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• How do you remind your Scrum Product Owner about his promises/actions?

  - by Felix Ogg

  ** EDIT: Rephrased the question to re-focus ** Our Scrum team meets as seldomly as possible, but we meet with the product owner every chance we get. We track everyone's agreed action points (particularly theirs). We are 100% agile, but our product owner lives in traditional world, we remain off-site. We facilitate him in crossing over to our fast-paced world. There's not much wrong. The team and the PO are in good spirits. PO is present at every meeting and positively energized. Just imagine this person as a 70 year old, slow grandpa, who is forgetful, yet kind. In reality he isn't, but he is used to a working environment (public servants) that is much slooooower. Manyana-manyana etc. It is frustrating for my team to cooperate: PO lives in a non-prioritized environment, and everyone in it has learned the productivity-technique of NGTD (Not Getting Things Done). He WANTS to, it's just that he forgets or 'sinks' somewhere along the away. We have experimented with a text file, maintained by the Scrum master (low-tech), which he broadcasts by e-mail every day JIRA, our issue tracker. Turns out this is nice for programmers, but too steep for 'regular people' I Googled for Issue tracking webtools but came up empty handed: All tools are aimed at IT issue tracking, instead of meeting action point tracking/planning for mere mortals. I did find TODO-lists like RememberTheMilk, but they don't track comments, and - to be honest - I doubt we could get our product owner to use it (too complicated). We have three requirements: Register action points, assign to a team member and a deadline Offer anyone to 'comment' on progress of any action point Do not build our own tool from scratch We do not need: - impressive authorization models, - multi-project, - workflow, - crosslinking. Is there any trick/tool you use to assist your product owner 'fly' like the rest of the rest of the team? Communication before tools I agree with the general consensus that one should not try to apply technology to a communication problem, however in this case I am merely looking for a tool to save me time in setting up prioritized lists. I found www.thymer.com today, may be what I am looking for. The guys are cool. It is getting rather feature-bloated though.

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• Precise explanation of JavaScript <-> DOM circular reference issue

  - by Joey Adams

  One of the touted advantages of jQuery.data versus raw expando properties (arbitrary attributes you can assign to DOM nodes) is that jQuery.data is "safe from circular references and therefore free from memory leaks". An article from Google titled "Optimizing JavaScript code" goes into more detail: The most common memory leaks for web applications involve circular references between the JavaScript script engine and the browsers' C++ objects' implementing the DOM (e.g. between the JavaScript script engine and Internet Explorer's COM infrastructure, or between the JavaScript engine and Firefox XPCOM infrastructure). It lists two examples of circular reference patterns: DOM element → event handler → closure scope → DOM DOM element → via expando → intermediary object → DOM element However, if a reference cycle between a DOM node and a JavaScript object produces a memory leak, doesn't this mean that any non-trivial event handler (e.g. onclick) will produce such a leak? I don't see how it's even possible for an event handler to avoid a reference cycle, because the way I see it: The DOM element references the event handler. The event handler references the DOM (either directly or indirectly). In any case, it's almost impossible to avoid referencing window in any interesting event handler, short of writing a setInterval loop that reads actions from a global queue. Can someone provide a precise explanation of the JavaScript ↔ DOM circular reference problem? Things I'd like clarified: What browsers are effected? A comment in the jQuery source specifically mentions IE6-7, but the Google article suggests Firefox is also affected. Are expando properties and event handlers somehow different concerning memory leaks? Or are both of these code snippets susceptible to the same kind of memory leak? // Create an expando that references to its own element. var elem = document.getElementById('foo'); elem.myself = elem; // Create an event handler that references its own element. var elem = document.getElementById('foo'); elem.onclick = function() { elem.style.display = 'none'; }; If a page leaks memory due to a circular reference, does the leak persist until the entire browser application is closed, or is the memory freed when the window/tab is closed?

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• Drop down table and jquery

  - by Marcelo

  Hi, I'm trying to make a drop down table using jQuery, with a similar code like here: (from the topic: Conditional simple drop down list?) <body> <div id="myQuestions"> <select id="QuestionOptions"> <option value="A">Question A</option> <option value="B">Question B</option> </select> </div> <div id="myAnswers"> <div id="A" style="display: none;"> <div id="QuestionC"> <p>Here is an example question C.</p> </div> <div id="QuestionD"> <select id="QuestionOptionsD"> <option value="G">Question G</option> <option value="H">Question H</option> </select> </div> </div> <div id="B" style="display: none;"> <div id="QuestionE"> <p>Here is an example question E.</p> </div> <div id="QuestionF"> <select id="QuestionOptionsF"> <option value="I">Question I</option> <option value="J">Question J</option> </select> </div> </div> </div> And the jQuery part $(function () { $('#QuestionOptions').change(function () { $('#myAnswers > div').hide(); $('#myAnswers').find('#' + $(this).val()).show(); }); }); My problem is, when I finish to table the part of "myQuestions", and start to table the part of "myAnswers", the dynamic part of the table doesn't work. In this case, the myAnswers part won't be hidden, it'll be shown since the beginning. I tried to put everything in one table, then I tried to create a different table for myQuestions, then another table for myAnswers and it didn't work. Does anyone know where am I mistaking ? Sorry for any mistake in English, I'm not a native speaker. Thanks in advance.

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• Live search results as you type... am I going about this the right way? jQuery + PHP

