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• Change Sprite Anchorpoint without moving it?

  - by OscarMk

  Hello, I am trying to change my Sprite anchor point so that I can rotate over a 0.0f,0.0f anchorpoint. At first my object is rotation at the default anchor point (0.5f,0.5f). However later on I need it to rotate over a 0.0,0.0 AnchorPoint. The problem is I cannot change the anchor point and change the position accordingly, so it stays on the same position, without the object appearing to quickly move and reposition to its original point. Is there a way I can set the anchor point and the position of my Sprite at once, without it moving at all?. Thank you. -Oscar

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• Select Range by string

  - by Petott

  How I can change this feature so I select the range of characters in a word document between the characters "E" and "F", if I have; xasdasdEcdscasdcFvfvsdfv is underlined to me the range - cdscasdc private void Rango() { Word.Range rng; Word.Document document = this.Application.ActiveDocument; object startLocation = "E"; object endLocation = "F"; // Supply a Start and End value for the Range. rng = document.Range(ref startLocation, ref endLocation); // Select the Range. rng.Select(); } This function will not let me pass by reference two objects of string type....... Thanks

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• Solution Items in Visual Studio 2005/2008

  - by Muneeb

  Is it possible to add a class as a solution item and use it as a linked item in all the projects in the solution? Basically I was thinking of creating a class (which will inherit ConfigurationSection) and keeping it as the Solution Item. I wanted to add it as a linked item in all the projects in the solution, so that everyone can use it to access the configuration properties. (Refer to this tutorial for more details) Now the issue I am facing is that when I create a class in the solution item, it doesn't have any namespace. And it shows up in intellisense, inside the projects but once I create an object of the solution item class, the object doesn't show up in intellisense. Any ideas why?

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• Custom control in DataViewGrid

  - by Winston

  I'm trying to embed a custom control in a Datagridview. I've looked at the Calendar (http://msdn.microsoft.com/en-us/library/7tas5c80.aspx) example but i just cant get it working for a custom control. I need the control to show for each object in the grid. Not just when the user edits the content. I need to do this so that i can bind my dataviewgrid to a datasource and have it create the required forms in the grid for each my object list. So that the user can do inline editing in the grid without having to double click the row and have a new dialog pop up. Any help would be greatly appreciated.

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• Macro VBA to get selected text in Outlook 2003

  - by balalakshmi

  I am trying to use this code snippet to get the selected text in outlook 2003 Sub SelectedTextDispaly() On Error Resume Next Err.Clear Dim oText As TextRange ''# Get an object reference to the selected text range. Set oText = ActiveWindow.Selection.TextRange ''# Check to see whether error occurred when getting text object ''# reference. If Err.Number <> 0 Then MsgBox "Invalid Selection. Please highlight some text " _ & "or select a text frame and run the macro again.", _ vbExclamation End End If ''# Display the selected text in a message box. If oText.Text = "" Then MsgBox "No Text Selected.", vbInformation Else MsgBox oText.Text, vbInformation End If End Sub When running this macro I get the error --------------------------- Microsoft Visual Basic --------------------------- Compile error: User-defined type not defined Do I need to add any references to fix this up?

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• Spring.NET & Immediacy CMS (or how to inject to server side controls without using PageHandlerFactor

