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  • confirm alert not working ....

    - by user318068
    I want the work of the Control Panel in my site for members ... I designed the page is displayed all the registered members on my site And i but it checkbox front each member name ,becuase it allowed to select multiple name then click delete button The following code works but now i want confirm alert before delete code working even , if clicked on ok the deletion is working , and if clicked on cancel the is not working .. how i can work it ?? while($row = mysql_fetch_array($sql1)) { ?> <tr> <td align="center" bgcolor="#FFFFFF"><input name="checkbox[]" type="checkbox" id="checkbox[]" value="<?php echo $row['MemberID']; ?>"></td> <td bgcolor="#FFFFFF"><?php echo $row['MemberName']; ; ?></td></tr> <?php } ?> <tr> <td colspan="5" align="center" bgcolor="#FFFFFF"><input name="delete" type="submit" id="delete" value="delete" onclick="javascript:return confirm('are you sure to delete this record???? ')"/></td> </tr> <?php $delete = $_REQUEST['delete']; $checkbox = $_REQUEST['checkbox']; $count = count($_REQUEST['checkbox']); // Check if delete button active, start this if($delete){ echo "<script language=\"Javascript\">\n"; for($i=0;$i<$count;$i++){ $del_id = $checkbox[$i]; $sql = "Delete FROM members where MemberID ='$del_id'"; $sq2 = "Delete FROM joinroom where MemberID ='$del_id'"; $result1 = mysql_query($sql); $result2 = mysql_query($sq2); echo "else {\n"; echo "alert ('Nothing deleted');\n }"; echo "</script>"; } } Thanks a lot.........

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  • Is XSLT worth investing time in and are there any actual alternatives?

    - by Keeno
    I realize this has been a few other questions on this topic, and people are saying use your language of choice to manipulate the XML etc etc however, not quite fit my question exactly. Firstly, the scope of the project: We want to develop platform independent e-learning, currently, its a bunch of HTML pages but as they grow and develop they become hard to maintain. The idea: Generate up an XML file + Schema, then produce some XSLT files that process the XML into the eLearning modiles. XML to HTML via XSLT. Why: We would like the flexibilty to be able to easy reformat the content (I realize CSS is a viable alternative here) If we decide to alter the pages layout or functionality in anyway, im guessing altering the "shared" XSLT files would be easier than updating the HTML files. So far, we have about 30 modules, with up to 10-30 pages each Depending on some "parameters" we could output drastically different page layouts/structures, above and beyond what CSS can do Now, all this has to be platform independent, and to be able to run "offline" i.e. without a server powering the HTML Negatives I've read so far for XSLT: Overhead? Not exactly sure why...is it the compute power need to convert to HTML? Difficult to learn Better alternatives Now, what I would like to know exactly is: are there actually any viable alternatives for this "offline"? Am I going about it in the correct manner, do you guys have any advice or alternatives. Thanks!

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  • Easyslider content loading sooner than I would like.

    - by Jason
    I am using a jquery easyslider on a page and also pulling some rss feeds using php. Pulling the feeds is taking a long time and as a result delaying the load of the easy slider until after the feeds have been pulled in. This can be seen here: http://perksconsulting.com/dev/ I am looking for a way to display a loader image in the space where the easy slider is so the images do not appear stacked vertically for a few seconds while the php is interpreted by the server, but I have never used a loader image and am not sure how I would do that. I am currently using this script to hide the page contents until everything is loaded, but the one thing it is not hiding is the images from the easy slider: <SCRIPT TYPE="text/javascript" LANGUAGE="javascript"> function waitPreloadPage() { //DOM if (document.getElementById){ document.getElementById('prepage').style.visibility='hidden'; }else{ if (document.layers){ //NS4 document.prepage.visibility = 'hidden'; } else { //IE4 document.all.prepage.style.visibility = 'hidden'; } } } // End --> </SCRIPT> Ideally I would like to be able to display a loading image in place of the slider in the middle of the page until everything loads. Could anyone tell me how to do this? Thank you.