  - by dallen

  This is my first time building a tool like this, so please bare with me. I'm doing this to learn more about jQuery and AJAX. Basically, I have a search input and a hidden div. When you start typing in the search input, the hidden div becomes visible and results are brought in. In this case, I'm searching for client names. It all works fine, however I think my code could be better but I'm not sure exactly where to begin. Each keyup requests a PHP script which accesses a table in a database to find a like string. But in my PHP script, I'm echo'ing some JS/jQuery which I'm not sure is good practice. Below is my code. Am I going about this the right way or am I totally off base? Any suggestions for improvement? Javascript $("#search").keyup(function() { $("#search_results").show("fast"); $.ajax ({ type: "POST", url: "http://localhost:8888/index.php/welcome/search/" + $("#search").val(), success: function(html) { $("#search_results").html(html); } }); }); PHP function search($search_string = false) { if ($search_string) { $this->db->like('name', $search_string); $query = $this->db->get('clients'); if ($query->num_rows() == 0) { echo "No client exists."; } else { foreach ($query->result() as $row) { echo '<script>'; echo ' $("#client_results_'.$row->id.'").hide(); $("#'.$row->id.'").toggle(function() { $.ajax ({ type: "POST", url: "http://localhost:8888/index.php/welcome/search_client_ads/" + '.$row->id.', success: function(html) { $("#client_results_'.$row->id.'").html(html).show("fast"); } }); }, function() { $("#client_results_'.$row->id.'").hide("fast").html(""); });'; echo '</script>'; echo '<p><span id="'.$row->id.'">'.$row->name.'</span></p>'; echo '<div id="client_results_'.$row->id.'"></div>'; } } } else { echo ''; } } function search_client_ads($client_id) { $query = $this->db->get_where('online_ads', array('client' => $client_id)); if ($query->num_rows() == 0) { echo "No ads exist."; } else { foreach ($query->result() as $row) { echo $row->id; } } }

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• User Defined Exceptions with JMX

  - by Daniel

  I have exposed methods for remote management in my application server using JMX by creating an MXBean interface, and a class to implement it. Included in this interface are operations for setting attributes on my server, and for getting the current value of attributes. For example, take the following methods: public interface WordManagerMXBean { public void addWord(String word); public WordsObject getWords(); public void removeWord(String word); } The WordsObject is a custom, serializable class used to retrieve data about the state of the server. Then I also have a WordManager class that implements the above interface. I then create a JMX agent to manage my resource: MBeanServer mbs = ManagementFactory.getPlatformMBeanServer(); ObjectName wordManagerName = new ObjectName("com.example:type=WordManager"); mbs.registerMBean(wordManager, wordManagerName); I have created a client that invokes these methods, and this works as expected. However, I would like to extend this current configuration by adding user defined exceptions that can be sent back to my client. So I would like to change my interface to something like this: public interface WordManagerMXBean { public void addWord(String word) throws WordAlreadyExistsException; public WordsObject getWords(); public void removeWord(String word); } My WordAlreadyExistsException looks like this: public class WordAlreadyExistsException extends Exception implements Serializable { private static final long serialVersionUID = -9095552123119275304L; public WordAlreadyExistsException() { super(); } } When I call the addWord() method in my client, I would like to get back a WordAlreadyExistsException if the word already exists. However, when I do this, I get an error like this: java.rmi.UnmarshalException: Error unmarshaling return; nested exception is: java.lang.ClassNotFoundException: com.example.WordAlreadyExistsException The WordAlreadyExistsException, the WordsObject and the WordManagerMXBean interface are all in a single jar file that is available to both the client and the server. If I call the getWords() method, the client has no difficulty handling the WordsObject. However, if a user defined exception, like the one above, is thrown, then the client gives the error shown above. Is it possible to configure JMX to handle this exception correctly in the client? Following some searching, I noticed that there is an MBeanException class that is used to wrap exceptions. I'm not sure if this wrapping is performed by the agent automatically, or if I'm supposed to do the wrapping myself. I tried both, but in either case I get the same error on the client. I have also tried this with both checked and unchecked exceptions, again the same error occurs. One solution to this is to simply pass back the error string inside a generic error, as all of the standard java exceptions work. But I'd prefer to get back the actual exception for processing by the client. Is it possible to handle user defined exceptions in JMX? If so, any ideas how?

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• Why does my Spring Controller direct me to the wrong page?

  - by kc2001

  I am writing my first Spring 3.0.5 MVC app and am confused about why my controller mappings aren't doing what I expect. I have a VerifyPasswordController that is called after a user tries to log in by entering his name and password. // Called upon clicking "submit" from /login @RequestMapping(value = "/verifyPassword", method = RequestMethod.POST) @ModelAttribute("user") public String verifyPassword(User user, BindingResult result) { String email = user.getEmail(); String nextPage = CHOOSE_OPERATION_PAGE; // success case if (result.hasErrors()) { nextPage = LOGIN_PAGE; } else if (!passwordMatches(email, user.getPassword())) { nextPage = LOGIN_FAILURE_PAGE; } else { // success } return nextPage; } I can verify in the debugger that this method is being called, but afterwards, the verifyPassword page is displayed rather than the chooseOperation page. The console output of WebLogic seems to show that my mapping are correct: INFO : org.springframework.web.servlet.mvc.annotation.DefaultAnnotationHandlerMapping - Mapped URL path [/chooseOperation] onto handler 'chooseOperationController' INFO : org.springframework.web.servlet.mvc.annotation.DefaultAnnotationHandlerMapping - Mapped URL path [/chooseOperation.*] onto handler 'chooseOperationController' INFO : org.springframework.web.servlet.mvc.annotation.DefaultAnnotationHandlerMapping - Mapped URL path [/chooseOperation/] onto handler 'chooseOperationController' Here is the ChooseOperationController: @Controller @SessionAttributes("leaveRequestForm") public class ChooseOperationController implements PageIfc, AttributeIfc { @RequestMapping(value = "/chooseOperation") @ModelAttribute("leaveRequestForm") public LeaveRequest setUpLeaveRequestForm( @RequestParam(NAME_ATTRIBUTE) String name) { LeaveRequest form = populateFormFromDatabase(name); return form; } // helper methods omited } I welcome any advice, particularly "generic" techniques for debugging such mapping problems. BTW, I've also tried to "redirect" to the desired page, but got the same result. servlet-context.xml: <?xml version="1.0" encoding="UTF-8"?> <beans:beans xmlns="http://www.springframework.org/schema/mvc" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:beans="http://www.springframework.org/schema/beans" xmlns:context="http://www.springframework.org/schema/context" xsi:schemaLocation=" http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-3.0.xsd http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.0.xsd"> <!-- DispatcherServlet Context: defines this servlet's request-processing infrastructure --> <!-- Enables the Spring MVC @Controller programming model --> <annotation-driven /> <!-- Handles HTTP GET requests for /resources/** by efficiently serving up static resources in the ${webappRoot}/resources directory --> <resources mapping="/resources/**" location="/resources/" /> <!-- Resolves views selected for rendering by @Controllers to .jsp resources in the /WEB-INF/views directory --> <beans:bean class="org.springframework.web.servlet.view.InternalResourceViewResolver"> <beans:property name="prefix" value="/WEB-INF/views/" /> <beans:property name="suffix" value=".jsp" /> </beans:bean> <context:component-scan base-package="com.engilitycorp.leavetracker" /> <beans:bean id="leaveRequestForm" class="com.engilitycorp.leavetracker.model.LeaveRequest" /> </beans:beans> The constants: String LOGIN_FAILURE_PAGE = "loginFailure"; String LOGIN_PAGE = "login"; String CHOOSE_OPERATION_PAGE = "chooseOperation";