  - by Simon Rice

  Is there any way to inject dependencies into an Immediacy CMS control using Spring.NET, ideally without having to use to ContextRegistry when initialising the control? Update, with my own answer The issue here is that Immediacy already has a handler defined in web.config that deals with all aspx pages, & so it's not possible add an entry for Spring.NET's PageHandlerFactory in web.config as per a normal webforms app. That rules out making the control implement ISupportsWebDependencyInjection. Furthermore, most of Immediacy's generated pages are aspx pages that don't physically exist on the drive. I have changed the title of the question to reflect this. What I have done to get Dependency Injection working is: Add the usual entries to web.config for Spring.NET as outlined in the documentation, except for the adding the entry to the <httpHandlers> section. In this case I've got my object definitions in Spring.config. Create the following abstract base class that will deal with all of the Dependency Injection work: DIControl.cs public abstract class DIControl : ImmediacyControl { protected virtual string DIName { get { return this.GetType().Name; } } protected override void OnInit(EventArgs e) { if (ContextRegistry.GetContext().GetObject(DIName, this.GetType()) != null) ContextRegistry.GetContext().ConfigureObject(this, DIName); base.OnInit(e); } } For non-immediacy controls, you can make this server side control inherit from Control or whatever subclass of that you like. For any control with which you wish to use with Spring.NET's Inversion of Control container, define it to inherit from DIControl & add the relelvant entry to Spring.config, for example: SampleControl.cs public class SampleControl : DIControl, INamingContainer { public string Text { get; set; } protected string InjectedText { get; set; } public SampleControl() : base() { Text = "Hello world"; } protected override void RenderContents(HtmlTextWriter output) { output.Write(string.Format("{0} {1}", Text, InjectedText)); } } Spring.config <objects xmlns="http://www.springframework.net"> <object id="SampleControl" type="MyProject.SampleControl, MyAssembly"> <property name="InjectedText" value="from Spring.NET" /> </object> </objects> You can optionally override DIName if you wish to name your entry in Spring.config differently from the name of your class. Provided everything's done correctly, you will have the control writing out "Hello world from Spring.NET!" when used in a page. This solution uses Spring.NET's ContextRegistry from within the control, but I would be surprised if there's no way around that for Immediacy at least since the page objects themselves aren't accessible. However, can this be improved at all from a Spring.NET perspective? Is there maybe an Immediacy plugin that already does this that I'm completely unaware of? Or is there an approach that does this in a more elegant way? I'm open to suggestions.

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• Bound DataGridView not updating data source

  - by Max Yaffe

  I'm trying to bind a table of structures to a DataGridView. Loading and viewing the table is working fine but I can't edit a value and get it stored back into the table. Here's what I'm doing. I have a "primitive" data type, Real defined by public struct MyReal:IMyPrimative { public Double m_Real; //... public MyReal(String val) { m_Real = default(Double); Init(val); } //... } It gets used in a structure: public struct MyReal_Record : IMyRecord { public MyReal Freq { get; set;} MyReal_Record(String[] vals) { Init(vals); } } And the structure is used to define a table using a generic Binding List public class MyTable<S> : BindingList<S> where S: struct, IMyRecord { public Type typeofS; public MyTable() { typeofS = typeof(S); // ... } This table is used as a binding source for a grid, dynamically. private void miLoadFile_Click(object sender, EventArgs e) { MyModel.Table<Real_Record> RTable = new MyModel.Table<Real_Record>(); //... Table initialized here //set up grid with virtual mode dataGridView1.DataSource = RTable; } All of this works fine and I can create RTable, initialize it and display it in a grid. The grid allows editing and has events set for CellParsing and CellFormatting which look like: private void dataGridView1_CellFormatting(object sender, DataGridViewCellFormattingEventArgs e) { if (e.DesiredType != typeof(String)) return; e.Value = e.Value.ToString(); } private void dataGridView1_CellParsing(object sender, DataGridViewCellParsingEventArgs e) { if (e.DesiredType != typeof(MyReal)) return; e.Value = new MyReal(e.Value.ToString()); e.ParsingApplied = true; this.dataGridView1.UpdateCellValue(e.ColumnIndex, e.RowIndex); } When I edit a value in a cell, I can change the text. On leaving the cell, CellParsing fires and the event handler is called. Everything seems to be correct going into the CellParsing handler. e.DesiredType is MyReal. e.Value is a string with the new value. After the new MyReal is created from the string, e.Value is set correctly. RowIndex and ColumnIndex are correct. ReadOnly is set false. However, when I leave the cell, the system restores the original value to the cell. I thought the UpdateCellValue would replace the value in the dataSource but I seem to be missing something. What did I miss? Thanks, Max

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• Cast an instance of a class to a @protocol in Objective-C

