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• When I mix JSTL 1.0 and JSTL 1.1 taglib declarations, it causes a ParseException on some of my serve

  - by sangfroid

  Hello all, When I mix JSTL 1.0 and JSTL 1.1 taglib declarations, it causes a ParseException on some of my servers, but not all of them. Here is the block of code that's giving me trouble : <%@ taglib prefix="c" uri="http://java.sun.com/jstl/core"%> <%@ taglib prefix="fn" uri="http://java.sun.com/jsp/jstl/functions"%> <c:set var="TEXTVARIABLE">|STRINGOFTEXT|</c:set> <c:set var="OTHERTEXTVARIABLE">${fn:contains(TEXTVARIABLE, '|STRINGOFTEXT|')}</c:set> And here is the exception : javax.servlet.jsp.JspException: com.caucho.jsp.JspLineParseException: /WEB-INF/jsp/online/system/modules/com.MYCOMPANY.marketing/templates/common/MY_JSP_PAGE.jsp:1: tag = 'out' / attribute = 'value': An error occurred while parsing custom action attribute "value" with value "${fn:contains(TEXTVARIABLE, '|STRINGOFTEXT|')}": org.apache.taglibs.standard.lang.jstl.parser.ParseException: EL functions are not supported. However, everything works fine if I change the URI for the core declaration to http://java.sun.com/jsp/jstl/core So here's the really weird part : for some reason, mixing 1.0 and 1.1 taglib declarations only causes an exception on two of my servers -- my staging server and my production server. It causes no problems at all on my local machine or my development server. Why is this? What could possibly be causing this difference in behavior? The three servers are extremely similar in setup and configuration. The JSP page is being served up by OpenCMS, and I'm using the Caucho's Resin webserver. I understand that you don't know how my servers or CMS are set up, but really, what I'm looking for is ideas. Any ideas at all would help -- this problem has been driving me absolutely batty. Even if you don't know what could be causing the problem, if you have any suggestions at all for how I could approach the problem, that would be extremely helpful. I just don't understand what could cause this difference in behavior between my servers. For reference, here's the full stack trace : javax.servlet.jsp.JspException: com.caucho.jsp.JspLineParseException: /WEB-INF/jsp/online/system/modules/com.MYCOMPANY.marketing/templates/common/MY_JSP_PAGE.jsp:1: tag = 'out' / attribute = 'value': An error occurred while parsing custom action attribute "value" with value "${fn:contains(TEXTVARIABLE, '|STRINGOFTEXT|')}": org.apache.taglibs.standard.lang.jstl.parser.ParseException: EL functions are not supported. at org.opencms.jsp.CmsJspTagInclude.includeActionWithCache(CmsJspTagInclude.java:369) at org.opencms.jsp.CmsJspTagInclude.includeTagAction(CmsJspTagInclude.java:241) at org.opencms.jsp.CmsJspTagInclude.doEndTag(CmsJspTagInclude.java:472) at _jsp._WEB_22dINF._jsp._online._system._modules.com_MYCOMPANY__marketing._templates._MAIN_0PAGE__jsp._jspService(_MAIN_0PAGE__jsp.java:153) at com.caucho.jsp.JavaPage.service(JavaPage.java:60) at com.caucho.jsp.Page.pageservice(Page.java:579) at com.caucho.server.dispatch.PageFilterChain.doFilter(PageFilterChain.java:179) at shared.filter.RemoteAddrFilterBase.doFilter(RemoteAddrFilterBase.java:57) at com.caucho.server.dispatch.FilterFilterChain.doFilter(FilterFilterChain.java:70) at com.caucho.server.webapp.DispatchFilterChain.doFilter(DispatchFilterChain.java:115) at com.caucho.server.cache.CacheFilterChain.doFilter(CacheFilterChain.java:175) at com.caucho.server.dispatch.ServletInvocation.service(ServletInvocation.java:229) at com.caucho.server.webapp.RequestDispatcherImpl.include(RequestDispatcherImpl.java:485) at com.caucho.server.webapp.RequestDispatcherImpl.include(RequestDispatcherImpl.java:350) at org.opencms.flex.CmsFlexRequestDispatcher.includeExternal(CmsFlexRequestDispatcher.java:194) at org.opencms.flex.CmsFlexRequestDispatcher.include(CmsFlexRequestDispatcher.java:169) at org.opencms.loader.CmsJspLoader.service(CmsJspLoader.java:1193) at org.opencms.flex.CmsFlexRequestDispatcher.includeInternalWithCache(CmsFlexRequestDispatcher.java:423) at org.opencms.flex.CmsFlexRequestDispatcher.include(CmsFlexRequestDispatcher.java:173) at org.opencms.loader.CmsJspLoader.dispatchJsp(CmsJspLoader.java:1227) at org.opencms.loader.CmsJspLoader.load(CmsJspLoader.java:1171) at