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  • In Java Concurrency In Practice by Brian Goetz, why is the Memoizer class not annotated with @ThreadSafe?

    - by dig_dug
    Java Concurrency In Practice by Brian Goetz provides an example of a efficient scalable cache for concurrent use. The final version of the example showing the implementation for class Memoizer (pg 108) shows such a cache. I am wondering why the class is not annotated with @ThreadSafe? The client, class Factorizer, of the cache is properly annotated with @ThreadSafe. The appendix states that if a class is not annotated with either @ThreadSafe or @Immutable that it should be assumed that it isn't thread safe. Memoizer seems thread-safe though. Here is the code for Memoizer: public class Memoizer<A, V> implements Computable<A, V> { private final ConcurrentMap<A, Future<V>> cache = new ConcurrentHashMap<A, Future<V>>(); private final Computable<A, V> c; public Memoizer(Computable<A, V> c) { this.c = c; } public V compute(final A arg) throws InterruptedException { while (true) { Future<V> f = cache.get(arg); if (f == null) { Callable<V> eval = new Callable<V>() { public V call() throws InterruptedException { return c.compute(arg); } }; FutureTask<V> ft = new FutureTask<V>(eval); f = cache.putIfAbsent(arg, ft); if (f == null) { f = ft; ft.run(); } } try { return f.get(); } catch (CancellationException e) { cache.remove(arg, f); } catch (ExecutionException e) { throw launderThrowable(e.getCause()); } } } }

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  • dynamically create class in scala, should I use interpreter?

    - by Phil
    Hi, I want to create a class at run-time in Scala. For now, just consider a simple case where I want to make the equivalent of a java bean with some attributes, I only know these attributes at run time. How can I create the scala class? I am willing to create from scala source file if there is a way to compile it and load it at run time, I may want to as I sometimes have some complex function I want to add to the class. How can I do it? I worry that the scala interpreter which I read about is sandboxing the interpreted code that it loads so that it won't be available to the general application hosting the interpreter? If this is the case, then I wouldn't be able to use the dynamically loaded scala class. Anyway, the question is, how can I dynamically create a scala class at run time and use it in my application, best case is to load it from a scala source file at run time, something like interpreterSource("file.scala") and its loaded into my current runtime, second best case is some creation by calling methods ie. createClass(...) to create it at runtime. Thanks, Phil

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  • How can I access a method of the consumer class inside a method created at runtime in a method of th

    - by xxxxxxx
    I define a method inside a parametrized role that needs to create a new class at run time using Moose::Meta::Class->create and apply that exact parametrized role to it. I am also making a new method for that role using $new_class->meta->add_method( some_name => sub { my ($self) = @_; ... }) inside the sub {...} I want to access a method of the consumer class and use it for something, I have tried using $self->get_method, it didn't work, how do I do this? Please notice that the $self inside the sub above is MooseX::Role::Parameterized::Meta::Role::Parameterizable I also have another question, if I do this: my $object = Moose::Meta::Class->create( "some_type", ); Why isn't $object of type some_type and it's some ugly MooseX::Role::Parameterized::Meta::Role::Parameterizable and how do I get to the object of type some_type?

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  • Why won't my DIV height grow? Is it because I am using floats?