  - by Ford

  I have an object (a UIViewController) which may or may not conform to a protocol I've defined. I know I can determine if the object conforms to the protocol, then safely call the method: if([self.myViewController conformsToProtocol:@protocol(MyProtocol)]) { [self.myViewController protocolMethod]; // <-- warning here } However, XCode shows a warning: warning 'UIViewController' may not respond to '-protocolMethod' What's the right way to prevent this warning? I can't seem to cast self.myViewController as a MyProtocol class. Update Andy's answer below is close, but includes an unneccesary '*'. The following works: [(id<MyProtocol>)self.myViewController protocolMethod];

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• GWT : Type of Container

  - by moorsu

  I see that there are two ways of transferring objects from server to client Use the same domain object (Contact.java) as used in the service layer. (I do not use hibernate) Use the HashMap to send the domain object field values in the form of Map with the help of BeanUtilsBean class. For multiple objects, use the List. Similary, use the Map to submit form values from client to server Is there any performance advantage for option 1 over 2?. Is there a way to hide the classname/package name that is sent to the browser if we use option 1?. thanks!.

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• Storing cookielib cookies in a database

  - by Mridang Agarwalla

  Hi, I'm using the cookielib module to handle HTTP cookies when using the urllib2 module in Python 2.6 in a way similar to this snippet: import cookielib, urllib2 cj = cookielib.CookieJar() opener = urllib2.build_opener(urllib2.HTTPCookieProcessor(cj)) r = opener.open("http://example.com/") I'd like to store the cookies in a database. I don't know whats better - serialize the CookieJar object and store it or extract the cookies from the CookieJar and store that. I don't know which one's better or how to implement either of them. I should be also be able to recreate the CookieJar object. Could someone help me out with the above? Thanks in advance.

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• Nginx reverse proxy IP issue

  - by Tiffany Walker

  For some reason Apache is still seeing my SERVERS ip. Is this an nginx problem? /etc/nginx.conf user nobody; # no need for more workers in the proxy mode worker_processes 4; error_log /var/log/nginx/error.log info; worker_rlimit_nofile 20480; events { worker_connections 5120; # increase for busier servers use epoll; # you should use epoll here for Linux kernels 2.6.x } http { server_name_in_redirect off; server_names_hash_max_size 10240; server_names_hash_bucket_size 1024; include mime.types; default_type application/octet-stream; server_tokens off; disable_symlinks if_not_owner; sendfile on; tcp_nopush on; tcp_nodelay on; keepalive_timeout 5; gzip on; gzip_vary on; gzip_disable "MSIE [1-6]\."; gzip_proxied any; gzip_http_version 1.1; gzip_min_length 1000; gzip_comp_level 6; gzip_buffers 16 8k; # You can remove image/png image/x-icon image/gif image/jpeg if you have slow CPU gzip_types text/plain text/xml text/css application/x-javascript application/xml image/png image/x-icon image/gif image/jpeg application/xml+rss text/javascript application/atom+xml; ignore_invalid_headers on; client_header_timeout 3m; client_body_timeout 3m; send_timeout 3m; reset_timedout_connection on; connection_pool_size 256; client_header_buffer_size 256k; large_client_header_buffers 4 256k; client_max_body_size 200M; client_body_buffer_size 128k; request_pool_size 32k; output_buffers 4 32k; postpone_output 1460; proxy_temp_path /tmp/nginx_proxy/; client_body_in_file_only on; log_format bytes_log "$msec $bytes_sent ."; include "/etc/nginx/vhosts/*"; } proxy.inc proxy_connect_timeout 59s; proxy_send_timeout 600; proxy_read_timeout 600; proxy_buffer_size 64k; proxy_buffers 16 32k; proxy_busy_buffers_size 64k; proxy_temp_file_write_size 64k; proxy_pass_header Set-Cookie; proxy_redirect off; proxy_hide_header Vary; proxy_set_header Accept-Encoding ''; proxy_ignore_headers Cache-Control Expires; proxy_set_header Referer $http_referer; proxy_set_header Host $host; proxy_set_header Cookie $http_cookie; proxy_set_header X-Real-IP $remote_addr; proxy_set_header X-Forwarded-Host $host; proxy_set_header X-Forwarded-Server $host; proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for; vhost file: server { error_log /var/log/nginx/vhost-error_log warn; listen 63.6.1.12:80; server_name photo-rolldomain.com www.domain.com; access_log /usr/local/apache/domlogs/domain.com-bytes_log bytes_log; access_log /usr/local/apache/domlogs/domain.com combined; root /home/mtech/public_html; location / { location ~.*\.(3gp|gif|jpg|jpeg|png|ico|wmv|avi|asf|asx|mpg|mpeg|mp4|pls|mp3|mid|wav|swf|flv|html|htm|txt|js|css|exe|zip|tar|rar|gz|tgz|bz2|uha|7z|doc|docx|xls|xlsx|pdf|iso)$ { expires 7d; try_files $uri @backend; } error_page 405 = @backend; add_header X-Cache "HIT from Backend"; proxy_pass http://63.6.1.12:8081; include proxy.inc; } location @backend { internal; proxy_pass http://63.6.1.12:8081; include proxy.inc; } location ~ .*\.(php|jsp|cgi|pl|py)?$ { proxy_pass http://63.6.1.12:8081; include proxy.inc; } location ~ /\.ht { deny all; } }

