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  • Getting can't modify frozen string when using string.insert

    - by Richard
    Hi, This is a quick question. I have the following ruby code, which works fine. def add_zeros number, zeros number = number.to_s zeros_to_add = zeros - number.length zeros_to_add.times do number = "0#{number}" end number end But if I replace number = "0#{number}" With number.insert(0, "0") Then I get TypeError: can't modify frozen string, does anyone know why this is?

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  • Where can I learn more about datastructure tricky questions?

    - by Sandbox
    I am relatively new to programming (around 1 year programming C#-winforms). Also, I come from a non CS background (no formal degree) Recently, while being interviewed for a job, I was asked about implementing a queue using a stack. I fumbled and wan't able to answer the question. After, the interview I could do it(had to spend some time). I have learnt (and think that I know it well) basic algorithms in datastructures using the book Data Structures: A Pseudocode Approach with C - Richard F. Gilberg (Author) . I want to know about sites/ books which have such questions along with answers. I think this will allow me to develop my CS specific problem solving skills. Any help is appreciated. BOUNTY: I am looking at some blog/website with datastructure and algorithms Q&A.

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  • how to change color of text following function in javascript

    - by OVERTONE
    Ok before i make spaghetti of this code i thought id ask around here. ive made a quiz for an online site. The answers are stored in an array, and ive a function that checks the answers array to what youve clicked. then it counts them and gives you your score. but i want to change the clor of the right answer wen the user clicks the score button. so the correct answers are highlighted. something like this https://www.shutterpoint.com/Home-Quiz.cfm (just hit submit at the bottom, no need to do the quiz). the little answer icon at the side looks flashy but id rather just have the text change color. heres how my questions are formatted <p>Depth of field is controlled by :?</p> <p id = "question2"><input type="radio" name="question2" id="Answer1" value = "a" onClick ="recordAnswer(2,this.value)"/> The focal length of the lens. <br/> <input type="radio" name="question2" id="Answer2" value = "b" onClick = "recordAnswer(2,this.value)"/> The size of the aperture opening. <br/> <input type="radio" name="question2" id="Answer3" value = "c" onClick = "recordAnswer(2,this.value)"/> The distance between the camera and lens. <br/> <input type="radio" name="question2" id="Answer4" value = "d" onClick = "recordAnswer(2,this.value)"/> All of these. <br/></p> and these are the two functions that are called throughout. record answer is called every time the user clicks a button function recordAnswer(question,answer) { answers[question-1] = answer; } this is the final button which calculates the score function scoreQuiz() { var totalCorrect = 0; for(var count = 0; count<correctAnswers.length;count++) { if(answers[count]== correctAnswers[count]) totalCorrect++; } <!-- alert("You scored " + totalCorrect + " out of 12 correct!"); --> } another function is best i think. ive already made attemots at it and know i have to set the color using document.getElementById('question2').style.color = '#0000ff'; question2 being the p id i think if i take in the value part of (input type....) ill be able to compare it to the answers array. but im not quite sure how to do this. any helpers? maybe something like this document.getElementById("Answer1").style.color = '#0000ff'; using the id part of the (input type line) i think i got it actually. ill post my answer in a sec

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  • AJAX, same-origin Policy and working XML Requests