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  • Changing <object> height and width works in Chrome but not Firefox or IE. Why?

    - by Michael Hopkins
    I am making a site with two Youtube videos. These videos use the raw embed code from Youtube. The site's design doesn't work with any of the default Youtube sizes, so I am writing code to automatically resize the video. Here is my code. There will never be more than these two tags on the page, otherwise I'd do a better job selecting the videos. <script language='JavaScript' type='text/javascript'> var x=document.getElementsByTagName('object'); x.[0].width='350'; x.[0].height='350'; x.[1].width='350'; x.[1].height='350'; </script> For reference, here's a sample default Youtube embed that the code might alter: <object width="480" height="385"> <param name="movie" value="http://www.youtube-nocookie.com/v/zSgiXGELjbc&hl=en_US&fs=1&rel=0"></param> <param name="allowFullScreen" value="true"></param> <param name="allowscriptaccess" value="always"></param> <embed src="http://www.youtube-nocookie.com/v/zSgiXGELjbc&hl=en_US&fs=1&rel=0" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="480" height="385"></embed> </object> In Chrome, the video players sit perfectly in a 350x350 box. In IE and FF (latest versions), the videos are the unchanged, normal size. I cannot find anything in Google that explans why this won't work. I have tried using setattribute, for loops, adjusting both and , single-quotes and double-quotes, etc. Any ideas what is going wrong?

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  • How do I loop through elements inside a div?

    - by crosenblum
    I have to make a custom function for search/replace text, because firefox counts text nodes differently than IE, Google Chrome, etc.. I am trying to use this code, that I saw at Firefox WhiteSpace Issue since in my other function, I am looping numerically through nodes, which serves my functional needs perfectly, in other browsers. But refuses to work, as part of a search/replace function that takes place after some ajax content is loaded. Here is the code, that I have tried to get to work, but I must be missing the correct understanding of the context of how to loop thru elements inside a div. // get all childnodes inside div function div_translate(divid) { // list child nodes of parent if (divid != null) { // var children = parent.childNodes, child; var parentNode = divid; // start loop thru child nodes for(var node=parentNode.firstChild;node!=null;node=node.nextSibling){ // begin check nodeType if(node.nodeType == 1){ // get value of this node var value = content(node); // get class of this node var myclass = node.attr('class'); console.log(myclass); // begin check if value undefined if (typeof(value) != 'undefined' && value != null) { console.log(value); // it is a text node. do magic. for (var x = en_count; x > 0; x--) { // get current english phrase var from = en_lang[x]; // get current other language phrase var to = other_lang[x]; if (value.match(from)) { content(node, value.replace(from, to)); } } } // end check if value undefined } // end check nodeType } // end loop thru child nodes } }

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  • Open source libraries to design directed graphs

    - by Benjamin
    Hi all, I'm going to need to write a software that takes a list of persons and connects them together in a directed-graph-like manner. The GUI aspect of the whole project is very important. The graph must allow a lot of interaction. Such as selecting several people and hiding the others, moving them around. Additionally, the software will need to be able to provide other kind of GUI-features such as several tabs, text boxes etc. The application must be quite performant. As in, it must be able to handle hundreds if not thousands of widgets. Hence, I would like to know which open source libraries (at this point the programming language they are written in does not matter - I just want an overview of everything good that is out there) would allow me to develop such piece of software? What would you recommend? Thanks for that. Edit: Could you please also link to tutorials explaining how I could program a GUI that can interact with the generated graph? For example mouse events.

