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  • Html.Editor() helper in ASP.NET MVC 3 does not work as expected with array in model

    - by SlimShaggy
    In my ASP.NET MVC 3 application I have classes like the following: public class Localization<T> { public int VersionID { get; set; } public T Value { get; set; } ... } public class Localizable<T> { public Localization<T>[] Name { get; set; } ... } Then, I have the following view: @model dynamic ... @for (int i = 0; i < VersionCount; i++) { ... @Html.Editor(string.Format("Name[{0}.Value", i)) ... } Now, when I display this view, passing a subclass of Localizable<string> as the model, the textboxes for the strings are rendered, but they are empty. If I replace @Html.Editor(string.Format("Name[{0}.Value", i)) with @InputExtensions.TextBox(Html, string.Format("Name[{0}].Value", i), Model.Name[i].Value), the textboxes are correctly filled with values from the model. However, using TextBox instead of Editor is not an option for me, because I want to use different editor templates for different types of T. So, what am I doing wrong, or is it a bug in MVC, and is there any workaround?

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  • Passing trough a datagrid value

    - by Tonz
    I have a datagrid with 2 columns. One databound which display names and the other one is a hyperlink column. Column1 = databound column, Column2 = hyperlink column. column1: column2: --------------------- Name1 Modify Name2 Modify Next when i click on any of the values in Column2 i simply get redirected to a other page. This page contains 2 buttons/hyperlinks with Yes or No. (does not mather wich control, which one would bring the most easy to implement solution atm) When clicked on No it simply redirects back to the orignal page. Now the question is when i press "Yes" how exactly do i acces "Name1" (or Name2 if i press on the second modify)? Meaning if i press Yes i want to use this Name for certain opertions (xml). To put it short if i press on "modify" i want to be able to get that name associated with it (which is already displayed in the first bound column left of it). So the goal is to use that name in Xpath for example so i can make a query towards that node with that certain name. Hopefully this made some sence.

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  • Ruby on rails 2 level model

    - by jony17
    I need some help creating a very simple forum in a existing model. What I want in a Game page, have a mini forum, where is possible create some topics and some comments to this topics. In the beginning I'm only implement topics. This is the error I have: Mysql2::Error: Column 'user_id' cannot be null: INSERT INTO `topics` (`game_id`, `question`, `user_id`) VALUES (1, 'asd', NULL) This is my main model: game.rb class Game < ActiveRecord::Base attr_accessible :name validates :user_id, presence: true validates :name, presence: true, length: { maximum: 50 } belongs_to :user has_many :topics, dependent: :destroy end topic.rb class Topic < ActiveRecord::Base validates_presence_of :question validates_presence_of :game_id attr_accessible :question, :user_id validates :question, length: {maximum: 50}, allow_blank: false belongs_to :game belongs_to :user end topic_controller.rb def create @game = Game.find(params[:game_id]) @topic = @game.topics.create(params[:topic]) @topic.user_id = current_user.id respond_to do |format| if @topic.save format.html { redirect_to @game, notice: 'Topic was successfully created.' } else format.html { render action: "new" } end end end game/show.html.erb <h2>Topics</h2> <% @game.topics.each do |topic| %> <p> <b>Question:</b> <%= topic.question %> </p> <% end %> <h2>Add a topic:</h2> <%= form_for([@game, @game.topics.build]) do |f| %> <div class="field"> <%= f.label :question %><br /> <%= f.text_field :question %> </div> <div class="actions"> <%= f.submit %> </div> <% end %> Thanks ;)

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  • Error in inserting data into database

    - by Matthew
    When I try to run this code it will not insert the data into the database? <?php class Database { private $dsn; function __construct($dbname, $host, $user, $password, $enckey) { $this->dsn = "mysql:dbname=" . $dbname . ';host=' . $host; $this->user = $user; $this->password = $password; } private function createDSN() { return $this->dsn; } public function createConnection() { try { $dbh = new PDO(self::createDSN(), $this->user, $this->password); } catch (PDOException $e) { echo 'Connection failed: ' . $e->getMessage(); } return $dbh; } } $db = new Database('mytest', 'localhost', 'root', 'hashedpassword', null); $dbh = $db->createConnection(); $sql = $dbh->prepare("INSERT INTO contacts (firstname, lastname) VALUES (?,?)"); $sql->execute(array("abc", "xyz")); ?>