    - by user1684636
    Please help! I am trying to create some div sections and some of these div sections have some other divs that are floated. All of which I have cleared. But the sections are not growing to accomodate the content inside of them. The following is my HTML - <div class="data"> <div class="name">Data</div> <div class="first section"> <div class="title">First Section</div> <div class="left settings"> <div class="row"> <div class="field">First Name</div> <div class="value">John</div> </div> <div class="row"> <div class="field">Last Name</div> <div class="value">Smith</div> </div> </div> <div class="right settings"> <div class="row"> <div class="field">ID</div> <div class="value">321</div> </div> <div class="row"> <div class="field">Group</div> <div class="value">Eng</div> </div> </div> </div> <div class="second section"> <div class="title">Second Section</div> </div> <div class="third section"> <div class="title">Third Section</div> </div> </div> The following is my CSS - div.data { position: relative; top: 1em; width: 100em; } div.data div.name { color: #0066FF; font-weight: bold; } div.data div.section div.title { color: green; font-weight: bold; } /** first section **/ div.data div.first div.settings { position: relative; width: 799px; border-top: 1px solid; float: left; } div.data div.first div.left { border-left: 1px solid; } div.data div.first div.settings div.row { border-bottom: 1px solid; clear: both; height: 2em; } div.data div.first div.settings div.row div { float: left; height: 22px; padding: 5px; border-right: 1px solid; } div.data div.first div.settings div.row div.field { width: 192px; } div.data div.first div.settings div.row div.value { width: 585px; } /** second section **/ div.data div.second { clear: both; } For the first section, I have a title and a table that is made up of a left and right. Both of these are floated left and cleared. The rows of the left and right table have a field and value which are also floated left and right and cleared. At this point, I expect "first section" to grow as the content inside of it grows. But instead the height is stuck at 22px, the same height as the section title! What is going on? I tried overflow:auto for div.section and that worked. But when I tried to set this style for div.settings in "first section": div.data div.first div.settings { position: relative; top: 1em; } I end up with these scroll bars, instead of the height growing to fit the new changes. And everything was out of whack. I am really at my wit's end trying to figure this out. If anyone can give me any suggestions on what I am doing wrong, it would be a great help. Thanks.

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  • Why can't I use WCF DataContract and ISerializable on the same class?

    - by Dave
    Hi all, I have a class that I need to be able to serialize to a SQLServer session variable and be available over a WCF Service. I have declared it as follows namespace MyNM { [Serializable] [DataContract(Name = "Foo", Namespace = "http://www.mydomain.co.uk")] public class Foo : IEntity, ISafeCopy<Foo> { [DataMember(Order = 0)] public virtual Guid Id { get; set; } [DataMember(Order = 1)] public virtual string a { get; set; } DataMember(Order = 2)] public virtual Bar c { get; set; } /* ISafeCopy implementation */ } [Serializable] [DataContract(Name = "Bar ", Namespace = "http://www.mydomain.co.uk")] public class Bar : IEntity, ISafeCopy<Bar> { #region Implementation of IEntity DataMember(Order = 0)] public virtual Guid Id { get; set; } [DataMember(Order = 1)] public virtual Baz y { get; set; } #endregion /* ISafeCopy implementation*/ } [Serializable] [DataContract] public enum Baz { [EnumMember(Value = "one")] one, [EnumMember(Value = "two")] two, [EnumMember(Value = "three")] three } But when I try and call this service, I get the following error in the trace log. "System.Runtime.Serialization.InvalidDataContractException: Type 'BarProxybcb100e8617f40ceaa832fe4bb94533c' cannot be ISerializable and have DataContractAttribute attribute." If I take out the Serializable attribute, the WCF service works, but when the object can't be serialized to session. If I remove the DataContract attribute from class Bar, the WCF service fails saying Type 'BarProxy3bb05a31167f4ba492909ec941a54533' with data contract name 'BarProxy3bb05a31167f4ba492909ec941a54533:http://schemas.datacontract.org/2004/07/' is not expected. Add any types not known statically to the list of known types - for example, by using the KnownTypeAttribute attribute or by adding them to the list of known types passed to DataContractSerializer I've tried adding a KnownType attribute to the foo class [KnownType(typeof(Bar))] But I still get the same error. Can anyone help me out with this? Many thanks Dave

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  • EntityFramework repository template- how to write GetByID lamba within a template class?

    - by FerretallicA
    I am trying to write a generic one-size-fits-most repository pattern template class for an Entity Framework-based project I'm currently working on. The (heavily simplified) interface is: internal interface IRepository<T> where T : class { T GetByID(int id); IEnumerable<T> GetAll(); IEnumerable<T> Query(Func<T, bool> filter); } GetByID is proving to be the killer. In the implementation: public class Repository<T> : IRepository<T>,IUnitOfWork<T> where T : class { // etc... public T GetByID(int id) { return this.ObjectSet.Single<T>(t=>t.ID == id); } t=t.ID == id is the particular bit I'm struggling with. Is it even possible to write lamba functions like that within template classes where no class-specific information is going to be available?