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  • Type errors when using same name

    - by lykimq
    I have 3 files: 1) cpf0.ml type string = char list type url = string type var = string type name = string type symbol = | Symbol_name of name 2) problem.ml: type symbol = | Ident of string 3) test.ml open Problem;; open Cpf0;; let symbol b = function | Symbol_name n -> Ident n When I combine test.ml: ocamlc -c test.ml. I received an error: This expression has type Cpf0.name = char list but an expression was expected of type string Could you please help me to correct it? Thank you very much EDIT: Thank you for your answer. I want to explain more about these 3 files: Because I am working with extraction in Coq to Ocaml type: cpf0.ml is generated from cpf.v : Require Import String. Definition string := string. Definition name := string. Inductive symbol := | Symbol_name : name -> symbol. The code extraction.v: Set Extraction Optimize. Extraction Language Ocaml. Require ExtrOcamlBasic ExtrOcamlString. Extraction Blacklist cpf list. where ExtrOcamlString I opened: open Cpf0;; in problem.ml, and I got a new problem because in problem.ml they have another definition for type string This expression has type Cpf0.string = char list but an expression was expected of type Util.StrSet.elt = string Here is a definition in util.ml defined type string: module Str = struct type t = string end;; module StrOrd = Ord.Make (Str);; module StrSet = Set.Make (StrOrd);; module StrMap = Map.Make (StrOrd);; let set_add_chk x s = if StrSet.mem x s then failwith (x ^ " already declared") else StrSet.add x s;; I was trying to change t = string to t = char list, but if I do that I have to change a lot of function it depend on (for example: set_add_chk above). Could you please give me a good idea? how I would do in this case.

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  • ASP.NET MVC (VB) error when publishing to test server

    - by Colin
    I have an ASP.NET MVC project that works fine on my local machine (no build errors, server errors or anything). However, when I publish the project to a test server, I get an "Object reference not set to an instance of an object" error on a For Each I have in my view. I have a function within a model that returns a DataRowCollection. I'm calling that function in my controller and passing the DataRowCollection to my View, which then iterates over the rows and displays the necessary information: In the Controller I have: Function Index() As ActionResult Dim MyModel As New Model ViewData("MyDataRowCollection") = MyModel.GetDataRowCollection() Return View() End Function And then in the View, which is throwing the error: <%@ Page Language="VB" MasterPageFile="~/Views/Shared/Site.Master" Inherits="System.Web.Mvc.ViewPage" %> <asp:Content ID="indexTitle" ContentPlaceHolderID="TitleContent" runat="server"> My Page Title </asp:Content> <asp:Content ID="indexContent" ContentPlaceHolderID="MainContent" runat="server"> <% For Each MyDataRow In ViewData("MyDataRowCollection") ' do stuff with each MyDataRow Next %> I'm pretty new to ASP.NET MVC so I'm sure there might be a better way to do what I'm doing (I'd be happy to hear if there is), but my main concern is why this works fine on my local machine but throws an error on the For Each on the test server? Please let me know if I can clarify any of the above, and thanks in advance for any information.

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  • VB.NET Syntax Coding

    - by Yiu Korochko
    I know many people ask how some of these are done, but I do not understand the context in which to use the answers, so... I'm building a code editor for a subversion of Python language, and I found a very decent way of highlighting keywords in the RichTextBox through this: bluwords.Add(KEYWORDS GO HERE) If scriptt.Text.Length > 0 Then Dim selectStart2 As Integer = scriptt.SelectionStart scriptt.Select(0, scriptt.Text.Length) scriptt.SelectionColor = Color.Black scriptt.DeselectAll() For Each oneWord As String In bluwords Dim pos As Integer = 0 Do While scriptt.Text.ToUpper.IndexOf(oneWord.ToUpper, pos) >= 0 pos = scriptt.Text.ToUpper.IndexOf(oneWord.ToUpper, pos) scriptt.Select(pos, oneWord.Length) scriptt.SelectionColor = Color.Blue pos += 1 Loop Next scriptt.SelectionStart = selectStart2 End If (scriptt is the richtextbox) But when any decent amount of code is typed (or loaded via OpenFileDialog) chunks of the code go missing, the syntax selection falls apart, and it just plain ruins it. I'm looking for a more efficient way of doing this, maybe something more like visual studio itself...because there is NO NEED to highlight all text, set it black, then redo all of the syntaxing, and the text begins to over-right if you go back to insert characters between text. Also, in this version of Python, hash (#) is used for comments on comment only lines and double hash (##) is used for comments on the same line. Now I saw that someone had asked about this exact thing, and the working answer to select to the end of the line was something like: ^\'[^\r\n]+$|''[^\r\n]+$ which I cannot seem to get into practice. I also wanted to select text between quotes and turn it turquoise, such as between the first quotation mark and the second, the text is turquoise, and the same between the 3rd and 4th etcetera... Any help is appreciated!