    - by Joern
    Hello guys, so, currently I develop Widgets for Smartphones and am going a bit more advanced into fields of data exchange between client and server applications. My problem is: For my current project I want my client file to request data from a PHP script with the help of AJAX XmlHttpRequest and the POST method: function xmlRequestNotes() { var parameter = 'p=1234'; xmlhttp = new XMLHttpRequest(); xmlhttp.open("POST", url, true); // Http Header xmlhttp.setRequestHeader("Content-Type", "application/x-www-form-urlencoded"); xmlhttp.setRequestHeader("Content-length", parameter.length); xmlhttp.setRequestHeader("Connection", "close"); xmlhttp.onreadystatechange=function() { if (xmlhttp.readyState==4 && xmlhttp.status==200) { json = JSON.parse(xmlhttp.responseText); // Doing Stuff with the Response } }; xmlhttp.send(parameter); } This works perfectly fine on my local server set up in XAMPP and the local Widget emulator. But if it gets onto the device (also with access to the target network) I receive the 101 Network Error. And as far as I have read, this is due to the "Same-Origin Policy" of XmlHttpRequests? My problem is to really understand that. Although the idea of this policy is clear to me, I'm a bit confused by the fact that another XmlHttpRequest for a Yahoo Weather XML Feed works fine. Now, could anyone be so helpful to enlighten me? Here is the request that returns a city name from Yahoo's weather feed: function getCityName() { xmlhttp = new XMLHttpRequest(); xmlhttp.open("GET", "http://weather.yahooapis.com/forecastrss?w=645458&u=c", true); xmlhttp.onreadystatechange = function() { if (xmlhttp.readyState==4 && xmlhttp.status==200) { xmlhttp.responseXML; var yweather = "http://xml.weather.yahoo.com/ns/rss/1.0"; alert(xmlhttp.responseXML.getElementsByTagNameNS(yweather, "location")[0].getAttribute("city")); } }; xmlhttp.send(null); } Obvious differences are the POST and GET methods for once, but seeing that the Same-Origin Policy takes effect no matter what method, I can't really make much sense of it. Why does the latter request work but not the first? I would really appreciate some help here. Greetings and a merry Christmas to you guys!

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  • Will this ever result in a stack overflow error?

    - by David
    Will incrementing the instance variables of an object ever lead to a stack overflow error? For example: This method (java) will cause a stack overflow error: class StackOverflow { public static void StackOverflow (int x) { System.out.println (x) ; StackOverflow(x+1) ; } public static void main (String[]arg) { StackOverflow (0) ; } but will this?: (..... is a gap that i've put in to shorten the code. its long enough as it is.) import java.util.*; class Dice { String name ; int x ; int[] sum ; .... public Dice (String name) { this.name = name ; this.x = 0 ; this.sum = new int[7] ; } .... public static void main (String[] arg) { Dice a1 = new Dice ("a1") ; for (int i = 0; i<6000000; i++) { a1.roll () ; printDice(a1) ; } } .... public void roll () { this.x = randNum(1, this.sum.length) ; this.sum[x] ++ ; } public static int randNum (int a, int b) { Random random = new Random() ; int c = (b-a) ; int randomNumber = ((random.nextInt(c)) + a) ; return randomNumber ; } public static void printDice (Dice Dice) { System.out.println (Dice.name) ; System.out.println ("value: "+Dice.x) ; printValues (Dice) ; } public static void printValues (Dice Dice) { for (int i = 0; i<Dice.sum.length; i++) System.out.println ("#of "+i+"'s: "+Dice.sum[i]) ; } } The above doesn't currently cause a stack overflow error but could i get it too if i changed this line in main: for (int i = 0; i<6000000; i++) so that instead of 6 million something sufficiently high were there?

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  • Printings using CUPS, when can my app quit?

    - by KPexEA
    I have an linux app that uses cups for printing, but I've noticed that if I print and then quit my app right away my printout never appears. So I assume that my app has to wait for it to actually come out of the printer before quitting, so does anyone know how to tell when it's finished printing?? I'm using libcups to print a postscript file that my app generates. So I use the command to print the file and it then returns back to my app. So my app thinks that the document is off to the printer queue when I guess it has not made it there yet. So rather than have all my users have to look on the screen for the printer icon in the system tray I would rather have a solution in code, so if they try and quit before it has really been sent off I can alert them to the fact. Also the file I generate is a temporary file so it would be nice to know when it is finished with so I can delete it.