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• Hibernate MappingException Unknown entity: $Proxy2

  - by slynn1324

  I'm using Hibernate annotations and have a VERY basic data object: import java.io.Serializable; import javax.persistence.Entity; import javax.persistence.Id; @Entity public class State implements Serializable { /** * */ private static final long serialVersionUID = 1L; @Id private String stateCode; private String stateFullName; public String getStateCode() { return stateCode; } public void setStateCode(String stateCode) { this.stateCode = stateCode; } public String getStateFullName() { return stateFullName; } public void setStateFullName(String stateFullName) { this.stateFullName = stateFullName; } } and am trying to run the following test case: public void testCreateState(){ Session s = HibernateUtil.getSessionFactory().getCurrentSession(); Transaction t = s.beginTransaction(); State state = new State(); state.setStateCode("NE"); state.setStateFullName("Nebraska"); s.save(s); t.commit(); } and get an org.hibernate.MappingException: Unknown entity: $Proxy2 at org.hibernate.impl.SessionFactoryImpl.getEntityPersister(SessionFactoryImpl.java:628) at org.hibernate.impl.SessionImpl.getEntityPersister(SessionImpl.java:1366) at org.hibernate.event.def.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:121) .... I haven't been able to find anything referencing the $Proxy part of the error - and am at a loss.. Any pointers to what I'm missing would be greatly appreciated. hibernate.cfg.xml <property name="hibernate.connection.driver_class">org.hsqldb.jdbcDriver</property> <property name="connection.url">jdbc:hsqldb:hsql://localhost/xdb</property> <property name="connection.username">sa</property> <property name="connection.password"></property> <property name="current_session_context_class">thread</property> <property name="dialect">org.hibernate.dialect.HSQLDialect</property> <property name="show_sql">true</property> <property name="hbm2ddl.auto">update</property> <property name="hibernate.transaction.factory_class">org.hibernate.transaction.JDBCTransactionFactory</property> <mapping class="com.test.domain.State"/> in HibernateUtil.java public static SessionFactory getSessionFactory(boolean testing ) { if ( sessionFactory == null ){ try { String configPath = HIBERNATE_CFG; AnnotationConfiguration config = new AnnotationConfiguration(); config.configure(configPath); sessionFactory = config.buildSessionFactory(); } catch (Exception e){ e.printStackTrace(); throw new ExceptionInInitializerError(e); } } return sessionFactory; }

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• Multiple instances of this carousel on a single page - can't get it to work

  - by Andy

  This code comes from a tutorial so it's not originally my own work. What I am trying to do is implement this several times on a single page. I have tried and so far failed - by numbering the id "carousel" and so forth. Any help would be seriously appreciated. I'm tearing my hair out. http://jsfiddle.net/AndyMP/zcKDV/5/ For completeness.. this is the carousel JQuery as it stands. //rotation speed and timer var speed = 5000; var run = setInterval('rotate()', speed); //grab the width and calculate left value var item_width = $('#slides li').outerWidth(); var left_value = item_width * (-1); //move the last item before first item, just in case user click prev button $('#slides li:first').before($('#slides li:last')); //set the default item to the correct position $('#slides ul').css({'left' : left_value}); //if user clicked on prev button $('#prev').click(function() { //get the right position var left_indent = parseInt($('#slides ul').css('left')) + item_width; //slide the item $('#slides ul').animate({'left' : left_indent}, 200,function(){ //move the last item and put it as first item $('#slides li:first').before($('#slides li:last')); //set the default item to correct position $('#slides ul').css({'left' : left_value}); }); //cancel the link behavior return false; }); //if user clicked on next button $('#next').click(function() { //get the right position var left_indent = parseInt($('#slides ul').css('left')) - item_width; //slide the item $('#slides ul').animate({'left' : left_indent}, 200, function () { //move the first item and put it as last item $('#slides li:last').after($('#slides li:first')); //set the default item to correct position $('#slides ul').css({'left' : left_value}); }); //cancel the link behavior return false; }); //if mouse hover, pause the auto rotation, otherwise rotate it $('#slides').hover( function() { clearInterval(run); }, function() { run = setInterval('rotate()', speed); } ); //a simple function to click next link //a timer will call this function, and the rotation will begin :) function rotate() { $('#next').click(); }

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• Issue accessing class variable from thread.

  - by James

  Hello, The code below is meant to take an arraylist of product objects as an input, spun thread for each product(and add the product to the arraylist 'products'), check product image(product.imageURL) availability, remove the products without images(remove the product from the arraylist 'products'), and return an arraylist of products with image available. package com.catgen.thread; import java.util.ArrayList; import java.util.Iterator; import java.util.List; import com.catgen.Product; import com.catgen.Utils; public class ProductFilterThread extends Thread{ private Product product; private List<Product> products = new ArrayList<Product>(); public ProductFilterThread(){ } public ProductFilterThread(Product product){ this.product = product; } public synchronized void addProduct(Product product){ System.out.println("Before add: "+getProducts().size()); getProducts().add(product); System.out.println("After add: "+getProducts().size()); } public synchronized void removeProduct(Product product){ System.out.println("Before rem: "+getProducts().size()); getProducts().remove(product); System.out.println("After rem: "+getProducts().size()); } public synchronized List<Product> getProducts(){ return this.products; } public synchronized void setProducts(List<Product> products){ this.products = products; } public void run(){ boolean imageExists = Utils.fileExists(this.product.ImageURL); if(!imageExists){ System.out.println(this.product.ImageURL); removeProduct(this.product); } } public List<Product> getProductsWithImageOnly(List<Product> products){ ProductFilterThread pft = null; try{ List<ProductFilterThread> threads = new ArrayList<ProductFilterThread>(); for(Product product: products){ pft = new ProductFilterThread(product); addProduct(product); pft.start(); threads.add(pft); } Iterator<ProductFilterThread> threadsIter = threads.iterator(); while(threadsIter.hasNext()){ ProductFilterThread thread = threadsIter.next(); thread.join(); } }catch(Exception e){ e.printStackTrace(); } System.out.println("Total returned products = "+getProducts().size()); return getProducts(); } } Calling statement: displayProducts = new ProductFilterThread().getProductsWithImageOnly(displayProducts); Here, when addProduct(product) is called from within getProductsWithImageOnly(), getProducts() returns the list of products, but that's not the case(no products are returned) when the method removeProduct() is called by a thread, because of which the products without images are never removed. As a result, all the products are returned by the module whether or not the contained products have images. What can be the problem here? Thanks in advance. James.