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  • jQuery "best practices" is an oxymoron [closed]

    - by n00b
    jQuery "best practices", oxymoron for several reasons sadly To speak candidly, the entire jQuery library has a HIGHLY inconsistent API, and virtually no coding standards. It's basically a subset of JavaScript, a new language if you will, which is probably the most confusing part for normal javascript developers. In my opinion, use normal JavaScript where possible to save on memory consumption. Or, better yet, use a professional tool like YUI. If you already come from a javascript background, you will appreciate it much more than jQuery because it doesn't have n00b wrappers around everything. In tools like YUI, you interact directly with the native DOM to do things, instead of a super-jQuery object that tries to do everything. I'll get voted down for saying the truth. Don't get me wrong, jQuery is cool if you wanna throw something flashy up quick, but if you're going to build a larger app you're going to need a more refined tool (especially since jQuery leaks memory like no other once you start chaining too much things). jQuery does have one of the lowest learning curves, and you won't outgrow it for awhile, but when you do it will be highly apparent and tedious to merge to something else. over 60 years programming experience someone clean this up and community wiki please

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  • How to (kindly) ask your users to upgrade from IE6?

    - by nickf
    It's no secret at all that IE6 has been a major roadblock to the advancement of the web over the last few years. I couldn't count the number of hours I've spent bashing my head against a wall trying to fix or debug IE6 issues. The way I see it, there are two types of IE6 user. a) the poor corporate schmoe whose IT department doesn't want to upgrade in case something breaks, and b) the mums and dads of the world who think the internet is the blue E on their desktop (and I don't mean that in a nasty way). There's probably a couple of people who know about all the other browsers, but still choose to run IE6. They get what they deserve, IMO. Anyway, getting to the point, I'd say that 90% of my IE6-using visitors are in the the mums and dads category - they're not stupid, they just don't know WHY they should upgrade to IE7 or Firefox or whatever. How do I educate these people without pissing them off? Is there a nice and friendly website I can direct these people to, which explains the reasons for upgrading in plain language? Any mention of "security" or "web standards" I think would just come across as scary. I've just seen http://www.whatbrowser.org which seems to fit the bill nicely. It explains in very basic terms: what a web browser is why you'd want to upgrade it how old your current browser is (subtle hint to those with a 9 year old browser) ..aaaand it's in 22 languages. It's from Google but displays no bias (it links to Firefox, Chrome, Opera, Safari, Internet Explorer displayed in a random order).

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  • Can I get the amount of time for which a key is pressed on a keyboard

    - by Adi
    Dear all, I am working on a project in which I have to develop bio-passwords based on user's keystroke style. Suppose a user types a password for 20 times, his keystrokes are recorded, like holdtime : time for which a particular key is pressed. digraph time : time it takes to press a different key. suppose a user types a password " COMPUTER". I need to know the time for which every key is pressed. something like : holdtime for the above password is C-- 200ms O-- 130ms M-- 150ms P-- 175ms U-- 320ms T-- 230ms E-- 120ms R-- 300ms The rational behind this is , every user will have a different holdtime. Say a old person is typing the password, he will take more time then a student. And it will be unique to a particular person. To do this project, I need to record the time for each key pressed. I would greatly appreciate if anyone can guide me in how to get these times. Editing from here.. Language is not important, but I would prefer it in C. I am more interested in getting the dataset.

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  • Do you like languages that let you put the "then" before the "if"?