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  • Simple RSA encryption (Java)

    - by jake blue
    This is simply for fun. This will not be used for any actual encryption. I'm only first year comp sci student and love cryptography. This took a long time to get working. At approximately N = 18, it begins breaking down. It won't encrypt messages properly after that point. I'm not sure why. Any insights? I'd also appreciate any links you could provide me to tutorials or interesting reading about Cryptography. import java.math.BigInteger; import java.security.SecureRandom; /** * Cryptography. * * Generates public and private keys used in encryption and * decryption * */ public class RSA { private final static BigInteger one = new BigInteger("1"); private final static SecureRandom random = new SecureRandom(); // prime numbers private BigInteger p; private BigInteger q; // modulus private BigInteger n; // totient private BigInteger t; // public key private BigInteger e; // private key private BigInteger d; private String cipherText; /** * Constructor for objects of class RSA */ public RSA(int N) { p = BigInteger.probablePrime(N/2, random); q = BigInteger.probablePrime(N/2, random); // initialising modulus n = p.multiply(q); // initialising t by euclid's totient function (p-1)(q-1) t = (p.subtract(one)).multiply(q.subtract(one)); // initialising public key ~ 65537 is common public key e = new BigInteger("65537"); } public int generatePrivateKey() { d = e.modInverse(t); return d.intValue(); } public String encrypt(String plainText) { String encrypted = ""; int j = 0; for(int i = 0; i < plainText.length(); i++){ char m = plainText.charAt(i); BigInteger bi1 = BigInteger.valueOf(m); BigInteger bi2 = bi1.modPow(e, n); j = bi2.intValue(); m = (char) j; encrypted += m; } cipherText = encrypted; return encrypted; } public String decrypt() { String decrypted = ""; int j = 0; for(int i = 0; i < cipherText.length(); i++){ char c = cipherText.charAt(i); BigInteger bi1 = BigInteger.valueOf(c); BigInteger bi2 = bi1.modPow(d, n); j = bi2.intValue(); c = (char) j; decrypted += c; } return decrypted; } }

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  • Objective-c garbage collection

    - by Chris
    If garbage collection is not required: - (void) awakeFromNib{ //Create the NSStatusBar and set its length statusItem = [[[NSStatusBar systemStatusBar] statusItemWithLength:NSSquareStatusItemLength] retain]; ... Do I have to release that? And if I do, would that be in a finalize method or dealloc method? If garbage collection is required, then is the retain call above ignored automatically?

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  • Cocoa equivalent of diskEvt/kEventClassVolume?

    - by tewha
    We have a drop-down menu of volumes in our UI, and I'd like to update it when a new disk is mounted. In the Classic days, this would involve watching for a diskEvt event. In Carbon, I think this was kEventClassVolume. What's the Cocoa equivalent? (A pointer into Apple's documentation on this would satisfy the question. I've been unable to find anything!)

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  • Import Excel to sqlserver 2005 using Sqlbulkupload

    - by Jayesh
    Hi all, I want to upload excel file using SqlBulkCopy into sql server 2005 table. My excel file size is 43MB. When i am uploading this file it will display error message that "The request filtering module is configured to deny a request that exceeds the request content length.". My web.config file setting is <httpRuntime executionTimeout="12000" maxRequestLength="2097151" useFullyQualifiedRedirectUrl="false" minFreeThreads="8" minLocalRequestFreeThreads="4" appRequestQueueLimit="100"/> Thanks in advance.

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  • IconDownloader, problem with lazy downloading

    - by Junior B.
    My problem is simple to be described but it seems to be hard to solve. The problem is loading icons, with a custom class like IconDownloader.m provided by an official example from Apple, avoiding crashes if I release the view. I've added the IconDownloader class to my app, but it's clear that this approach is good only if the tableview is the root. The big problem is when the view is not the root one. F.e: if I start to scroll my second view (the app now load the icons) and, without leaving it the time to finish the download, I go back to root, the app crash because the view that have to be updated with new icons doesn't exist anymore. One possible solution could be implement an OperationQueue in the view, but with this approach I've to stop the queue when I change the view and restart it when I come back and the idea to have N queues don't make me enthusiastic. Anyone found a good solution for this problem?