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  • Why can't I call methods within a class that explicitly implements an interface?

    - by tyrone302
    Here's the story. I created and interface, IVehicle. I explicitly implemented the interface in my class, Vehicle.cs. Here is my interface: Interface IVehicle { int getWheel(); } here is my class: class Vehicle: IVehicle { public int IVehicle.getWheel() { return wheel; } public void printWheel() { Console.WriteLine(getWheel()); } } Notice that "getWheel()" is explicitly implemented. Now, when I try to call that method within my Vehicle class, I receive an error indicating that getWheel() does not exist in the current context. Can someone help me understand what I am doing wrong?

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  • Parsing tables, cells with Html agility in C#

    - by Kaeso
    I need to parse Html code. More specifically, parse each cell of every rows in all tables. Each row represent a single object and each cell represent different properties. I want to parse these to be able to write an XML file with every data inside (without the useless HTML code). This is the way I thought it out initially but I ran out of ideas: HTML: <tr> <td class="statBox" style="border-width:0px 1px 1px 0px; background-color: #FFFFFF"> 1 </td> <td class="statBox" style="border-width:0px 1px 1px 0px; background-color: #FFFFFF" align="left"> <a href="/ice/player.htm?id=8471675">Sidney Crosby</a> </td> <td class="statBox" style="border-width:0px 1px 1px 0px; background-color: #FFFFFF" align="center"> PIT </td> <td class="statBox" style="border-width:0px 1px 1px 0px; background-color: #FFFFFF" align="center"> C </td> <td class="statBox" style="border-width:0px 1px 1px 0px; background-color: #FFFFFF" align="right"> 39 </td> <td class="statBox" style="border-width:0px 1px 1px 0px; background-color: #FFFFFF" align="right"> 32 </td> <td class="statBox" style="border-width:0px 1px 1px 0px; background-color: #FFFFFF" align="right"> 33 </td> <td class="statBox sorted" style="border-width:0px 1px 1px 0px; background-color: #E0E0E0" align="right"> <font color="#000000"> 65 </font> </td> <td class="statBox" style="border-width:0px 1px 1px 0px; background-color: #FFFFFF" align="right"> 20 </td> <td class="statBox" style="border-width:0px 1px 1px 0px; background-color: #FFFFFF" align="right"> 29 </td> <td class="statBox" style="border-width:0px 1px 1px 0px; background-color: #FFFFFF" align="right"> 10 </td> <td class="statBox" style="border-width:0px 1px 1px 0px; background-color: #FFFFFF" align="right"> 1 </td> <td class="statBox" style="border-width:0px 1px 1px 0px; background-color: #FFFFFF" align="right"> 3 </td> <td class="statBox" style="border-width:0px 0px 1px 0px; background-color: #FFFFFF" align="right"> </td> <td class="statBox" style="border-width:0px 1px 1px 0px; background-color: #FFFFFF" align="right"> 0 </td> <td class="statBox" style="border-width:0px 1px 1px 0px; background-color: #FFFFFF" align="right"> 154 </td> <td class="statBox" style="border-width:0px 1px 1px 0px; background-color: #FFFFFF" align="right"> 20.8 </td> <td class="statBox" style="border-width:0px 1px 1px 0px; background-color: #FFFFFF" align="right"> 21:54 </td> <td class="statBox" style="border-width:0px 1px 1px 0px; background-color: #FFFFFF" align="right"> 22.6 </td> <td class="statBox" style="border-width:0px 0px 1px 0px; background-color: #FFFFFF" align="right"> 55.7 </td> </tr> C#: using HtmlAgilityPack; using System.Data; namespace Stats { class StatsParser { private string htmlCode; private static string fileName = "[" + DateTime.Now.ToShortDateString() + " NHL Stats].xml"; public StatsParser(string htmlCode) { this.htmlCode = htmlCode; this.ParseHtml(); } public DataTable ParseHtml() { var result = new DataTable(); HtmlDocument doc = new HtmlDocument(); doc.LoadHtml(htmlCode); HtmlNode row = doc.DocumentNode.SelectNodes("//tr"); foreach (var statBox in row.SelectNodes("//td[@class='statBox']")) { System.Windows.MessageBox.Show(statBox.InnerText); } } } }