org.opencms.loader.A_CmsXmlDocumentLoader.load(A_CmsXmlDocumentLoader.java:232) at org.opencms.loader.CmsXmlContentLoader.load(CmsXmlContentLoader.java:52) at org.opencms.loader.CmsResourceManager.loadResource(CmsResourceManager.java:964) at org.opencms.main.OpenCmsCore.showResource(OpenCmsCore.java:1498) at org.opencms.main.OpenCmsServlet.doGet(OpenCmsServlet.java:152) at javax.servlet.http.HttpServlet.service(HttpServlet.java:115) at javax.servlet.http.HttpServlet.service(HttpServlet.java:92) at com.caucho.server.dispatch.ServletFilterChain.doFilter(ServletFilterChain.java:106) at com.caucho.filters.CmsGzipFilter.doFilter(CmsGzipFilter.java:177) at com.caucho.server.dispatch.FilterFilterChain.doFilter(FilterFilterChain.java:70) at shared.filter.RemoteAddrFilterBase.doFilter(RemoteAddrFilterBase.java:57) at com.caucho.server.dispatch.FilterFilterChain.doFilter(FilterFilterChain.java:70) at com.caucho.server.webapp.DispatchFilterChain.doFilter(DispatchFilterChain.java:115) at com.caucho.server.dispatch.ServletInvocation.service(ServletInvocation.java:229) at com.caucho.server.webapp.RequestDispatcherImpl.forward(RequestDispatcherImpl.java:277) at com.caucho.server.webapp.RequestDispatcherImpl.forward(RequestDispatcherImpl.java:106) at com.caucho.server.dispatch.ForwardFilterChain.doFilter(ForwardFilterChain.java:80) at com.caucho.server.cache.CacheFilterChain.doFilter(CacheFilterChain.java:207) at com.caucho.server.webapp.WebAppFilterChain.doFilter(WebAppFilterChain.java:173) at com.caucho.server.dispatch.ServletInvocation.service(ServletInvocation.java:229) at com.caucho.server.http.HttpRequest.handleRequest(HttpRequest.java:274) at com.caucho.server.port.TcpConnection.run(TcpConnection.java:514) at com.caucho.util.ThreadPool.runTasks(ThreadPool.java:520) at com.caucho.util.ThreadPool.run(ThreadPool.java:442) at java.lang.Thread.run(Thread.java:595) Caused by: com.caucho.jsp.JspLineParseException: /WEB-INF/jsp/online/system/modules/com.MYCOMPANY.marketing/templates/common/MY_JSP_PAGE.jsp:1: tag = 'out' / attribute = 'value': An error occurred while parsing custom action attribute "value" with value "${fn:contains(TEXTVARIABLE, '|STRINGOFTEXT|')}": org.apache.taglibs.standard.lang.jstl.parser.ParseException: EL functions are not supported. at com.caucho.jsp.java.JspNode.error(JspNode.java:1489) at com.caucho.jsp.java.JspNode.error(JspNode.java:1480) at com.caucho.jsp.java.JavaJspGenerator.validate(JavaJspGenerator.java:466) at com.caucho.jsp.JspCompilerInstance.generate(JspCompilerInstance.java:475) at com.caucho.jsp.JspCompilerInstance.compile(JspCompilerInstance.java:373) at com.caucho.jsp.JspManager.compile(JspManager.java:233) at com.caucho.jsp.JspManager.createPage(JspManager.java:177) at com.caucho.jsp.JspManager.createPage(JspManager.java:157) at com.caucho.jsp.PageManager.getPage(PageManager.java:248) at com.caucho.jsp.PageManager.getPage(PageManager.java:166) at com.caucho.jsp.QServlet.getSubPage(QServlet.java:292) at com.caucho.jsp.QServlet.getPage(QServlet.java:210) at com.caucho.server.dispatch.PageFilterChain.compilePage(PageFilterChain.java:206) at com.caucho.server.dispatch.PageFilterChain.doFilter(PageFilterChain.java:133) at shared.filter.RemoteAddrFilterBase.doFilter(RemoteAddrFilterBase.java:57) at com.caucho.server.dispatch.FilterFilterChain.doFilter(FilterFilterChain.java:70) at com.caucho.server.webapp.DispatchFilterChain.doFilter(DispatchFilterChain.java:115) at com.caucho.server.cache.CacheFilterChain.doFilter(CacheFilterChain.java:175) at com.caucho.server.dispatch.ServletInvocation.service(ServletInvocation.java:229) at com.caucho.server.webapp.RequestDispatcherImpl.include(RequestDispatcherImpl.java:485) at com.caucho.server.webapp.RequestDispatcherImpl.include(RequestDispatcherImpl.java:350) at org.opencms.flex.CmsFlexRequestDispatcher.includeExternal(CmsFlexRequestDispatcher.java:194) at org.opencms.flex.CmsFlexRequestDispatcher.include(CmsFlexRequestDispatcher.java:169) at org.opencms.loader.CmsJspLoader.service(CmsJspLoader.java:1193) at org.opencms.flex.CmsFlexRequestDispatcher.includeInternalWithCache(CmsFlexRequestDispatcher.java:423) at org.opencms.flex.CmsFlexRequestDispatcher.include(CmsFlexRequestDispatcher.java:173) at org.opencms.jsp.CmsJspTagInclude.includeActionWithCache(CmsJspTagInclude.java:364) ... 45 more Thanks for the help!