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  • GlassFish JDO and global object

    - by bach
    Hi, I'm thinking about the GlassFish platform for my new app. My app env. doesn't have a big volume of data to handle, but a lot of users writing/reading the same data A very volotile portion of the data updates every 200milsec by diff users. Therefore I'd like that type of data to be in memory only and accessible to the whole app My questions: How do I use a global object in memory with GF? a. use a static variable object - for that I guess I need to make sure GF is running on only 1 JVM -- how to I configure GF to run on 1 jvm? b. use HttpContext - same as a. How do I persist to the DB? a. can I use JDO interface? How do I Schedule tasks to be performed in the future (something like the task queue in GAE) thanks, J.S. Bach

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  • Why does Python array moduel handle strings and lists differently?

    - by Casey
    I'm having trouble understanding the result of the following statements: >>> from array import array >>> array('L',[0xff,0xff,0xff,0xff]) array('L', [255L, 255L, 255L, 255L]) >>> from array import array >>> array('L','\xff\xff\xff\xff') Traceback (most recent call last): File "<stdin>", line 1, in <module> ValueError: string length not a multiple of item size

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  • Just a small problem regarding javscript BOM question

    - by caramel1991
    The question is this: Create a page with a number of links. Then write code that fires on the window onload event, displaying the href of each of the links on the page. And this is my solution <html> <body language="Javascript" onload="displayLink()"> <a href="http://www.google.com/">First link</a> <a href="http://www.yahoo.com/">Second link</a> <a href="http://www.msn.com/">Third link</a> <script type="text/javascript" language="Javascript"> function displayLink() { for(var i = 0;document.links[i];i++) { alert(document.links[i].href); } } </script> </body> </html> This is the answer provided by the book <html> <head> <script language=”JavaScript” type=”text/javascript”> function displayLinks() { var linksCounter; for (linksCounter = 0; linksCounter < document.links.length; linksCounter++) { alert(document.links[linksCounter].href); } } </script> </head> <body onload=”displayLinks()”> <A href=”link0.htm” >Link 0</A> <A href=”link1.htm”>Link 2</A> <A href=”link2.htm”>Link 2</A> </body> </html> Before I get into the javascript tutorial on how to check user browser version or model,I was using the same method as the example,by acessing the length property of the links array for the loop,but after I read through the tutorial,I find out that I can also use this alternative ways,by using the method that the test condition will evalute to true only if the document.links[i] return a valid value,so does my code is written using the valid method??If it's not,any comment regarding how to write a better code??Correct me if I'm wrong,I heard some of the people say "a good code is not evaluate solely on whether it works or not,but in terms of speed,the ability to comprehend the code,and could posssibly let others to understand the code easily".Is is true??

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  • Can I use rest-client to POST a binary file to HTTP without multipart?

    - by Angela
    I have tried to do the following, but the web-service is NOT REST and does not take multi-part. What do I do in order to POST the image? @response = RestClient.post('http://www.postful.com/service/upload', {:upload => { :file => File.new("#{@postalcard.postalimage.path}",'rb') } }, {"Content-Type" => @postalcard.postalimage.content_type, "Content-Length" => @postalcard.postalimage.size, "Authorization" => 'Basic xxxxxx' } # end headers ) #close arguments to Restclient.post

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  • How to implement a mailing system with Rails that sends emails in the background

    - by Tam
    I want to implement a reliable mailing system with Ruby on Rails that sends emails in the background as sending email sometimes takes like 10 seconds or more so I don't want the user to wait. Some ideas I thought of: 1- Write to a table in DB a have a background process that go over and send email (concern: potential many reads/writes to DB slows down my application) 2- Messaging Queue background process / Rake task (concern: if server crashes queued mails will be lost also might eat up a lot of memory if many emails) I was wondering if you a know of a good solution that provides a balance between reliability and performance.