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  • Drupal Adding Span inside A tags in Nice Menus

    - by Chris
    I am trying to add drop down menus to a drupal theme which uses text sliding door CSS rounding. The current version uses a primary links injection of the span into the a tags, which works fine. But doesn't support drop down menus. Working code: <?php print theme('links', $primary_links, array('class' => 'links primary-links')) ?> In the template with a template.php file addition: <?php // function for injecting spans inside anchors which we need for the theme's rounded corner background images function strands_guybrush_links($links, $attributes = array('class' => 'links')) { $output = ''; if (count($links) > 0) { $output = '<ul'. drupal_attributes($attributes) .'>'; $num_links = count($links); $i = 1; foreach ($links as $key => $link) { $class = $key; // Add first, last and active classes to the list of links to help out themers. if ($i == 1) { $class .= ' first'; } if ($i == $num_links) { $class .= ' last'; } if (isset($link['href']) && ($link['href'] == $_GET['q'] || ($link['href'] == '<front>' && drupal_is_front_page()))) { $class .= ' active'; } $output .= '<li'. drupal_attributes(array('class' => $class)) .'>'; if (isset($link['href'])) { $link['title'] = '<span class="link">' . check_plain($link['title']) . '</span>'; $link['html'] = TRUE; // Pass in $link as $options, they share the same keys. $output .= l($link['title'], $link['href'], $link); } else if (!empty($link['title'])) { // Some links are actually not links, but we wrap these in <span> for adding title and class attributes if (empty($link['html'])) { $link['title'] = check_plain($link['title']); } $span_attributes = ''; if (isset($link['attributes'])) { $span_attributes = drupal_attributes($link['attributes']); } $output .= '<span'. $span_attributes .'>'. $link['title'] .'</span>'; } $i++; $output .= "</li>\n"; } $output .= '</ul>'; } return $output; } ?> So I have added the [Nice Menu module][1] which works well and allows the drop down menu functions for my navigation which is now addressed from the template using: <?php print theme_nice_menu_primary_links() ?> The issue is that the a tags need to have spans inside to allow for the selected state markup. I have tried every angle I could find to edit the drupal function menu_item_link which is used by nice menus to build the links. E.g. I looked at the drupal forum for two days and no joy. The lines in the module that build the links are: function theme_nice_menu_build($menu) { $output = ''; // Find the active trail and pull out the menus ids. menu_set_active_menu_name('primary-links'); $trail = menu_get_active_trail('primary-links'); foreach ($trail as $item) { $trail_ids[] = $item['mlid']; } foreach ($menu as $menu_item) { $mlid = $menu_item['link']['mlid']; // Check to see if it is a visible menu item. if ($menu_item['link']['hidden'] == 0) { // Build class name based on menu path // e.g. to give each menu item individual style. // Strip funny symbols. $clean_path = str_replace(array('http://', '<', '>', '&', '=', '?', ':'), '', $menu_item['link']['href']); // Convert slashes to dashes. $clean_path = str_replace('/', '-', $clean_path); $class = 'menu-path-'. $clean_path; $class .= in_array($mlid, $trail_ids) ? ' active' : ''; // If it has children build a nice little tree under it. if ((!empty($menu_item['link']['has_children'])) && (!empty($menu_item['below']))) { // Keep passing children into the function 'til we get them all. $children = theme('nice_menu_build', $menu_item['below']); // Set the class to parent only of children are displayed. $class .= $children ? ' menuparent ' : ''; // Add an expanded class for items in the menu trail. $output .= '<li id="menu-'. $mlid .'" class="'. $class .'">'. theme('menu_item_link', $menu_item['link']); // Build the child UL only if children are displayed for the user. if ($children) { $output .= '<ul>'; $output .= $children; $output .= "</ul>\n"; } $output .= "</li>\n"; } else { $output .= '<li id="menu-'. $mlid .'" class="'. $class .'">'. theme('menu_item_link', $menu_item['link']) .'</li>'."\n"; } } } return $output; } As you can see the $output uses menu_item_link to parse the array into links and to added the class of active to the selected navigation link. The question is how do I add a span inside the a tags OR how do I wrap the a tags with a span that has the active class to style the sliding door links? drupal.org/project/nice_menus drupal.org/node/53233