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• Match groups in Python

  - by Curd

  Is there a way in Python to access match groups without explicitely creating a match object (or another way to beautify the example below)? Here is an example to clarify my motivation for the question: Following perl code if ($statement =~ /I love (\w+)/) { print "He loves $1\n"; } elsif ($statement =~ /Ich liebe (\w+)/) { print "Er liebt $1\n"; } elsif ($statement =~ /Je t\'aime (\w+)/) { print "Il aime $1\n"; } translated into Python m = re.match("I love (\w+)", statement) if m: print "He loves",m.group(1) else: m = re.match("Ich liebe (\w+)", statement) if m: print "Er liebt",m.group(1) else: m = re.match("Je t'aime (\w+)", statement) if m: print "Il aime",m.group(1) looks very awkward (if-else-cascade, match object creation).

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• CakePHP 1.3.4: EmailComponent error - Undefined property: EmailComponent::$Controller

  - by Kevin S.

  I'm trying to develop an invitation system for my website which runs on CakePHP 1.3.4. I am trying to use the built in EmailComponent to send an email. I'm getting this error (expanded): Notice (8): Undefined property: EmailComponent::$Controller [CORE/cake/libs/controller/components/email.php, line 428] Code | Context */ function _render($content) { $viewClass = $this-Controller-view; $content = array( "", "" ) EmailComponent::_render() - CORE/cake/libs/controller/components/email.php, line 428 EmailComponent::send() - CORE/cake/libs/controller/components/email.php, line 368 UsersController::send_quick_add_email() - APP/controllers/users_controller.php, line 77 UsersController::quick_add() - APP/controllers/users_controller.php, line 104 SinglesResultsController::quick_add() - APP/controllers/singles_results_controller.php, line 63 Dispatcher::_invoke() - CORE/cake/dispatcher.php, line 204 Dispatcher::dispatch() - CORE/cake/dispatcher.php, line 171 [main] - APP/webroot/index.php, line 83 I also get the following, which I can expand if necessary: Notice (8): Trying to get property of non-object [CORE/cake/libs/controller/components/email.php, line 428] Notice (8): Undefined property: EmailComponent::$Controller [CORE/cake/libs/controller/components/email.php, line 433] Notice (8): Trying to get property of non-object [CORE/cake/libs/controller/components/email.php, line 433] Notice (8): Undefined property: View::$webroot [CORE/cake/libs/view/view.php, line 805] Warning (2): Cannot modify header information - headers already sent by (output started at /Applications/MAMP/htdocs/cake/cake/libs/debugger.php:673) [CORE/cake/libs/controller/controller.php, line 746] I think that the EmailComponent object holds a reference to the controller it's being called from. I don't know why it's undefined in this case. Here is the code that fails (specifically, it errors on the call to $this-Email-send()): function send_quick_add_email($email) { if($email) { $this->Email->reset(); $this->Email->to = $email; $this->Email->subject = 'Some subject text'; $this->Email->from = '[email protected]'; $this->Email->template = 'email_template'; $this->set('user', $user); $this->set('token', $token); $this->Email->delivery = 'debug'; $this->Email->send(); } } Ok, for more clarification: The main data I am collecting on the site is results of a game played in meatspace. SinglesResultsController has an action, quick_add, which expects email addresses of people not already registered on the site. If the email addresses aren't associated with Users, UsersController::quick_add is called, which creates an inactive user, and sends an invitation email in UsersController::send_quick_add_email() I think the problem is related to the fact that the email isn't being sent in the first controller initialized (SinglesResultsController). Any thoughts on how to make it work? The Email component is declared at the top of both Controllers.

