as it does not escape % and _. However, when I create my query as a mysqli prepared statement, the same flaw is still present. The query pulls a users salt value based on their username. I'd do something similar for passwords and other lookups. Code: $db = new sitedatalayer(); if ($stmt = $db->_conn->prepare("SELECT `salt` FROM admins WHERE `username` LIKE ? LIMIT 1")) { $stmt->bind_param('s', $username); $stmt->execute(); $stmt->bind_result($salt); while ($stmt->fetch()) { printf("%s\n", $salt); } $stmt->close(); } else return false; Am I composing the statement correctly? If I am what other characters need to be examined? What other flaws are there? What is best practice for doing these types of selects? Thanks,

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why does this knockout method receive a form element instead of the object its nested in?

- by ladookie

I have this HTML: <ul class="chat_list" data-bind="foreach: chats"> <li> <div class="chat_response" data-bind="visible: CommentList().length == 0"> <form data-bind="submit: $root.addComment"> <input class="comment_field" placeholder="Comment…" data-bind="value: NewCommentText" /> </form> </div> </li> </ul> and this JavaScript: function ChatListViewModel(chats) { // var self = this; self.chats = ko.observableArray(ko.utils.arrayMap(chats, function (chat) { return { CourseItemDescription: chat.CourseItemDescription, CommentList: ko.observableArray(chat.CommentList), CourseItemID: chat.CourseItemID, UserName: chat.UserName, ChatGroupNumber: chat.ChatGroupNumber, ChatCount: chat.ChatCount, NewCommentText: ko.observable("") }; })); self.newChatText = ko.observable(); self.addComment = function (chat) { var newComment = { CourseItemDescription: chat.NewCommentText(), ParentCourseItemID: chat.CourseItemID, CourseID: $.CourseLogic.dataitem.CourseID, AccountID: $.CourseLogic.dataitem.AccountID, SystemObjectID: $.CourseLogic.dataitem.CommentSystemObjectID, SystemObjectName: "Comments", UserName: chat.UserName }; chat.CommentList.push(newComment); chat.NewCommentText(""); }; } ko.applyBindings(new ChatListViewModel(initialData)); When I go into the debugger it shows that the chat parameter of the addComment() function is a form element instead of a chat object. Why is this happening?

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Error in bisection method code in Matlab

- by Amanda Collins

I need to write a proper implementation of the bisection method, which means I must address all possible user input errors. Here is my code: function [x_sol, f_at_x_sol, N_iterations] = bisection(f, xn, xp, eps_f, eps_x) % solving f(x)=0 with bisection method % f is the function handle to the desired function, % xn and xp are borders of search, % f(xn)<0 and f(xp)>0 required, % eps_f defines how close f(x) should be to zero, % eps_x defines uncertainty of solution x if(f(xp) < 0) error('xp must be positive') end; if(f(xn)>0) error('xn must be negative') end; if (xn >= xp) error ('xn must be less than xp') end; xg=(xp+xn)/2; %initial guess fg=f(xg); % initial function evaluation N_iterations=1; while ( (abs(fg) > eps_f) & (abs(xg-xp) > eps_x) ) if (fg>0) xp=xg; else xn=xg; end xg=(xp+xn)/2; %update guess fg=f(xg); %update function evaluation N_iterations=N_iterations+1; end x_sol=xg; %solution is ready f_at_x_sol=fg; if (f_at_x_sol > eps_f) error('No convergence') end and here is the error message I receive when I try to test this in Matlab: >> bisection(x.^2, 2, -1, 1e-8, 1e-10) Attempted to access f(-1); index must be a positive integer or logical. Error in bisection (line 9) if(f(xp)<0) I was attempting to see if my error codes worked, but it doesn't look like they do. I get the same error when I try to test it on a function that should work.

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Stupid newbie c++ two-dimensional array problem.

- by paulson scott

I've no idea if this is too newbie or generic for stackoverlflow. Apologies if that's the case, I don't intend to waste time. I've just started working through C++ Primer Plus and I've hit a little stump. This is probably super laughable but: for (int year = 0; year < YEARS; year++) { cout << "Year " << year + 1 << ":"; for (int month = 0; month < MONTHS; month++) { absoluteTotal = (yearlyTotal[year][year] += sales[year][month]); } cout << yearlyTotal[year][year] << endl; } cout << "The total number of books sold over a period of " << YEARS << " years is: " << absoluteTotal << endl; I wish to display the total of all 3 years. The rest of the code works fine: input is fine, individual yearly output is fine but I just can't get 3 years added together for one final total. I did have the total working at one point but I didn't have the individual totals working. I messed with it and reversed the situation. I've been messing with it for God knows how long. Any idea guys? Sorry if this isn't the place!

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