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  • Problem with memset after an instance of a user defined class is created and a file is opened

    - by Liberalkid
    I'm having a weird problem with memset, that was something to do with a class I'm creating before it and a file I'm opening in the constructor. The class I'm working with normally reads in an array and transforms it into another array, but that's not important. The class I'm working with is: #include <vector> #include <algorithm> using namespace std; class PreProcess { public: PreProcess(char* fileName,char* outFileName); void SortedOrder(); private: vector< vector<double > > matrix; void SortRow(vector<double> &row); char* newFileName; vector< pair<double,int> > rowSorted; }; The other functions aren't important, because I've stopped calling them and the problem persists. Essentially I've narrowed it down to my constructor: PreProcess::PreProcess(char* fileName,char* outFileName):newFileName(outFileName){ ifstream input(fileName); input.close(); //this statement is inconsequential } I also read in the file in my constructor, but I've found that the problem persists if I don't read in the matrix and just open the file. Essentially I've narrowed it down to if I comment out those two lines the memset works properly, otherwise it doesn't. Now to the context of the problem I'm having with it: I wrote my own simple wrapper class for matrices. It doesn't have much functionality, I just need 2D arrays in the next part of my project and having a class handle everything makes more sense to me. The header file: #include <iostream> using namespace std; class Matrix{ public: Matrix(int r,int c); int &operator()(int i,int j) {//I know I should check my bounds here return matrix[i*columns+j]; } ~Matrix(); const void Display(); private: int *matrix; const int rows; const int columns; }; Driver: #include "Matrix.h" #include <string> using namespace std; Matrix::Matrix(int r,int c):rows(r),columns(c) { matrix=new int[rows*columns]; memset(matrix,0,sizeof(matrix)); } const void Matrix::Display(){ for(int i=0;i<rows;i++){ for(int j=0;j<columns;j++) cout << (*this)(i,j) << " "; cout << endl; } } Matrix::~Matrix() { delete matrix; } My main program runs: PreProcess test1(argv[1],argv[2]); //test1.SortedOrder(); Matrix test(10,10); test.Display(); And when I run this with the input line uncommented I get: 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 -1371727776 32698 -1 0 0 0 0 0 6332656 0 -1 -1 0 0 6332672 0 0 0 0 0 0 0 0 0 0 0 0 0 -1371732704 32698 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 I really don't have a clue what's going on in memory to cause this, on a side note if I replace memset with: for(int i=0;i<rows*columns;i++) *(matrix+i) &= 0x0; Then it works perfectly, it also works if I don't open the file. If it helps I'm running GCC 64-bit version 4.2.4 on Ubuntu.I assume there's some functionality of memset that I'm not properly understanding.

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  • Making ANTLR generated class files into one jar file.

    - by prosseek
    With ANTLR, I get some java class files after compilation. And I need to make all the class files into one jar file. I make manifest.mf file that has one line "Main-class: Test" to indicate the main file. I run 'jar cmf manifest.mf hello.jar *.class' to get hello.jar file. But when I try to run 'java -jar hello.jar', I get the following error messages. $ java -jar hello.jar Exception in thread "main" java.lang.NoClassDefFoundError: Test Caused by: java.lang.ClassNotFoundException: Test at java.net.URLClassLoader$1.run(URLClassLoader.java:200) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(URLClassLoader.java:188) at java.lang.ClassLoader.loadClass(ClassLoader.java:315) at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:330) at java.lang.ClassLoader.loadClass(ClassLoader.java:250) at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:398) What's wrong? I get correct result when I run 'java Test'. The example that I used is the source code from the book 'The Definitive ANTLR Reference' that you can download from http://www.pragprog.com/titles/tpantlr/source_code The example is in /tour/trees/. I get a bunch of class files after compiling g and java files.