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• Painting to Form then to Printer

  - by jp2code

  I often find myself needing to create custom reports that do NOT work with Crystal Reports or Report Viewer. Often, I hack a DataTable together and dumping that into a DataGridView control. It is never pretty, and printing is difficult. What I need is a class that I can call using the OnPaint event, but I've never sat down and written all of the Pen and Brush commands until now. Painting to the screen and painting to a printer both use the Graphics object, so I want to build a class that I'd pass in the Graphics object, my window bounds (a Rectangle), and some data (in the form of an instance of my class) that I'd use to paint a form or a sheet of paper. That sounds like a great concept! Surely, someone has done something like this before. Does anyone know of a book, a website tutorial, or video that goes into this? If someone wants to write all that out for me here, more power to you - but I'd think that would be too much work.

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• Is there an easy way to convert C# classes to PHP?

  - by John

  I am used to writing C# Windows application. However I have some free hosted PHP web space that I would like to make use of. I have a basic understanding of PHP but have never used it's object oriented capabilities. Is there an easy way to convert C# classes to PHP classes or is it just not possible to write a fully object oriented application in PHP? Update: There are no reliance on the .NET framework beyond the basics. The main aim would be to restructure the class properties, variable enums, etc. The PHP will be hosted on a Linux server.

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• How to deal with databases for websites written in Java, more specifically Wicket?

  - by John

  Hi there. I'm new to website development using Java but I've got started with Wicket and make a little website. I'd like to expand on what I've already made (a website with a form, labels and links) and implement database connectivity. I've looked at a couple of examples, in example Mystic Paste, and I see that they're using Hibernate and Spring. I've never touched Hibernate or Spring before and to be honest the heavy use of annotations scare me a little bit as I haven't really made use of them before, with the exception of supressing warnings and overriding. At this point I have one Connection object which I set up in the WebApplication class upon initialization. I then retrieve this connection object whenever I need to perform queries. I don't know if this is a bad approach or not for a production web application. All help is greatly appreciated.

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• Is there any way to search within OneNote 2007 attachments

  - by jtolle

  I'm starting to use OneNote (2007) more. One thing I'd like to do is take notes on papers I have read. That is, I attach, say, a PDF file, and then type in some notes about it. Sometimes I do other stuff like copy some key text or figures from the paper, so OneNote is great for this because all that plus my own notes plus the file itself can all be in one place. However, the OneNote search doesn't seem to be able to search within said PDF files. Windows search finds things, but just in the OneNote cache, not the actual Onenote .one files. (Presumably that will only work for recently accessed stuff, and in any case doesn't take me to my actual notes.) Is there a way to do what I want? If not, does anyone have a suggestion (or link) as to how to best use OneNote to store (and later search for!) this kind of content and notes?

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• Discovering a functional algorithm from a mutable one