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• assistance required, hangman game.

  - by Phillip Gibson

  I am making a hangman game and am having trouble with part of it. I have selected a random word from a file, but I want to display the word as a series of undersocres __ and then match the letter chosen to a position in the undersocres. Can anyone help me? cout <<"1. Select to play the game\n"; cout <<"2. Ask for help\n"; cout <<"3. Select to quit the game\n"; cout << "Enter a selection: "; int number; cin >> number; while(number < 1 || number > 3 || cin.fail()) { if(cin.fail()) { cin.sync(); cin.clear(); cout << "You have not entered a number, please enter a menu selection between 1 and 3\n"; cin >> number; } else { cout << "Your selection must be between 1 and 3!\n"; cin >> number; } } switch (number) { case 1: { string word; string name; cout << " Whats your name? "; cin >> name; Player player(); ifstream FileReader; FileReader.open("words.txt"); if(!FileReader.is_open()) cout << "Error"; //this is for the random selection of words srand(time(0)); int randnum = rand()%10+1; for(int counter = 0; counter < randnum; counter++) { getline(FileReader, word, '\n'); } cout << "my word: " << word << "\n"; // get length of word int length; //create for loop for(int i = 0; i < length; i++) cout << "_"; //_ _ _ _ _ SetCursorPos(2,10); FileReader.close(); break;

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• How to develop a Jquery plugin to find the first child that match with a selector?

  - by Ivan

  I'm trying to make a Jquery plugin (findFirst()) to find the first child with a given characteristics (something in the middle of the find() and children() functions. For instance, given this markup: <div id="start"> <div> <span>Hello world</span> <ul class="valid-result"> ... </ul> <ul class="valid-result"> <li> <ul class="not-a-result"> ... </ul> </li> </ul> <div> <ul class="valid-result"> ... </ul> </div> </div> </div> If you ask for $("#start").findFirst('ul') it should return all ul lists that I have tagged with the valid-result class, but not the ul with class not-a-result. It is, this function has to find the first elements that matches with a given selector, but not the inner elements that match this selector. This is the first time I try to code a Jquery function, and what I've already read doesn't helps me too much with this. The function I have developed is this: jQuery.fn.findFirst = function (sel) { return this.map(function() { return $(this).children().map(function() { if ($(this).is(sel)) { return $(this); } else { return $(this).findFirst(sel); } }); }); } It works in the sense it tries to return the expected result, but the format it returns the result is very rare for me. I suppose the problem is something I don't understand about Jquery. Here you have the JFiddle where I'm testing. EDIT The expected result after $("#start").findFirst('ul') is a set with all UL that have the class 'valid-result' BUT it's not possible to use this class because it doesn't exist in a real case (it's just to try to explain the result). This is not equivalent to first(), because first returns only one element!

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• get renamed file names of multiple upload form [js array] in codeigniter

  - by artmania

  Hi friends, I use codeigniter. I have a multiple image upload form. The code below is working well for uploading, but I also need to save file names to database. How can I get the names in here? I spent hours & hours :/ but could not sort it :/ Appreciate helps!!! uploadform.php echo form_open_multipart('gallery/upload'); <input type="file" name="photo" size="50" /> <input type="file" name="thumb" size="50" /> <input type="submit" value="Upload" /> </form> I have a controller between form view and model load model (of course : )) but didnt post here because of no need. gallery_model.php function multiple_upload($upload_dir = 'uploads/', $config = array()) { /* Upload */ $CI =& get_instance(); $files = array(); if(empty($config)) { $config['upload_path'] = realpath($upload_dir); $config['allowed_types'] = 'gif|jpg|jpeg|jpe|png'; $config['max_size'] = '2048'; } $CI->load->library('upload', $config); $errors = FALSE; foreach($_FILES as $key => $value) { if( ! empty($value['name'])) { if( ! $CI->upload->do_upload($key)) { $data['upload_message'] = $CI->upload->display_errors(ERR_OPEN, ERR_CLOSE); // ERR_OPEN and ERR_CLOSE are error delimiters defined in a config file $CI->load->vars($data); $errors = TRUE; } else { // Build a file array from all uploaded files $files[] = $CI->upload->data(); } } } // There was errors, we have to delete the uploaded files if($errors) { foreach($files as $key => $file) { @unlink($file['full_path']); } } elseif(empty($files) AND empty($data['upload_message'])) { $CI->lang->load('upload'); $data['upload_message'] = ERR_OPEN.$CI->lang->line('upload_no_file_selected').ERR_CLOSE; $CI->load->vars($data); } else { return $files; } /* ------------------------------- Insert to database */ // problem is here, i need file names to add db. // if there is already same names file at the folder, it rename file itself. so in such case, I need renamed file name :/ } }

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• Hibernate Communications Link Failure in Restlet-Hibernate Based Java application powered by MySQL