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  • Is using the Class instance as a Map key a best practice?

    - by Pangea
    I have read somewhere that using the class instances as below is not a good idea as they might cause memory leaks. Can someone tell me if if that is a valid statement? Or are they any problems using it this way? Map<Class<?>,String> classToInstance=new HashMap(); classToInstanceMap.put(String.class,"Test obj");

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  • How can I add methods from a Java class as global functions in Javascript using Rhino?

    - by gooli
    I have a simple Java class that has some methods: public class Utils { public void deal(String price, int amount) { // .... } public void bid(String price, int amount) { // .... } public void offer(String price, int amount) { // .... } } I would like to create an instance of this class and allow the Javascript code to call the methods directly, like so: deal("1.3736", 100000); bid("1.3735", 500000); The only way I could figure out for now was to use ScriptEngine engine = new ScriptEngineManager().getEngineByName("js"); engine.put("utils", new Utils()); and then use utils.deal(...) in the Javascript code. I can also write wrapper functions in Javascript for each method, but there should be a simpler way to do this automatically for all the public methods of a class.

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  • How can I set the class for a <dt> element in a Zend_Form?

    - by Mallika Iyer
    I'm trying to set the width of the style for a group of < dt elements in a Zend_Form. Is there a way to set a class for a dt element, so the end result would be something like this: <dt id="name-label" class="xyz" > // trying to add the 'class="xyz" <label class="required" for="name">Name:</label> </dt> <dd id="name-element"> <input type="text" maxlength="255" size="30" value="" id="name" name="name"> </dd>

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  • MSDN: How can I see what inherits/implements a class/interface?

    - by d03boy
    One thing I really, really miss from Javadoc is the ability to see which classes inherit the class you're looking at. So if you are looking at an abstract class (such as List) then you would be able to see all classes that inherit/implement the class/interface you're looking at. Is this available in the MSDN and I'm just missing it or is this really a missing feature?

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  • Can't declare even the most simple class in PHP - Am I going insane?

    - by Phil
    I'm getting this error whenever I attempt to declare a class: Parse error: syntax error, unexpected T_VARIABLE, expecting T_OLD_FUNCTION or T_FUNCTION or T_VAR or '}' in /home3/foundloc/public_html/booka/page2.php on line 7 (line 7 is the class declaration by the way). Here's the incredibly simple class I am attempting to declare: Class abc { $a = “Hello!”; } Is there some setting on PHP that i need to turn on? I feel like this is one of those 'did you check if the TV is plugged in' type of issues....

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  • WCF: Is it safe to override the Client's Dispose method using a partial class?

    - by pdiddy
    I'd like to override the Dispose method of generated proxy (ClientBase) because of the fact that disposing of a proxy calls Close and can throw an exception when the channel is faulted. The only way I came up was to create a partial class to my generated proxy, make it inherit from IDisposable: public partial class MyServiceProxy : IDisposable { #region IDisposable Members public void Dispose() { if (State != System.ServiceModel.CommunicationState.Faulted) Close(); else Abort(); } #endregion } I did some test and my Dispose method is indeed called. Do you see any issue with this strategy? Also, I don't like the fact that I'll have to create this partial class for every generated proxy. It be nice if I was able to make my proxy inherit from a base class...

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  • Policy-based template design: How to access certain policies of the class?