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• Looking for an automated logging tool/library for .NET!

  - by tsocks

  Hello, I'm looking for an library/tool for .NET that logs almost everything that happens in my C# application (Windows Form). The problem is that I'm delivering an application to a client (Windows XP) and after doing some task, that classic Microsoft error window appears: "ApplicationName has encountered a problem and needs to close. We are sorry for the inconvenience" I'm currently handling my application exceptions, but this is something external and I can't get anything from that error, so I would like any automated library that helps me with that. It would work if it logs each line of code executed, orr just log what line was executing before that error appeared, or something that could give me more info about that error. Thank you! P.S: It's a multithreaded application, and have to Timer controls (one for watching a folder every 5secs, and another for watching thread list...). I'm using Windows 7 here and everything seems to work ok.

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• Creating CCD document from scratch (JAVA)

  - by Nikhil Patil

  Hi, I'm trying to build a CCD document. My application has some raw data which has to be converted into a CCD document. And I've no idea where I should start from!! From this thread I learned that MDHT and Braid can be used to create a CCD document. But thats all I could grasp. I thought that I need a CCD XSD, a java library which will transform my raw data into a CCD document using this XSD ( or may be the library itself takes care of it ). But I'm stuck at both. I suppose the CCD XSD has to be purchased. If I get hold of the XSD, how should I proceed ahead? I got really confused reading the Braid and MDHT sites. Sorry, I'm a complete nOOb in this domain. Can anyone guide me?

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• Entity Framework Performance Problem

  - by Steve Horn

  I'm hoping that someone can help me understand how to overcome a performance problem I'm running into with the latest version of the Entity Framework. In my test, I created my model from a database consisting of around 80 tables. The problem that I'm running into is that the cost of the very first query I run on a thread is very expensive. If I run without pre-compiling views the first query takes anywhere from 5800 to 6600 milliseconds. If I pre-compile the views (see this article) I can get the initial query cost down to about 2800 to 3200 milliseconds. 3 seconds for each request is still unacceptable for my needs. Subsequent queries are very fast. Can you please help me understand how to eliminate the poor performance of the initial query? I'm using the version of entity framework that ships with Visual Studio 2010 RC.