  - by Garrett Rowe

  This isn't necessarily a Scala question, it's a design question that has to do with avoiding mutable state, functional thinking and that sort. It just happens that I'm using Scala. Given this set of requirements: Input comes from an essentially infinite stream of random numbers between 1 and 10 Final output is either SUCCEED or FAIL There can be multiple objects 'listening' to the stream at any particular time, and they can begin listening at different times so they all may have a different concept of the 'first' number; therefore listeners to the stream need to be decoupled from the stream itself. Pseudocode: if (first number == 1) SUCCEED else if (first number >= 9) FAIL else { first = first number rest = rest of stream for each (n in rest) { if (n == 1) FAIL else if (n == first) SUCCEED else continue } } Here is a possible mutable implementation: sealed trait Result case object Fail extends Result case object Succeed extends Result case object NoResult extends Result class StreamListener { private var target: Option[Int] = None def evaluate(n: Int): Result = target match { case None => if (n == 1) Succeed else if (n >= 9) Fail else { target = Some(n) NoResult } case Some(t) => if (n == t) Succeed else if (n == 1) Fail else NoResult } } This will work but smells to me. StreamListener.evaluate is not referentially transparent. And the use of the NoResult token just doesn't feel right. It does have the advantage though of being clear and easy to use/code. Besides there has to be a functional solution to this right? I've come up with 2 other possible options: Having evaluate return a (possibly new) StreamListener, but this means I would have to make Result a subtype of StreamListener which doesn't feel right. Letting evaluate take a Stream[Int] as a parameter and letting the StreamListener be in charge of consuming as much of the Stream as it needs to determine failure or success. The problem I see with this approach is that the class that registers the listeners should query each listener after each number is generated and take appropriate action immediately upon failure or success. With this approach, I don't see how that could happen since each listener is forcing evaluation of the Stream until it completes evaluation. There is no concept here of a single number generation. Is there any standard scala/fp idiom I'm overlooking here?

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• Wordpress: Sort posts by meta value after AFTER querying from database

  - by Joseph Carrington

  Hello, I am pulling posts from my database by using Wordpress' WP_Query object like so: $shows_query = new WP_Query("category_name=shows&meta_key=band&meta_value=$artist_id"); I have another meta value I would like to sort the posts by, however. The meta key is 'date'. The WP_Query object can no work with multiple meta_keys, so this does not work: $shows_query = new WP_Query("category_name=shows&meta_key=band&meta_value=$artist_id&meta_key=date&orderby=meta_value&order=DESC"); So now I have to figure out a way to sort the posts in $shows_query['posts'] by one of their meta_values, which are not even IN their array. Any other, more sensible approach would also be appreciated.

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• Setup a proxy (Not reverse proxy) using Varnish/Squid.

  - by shabda

  I need to setup a proxy server where we can request remote urls and get them served locally. Basically what I need is mysever:8000/varnish/serverfault.com get me serverfault.com served from my local varnish or myserver:8080/squid/serverfault.com get me serverfault.com served from my local squid. (Both should cache the site for 24 hours) I am evaluating if Varnish or Squid will be a good choice for it. Which one will be a better fit? How do I do it. Links to tutorials would be good.

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• In Nginx, can I handle both a location:url or a content-type: text/html response from memcached?

  - by Sean Foo

  I'm setting up an nginx - apache reverse proxy where nginx handles the static files and apache the dynamic. I have a search engine and depending on search parameter I either directly forward the user to the page they are looking for or provide a set of search results. I cache these results in memcached as key:/search.cgi?q=foo value: LOCATION:http://www.example.com/foo.html and key:/search.cgi?q=bar value: CONTENT-TYPE: text/html <html> .... .... </html> I can pull the "Content-type...." values out of memcached using nginx and send them to the user, but I can't quite figure out how to handle a returned value like "Location..." Can I?

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• Is it possible to destroy a CDI scope?

  - by Matt Ball

  I'm working on a Java EE application, primarily JAX-RS with a JSF admin console, that uses CDI/Weld for dependency injection with @ApplicationScoped objects. Minor debugging issues aside, CDI has worked beautifully for this project. Now I need some very coarse-grained control over CDI-injected object lifecycles. I need the ability to: Remove an injected object from the application context, or Destroy/delete/clear/reset/remove the entire application context, or Define my own @ScopeType and implementing Context in which I could provide methods to perform one of the two above tasks. I'm fully aware that this is across, if not against, the grain of CDI and dependency injection in general. I just want to know Is this remotely possible? If yes, what is the easiest/simplest/quickest/foolproofiest way to get the job done?

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• Structure accessible by attribute name or index options

  - by Bruno DeGoia

  I am very new to Python, and trying to figure out how to create an object that has values that are accessible either by attribute name, or by index. For example, the way os.stat() returns a stat_result or pwd.getpwnam() returns a struct_passwd. In trying to figure it out, I've only come across C implementations of the above types. Nothing specifically in Python. What is the Python native way to create this kind of object? I apologize if this has been widely covered already. In searching for an answer, I must be missing some fundamental concept that is excluding me from finding an answer.