    - by Matt Hamilton
    I was reading through some C# code of mine today and found this line: if (ProgenyList.ItemContainerGenerator.Status != System.Windows.Controls.Primitives.GeneratorStatus.ContainersGenerated) return; Notice that you can tell without scrolling that it's an "if" statement that works with ItemContainerGenerator.Status, but you can't easily tell that if the "if" clause evaluates to "false" the method will return at that point. Realistically I should have moved the "return" statement to a line by itself, but it got me thinking about languages that allow the "then" part of the statement first. If C# permitted it, the line could look like this: return if (ProgenyList.ItemContainerGenerator.Status != System.Windows.Controls.Primitives.GeneratorStatus.ContainersGenerated); This might be a bit "argumentative", but I'm wondering what people think about this kind of construct. It might serve to make lines like the one above more readable, but it also might be disastrous. Imagine this code: return 3 if (x > y); Logically we can only return if x y, because there's no "else", but part of me looks at that and thinks, "are we still returning if x <= y? If so, what are we returning?" What do you think of the "then before the if" construct? Does it exist in your language of choice? Do you use it often? Would C# benefit from it?

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  • R plotting multiple histograms on single plot to .pdf as a part of R batch script

    - by Bryce Thomas
    I am writing R scripts which play just a small role in a chain of commands I am executing from a terminal. Basically, I do much of my data manipulation in a Python script and then pipe the output to my R script for plotting. So, from the terminal I execute commands which look something like $python whatever.py | R CMD BATCH do_some_plotting.R. This workflow has been working well for me so far, though I have now reached a point where I want to overlay multiple histograms on the same plot, inspired by this answer to another user's question on Stackoverflow. Inside my R script, my plotting code looks like this: pdf("my_output.pdf") plot(hist(d$original,breaks="FD",prob=TRUE), col=rgb(0,0,1,1/4),xlim=c(0,4000),main="original - This plot is in beta") plot(hist(d$minus_thirty_minutes,breaks="FD",prob=TRUE), col=rgb(1,0,0,1/4),add=T,xlim=c(0,4000),main="minus_thirty_minutes - This plot is in beta") Notably, I am using add=T, which is presumably meant to specify that the second plot should be overlaid on top of the first. When my script has finished, the result I am getting is not two histograms overlaid on top of each other, but rather a 3-page PDF whose 3 individual plots contain the titles: i) Histogram of d$original ii) original - This plot is in beta iii) Histogram of d$minus_thirty_minutes So there's two points here I'm looking to clarify. Firstly, even if the plots weren't overlaid, I would expect just a 2-page PDF, not a 3-page PDF. Can someone explain why I am getting a 3-page PDF? Secondly, is there a correction I can make here somewhere to get just the two histograms plotted, and both of them on the same plot (i.e. 1-page PDF)? The other Stackoverflow question/answer I linked to in the first paragraph did mention that alpha-blending isn't supported on all devices, and so I'm curious whether this has anything to do with it. Either way, it would be good to know if there is a R-based solution to my problem or whether I'm going to have to pipe my data into a different language/plotting engine.

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  • how to run href="#var=something" before onclick function fires in javascript?

    - by korben
    i'm using the below javascript to change an image on an aspx in asp.net c# <script language="JavaScript" type="text/javascript"> var updateImageWhenHashChanges = function() { theImage = document.getElementById("ctl00_ContentPlaceHolder1_Image1a"); if(window.location.hash == "#size=2") { theImage.src = "<%# Eval("realfilename", "/files/l{0}") %>"; } else if(window.location.hash == "#size=3") { theImage.src = "<%# Eval("realfilename", "/files/{0}") %>"; } else if(window.location.hash == "#size=1") { theImage.src = "<%# Eval("fullthumbname", "/thumbnails/{0}") %>"; } else { } } </script> here's how i call it with a link <a href="#size=3" onclick="updateImageWhenHashChanges();">test</a> the problem is that it only does what i'm expecting on the SECOND click of the link, because it seems onclick fires before the href, so the first time i'm just placing the var and the 2nd time i'm actually getting what i want. does anyone know how i can fix this? i'm trying to get the image to change on each click