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  • JVM terminated. Exit code = -1

    - by Lex
    Hello, I've been using Eclipse for some time already, and I didn't have any problems with it. However, when I tried to generate some javadoc, I found that I didn't have the SDK installed. I installed jdk 6u23, and from then on, Eclipse hasn't been working. At first it told me it couldn't find a JRE/SDK. After copying and placing the JRE in the Eclipse folder, the error changed to this: http://i258.photobucket.com/albums/hh261/magical_7/Eclipse.png I've searched around for some solutions, and found a few of varying nature. However, none of them seemed to work. I've tried emptying my eclipse.ini file without success. Altering some values in eclipse.ini didn't work either. Installing Java SDK 1.5 didn't work. Does anyone have other possible solutions? Update: I tried reinstalling Eclipse, but it didn't fix the problem. I did notice that it's a 32bit version, while I'm running a 64bit system. However, if this were to be the problem, I find it strange that it hasn't been an issue earlier.

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  • Big-Oh running time of code in Java (are my answers accurate

    - by Terry Frederick
    the Method hasTwoTrueValues returns true if at least two values in an array of booleans are true. Provide the Big-Oh running time for all three implementations proposed. // Version 1 public boolean has TwoTrueValues( boolean [ ] arr ) { int count = 0; for( int i = 0; i < arr. length; i++ ) if( arr[ i ] ) count++; return count >= 2; } // Version 2 public boolean hasTwoTrueValues( boolean [ ] arr ) { for( int i = 0; i < arr.length; i++ ) for( int j = i + 1; j < arr.length; j++ ) if( arr[ i ] && arr[ j ] ) return true; } // Version 3 public boolean hasTwoTrueValues( boolean [ ] arr ) { for( int i = 0; i < arr.length; i++ if( arr[ i ] ) for( int j = i + 1; j < arr.length; j++ ) if( arr[ j ] ) return true; return false; } For Version 1 I say the running time is O(n) Version 2 I say O(n^2) Version 3 I say O(n^2) I am really new to this Big Oh Notation so if my answers are incorrect could you please explain and help.

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  • How do I deal with different requests that map to the same response?

    - by daxim
    I'm designing a Web service. The request is idempotent, so I chose the GET method. The response is relatively expensive to calculate and not small, so I want to get caching (on the protocol level) right. (Don't worry about memoisation at my part, I have that already covered; my question here is actually also paying attention to the Web as a whole.) There's only one mandatory parameter and a number of optional parameter with default values if missing. For example, the following two map to the same representation of the response. (If this is a dumb way to go about it the interface, propose something better.) GET /service?mandatory_parameter=some_data HTTP/1.1 GET /service?mandatory_parameter=some_data;optional_parameter=default1;another_optional_parameter=default2;yet_another_optional_parameter=default3 HTTP/1.1 However, I imagine clients do not know this and would treat them separate and therefore waste cache storage. What should I do to avoid violating the golden rule of caching? Make up a canonical form, document it (e.g. all parameters are required after all and need to be sorted in a specific order) and return a client error unless the required form is met? Instead of an error, redirect permanently to the canonical form of a request? Or is it enough to not mind how the request looks like, and just respond with the same ETag for same responses?

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  • While in a transaction, how can reads to an affected row be prevented until the transaction is done?

    - by Mahn
    I'm fairly sure this has a simple solution, but I haven't been able to find it so far. Provided an InnoDB MySQL database with the isolation level set to SERIALIZABLE, and given the following operation: BEGIN WORK; SELECT * FROM users WHERE userID=1; UPDATE users SET credits=100 WHERE userID=1; COMMIT; I would like to make sure that as soon as the select inside the transaction is issued, the row corresponding to userID=1 is locked for reads until the transaction is done. As it stands now, UPDATEs to this row will wait for the transaction to be finished if it is in process, but SELECTs simply will read the previous value. I understand this is the expected behaviour in this case, but I wonder if there is a way to lock the row in such a way that SELECTs will also wait until the transaction is finished to return the values? The reason I'm looking for that is that at some point, and with enough concurrent users, it could happen that while the previous transaction is in process someone else reads the "credits" to calculate something else. Ideally the code run by that someone else should wait for the transaction to finish to use the new value, because otherwise it could lead to irreversible desync issues. Note that I don't want to lock the entire table for reads, just the specific row. Also, I could add a boolean "locked" field to the tables and set it to 1 every time I'm starting a transaction but I don't really feel this is the most elegant solution here, unless there is absolutely no other way to handle this through mysql directly.