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  • What's the difference between these two calls to a function taking a collection of structural types?

    - by James Moore
    Why does the call to fn(Iterator("foo") compile, but the call to fn(fooIterator) fail with an error "type mismatch; found : Iterator[java.lang.String] required: scala.Iterator[com.banshee.Qx.HasLength]" object Qx { type HasLength = {def length: Int} def fn(xs: Iterator[HasLength]) = 3 var tn = fn(Iterator("foo")) var fooIterator = Iterator("foo") var tnFails = fn(fooIterator) //doesn't compile } Aren't they the same thing?

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  • Writing csv header removes data from numpy array written below

    - by user338095
    I'm trying to export data to a csv file. It should contain a header (from datastack) and restacked arrays with my data (from datastack). One line in datastack has the same length as dataset. The code below works but it removes parts of the first line from datastack. Any ideas why that could be? s = ','.join(itertools.chain(dataset)) + '\n' newfile = 'export.csv' f = open(newfile,'w') f.write(s) numpy.savetxt(newfile, (numpy.transpose(datastack)), delimiter=', ') f.close()

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  • How do we simplify this kind of code in Java? Something like macros in C?

    - by Terry Li
    public static boolean diagonals(char[][] b, int row, int col, int l) { int counter = 1; // because we start from the current position char charAtPosition = b[row][col]; int numRows = b.length; int numCols = b[0].length; int topleft = 0; int topright = 0; int bottomleft = 0; int bottomright = 0; for (int i=row-1,j=col-1;i>=0 && j>=0;i--,j--) { if (b[i][j]==charAtPosition) { topleft++; } else { break; } } for (int i=row-1,j=col+1;i>=0 && j<=numCols;i--,j++) { if (b[i][j]==charAtPosition) { topright++; } else { break; } } for (int i=row+1,j=col-1;i<=numRows && j>=0;i++,j--) { if (b[i][j]==charAtPosition) { bottomleft++; } else { break; } } for (int i=row+1,j=col+1;i<=numRows && j<=numCols;i++,j++) { if (b[i][j]==charAtPosition) { bottomright++; } else { break; } } return topleft + bottomright + 1 >= l || topright + bottomleft + 1 >= l; //in this case l is 5 } After I was done posting the code above here, I couldn't help but wanted to simplify the code by merging the four pretty much the same loops into one method. Here's the kind of method I want to have: public int countSteps(char horizontal, char vertical) { } Two parameters horizontal and vertical can be either + or - to indicate the four directions to walk in. What I want to see if possible at all is i++; is generalized to i horizontal horizontal; when horizontal taking the value of +. What I don't want to see is if or switch statements, for example: public int countSteps(char horizontal, char vertical) { if (horizontal == '+' && vertical == '-') { for (int i=row-1,j=col+1;i>=0 && j<=numCols;i--,j++) { if (b[i][j]==charAtPosition) { topright++; } else { break; } } } else if (horizontal == '+' && vertical == '+') { for (int i=row+1,j=col+1;i>=0 && j<=numCols;i++,j++) { if (b[i][j]==charAtPosition) { topright++; } else { break; } } } else if () { } else { } } Since it is as tedious as the original one. Note also that the comparing signs for the loop condition i>=0 && j<=numCols; for example, >= && <= have correspondence with the value combination of horizontal and vertical. Sorry for my bad wording, please let me know if anything is not clear.

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  • While doesn't work

    - by Artem
    function Sort(td) { var t=document.getElementById("theList"); var rows=t.getElementsByTagName("td"); var cells=t.cells; var bb=true; while(bb==true) { alert(bb); for(var i=1;i<rows.length;i++) { if(cells[td.cellIndex+i*4].innerText<cells[td.cellIndex+(i+1)*4].innerText) { } } alert("Works"); } } The second alert will not be used. Can you tell me why?enter code here

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