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  • ASP.NET server data persistence

    - by Wayne Werner
    Hi, I'm not really sure exactly how the question should be phrased, so please be patient if I ask the wrong thing. I'm writing an ASP.NET application using VB as the code behind language. I have a data access class that connects to the DB to run the query (parameterized, of course), and another class to perform the validation tasks - I access this class from my aspx page. What I would like is to be able to store the data server side and wait for the user to choose from a few options based on the validity of the data. But unless my understanding is completely off, having persistent data objects on the server will give problems when multiple users connect? My ultimate goal is that once the data has been validated the end user can't modify it. Currently I'm validating the data, but I still have to retrieve it from the web form AFTER the user says OK, which obviously leaves open the possibility of injecting bad data either accidentally (unlikely) or on purpose (also unlikely for the use, but I'd prefer not to take the chance). So am I completely off in my understanding? If so, can someone point me to a resource that provides some instructions on keeping persistent data on the server, or provide instruction? Thanks!

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  • Rewriting jQuery to plain old javascript - are the performance gains worth it?

    - by Swader
    Since jQuery is an incredibly easy and banal library, I've developed a rather complex project fairly quickly with it. The entire interface is jQuery based, and memory is cleaned regularly to maintain optimum performance. Everything works very well in Firefox, and exceptionally so in Chrome (other browsers are of no concern for me as this is not a commercial or publicly available product). What I'm wondering now is - since pure plain old javascript is really not a complicated language to master, would it be performance enhancing to rewrite the whole thing in plain old JS, and if so, how much of a boost would you expect to get from it? If the answers prove positive enough, I'll go ahead and do it, run a benchmark and report back with the precise findings. Cheers Edit: Thanks guys, valuable insight. The purpose was not to "re-invent the wheel" - it was just for experience and personal improvement. Just because something exists, doesn't mean you shouldn't explore it into greater detail, know how it works or try to recreate it. This is the same reason I seldom use frameworks, I would much rather use my own code and iron it out and gain massive experience doing it, than start off by using someone else's code, regardless of how ironed out it is. Anyway, won't be doing it, thanks for saving me the effort :)

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  • Software Company Library

    - by dbemerlin
    Hi. A few days ago i had the idea to create a company library since my company has no training and many developers still develop as they did when they learned it 5 years ago. My hope is that they can lend books, read them and hopefully learn something from them (for example: object oriented programming or unit testing, which noone here knows how to use). After asking around most agreed that it was a good idea, so i brought my books, made a simple printed sheet with "Book A belongs to B" and "Developer A took the Book on dd.mm.yyyy" to get it started. Now i want to get some ideas for Books that i could add to the shelf (sadly from my own money since 100€/month for training is too much money for this multi-million euro company). We develop mostly PHP & MySQL so books specific to this topic would be preferred but i think if people learn other languages they might get ideas on how to develop better with the current language so other books are ok, too. Which books would you recommend? PS: Personally i'd like to add some Project Management books, too, as it's a topic i'm interested in, eventhough i'm just a junior developer (We've got Peopleware already, great book btw).

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  • Is there a programmatic way to transform a sequence of image files into a PDF?

    - by Salim Fadhley
    I have a sequence of JPG images. Each of the scans is already cropped to the exact size of one page. They are sequential pages of a valuable and out of print book. The publishing application requires that these pages be submitted as a single PDF file. I could take each of these images and just past them into a word-processor (e.g. OpenOffice) - unfortunately the problem here is that it's a very big book and I've got quite a few of these books to get through. It would obviously be time-consuming. This is volunteer work! My second idea was to use LaTeX - I could make a very simple document that consists of nothing more than a series of in-line image includes. I'm sure that this approach could be made to work, it's just a little on the complex side for something which seems like a very simple job. It occurred to me that there must be a simpler way - so any suggestions? I'm on Ubuntu 9.10, my primary programming language is Python, but if the solution is super-simple I'd happily adopt any technology that works.