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  • Python: Sorting array with custom pattern

    - by Binka
    In my little project here I have sorted a list in decending order, however, my goal is to sort it in this custom pattern. (largest - smallest - next largest - next smallest -)etc. In java I was able to do this like this... My goal is to do the same thing but in python, except backwards. Any ideas on how to convert that last for loop that does the wackysort into python and make it go backwards? public static void wackySort(int[] nums){ //first, this simply sorts the array by ascending order. int sign = 0; int temp = 0; int temp2 = 0; for (int i = 0; i < nums.length; i++){ for (int j = 0; j < nums.length -1; j++){ if (nums[j] > nums[j+1]){ temp = nums[j]; nums[j] = nums[j+1]; nums[j+1] = temp; } } } //prepare for new array to actually do the wacky sort. System.out.println(); int firstPointer = 0; int secondPointer = nums.length -1; int[] newarray = new int[nums.length]; int size = nums.length; //for loop that increments by two taking second slot replacing the last (n-1) term for (int i = 0; i < nums.length -1; i+=2){ newarray[i] = nums[firstPointer++]; newarray[i+1] = nums[secondPointer--]; } //storing those values back in the nums array for (int i = 0; i < nums.length; i++){ nums[i] = newarray[i]; } }

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  • How to increase my "advanced" knowledge of PHP further? (quickly)

    - by Kerry
    I have been working with PHP for years and gotten a very good grasp of the language, created many advanced and not-so-advanced systems that are working very well. The problem I'm running into is that I only learn when I find a need for something that I haven't learned before. This causes me to look up solutions and other code that handles the problem, and so I will learn about a new function or structure that I hadn't seen before. It is in this way that I have learned many of my better techniques (such as studying classes put out by Amazon, Google or other major companies). The main problem with this is the concept of not being able to learn something if you don't know it exists. For instance, it took me several months of programming to learn about the empty() function, and I simply would check the string length using strlen() to check for empty values. I'm now getting into building bigger and bigger systems, and I've started to read blogs like highscalability.com and been researching MySQL replication and server data for scaling. I know that structure of your code is very important to make full systems work. After reading a recent blog about reddit's structure, it made me question if there is some standard or "accepted systems" out there. I have looked into frameworks (I've used Kohana, which I regretted, but decided that PHP frameworks were not for me) and I prefer my own library of functions rather than having a framework. My current structure is a mix between WordPress, Kohana and my own knowledge. The ways I can see as being potentially beneficial are: Read blogs Read tutorials Work with someone else Read a book What would be the best way(s) to "get to the next level" the level of being a very good system developer?

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  • mine phrases (up to 3 words) from a given text