  - by Vatsala

  Let me describe my question - I have a Java application - Hibernate as the DB interfacing layer over MySQL. I get the communications link failure error in my application. The occurence of this error is a very specific case. I get this error , When I leave mysql server unattended for more than approximately 6 hours (i.e. when there are no queries issued to MySQL for more than approximately 6 hours). I am pasting a top 'exception' level description below, and adding a pastebin link for a detailed stacktrace description. javax.persistence.PersistenceException: org.hibernate.exception.JDBCConnectionException: Cannot open connection - Caused by: org.hibernate.exception.JDBCConnectionException: Cannot open connection - Caused by: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure - The last packet successfully received from the server was 1,274,868,181,212 milliseconds ago. The last packet sent successfully to the server was 0 milliseconds ago. - Caused by: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure - The last packet successfully received from the server was 1,274,868,181,212 milliseconds ago. The last packet sent successfully to the server was 0 milliseconds ago. - Caused by: java.net.ConnectException: Connection refused: connect the link to the pastebin for further investigation - http://pastebin.com/4KujAmgD What I understand from these exception statements is that MySQL is refusing to take in any connections after a period of idle/nil activity. I have been reading up a bit about this via google search, and came to know that one of the possible ways to overcome this is to set values for c3p0 properties as c3p0 comes bundled with Hibernate. Specifically, I read from here http://www.mchange.com/projects/c3p0/index.html that setting two properties idleConnectionTestPeriod and preferredTestQuery will solve this for me. But these values dont seem to have had an effect. Is this the correct approach to fixing this? If not, what is the right way to get over this? The following are related Communications Link Failure questions at stackoverflow.com, but I've not found a satisfactory answer in their answers. http://stackoverflow.com/questions/2121829/java-db-communications-link-failure http://stackoverflow.com/questions/298988/how-to-handle-communication-link-failure Note 1 - i dont get this error when I am using my application continuosly. Note 2 - I use JPA with Hibernate and hence my hibernate.dialect,etc hibernate properties reside within the persistence.xml in the META-INF folder (does that prevent the c3p0 properties from working?)

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• Activity gets killed while executing the camera intent

  - by BlackRider

  In my app I call the system camera to take a picture, and then handle the result in onActivityResult. You know, the usual. It used to work, but now my calling activity gets killed while I'm taking the picture. Specifically, onDestroy() is called on my activity right after I press the camera shutter. The photo does get taken & saved (I've checked that the file gets written on the SD card). After I accept the photo, instead of returning to the calling activity and invoking onActivityResult, the previous activity in the activity stack gets called. I see no exceptions in the logcat. My custom exception handler doesn't get called. If it matters, my app also includes a service that listens to GPS updates, but I unregister all the receivers in onPause(). Here's the call stack for MyCallingActivity.onDestroy(): Thread [<1> main] (Suspended (breakpoint at line 303 in NewPlaceDetailsActivity)) NewPlaceDetailsActivity.onDestroy() line: 303 ActivityThread.performDestroyActivity(IBinder, boolean, int, boolean) line: 2663 ActivityThread.handleDestroyActivity(IBinder, boolean, int, boolean) line: 2694 ActivityThread.access$2100(ActivityThread, IBinder, boolean, int, boolean) line: 117 BinderProxy(ActivityThread$H).handleMessage(Message) line: 968 ActivityThread$H(Handler).dispatchMessage(Message) line: 99 Looper.loop() line: 130 ActivityThread.main(String[]) line: 3687 Method.invokeNative(Object, Object[], Class, Class[], Class, int, boolean) line: not available [native method] Method.invoke(Object, Object...) line: 507 ZygoteInit$MethodAndArgsCaller.run() line: 842 ZygoteInit.main(String[]) line: 600 NativeStart.main(String[]) line: not available [native method] This is how I start the camera activity, in case you're wondering: protected void startCamera() { createPhotoDirsIfNeeded(); String fileName = "temp.jpg"; ContentValues values = new ContentValues(); values.put(MediaStore.Images.Media.TITLE, fileName); m_capturedImageUri = getContentResolver().insert(MediaStore.Images.Media.EXTERNAL_CONTENT_URI, values); m_photoFileName = APP_PHOTO_PATH + "/" + DateFormat.format(DATE_FORMAT, Calendar.getInstance().getTime()) + ".jpg"; File picFile = new File(m_photoFileName); if(picFile.exists()) { picFile.delete(); } // start the camera activity Intent intent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE); intent.putExtra(MediaStore.EXTRA_OUTPUT, Uri.fromFile(picFile)); startActivityForResult(intent, IntentHelper.REQUEST_TAKE_PHOTO); } How can I find out why does my activity get killed, AND removed from the stack instead of being created again?

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• Converting C source to C++

  - by Barry Kelly

  How would you go about converting a reasonably large (300K), fairly mature C codebase to C++? The kind of C I have in mind is split into files roughly corresponding to modules (i.e. less granular than a typical OO class-based decomposition), using internal linkage in lieu private functions and data, and external linkage for public functions and data. Global variables are used extensively for communication between the modules. There is a very extensive integration test suite available, but no unit (i.e. module) level tests. I have in mind a general strategy: Compile everything in C++'s C subset and get that working. Convert modules into huge classes, so that all the cross-references are scoped by a class name, but leaving all functions and data as static members, and get that working. Convert huge classes into instances with appropriate constructors and initialized cross-references; replace static member accesses with indirect accesses as appropriate; and get that working. Now, approach the project as an ill-factored OO application, and write unit tests where dependencies are tractable, and decompose into separate classes where they are not; the goal here would be to move from one working program to another at each transformation. Obviously, this would be quite a bit of work. Are there any case studies / war stories out there on this kind of translation? Alternative strategies? Other useful advice? Note 1: the program is a compiler, and probably millions of other programs rely on its behaviour not changing, so wholesale rewriting is pretty much not an option. Note 2: the source is nearly 20 years old, and has perhaps 30% code churn (lines modified + added / previous total lines) per year. It is heavily maintained and extended, in other words. Thus, one of the goals would be to increase mantainability. [For the sake of the question, assume that translation into C++ is mandatory, and that leaving it in C is not an option. The point of adding this condition is to weed out the "leave it in C" answers.]