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  • Should uni provide "correct answer" after programming assignment is due?

    - by Michael Mao
    Hi all: This is my very first subjective question. And I think it is programming related - the assignment is to be written in a programming language. I am not for "getting the full marks out of a subject". I am actually not for a "correct answer", but for a "better solution", so that I can compare, and can improve. I reckon it is good that I practice programming first and check the solution later to pick up the things I've done wrong/bad. Without a "benchmark" to against, this would be much harder. Unfortunately as far as I know, not all programming subjects taught in uni would kindly provide the students with a "correct answer" in the end, after the assignment is due. One bad metaphor for this is like someone asks you a question which they don't have a clear answer themselves and hope to take advantage of your answer as the basis for their answer. Personally, I feel having a assignment solution provided by the academic staff is essential to students. I do appreciate this, and I feel I might not be the only one. I am a very proactive student in uni. I learn more, I practice more, an assignment for me is more like a challenge to achieve "the best solution I can come up with", not something "I have to pass"... The cause of this question is that for the past few days I have crafted 500+ lines of Perl code, for a tiny assignment. I feel pain when I look at my solution(not finished yet) and I feel like I am an idiot doing some crap code. I know there must be a much better solution. And I reckon it is better for the lecturer in this subject to get me one, rather than asking for an answer here, even I would shamelessly add the link to my solution apart from the assignment requirements. I know in SO, there are a lot of tutors/lecturers for programming subjects/courses. I'd like to hear your words on this question.

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  • Haskell Cons Operator (:)

    - by Carson Myers
    I am really new to Haskell (Actually I saw "Real World Haskell" from O'Reilly and thought "hmm, I think I'll learn functional programming" yesterday) and I am wondering: I can use the construct operator to add an item to the beginning of a list: 1 : [2,3] [1,2,3] I tried making an example data type I found in the book and then playing with it: --in a file data BillingInfo = CreditCard Int String String | CashOnDelivery | Invoice Int deriving (Show) --in ghci $ let order_list = [Invoice 2345] $ order_list [Invoice 2345] $ let order_list = CashOnDelivery : order_list $ order_list [CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, ...- etc... it just repeats forever, is this because it uses lazy evaluation? -- EDIT -- okay, so it is being pounded into my head that let order_list = CashOnDelivery:order_list doesn't add CashOnDelivery to the original order_list and then set the result to order_list, but instead is recursive and creates an infinite list, forever adding CashOnDelivery to the beginning of itself. Of course now I remember that Haskell is a functional language and I can't change the value of the original order_list, so what should I do for a simple "tack this on to the end (or beginning, whatever) of this list?" Make a function which takes a list and BillingInfo as arguments, and then return a list? -- EDIT 2 -- well, based on all the answers I'm getting and the lack of being able to pass an object by reference and mutate variables (such as I'm used to)... I think that I have just asked this question prematurely and that I really need to delve further into the functional paradigm before I can expect to really understand the answers to my questions... I guess what i was looking for was how to write a function or something, taking a list and an item, and returning a list under the same name so the function could be called more than once, without changing the name every time (as if it was actually a program which would add actual orders to an order list, and the user wouldn't have to think of a new name for the list each time, but rather append an item to the same list).

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  • Can someone explain the declaration of these java generic methods?

    - by Tony Giaccone
    I'm reading "Generics in the Java Programming Language" by Gilad Bracha and I'm confused about a style of declaration. The following code is found on page 8: interface Collection<E> { public boolean containsAll(Collection<?> c); public boolean addAll(Collection<? extends E> c); } interface Collection<E> { public <T> boolean containsAll(Collection<T> c); public <T extends E> boolean addAll(Collection<T> c); // hey, type variables can have bounds too! } My point of confusion comes from the second declaration. It's not clear to me what the purpose the <T> declaration serves in the following line: public <T> boolean containsAll(Collection<T> c); The method already has a type (boolean) associated with it. Why would you use the <T> and what does it tell the complier? I think my question needs to be a bit more specific. Why would you write: public <T> boolean containsAll(Collection<T> c); vs public boolean containsAll(Collection<T> c); It's not clear to me, what the purpose of <T> is, in the first declaration of containsAll.