    - by DS_web_developer
    I asked before for a simple solution to my problem (using sphinx search service) but I got nowhere... someone has kindly provided me with this code <?php /** * $Project: GeoGraph $ * $Id$ * * GeoGraph geographic photo archive project * This file copyright (C) 2005 Barry Hunter ([email protected]) * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public License * as published by the Free Software Foundation; either version 2 * of the License, or (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program; if not, write to the Free Software * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */ /** * Provides the methods for updating the worknet tables * * @package Geograph * @author Barry Hunter <[email protected]> * @version $Revision$ */ function addTwoLetterPhrase($phrase) { global $w2; $w2[$phrase] = (isset($w2[$phrase]))?($w2[$phrase]+1):1; } function addThreeLetterPhrase($phrase) { global $w3; $w3[$phrase] = (isset($w3[$phrase]))?($w3[$phrase]+1):1; } function updateWordnet(&$db,$text,$field,$id) { global $w1,$w2,$w3; $alltext = strtolower(preg_replace('/\W+/',' ',str_replace("'",'',$text))); if (strlen($text)< 1) return; $words = preg_split('/ /',$alltext); $w1 = array(); $w2 = array(); $w3 = array(); //build a list of one word phrases foreach ($words as $word) { $w1[$word] = (isset($w1[$word]))?($w1[$word]+1):1; } //build a list of two word phrases $text = $alltext; $text = preg_replace('/(\w+) (\w+)/e','addTwoLetterPhrase("$1 $2")',$text); $text = $alltext; $text = preg_replace('/(\w+)/','',$text,1); $text = preg_replace('/(\w+) (\w+)/e','addTwoLetterPhrase("$1 $2")',$text); //build a list of three word phrases $text = $alltext; $text = preg_replace('/(\w+) (\w+) (\w+)/e','addThreeLetterPhrase("$1 $2 $3")',$text); $text = $alltext; $text = preg_replace('/(\w+)/','',$text,1); $text = preg_replace('/(\w+) (\w+) (\w+)/e','addThreeLetterPhrase("$1 $2 $3")',$text); $text = $alltext; $text = preg_replace('/(\w+) (\w+)/','',$text,1); $text = preg_replace('/(\w+) (\w+) (\w+)/e','addThreeLetterPhrase("$1 $2 $3")',$text); foreach ($w1 as $word=>$count) { $db->Execute("insert into wordnet1 set gid = $id,words = '$word',$field = $count");// ON DUPLICATE KEY UPDATE $field=$field+$count"); } foreach ($w2 as $word=>$count) { $db->Execute("insert into wordnet2 set gid = $id,words = '$word',$field = $count"); } foreach ($w3 as $word=>$count) { $db->Execute("insert into wordnet3 set gid = $id,words = '$word',$field = $count"); } } ?> It works fine and does almost exactly what I need....... except.... it is not utf8 friendly... I mean... it splits whole words into parts (on special chars) where it shouldn't! so my guess is I should use multibyte functions instead of regular preg_replace... I tried to replace preg_replace with mb_ereg_replace but it is not working as it should... at least not for 2 and 3 words phrases any ideas?

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  • JDBC with JSP fails to insert

    - by StrykeR
    I am having some issues right now with JDBC in JSP. I am trying to insert username/pass ext into my MySQL DB. I am not getting any error or exception, however nothing is being inserted into my DB either. Below is my code, any help would be greatly appreciated. <% String uname=request.getParameter("userName"); String pword=request.getParameter("passWord"); String fname=request.getParameter("firstName"); String lname=request.getParameter("lastName"); String email=request.getParameter("emailAddress"); %> <% try{ String dbURL = "jdbc:mysql:localhost:3306/assi1"; String user = "root"; String pwd = "password"; String driver = "com.mysql.jdbc.Driver"; String query = "USE Users"+"INSERT INTO User (UserName, UserPass, FirstName, LastName, EmailAddress) " + "VALUES ('"+uname+"','"+pword+"','"+fname+"','"+lname+"','"+email+"')"; Class.forName(driver); Connection conn = DriverManager.getConnection(dbURL, user, pwd); Statement statement = conn.createStatement(); statement.executeUpdate(query); out.println("Data is successfully inserted!"); } catch(SQLException e){ for (Throwable t : e) t.printStackTrace(); } %> DB script here: CREATE DATABASE Users; use Users; CREATE TABLE User ( UserID INT NOT NULL AUTO_INCREMENT, UserName VARCHAR(20), UserPass VARCHAR(20), FirstName VARCHAR(30), LastName VARCHAR(35), EmailAddress VARCHAR(50), PRIMARY KEY (UserID) );

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  • Website hosting from home - IIS6 [closed]

    - by Paul
    I'm wanting to host a few websites from home, primarily because I'm using some BETA Microsoft software (.NET 4 and EF) and don't want to install it on my production server which is hosted at eukhost.com. Basically, I'm completely new to this sort of thing. So far, here is what I've done: Registered the domain name at namecheap.com (let's call it mydomain.com) Gone to "Nameserver Registration" in the panel and entered my IP address for the NS1 and NS2 records (let's say the IP is 0.0.0.0). Gone to "Domain Name Server Setup" and entered ns1.mydomain.com & ns2.mydomain.com Forwarded requests from port 80 to my internal IP (let's say 192.168.1.254) Created the website in IIS (I'm just testing with a single website so far, so have not created any host header values) Now, if I type in the IP address (http://0.0.0.0) I get the site as expected. However, if I enter http://www.mydomain.com I get an error saying "DNS Error - Cannot find server". I'm aware that there is a service from DynDNS that will automatically change the IP if I have a dynamic address, however my IP has remained static since I installed the ISP (since October) so I don't need this. Is there any way that I can get the DNS to work just by configuring IIS or something in Windows? I don't really want to have to pay for any 3rd party service. Thanks,

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  • Abstract away a compound identity value for use in business logic?