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• WinForms form freezes

  - by andrew

  On a form (F1) i have a button, from which if i create another form (lets call it F2) and show it there's no problem but i'd like to do something like this Some thread in my app is running a connection and listens for messages from a server. when a message arrives, my main form is registered to get an event that runs a function. From that function i'm trying to create and show the F2 type form (empty, nothing modified in it): it shows it but then it freezes my application. more exactly: public partial class Form1 : Form { public Form1() { InitializeComponent(); ConnectionManagerThread.getResponseListener().MessageReceived += Form1_OnMessageReceived; } private void Form1_OnMessageReceived(object sender, MessageEventArgs e) { Form2 f2 = new Form2(); f2.Show(); } }

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• Java Scripting Engine importing my classes does not work

  - by Ayman

  A code is worth 1000 words of explaining it :-) package jasim; import javax.script.ScriptEngine; import javax.script.ScriptEngineManager; import javax.script.ScriptException; public class JSTest { public static void main(String[] args) throws ScriptException { ScriptEngine jse = new ScriptEngineManager().getEngineByExtension("js"); jse.eval("println(new jasim.JSTest().toString)"); } @Override public String toString() { return "JSTest Object"; } } This code will fail with the below exception: Exception in thread "main" javax.script.ScriptException: sun.org.mozilla.javascript.internal.EcmaError: ReferenceError: "jasim" is not defined. (<Unknown source>#1) in <Unknown source> at line number 1 How do I import my own classes into the ScriptEngine?

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• Sysadmin 101: How can I figure out why my server crashes and monitor performance?

  - by bflora

  I have a Drupal-powered site that seems to have neverending performance problems. It was butt-slow about 5 months ago. I brought in some guys who installed nginx for anonymous visitors, ajaxified a few queries so they wouldn't fire during page load, and helped me find a few bottlenecks in the code. For about a month, the site was significantly faster, though not "fast" by any stretch of the word. Meanwhile, I'm now shelling out $400/month to Slicehost to host a site that gets less than 5,000/uniques a day. Yes, you read that right. Go Drupal. Recently the site started crashing again and is slow again. I can't afford to hire people to come in, study my code from top to bottom, and make changes that may or may not help anymore. And I can't afford to throw more hardware at the problem. So I need to figure out what the problem is myself. Questions: When apache crashes, is it possible to find out what caused it to crash? There has to be a way, right? If so, how can I do this? Is there software I can use that will tell me which process caused my server to die? (e.g. "Apache crashed because someone visited page X." or "Apache crashed because you were importing too many RSS items from feed X.") There's got to be a way to learn this, right? What's a good, noob-friendly way to monitor my current apache performance? My developer friends tell me to "just use Top, dude," but Top shows me a bunch of numbers without any context. I have no clue what qualifies as a bad number or a good number in Top, or which processes are relevant and which aren't. Are there any noob-friendly server monitoring tools out there? Ideally, I could have a page that would give me a color-coded indicator about how apache is performing and then show me a list of processes or pages that are sucking right now. This way, I could know when performance is bad and then what's causing it to be so bad. Why does PHP memory matter? My apparently has a 30MB memory foot print. Will it run faster if I bring that number down? Thanks for any advice. I spent a year or so trying to boost my advertising income so I could hire a contractor to solve my performance woes. I didn't want to have to learn all this sysadmin voodoo. I'm now resigned to the fact that might not have a choice.

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• How can I set up .Net unhanlded exception handling in a windows service?

  - by Mike Pateras

  protected override void OnStart(string[] args) { AppDomain.CurrentDomain.UnhandledException += new UnhandledExceptionEventHandler(CurrentDomain_UnhandledException); Thread.Sleep(10000); throw new Exception(); } void CurrentDomain_UnhandledException(object sender, UnhandledExceptionEventArgs e) { } I attached a debugger to the above code in my windows service, setting a breakpoint in CurrentDomain_UnhandledException, but it was never hit. The exception pops up saying that it is unhandled, and then the service stops. I even tried putting some code in the event handler, in case it was getting optimized away. Is this not the proper way to set up unhandled exception handling in a windows service?