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  • Would an immutable keyword in Java be a good idea?

    - by berry120
    Generally speaking, the more I use immutable objects in Java the more I'm thinking they're a great idea. They've got lots of advantages from automatically being thread-safe to not needing to worry about cloning or copy constructors. This has got me thinking, would an "immutable" keyword go amiss? Obviously there's the disadvantages with adding another reserved word to the language, and I doubt it will actually happen primarily for the above reason - but ignoring that I can't really see many disadvantages. At present great care has to be taken to make sure objects are immutable, and even then a dodgy javadoc comment claiming a component object is immutable when it's in fact not can wreck the whole thing. There's also the argument that even basic objects like string aren't truly immutable because they're easily vunerable to reflection attacks. If we had an immutable keyword the compiler could surely recursively check and give an iron clad guarantee that all instances of a class were immutable, something that can't presently be done. Especially with concurrency becoming more and more used, I personally think it'd be good to add a keyword to this effect. But are there any disadvantages or implementation details I'm missing that makes this a bad idea?

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  • Project Euler #14 and memoization in Clojure

    - by dbyrne
    As a neophyte clojurian, it was recommended to me that I go through the Project Euler problems as a way to learn the language. Its definitely a great way to improve your skills and gain confidence. I just finished up my answer to problem #14. It works fine, but to get it running efficiently I had to implement some memoization. I couldn't use the prepackaged memoize function because of the way my code was structured, and I think it was a good experience to roll my own anyways. My question is if there is a good way to encapsulate my cache within the function itself, or if I have to define an external cache like I have done. Also, any tips to make my code more idiomatic would be appreciated. (use 'clojure.test) (def mem (atom {})) (with-test (defn chain-length ([x] (chain-length x x 0)) ([start-val x c] (if-let [e (last(find @mem x))] (let [ret (+ c e)] (swap! mem assoc start-val ret) ret) (if (<= x 1) (let [ret (+ c 1)] (swap! mem assoc start-val ret) ret) (if (even? x) (recur start-val (/ x 2) (+ c 1)) (recur start-val (+ 1 (* x 3)) (+ c 1))))))) (is (= 10 (chain-length 13)))) (with-test (defn longest-chain ([] (longest-chain 2 0 0)) ([c max start-num] (if (>= c 1000000) start-num (let [l (chain-length c)] (if (> l max) (recur (+ 1 c) l c) (recur (+ 1 c) max start-num)))))) (is (= 837799 (longest-chain))))

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  • Javascript to check if there is flash player installed and redirect to the neededn page.

    - by themajiks
    Hi. I have this script. This determines if there is a flash player installed in the browser, it redirects the browser to a flash website. if not, then it opens a non-flash website. The Code is here: <SCRIPT LANGUAGE="JavaScript"> <!-- if ((navigator.appName == "Microsoft Internet Explorer" && navigator.appVersion.indexOf("Mac") == -1 && navigator.appVersion.indexOf("3.1") == -1) || (navigator.plugins && navigator.plugins["Shockwave Flash"])|| navigator.plugins["Shockwave Flash 2.0"]){ window.location='flash/index.html'; } else { window.location='index.html'; } --> </SCRIPT> What i want is to embed this code in the non-flash index page. it should just check if there is no flash then simply go with the current index file that already has been opened, or if there is no flash player, then load the index file from within the flash website. Currently, when index.html (non-flash) is opened, it goes into loop and keeps on checking for the flash player. Can I modify the window.location='index.html'; statement no to load any file here, just go on with the file already opened.??

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