    - by John K
    While separating business logic and data access logic into two different assemblies, I want to abstract away the concept of identity so that the business logic deals with one consistent identity without having to understand its actual representation in the data source. I've been calling this a compound identity abstraction. Data sources in this project are swappable and various and the business logic shouldn't care which data source is currently in use. The identity is the toughest part because its implementation can change per kind of data source, whereas other fields like name, address, etc are consistently scalar values. What I'm searching for is a good way to abstract the concept of identity, whether it be an existing library, a software pattern or just a solid good idea of some kind is provided. The proposed compound identity value would have to be comparable and usable in the business logic and passed back to the data source to specify records, entities and/or documents to affect, so the data source must be able to parse back out the details of its own compound ids. Data Source Examples: This serves to provide an idea of what I mean by various data sources having different identity implementations. A relational data source might express a piece of content with an integer identifier plus a language specific code. For example. content_id language Other Columns expressing details of content 1 en_us 1 fr_ca The identity of the first record in the above example is: 1 + en_us However when a NoSQL data source is substituted, it might somehow represent each piece of content with a GUID string 936DA01F-9ABD-4d9d-80C7-02AF85C822A8 plus language code of a different standardization, And a third kind of data source might use just a simple scalar value. So on and so forth, you get the idea.

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  • Best way to store this data?

    - by Malfist
    I have just been assigned to renovate an old website, and I get to move it from some old archaic system to drupal. The only problem is that it's a real-estate system and a lot of data is stored. Currently all the information is stored in a single table, an id represents the house and then everything else is key/value pairs. There are a possible 243 keys per estate, there are 23840 estates in the system. As you can imagine the system is slow and difficult to query. I don't think a table with 243 rows would be a very good idea, and probably worse than the current situation. I've done some investigating and here's what I've found out: Missing data does not indicate a 0 value, data is merged from two, unique sources/formats. Some guessing is involved. I have no control over the source of the data. There are 4 keys that are common to all estates, all values look like something that is commonly searched for and could be indexed There are 10 keys that are in the [90-100)% range 8 of these are information like who's selling it, and it's address. The other two seem to belong with the below range There are 80 keys that are in the [80-90)% range This range seems to mostly just list room types and how many the house has (e.g. bedrooms_possible, bathrooms, family_room_3rd, etc) This range also includes some minor information like school districts, one or two more pieces of data on the address. The 179 keys that are in the [0-80)% range include all sorts of miscellaneous information about the estate My best idea was a hybrid approach, create a table that stores important, common information and keep a smaller key/value table. How would you store this information?

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  • pass variable by reference within class? in php

    - by user151841
    I'm working on a hex color class where you can change the color values of any hex code color. In my example, I haven't finished the hex math, but it's not completely relevant to what I'm explaining here. Naively, I wanted to start to do something that I don't think can be done. I wanted to pass object properties in a method call. Is this possible? class rgb { private $r; private $b; private $g; public function __construct( $hexRgb ) { $this->r = substr($hexRgb, 0, 2 ); $this->g = substr($hexRgb, 2, 2 ); $this->b = substr($hexRgb, 4, 2 ); } private function add( & $color, $amount ) { $color += amount; // $color should be a class property, $this->r, etc. } public function addRed( $amount ) { self::add( $this->r, $amount ); } public function addGreen( $amount ) { self::add( $this->g, $amount ); } public function addBlue( $amount ) { self::add( $this->b, $amount ); } } If this is not possible in PHP, what is this called and in what languages is it possible? I know I could do something like public function add( $var, $amount ) { if ( $var == "r" ) { $this->r += $amount } else if ( $var == "g" ) { $this->g += $amount } ... } But I want to do it this cool way.