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• propertyplaceholderconfigurer class name substitution problem

  - by Alex

  The following example works for "class name substitution using the PropertyPlaceHolderConfigurer": http://forum.springsource.org/showpost.php?p=228136&postcount=2 HOWEVER, when porting this code over (messages.properties, com.spring.ioc.TestClass, and spring-config.xml) to a web application, the class name substitution now fails! 1) I am running on the webapp on Tomcat through the Eclipse plugin. 2) In the web.xml I have the following: <context-param> <param-name>contextConfigLocation</param-name> <param-value>/WEB-INF/spring-config.xml</param-value> </context-param> <listener> <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class> </listener> 3) The following is output in the log: 282 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Ignoring bean class loading failure for bean 'test' org.springframework.beans.factory.CannotLoadBeanClassException: Cannot find class [${test.class}] for bean with name 'test' defined in ServletContext resource [/WEB-INF/spring-config.xml]; nested exception is java.lang.ClassNotFoundException: ${test.class} at org.springframework.beans.factory.support.AbstractBeanFactory.resolveBeanClass(AbstractBeanFactory.java:1141) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.predictBeanType(AbstractAutowireCapableBeanFactory.java:524) at org.springframework.beans.factory.support.AbstractBeanFactory.isFactoryBean(AbstractBeanFactory.java:1177) at org.springframework.beans.factory.support.DefaultListableBeanFactory.getBeanNamesForType(DefaultListableBeanFactory.java:222) at org.springframework.context.support.AbstractApplicationContext.invokeBeanFactoryPostProcessors(AbstractApplicationContext.java:505) at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:362) at org.springframework.web.context.ContextLoader.createWebApplicationContext(ContextLoader.java:255) at org.springframework.web.context.ContextLoader.initWebApplicationContext(ContextLoader.java:199) at org.springframework.web.context.ContextLoaderListener.contextInitialized(ContextLoaderListener.java:45) at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:3795) at org.apache.catalina.core.StandardContext.start(StandardContext.java:4252) at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1014) at org.apache.catalina.core.StandardHost.start(StandardHost.java:736) at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1014) at org.apache.catalina.core.StandardEngine.start(StandardEngine.java:443) at org.apache.catalina.core.StandardService.start(StandardService.java:448) at org.apache.catalina.core.StandardServer.start(StandardServer.java:700) at org.apache.catalina.startup.Catalina.start(Catalina.java:552) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:295) at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:433) Caused by: java.lang.ClassNotFoundException: ${test.class} at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1438) at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1284) at org.springframework.util.ClassUtils.forName(ClassUtils.java:211) at org.springframework.beans.factory.support.AbstractBeanDefinition.resolveBeanClass(AbstractBeanDefinition.java:385) at org.springframework.beans.factory.support.AbstractBeanFactory.resolveBeanClass(AbstractBeanFactory.java:1138) ... 23 more Note: I haven't included it, but the PropertyPlaceHolderConfigurer is successfully locating the messages.properties file, but this seems to happen AFTER the above error is output?! DOES ANYBODY KNOW WHY THIS IS THE CASE AND HOW I CAN OVERCOME THIS PROBLEM?

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• Perl - Calling subclass constructor from superclass (OO)

  - by Emmel

  This may turn out to be an embarrassingly stupid question, but better than potentially creating embarrassingly stupid code. :-) This is an OO design question, really. Let's say I have an object class 'Foos' that represents a set of dynamic configuration elements, which are obtained by querying a command on disk, 'mycrazyfoos -getconfig'. Let's say that there are two categories of behavior that I want 'Foos' objects to have: Existing ones: one is, query ones that exist in the command output I just mentioned (/usr/bin/mycrazyfoos -getconfig`. Make modifications to existing ones via shelling out commands. Create new ones that don't exist; new 'crazyfoos', using a complex set of /usr/bin/mycrazyfoos commands and parameters. Here I'm not really just querying, but actually running a bunch of system() commands. Affecting changes. Here's my class structure: Foos.pm package Foos, which has a new($hashref-{name = 'myfooname',) constructor that takes a 'crazyfoo NAME' and then queries the existence of that NAME to see if it already exists (by shelling out and running the mycrazyfoos command above). If that crazyfoo already exists, return a Foos::Existing object. Any changes to this object requires shelling out, running commands and getting confirmation that everything ran okay. If this is the way to go, then the new() constructor needs to have a test to see which subclass constructor to use (if that even makes sense in this context). Here are the subclasses: Foos/Existing.pm As mentioned above, this is for when a Foos object already exists. Foos/Pending.pm This is an object that will be created if, in the above, the 'crazyfoo NAME' doesn't actually exist. In this case, the new() constructor above will be checked for additional parameters, and it will go ahead and, when called using -create() shell out using system() and create a new object... possibly returning an 'Existing' one... OR As I type this out, I am realizing it is perhaps it's better to have a single: (an alternative arrangement) Foos class, that has a -new() that takes just a name -create() that takes additional creation parameters -delete(), -change() and other params that affect ones that exist; that will have to just be checked dynamically. So here we are, two main directions to go with this. I'm curious which would be the more intelligent way to go.

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• LINQ Except operator and object equality

  - by Abhijeet Patel

  Here is an interesting issue I noticed when using the Except Operator: I have list of users from which I want to exclude some users: The list of users is coming from an XML file: The code goes like this: interface IUser { int ID { get; set; } string Name { get; set; } } class User: IUser { #region IUser Members public int ID { get; set; } public string Name { get; set; } #endregion public override string ToString() { return ID + ":" +Name; } public static IEnumerable<IUser> GetMatchingUsers(IEnumerable<IUser> users) { IEnumerable<IUser> localList = new List<User> { new User{ ID=4, Name="James"}, new User{ ID=5, Name="Tom"} }.OfType<IUser>(); var matches = from u in users join lu in localList on u.ID equals lu.ID select u; return matches; } } class Program { static void Main(string[] args) { XDocument doc = XDocument.Load("Users.xml"); IEnumerable<IUser> users = doc.Element("Users").Elements("User").Select (u => new User { ID = (int)u.Attribute("id"), Name = (string)u.Attribute("name") } ).OfType<IUser>(); //still a query, objects have not been materialized var matches = User.GetMatchingUsers(users); var excludes = users.Except(matches); // excludes should contain 6 users but here it contains 8 users } } When I call User.GetMatchingUsers(users) I get 2 matches as expected. The issue is that when I call users.Except(matches) The matching users are not being excluded at all! I am expecting 6 users ut "excludes" contains all 8 users instead. Since all I'm doing in GetMatchingUsers(IEnumerable users) is taking the IEnumerable and just returning the IUsers whose ID's match( 2 IUsers in this case), my understanding is that by default "Except" will use reference equality for comparing the objects to be excluded. Is this not how "Except" behaves? What is even more interesting is that if I materialize the objects using .ToList() and then get the matching users, and call "Except", everything works as expected! Like so: IEnumerable users = doc.Element("Users").Elements("User").Select (u = new User { ID = (int)u.Attribute("id"), Name = (string)u.Attribute("name") } ).OfType().ToList(); //explicity materializing all objects by calling ToList() var matches = User.GetMatchingUsers(users); var excludes = users.Except(matches); // excludes now contains 6 users as expected I don't see why I should need to materialize objects for calling "Except" given that its defined on IEnumerable? Any suggesstions / insights would be much appreciated.