    - by dehmann
    I have a class that uses several policies that are templated. It is called Dish in the following example. I store many of these Dishes in a vector (using a pointer to simple base class), but then I'd like to extract and use them. But I don't know their exact types. Here is the code; it's a bit long, but really simple: #include <iostream> #include <vector> struct DishBase { int id; DishBase(int i) : id(i) {} }; std::ostream& operator<<(std::ostream& out, const DishBase& d) { out << d.id; return out; } // Policy-based class: template<class Appetizer, class Main, class Dessert> class Dish : public DishBase { Appetizer appetizer_; Main main_; Dessert dessert_; public: Dish(int id) : DishBase(id) {} const Appetizer& get_appetizer() { return appetizer_; } const Main& get_main() { return main_; } const Dessert& get_dessert() { return dessert_; } }; struct Storage { typedef DishBase* value_type; typedef std::vector<value_type> Container; typedef Container::const_iterator const_iterator; Container container; Storage() { container.push_back(new Dish<int,double,float>(0)); container.push_back(new Dish<double,int,double>(1)); container.push_back(new Dish<int,int,int>(2)); } ~Storage() { // delete objects } const_iterator begin() { return container.begin(); } const_iterator end() { return container.end(); } }; int main() { Storage s; for(Storage::const_iterator it = s.begin(); it != s.end(); ++it){ std::cout << **it << std::endl; std::cout << "Dessert: " << *it->get_dessert() << std::endl; // ?? } return 0; } The tricky part is here, in the main() function: std::cout << "Dessert: " << *it->get_dessert() << std::endl; // ?? How can I access the dessert? I don't even know the Dessert type (it is templated), let alone the complete type of the object that I'm getting from the storage. This is just a toy example, but I think my code reduces to this. I'd just like to pass those Dish classes around, and different parts of the code will access different parts of it (in the example: its appetizer, main dish, or dessert).

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  • How to determine whether a class has a particular templated member function?

    - by Aozine
    I was wondering if it's possible to extend the SFINAE approach to detecting whether a class has a certain member function (as discussed here: "Is there a Technique in C++ to know if a class has a member function of a given signature?" http://stackoverflow.com/questions/87372/is-there-a-technique-in-c-to-know-if-a-class-has-a-member-function-of-a-given-s ) to support templated member functions? E.g. to be able to detect the function foo in the following class: struct some_class { template < int _n > void foo() { } }; I thought it might be possible to do this for a particular instantiation of foo, (e.g. check to see if void foo< 5 >() is a member) as follows: template < typename _class, int _n > class foo_int_checker { template < typename _t, void (_t::*)() > struct sfinae { }; template < typename _t > static big test( sfinae< _t, &_t::foo< _n > > * ); template < typename _t > static small test( ... ); public: enum { value = sizeof( test< _class >( 0 ) ) == sizeof( big ) }; }; Then do foo_int_checker< some_class, 5 >::value to check whether some_class has the member void foo< 5 >(). However on MSVC++ 2008 this always returns false while g++ gives the following syntax errors at the line test( sfinae< _t, &_t::foo< _n > > ); test.cpp:24: error: missing `>' to terminate the template argument list test.cpp:24: error: template argument 2 is invalid test.cpp:24: error: expected unqualified-id before '<' token test.cpp:24: error: expected `,' or `...' before '<' token test.cpp:24: error: ISO C++ forbids declaration of `parameter' with no type Both seem to fail because I'm trying to get the address of a template function instantiation from a type that is itself a template parameter. Does anyone know whether this is possible or if it's disallowed by the standard for some reason? EDIT: It seems that I missed out the ::template syntax to get g++ to compile the above code correctly. If I change the bit where I get the address of the function to &_t::template foo< _n > then the program compiles, but I get the same behaviour as MSVC++ (value is always set to false). If I comment out the ... overload of test to force the compiler to pick the other one, I get the following compiler error in g++: test.cpp: In instantiation of `foo_int_checker<A, 5>': test.cpp:40: instantiated from here test.cpp:32: error: invalid use of undefined type `class foo_int_checker<A, 5>' test.cpp:17: error: declaration of `class foo_int_checker<A, 5>' test.cpp:32: error: enumerator value for `value' not integer constant where line 32 is the enum { value = sizeof( test< _class >( 0 ) ) == sizeof( big ) }; line. Unfortunately this doesn't seem to help me diagnose the problem :(. MSVC++ gives a similar nondescript error: error C2770: invalid explicit template argument(s) for 'clarity::meta::big checker<_checked_type>::test(checker<_checked_type>::sfinae<_t,&_t::template foo<5>> *)' on the same line. What's strange is that if I get the address from a specific class and not a template parameter (i.e. rather than &_t::template foo< _n > I do &some_class::template foo< _n >) then I get the correct result, but then my checker class is limited to checking a single class (some_class) for the function. Also, if I do the following: template < typename _t, void (_t::*_f)() > void f0() { } template < typename _t > void f1() { f0< _t, &_t::template foo< 5 > >(); } and call f1< some_class >() then I DON'T get a compile error on &_t::template foo< 5 >. This suggests that the problem only arises when getting the address of a templated member function from a type that is itself a template parameter while in a SFINAE context. Argh!