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  • Create a new site programmatically and select parent site? (SharePoint)

    - by peter
    Hi, I am using the following code to create a new site: newWeb = SPContext.GetContext(HttpContext.Current).Web.Webs.Add(newSiteUrl, newSiteName, null, (uint)1033, siteTemplate, true, false); try { newWeb.Update(); } NewSiteUrl and newSiteName are values from two textboxes and on whichever site I use this code (in a web part) the new site will be a subsite to this site. I would now like to be able to select a parent site so that the new site can sit anywhere in the site collection, not just as a subsite to the site where I use the web part. I created the following function to get all the sites in the site collection and populate a drop down with the name and url for every site private void getSites() { SPSite oSiteCollection = SPContext.Current.Site; SPWebCollection collWebsite = oSiteCollection.AllWebs; for (int i = 0; i < collWebsite.Count; i++) { ddlParentSite.Items.Add(new ListItem(collWebsite[i].Title, collWebsite[i].Url)); } oSiteCollection.Dispose(); } If the user selects a site in the dropdown, is it possible to use that URL in newSiteUrl so decide where the new site should be? I don't get it to work really and the new site still becomes a subsite to the current one. I guess it has to do with HttpContext.Current? Any ideas on how I should do it instead? It's the first time I write custom web parts and the sharepoint object model is a bit overwhelming at the moment. Thanks in advance.

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  • How can I get the contents of my table with dynamic row adding?

    - by user359706
    how to retrieve from the server-side contained a table html constructed this way: <table id="myTable"> <tr> <th> <input type="text"> name </th> <th> <input type="text"> quantity </th> </tr> <tr> <th> <input id="name_1"> phone </th> <th> <input id="quantity_1"> 15 </th> </tr> <tr> <th> <input ="name_2"> id mp3 </th> <th> <input id="quantity_2"> 26 <</th> </tr> ... I can not make use of <asp:Table> ... because for technical reasons I did not find a solution following this post: http://stackoverflow.com/questions/3003912/how-to-dynamic-adding-rows-into-asp-net-table How can retrieve the contents values of my table (dynamic) for each row. Rows will be added in client-side js Thank you.

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  • javascript accordion - tracking time question

    - by JohnMerlino
    Hey all, I was reading up on this javascript tutorial: http://www.switchonthecode.com/tutor...ccordion-menus Basically, it shows you how to create an accordion using pure javascript, not jquery. All made sense to me until the actual part of tracking the animation. He says "Because of all that, the first thing we do in the animation function is figure out how much time has passed since the last animation iteration." And then uses this code: Code: var elapsedTicks = curTick - lastTick; lastTick is equal to the value of when the function was called (Date().getTime()) and curTick is equal to the value when the function was received. I don't understand why we are subtracting one from the other right here. I can't imagine that there's any noticeable time difference between these two values. Or maybe I'm missing something. Is that animate() function only called once every time a menu title is clicked or is it called several times to create the incremental animation effect? setTimeout("animate(" + new Date().getTime() + "," + TimeToSlide + ",'" + openAccordion + "','" + nID + "')", 33); Thanks for any response.

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  • Pair equal operator overloading for inserting into set

    - by Petwoip
    I am trying to add a pair<int,int> to a set. If a pair shares the same two values as another in the set, it should not be inserted. Here's my non-working code: typedef std::pair<int, int> PairInt; template<> bool std::operator==(const PairInt& l, const PairInt& r) { return (l.first == r.first && l.second == r.second) || (l.first == r.second && l.second == r.first); } int main() { std::set<PairInt> intSet; intSet.insert(PairInt(1,3)); intSet.insert(PairInt(1,4)); intSet.insert(PairInt(1,4)); intSet.insert(PairInt(4,1)); } At the moment, the (4,1) pair gets added even though there is already a (1,4) pair. The final contents of the set are: (1 3) (1 4) (4 1) and I want it to be (1 3) (1 4) I've tried putting breakpoints in the overloaded method, but they never get reached. What have I done wrong?

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  • When to use () with classes?

    - by SoulBeaver
    This is really starting to confuse the hell out of me. When do I use them, when don't I? For example I was reading a .cpp on linked lists whose class declaration was: struct CarPart { long PartNumber; char Partname[40]; double UnitPrice; CarPart *next; }; class ListOfParts { int size; public: CarPart *head; ListOfParts(); ~ListOfParts(); const int count() const; void insert( CarPart *item ); CarPart *retrieve( int pos ); }; With this code, why am I allowed to write ListOfParts *pPart = new ListOfParts(); CarPart *pCarPart = new CarPart; Declaring an instance of ListOfParts requires (), but not my CarPart? That's confusing me. When I asked a question before and people told me that such a declaration is a function that returns a ListOfParts object, but not the actual constructor. So I'm guessing this is still something different. What's happening here? PS: Am I correct to assume that the const to the right of count() means I cannot modify any values in count?