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• How to convert a DOM node list to an array in Javascript?

  - by Guss

  I have a Javascript function that accepts a list of HTML nodes, but it expects a Javascript array (it runs some Array methods on that) and I want to feed it the output of Document.getElementsByTagName that returns a DOM node list. Initially I thought of using something simple like: Array.prototype.slice.call(list,0) And that works fine in all browsers, except of course Internet Explorer which returns the error "JScript object expected", as apparently the DOM node list returned by Document.getElement* methods is not a JScript object enough to be the target of a function call. Caveats: I don't mind writing Internet Explorer specific code, but I'm not allowed to use any Javascript libraries such as JQuery because I'm writing a widget to be embedded into 3rd party web site, and I cannot load external libraries that will create conflict for the clients. My last ditch effort is to iterate over the DOM node list and create an array myself, but is there a nicer way to do that?

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• Languages and VMs: Features that are hard to optimize and why

  - by mrjoltcola

  I'm doing a survey of features in preparation for a research project. Name a mainstream language or language feature that is hard to optimize, and why the feature is or isn't worth the price paid, or instead, just debunk my theories below with anecdotal evidence. Before anyone flags this as subjective, I am asking for specific examples of languages or features, and ideas for optimization of these features, or important features that I haven't considered. Also, any references to implementations that prove my theories right or wrong. Top on my list of hard to optimize features and my theories (some of my theories are untested and are based on thought experiments): 1) Runtime method overloading (aka multi-method dispatch or signature based dispatch). Is it hard to optimize when combined with features that allow runtime recompilation or method addition. Or is it just hard, anyway? Call site caching is a common optimization for many runtime systems, but multi-methods add additional complexity as well as making it less practical to inline methods. 2) Type morphing / variants (aka value based typing as opposed to variable based) Traditional optimizations simply cannot be applied when you don't know if the type of someting can change in a basic block. Combined with multi-methods, inlining must be done carefully if at all, and probably only for a given threshold of size of the callee. ie. it is easy to consider inlining simple property fetches (getters / setters) but inlining complex methods may result in code bloat. The other issue is I cannot just assign a variant to a register and JIT it to the native instructions because I have to carry around the type info, or every variable needs 2 registers instead of 1. On IA-32 this is inconvenient, even if improved with x64's extra registers. This is probably my favorite feature of dynamic languages, as it simplifies so many things from the programmer's perspective. 3) First class continuations - There are multiple ways to implement them, and I have done so in both of the most common approaches, one being stack copying and the other as implementing the runtime to use continuation passing style, cactus stacks, copy-on-write stack frames, and garbage collection. First class continuations have resource management issues, ie. we must save everything, in case the continuation is resumed, and I'm not aware if any languages support leaving a continuation with "intent" (ie. "I am not coming back here, so you may discard this copy of the world"). Having programmed in the threading model and the contination model, I know both can accomplish the same thing, but continuations' elegance imposes considerable complexity on the runtime and also may affect cache efficienty (locality of stack changes more with use of continuations and co-routines). The other issue is they just don't map to hardware. Optimizing continuations is optimizing for the less-common case, and as we know, the common case should be fast, and the less-common cases should be correct. 4) Pointer arithmetic and ability to mask pointers (storing in integers, etc.) Had to throw this in, but I could actually live without this quite easily. My feelings are that many of the high-level features, particularly in dynamic languages just don't map to hardware. Microprocessor implementations have billions of dollars of research behind the optimizations on the chip, yet the choice of language feature(s) may marginalize many of these features (features like caching, aliasing top of stack to register, instruction parallelism, return address buffers, loop buffers and branch prediction). Macro-applications of micro-features don't necessarily pan out like some developers like to think, and implementing many languages in a VM ends up mapping native ops into function calls (ie. the more dynamic a language is the more we must lookup/cache at runtime, nothing can be assumed, so our instruction mix is made up of a higher percentage of non-local branching than traditional, statically compiled code) and the only thing we can really JIT well is expression evaluation of non-dynamic types and operations on constant or immediate types. It is my gut feeling that bytecode virtual machines and JIT cores are perhaps not always justified for certain languages because of this. I welcome your answers.

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