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  • Jquery fade and swap an element when clicked which will also relate to an accordian menu

    - by Nik
    You will notice when you click posture 1 the description drops down and images appear on the right. Now when you click posture 2 or posture 3 the images and description change as they should. What I need to do now is - If posture 1 has been clicked and then posture 2 is clicked the posture 1 menu needs to close so that there is only one posture description visible at one time. If I could also make it so that if the current open posture item is clicked so that it closes and there are no open posture descriptions that there also no images displayed on the right. Finally is there a way to make sure only one set of animation images is running, because just say the user goes through all 26 options and they continue to run in the background it may get sluggish (thanks to Nick Craver for bringing that up). At this stage only posture 1, 2 and 3 are available. Ok finally some code - //Description drop-down boxes $(document).ready(function(){ //Hide (Collapse) the toggle containers on load $(".toggle_container").hide(); //Switch the "Open" and "Close" state per click $("h5.trigger").toggle(function(){ $(this).addClass("active"); }, function () { $(this).removeClass("active"); }); //Slide up and down on click $("h5.trigger").click(function(){ $(this).next(".toggle_container").slideToggle("slow"); }); }); //Images on the right fade in and out thanks to aSeptik $(document).ready(function(){ $('#section_Q_01,#section_Q_02,#section_Q_03').hide(); $(function() { $('h5.trigger a').click( function(e) { e.preventDefault(); var trigger_id = $(this).parent().attr('id'); //get id Q_## $('.current').removeClass('current').hide(); //add a class for easy access & hide $('#section_' + trigger_id).addClass('current').fadeIn(5000); //show clicked one }); }); }); //Fading pics $(document).ready(function(){ $('.pics').cycle({ fx: 'fade', speed: 2500 }); }); Description boxes - <h5 class="trigger" id="Q_01" ><a href="#">Posture 1 : Standing Deep Breathing :</a></h5> <div class="toggle_container" > <div class="block"> <span class="sc">Pranayama Series</span> <p class="bold">Benefits:</p> </div> </div> <h5 class="trigger" id="Q_02" ><a href="#">Posture 2 : Half Moon Pose With Hands To Feet Pose :</a></h5> <div class="toggle_container"> <div class="block"> <span class="sc">Ardha Chandrasana with Pada-Hastasana</span> <p class="bold">Benefits:</p> </div> </div> <h5 class="trigger" id="Q_03" ><a href="#">Posture 3 : Awkward Pose :</a></h5> <div class="toggle_container"> <div class="block"> <span class="sc">Utkatasana</span> <p class="bold">Benefits:</p> </div> </div> and the images on the right - <div id="section_Q_01" class="01"> <div class="pics"> <img src="../images/multi/poses/pose1/Pranayama._01.jpg"/> <img src="../images/multi/poses/pose1/Pranayama._02.jpg"/> <img src="../images/multi/poses/pose1/Pranayama._03.jpg"/> </div> </div> <div id="section_Q_02" class="02"> <div class="pics"> <img src="../images/multi/poses/pose2/Half_Moon_Pose_04.jpg" /> <img src="../images/multi/poses/pose2/Backward_Bending_05.jpg" /> <img src="../images/multi/poses/pose2/Hands_to_Feet_Pose_06.jpg" /> </div> </div> <div id="section_Q_03" class="03"> <div class="pics"> <img src="../images/multi/poses/pose3/Awkward_01.jpg" /> <img src="../images/multi/poses/pose3/Awkward_02.jpg" /> <img src="../images/multi/poses/pose3/Awkward_03.jpg" /> </div> </div> It would be a bonus if images faded out when another element is clicked... but not a big deal. Thanks for having a look

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