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• How to reduce redundant code when adding new c++0x rvalue reference operator overloads

  - by Inverse

  I am adding new operator overloads to take advantage of c++0x rvalue references, and I feel like I'm producing a lot of redundant code. I have a class, tree, that holds a tree of algebraic operations on double values. Here is an example use case: tree x = 1.23; tree y = 8.19; tree z = (x + y)/67.31 - 3.15*y; ... std::cout << z; // prints "(1.23 + 8.19)/67.31 - 3.15*8.19" For each binary operation (like plus), each side can be either an lvalue tree, rvalue tree, or double. This results in 8 overloads for each binary operation: // core rvalue overloads for plus: tree operator +(const tree& a, const tree& b); tree operator +(const tree& a, tree&& b); tree operator +(tree&& a, const tree& b); tree operator +(tree&& a, tree&& b); // cast and forward cases: tree operator +(const tree& a, double b) { return a + tree(b); } tree operator +(double a, const tree& b) { return tree(a) + b; } tree operator +(tree&& a, double b) { return std::move(a) + tree(b); } tree operator +(double a, tree&& b) { return tree(a) + std::move(b); } // 8 more overloads for minus // 8 more overloads for multiply // 8 more overloads for divide // etc which also has to be repeated in a way for each binary operation (minus, multiply, divide, etc). As you can see, there are really only 4 functions I actually need to write; the other 4 can cast and forward to the core cases. Do you have any suggestions for reducing the size of this code? PS: The class is actually more complex than just a tree of doubles. Reducing copies does dramatically improve performance of my project. So, the rvalue overloads are worthwhile for me, even with the extra code. I have a suspicion that there might be a way to template away the "cast and forward" cases above, but I can't seem to think of anything.

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• IOC/Autofac problem

  - by Krazzy

  I am currently using Autofac, but am open to commentary regarding other IOC containers as well. I would prefer a solution using Autofac if possible. I am also somewhat new to IOC so I may be grossly misunderstanding what I should be using an IOC container for. Basically, the situation is as follows: I have a topmost IOC container for my app. I have a tree of child containers/scopes where I would like the same "service" (IWhatever) to resolve differently depending on which level in the tree it is resolved. Furthermore if a service is not registered at some level in the tree I would like the tree to be transversed upward until a suitable implementation is found. Furthermore, when constructing a given component, it is quite possible that I will need access to the parent container/scope. In many cases the component that I'm registering will have a dependency on the same or a different service in a parent scope. Is there any way to express this dependency with Autofac? Something like: builder.Register(c=> { var parentComponent = ?.Resolve<ISomeService>(); var childComponent = new ConcreteService(parentComponent, args...); return childComponent; }).As<ISomeService>(); I can't get anything similar to the above pseudocode to work for serveral reasons: A) It seems that all levels in the scope tree share a common set of registrations. I can't seem to find a way to make a given registration confined a certain "scope". B) I can't seem to find a way to get a hold of the parent scope of a given scope. I CAN resolve ILifetimeScope in the container and then case it to a concrete LifetimeScope instance which provides its parent scope, but I'm guessing it is probably note meant to be used this way. Is this safe? C) I'm not sure how to tell Autofac which container owns the resolved object. For many components I would like component to be "owned" by the scope in which it is constructed. Could tagged contexts help me here? Would I have to tag every level of the tree with a unique tag? This would be difficult because the tree depth is determined at runtime. Sorry for the extremely lengthy question. In summary: 1) Is there any way to do what I want to do using Autofac? 2) Is there another container more suited to this kind of dependency structure? 3) Is IOC the wrong tool for this altogether?

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• Template function as a template argument

  - by Kos

  I've just got confused how to implement something in a generic way in C++. It's a bit convoluted, so let me explain step by step. Consider such code: void a(int) { // do something } void b(int) { // something else } void function1() { a(123); a(456); } void function2() { b(123); b(456); } void test() { function1(); function2(); } It's easily noticable that function1 and function2 do the same, with the only different part being the internal function. Therefore, I want to make function generic to avoid code redundancy. I can do it using function pointers or templates. Let me choose the latter for now. My thinking is that it's better since the compiler will surely be able to inline the functions - am I correct? Can compilers still inline the calls if they are made via function pointers? This is a side-question. OK, back to the original point... A solution with templates: void a(int) { // do something } void b(int) { // something else } template<void (*param)(int) > void function() { param(123); param(456); } void test() { function<a>(); function<b>(); } All OK. But I'm running into a problem: Can I still do that if a and b are generics themselves? template<typename T> void a(T t) { // do something } template<typename T> void b(T t) { // something else } template< ...param... > // ??? void function() { param<SomeType>(someobj); param<AnotherType>(someotherobj); } void test() { function<a>(); function<b>(); } I know that a template parameter can be one of: a type, a template type, a value of a type. None of those seems to cover my situation. My main question is hence: How do I solve that, i.e. define function() in the last example? (Yes, function pointers seem to be a workaround in this exact case - provided they can also be inlined - but I'm looking for a general solution for this class of problems).

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• Question about POP3 message termination octet

  - by user361633

  This is from the POP3 RFC. "Responses to certain commands are multi-line. In these cases, which are clearly indicated below, after sending the first line of the response and a CRLF, any additional lines are sent, each terminated by a CRLF pair. When all lines of the response have been sent, a final line is sent, consisting of a termination octet (decimal code 046, ".") and a CRLF pair. If any line of the multi-line response begins with the termination octet, the line is "byte-stuffed" by pre-pending the termination octet to that line of the response. Hence a multi-line response is terminated with the five octets "CRLF.CRLF". When examining a multi-line response, the client checks to see if the line begins with the termination octet. If so and if octets other than CRLF follow, the first octet of the line (the termination octet) is stripped away. If so and if CRLF immediately follows the termination character, then the response from the POP server is ended and the line containing ".CRLF" is not considered part of the multi-line response." Well, i have problem with this, for example gmail sometimes sends the termination octet and then in the NEXT LINE sends the CRLF pair. For example: "+OK blah blah" "blah blah." "\r\n" That's very rare, but it happens sometimes, so obviously i'm unable to determine the end of the message in such case, because i'm expecting a line that consists of '.\r\n'. Seriously, is Gmail violating the POP3 protocol or i'm doing something wrong? Also i have a second question, english is not my first language so i cannot understand that completely: "If any line of the multi-line response begins with the termination octet, the line is "byte-stuffed" by pre-pending the termination octet to that line of the response. Hence a multi-line response is terminated with the five octets "CRLF.CRLF"." When exactly CRLF.CRLF is used? Can someone gives me a simple example? The rfc says that is used when any line of the response begins with the termination octet. But i don't see any lines that starts with '.' in the messages that are terminated with CRLF.CRLF. I checked that. Maybe i don't understand something, that's why i'm asking.