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• Javascript timers

  - by resopollution

  I'm starting on a javascript MMORPG that will actually work smoothly. Currently, I created a demo to prove that I can move characters around and have them chat with each other, as well as see eachother move around live. http://set.rentfox.net/ Now Javascript timers are something I have not used extensively, but from what I know, correct me if I'm wrong, is that having multiple setIntervals happening at the same time doesn't really work well b/c it's all on a single thread. Lets say I wanted to have 10 different people nuking fireballs at a monster by using sprite background positioning with setInterval -- that animation would require 10 setIntervals doing repainting of the DOM for sprite background-position shifts. Wouldn't that be a big buggy? I was wondering if there was a way around all this, perhaps using Canvas, so that animations can all happen concurrently without creating an event queue and I don't have to worry about timers. Hope that makes sense, and please let me know if I need to clarify further.

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• sql server 2008 express one row write problem

  - by bojanskr

  Hi everyone, I have the most bizarre problem(at least it is bizarre to me) with MSSQL Server Express 2008. The problem is the following: On the development machine I use MS SQL Server 2008 Enterprise....I get some data from a WCF service and write that data to the db (simple as it can be)....I should point out however that the writing, it is done in a separate thread. BUt, anyway no problems during development...all the data is there. Then I set everything up(connection strings .\SQLEXPRESS, other settings) build in Release and copy that to a test machine that has MS SQL Server Express installed(because my application is a client application and it should work with Express)...I run the program....the program retrieves the data from the service...and when I look at the database...I'm in for a big suprise...there's only one row written(the first row received from the WCF service). I would really appreciate any help...I'm in a deadlock here. Thanks in advance. Bojan

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• Rendering to a single Bitmap object from multiple threads

  - by Lee Treveil

  What im doing is rendering a number of bitmaps to a single bitmap. There could be hundreds of images and the bitmap being rendered to could be over 1000x1000 pixels. Im hoping to speed up this process by using multiple threads but since the Bitmap object is not thread-safe it cant be rendered to directly concurrently. What im thinking is to split the large bitmap into sections per cpu, render them separately then join them back together at the end. I haven't done this yet incase you guys/girls have any better suggestions. Any ideas? Thanks

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• Good .NET based CMS?

  - by rAm

  For many projects we had to choose a CMS platform. I came across a few CMS platforms based on .NET. I want to know your experience. Community Server (cannot be called a true CMS) DotNetNuke (DNN) Umbraco Kentico Sitefinity Can you please touch upon the following points: UI customization. Feature extension. Third party extensions Support And most important: how much time it takes to learn, as a programmer and someone who manages the application with little or no programming knowledge. Update: thanks for all the responses, I have seen the other thread but did not get a satisfactory reply addressing the Support and Time? (which I forgot to add earlier).

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• How do you implement Software Transactional Memory?

  - by Joseph Garvin

  In terms of actual low level atomic instructions and memory fences (I assume they're used), how do you implement STM? The part that's mysterious to me is that given some arbitrary chunk of code, you need a way to go back afterward and determine if the values used in each step were valid. How do you do that, and how do you do it efficiently? This would also seem to suggest that just like any other 'locking' solution you want to keep your critical sections as small as possible (to decrease the probability of a conflict), am I right? Also, can STM simply detect "another thread entered this area while the computation was executing, therefore the computation is invalid" or can it actually detect whether clobbered values were used (and thus by luck sometimes two threads may execute the same critical section simultaneously without need for rollback)?

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• "Microsoft DNS Client" vs. getaddrinfo?

  - by Josh K

  Right now, my application is using the c-ares asynchronous DNS resolver library on Windows below cURL, and I have users complaining that it behaves differently from other windows apps. One particular user said that "other applications are using the Microsoft DNS client" and experiences no problems. cURL itself has an asynchronous DNS implementation that uses getaddrinfo() in a thread. My guess is that would be equivalent behavior to using the "DNS Client" and its host of functions (e.g. DnsQuery?) So, dear Lazyweb, I ask if there is a tangible difference between the behavior of getaddrinfo() vs. using the actual Dns* APIs from the Win32 API.