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  • java class that simulates a simple database table

    - by ericso
    I have a collection of heterogenous data that I pull from a database table mtable. Then, for every unique value uv in column A, I compute a function of (SELECT * FROM mtable WHERE A=uv). Then I do the same for column B, and column C. There are rather a lot of unique values, so I don't want to hit the db repeatedly - I would rather have a class that replicates some of the functionality (most importantly some version of SELECT WHERE). Additionally, I would like to abstract the column names away from the class definition, if that makes any sense - the constructor should take a list of names as a parameter, and also, I suppose, a list of types (right now this is just a String[], which seems hacky). I'm getting the initial data from a RowSet. I've more or less done this by using a hashmap that maps Strings to lists/arrays of Objects, but I keep getting bogged down in comparisons and types, and am thinking that my current implementation really isn't as clean and clear as it could be. I'm pretty new to java, also, and am not sure if I'm not going down a completely incorrect path. Does anyone have any suggestions?

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  • swap! alter and alike

    - by mekka
    Hello, I am having a problem understanding how these functions update the underlying ref, atom etc. The docs say: (apply f current-value-of-identity args) (def one (atom 0)) (swap! one inc) ;; => 1 So I am wondering how it got "expanded" to the apply form. It's not mentioned what exactly 'args' in the apply form is. Is it a sequence of arguments or are these separate values? Was it "expanded" to: (apply inc 0) ; obviously this wouldnt work, so that leaves only one possibility (apply inc 0 '()) (swap! one + 1 2 3) ;; #=> 7 Was it: (apply + 1 1 2 3 '()) ;or (apply + 1 [1 2 3]) (def two (atom [])) (swap! two conj 10 20) ;; #=> [10 20] Was it: (apply conj [] [10 20]) ;or (apply conj [] 10 20 '()) If I swap with a custom function like this: (def three (atom 0)) (swap! three (fn [current elem] (println (class elem))) 10) ;;#=> java.Lang.Integer Which means that the value '10' doesnt magically get changed into a seq '(10) and leads me to the conclusion, that it gets "expanded" to: (apply f current-value-of-identity arg1 arg2 arg3... '()) Is that a correct assumption and the docs are simply lacking a better description?

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  • Is this Leftist Tree piece of code from Wikipedia correct?

    - by they changed my name
    Link public Node merge(Node x, Node y) { if(x == null) return y; if(y == null) return x; // if this was a max height biased leftist tree, then the // next line would be: if(x.element < y.element) if(x.element.compareTo(y.element) > 0) { // x.element > y.element Node temp = x; x = y; y = temp; } x.rightChild = merge(x.rightChild, y); if(x.leftChild == null) { // left child doesn't exist, so move right child to the left side x.leftChild = x.rightChild; x.rightChild = null; x.s = 1; } else { // left child does exist, so compare s-values if(x.leftChild.s < x.rightChild.s) { Node temp = x.leftChild; x.leftChild = x.rightChild; x.rightChild = temp; } // since we know the right child has the lower s-value, we can just // add one to its s-value x.s = x.rightChild.s + 1; } return x; } What makes me ask this question is: if(x.element.compareTo(y.element) > 0) { // x.element > y.element Node temp = x; x = y; y = temp; } Isn't that just not gonna work, since the references are only switched inside the method?

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  • String generator issue

    - by Andrey
    I want to write a method which returns a string. So far so good. The creation of the string however is quite complicated. I have 3 string lists - the first one has 155 entries, the second one - 9, the third one 21. I want my method if called enough times(155*9*21) to return all the possible combinations of values from the 3 lists (basically this method should keep count on how many times it was called and return only one combination each time). Any ideas how to accomplish that? I have 155*9*22 possible combinations. The first time the method is called it should take List1(0), List2(0), List3(0). After that in the next 21 iterations, the index of the third list is only changed. Once all the elements from the third list have been used increment the index of the second list and so on. Once the method has produced all the possible combinations (155*9*22) I want it to start from the beginning.

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