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• Spring 3 MVC - Form Failure Causes Exception When Reloading JSP

  - by jboyd

  Using Spring 3 MVC, please bear with the long code example, it's quite simple, but I want to make sure all relevant information is posted. Basically here is the use case: There is a registration page, a user can login, OR fill out a registration form. The login form is a simple HTML form, the registration form is a more complicated, Spring bound form that uses a RegistrationFormData bean. Here is the relevant code: UserController.java ... @RequestMapping(value = "/login", method = RequestMethod.GET) public String login(Model model) { model.addAttribute("registrationInfo", new ProfileAdminFormData()); return "login"; } ... @RequestMapping(value = "/login.do", method = RequestMethod.POST) public String doLogin( @RequestParam(value = "userName") String userName, @RequestParam(value = "password") String password, Model model) { logger.info("login.do : userName=" + userName + ", password=" + password); try { getUser().login(userName, password); } catch (UserNotFoundException ex) { logger.error(ex); model.addAttribute("loginError", ex.getWebViewableErrorMessage()); return "login"; } return "redirect:/"; } ... @RequestMapping(value = "/register.do") public String register( @ModelAttribute(value = "registrationInfo") ProfileAdminFormData profileAdminFormData, BindingResult result, Model model) { //todo: redirect if (new RegistrationValidator(profileAdminFormData, result).validate()) { try { User().register(profileAdminFormData); return "index"; } catch (UserException ex) { logger.error(ex); model.addAttribute("registrationErrorMessage", ex.getWebViewableErrorMessage()); return "login"; } } return "login"; } and the JSP: ... <form:form commandName="registrationInfo" action="register.do"> ... So the problem here is that when login fails I get an exception because there is no bean "registrationInfo" in the model attributes. What I need is that regardless of the path through this controller that the "registrationInfo" bean is not null, that way if login fails, as opposed to registration, that bean is still in the model. As you can see I create the registrationInfo object explicitly in my controller in the method bound to "/login", which is what I thought was going to be kind of a setup method" Something doesn't feel right about the "/login" method which sets up the page, but I needed to that in order to get the page to render at all without throwing an exception because there is no "registrationInfo" model attribute, as needed by the form in the JSP

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• Removing elements from heap

  - by user193138

  I made a heap. I am curious if there's something subtley wrong with my remove function: int Heap::remove() { if (n == 0) exit(1); int temp = arr[0]; arr[0] = arr[--n]; heapDown(0); arr[n] = 0; return temp; } void Heap::heapDown(int i) { int l = left(i); int r = right(i); // comparing parent to left/right child // each has an inner if to handle if the first swap causes a second swap // ie 1 -> 3 -> 5 // 3 5 1 5 1 3 if (l < n && arr[i] < arr[l]) { swap(arr[i], arr[l]); heapDown(l); if (r < n && arr[i] < arr[r]) { swap(arr[i], arr[r]); heapDown(r); } } else if (r < n && arr[i] < arr[r]) { swap(arr[i], arr[r]); heapDown(r); if (l < n && arr[i] < arr[l]) { swap(arr[i], arr[l]); heapDown(l); } } } Here's my output i1i2i3i4i5i6i7 p Active heap: 7 4 6 1 3 2 5 r Removed 7 r Removed 6 p Active heap: 5 3 4 1 2 Here's my teacher's sample output: p Active heap : 7 4 6 1 3 2 5 r Removed 7 r Removed 6 p Active heap : 5 4 2 1 3 s Heapsorted : 1 2 3 4 5 While our outputs are completely different, I do seem to hold maxheap principle of having everything left oriented and for all nodes parent child(in every case I tried). I try to do algs like this from scratch, so maybe I'm just doing something really weird and wrong (I would only consider it "wrong" if it's O(lg n), as removes are intended to be for heaps). Is there anything in particular "wrong" about my remove? Thanks, http://ideone.com/PPh4eQ

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• Specializating a template function that takes a universal reference parameter

  - by David Stone

  How do I specialize a template function that takes a universal reference parameter? foo.hpp: template<typename T> void foo(T && t) // universal reference parameter foo.cpp template<> void foo<Class>(Class && class) { // do something complicated } Here, Class is no longer a deduced type and thus is Class exactly; it cannot possibly be Class &, so reference collapsing rules will not help me here. I could perhaps create another specialization that takes a Class & parameter (I'm not sure), but that implies duplicating all of the code contained within foo for every possible combination of rvalue / lvalue references for all parameters, which is what universal references are supposed to avoid. Is there some way to accomplish this? To be more specific about my problem in case there is a better way to solve it: I have a program that can connect to multiple game servers, and each server, for the most part, calls everything by the same name. However, they have slightly different versions for a few things. There are a few different categories that these things can be: a move, an item, etc. I have written a generic sort of "move string to move enum" set of functions for internal code to call, and my server interface code has similar functions. However, some servers have their own internal ID that they communicate with, some use strings, and some use both in different situations. Now what I want to do is make this a little more generic. I want to be able to call something like ServerNamespace::server_cast<Destination>(source). This would allow me to cast from a Move to a std::string or ServerMoveID. Internally, I may need to make a copy (or move from) because some servers require that I keep a history of messages sent. Universal references seem to be the obvious solution to this problem. The header file I'm thinking of right now would expose simply this: namespace ServerNamespace { template<typename Destination, typename Source> Destination server_cast(Source && source); } And the implementation file would define all legal conversions as template specializations.

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