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• SQL Server Process Queue Race Condition

  - by William Edmondson

  I have an order queue that is accessed by multiple order processors through a stored procedure. Each processor passes in a unique ID which is used to lock the next 20 orders for its own use. The stored procedure then returns these records to the order processor to be acted upon. There are cases where multiple processors are able to retrieve the same 'OrderTable' record at which point they try to simultaneously operate on it. This ultimately results in errors being thrown later in the process. My next course of action is to allow each processor grab all available orders and just round robin the processors but I was hoping to simply make this section of code thread safe and allow the processors to grab records whenever they like. So Explicitly - Any idea why I am experiencing this race condition and how I can solve the problem. BEGIN TRAN UPDATE OrderTable WITH ( ROWLOCK ) SET ProcessorID = @PROCID WHERE OrderID IN ( SELECT TOP ( 20 ) OrderID FROM OrderTable WITH ( ROWLOCK ) WHERE ProcessorID = 0) COMMIT TRAN SELECT OrderID, ProcessorID, etc... FROM OrderTable WHERE ProcessorID = @PROCID

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• How can I keep a WPF Image from blocking if the ImageSource references an unreachable Url?

  - by Corey O'Brien

  I'm writing a WPF application and trying to bind an image to my view model with the following XAML: <Image Source="{Binding Author.IconUrl, IsAsync=True}" /> The problem is that the image URLs are defined by users and can often refer to images hosted on intranet web servers. When the WPF application is run remotely, it locks up while trying to resolve the images that are now unreachable. I thought the "IsAsync" binding property would cause the load to happen in the background, but it appears that the DNS resolution may still happen in the main thread? What can I do to keep my app from locking, even if the images are unreachable? Thanks, Corey

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• Crashes when using AVAudioPlayer on iPhone

  - by mindthief

  Hi all, I am trying to use AVAudioPlayer to play some sounds in quick succession. When I invoke the sound-playing function less frequently so that the sounds play fully before the function is invoked again, the application runs fine. But if I invoke the function quickly in rapid succession (so that sounds are played while the previous sounds are still being played), the app eventually crashes after ~20 calls to the function, with the message "EXC_BAD_ACCESS". Here is code from the function: NSString *nsWavPath = [[[NSBundle mainBundle] resourcePath] stringByAppendingPathComponent:wavFileName]; AVAudioPlayer* theAudio = [[AVAudioPlayer alloc] initWithContentsOfURL:[NSURL fileURLWithPath:nsWavPath] error:NULL]; theAudio.delegate = self; [theAudio play]; As mentioned in another thread, I implemented the following delegate function: - (void) audioPlayerDidFinishPlaying:(AVAudioPlayer *)player successfully:(BOOL)flag { if(!flag) NSLog(@"audio did NOT finish successfully\n"); [player release]; } But the app still crashes after around ~20 rapid calls to the function. Any idea what I'm doing wrong?

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• Pipe data from InputStream to OutputStream in Java

  - by Wangnick

  Dear all, I'd like to send a file contained in a ZIP archive unzipped to an external program for further decoding and to read the result back into Java. ZipInputStream zis = new ZipInputStream(new FileInputStream(ZIPPATH)); Process decoder = new ProcessBuilder(DECODER).start(); ??? BufferedReader br = new BufferedReader(new InputStreamReader( decoder.getInputStream(),"us-ascii")); for (String line = br.readLine(); line!=null; line = br.readLine()) { ... } What do I need to put into ??? to pipe the zis content to the decoder.getOutputStream()? I guess a dedicated thread is needed, as the decoder process might block when its output is not consumed.

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• Blog Engine .NET with XML Data Storage How is it so fast ?

  - by Kubi

  I am looking for a way to embed a blog engine into my own application and I am too curious about Blog Engine algorithm. This may not be the correct place to ask but, How is that possible to store blog entry data in an XML file like BlogEngine.Net with Default Configuration. It must be getting slower everyday while the file is getting larger and larger. I am wondering the algorithm behind that. Is it loading with a different way ? Or Am I wrong with the time estimation ? I know it is open source but I thought it would be better to see a discussion here for some others might be thinking the same and this thread can be a reference.

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• Threading extra state through a parser in Scala

  - by Travis Brown

  I'll give you the tl;dr up front I'm trying to use the state monad transformer in Scalaz 7 to thread extra state through a parser, and I'm having trouble doing anything useful without writing a lot of t m a -> t m b versions of m a -> m b methods. An example parsing problem Suppose I have a string containing nested parentheses with digits inside them: val input = "((617)((0)(32)))" I also have a stream of fresh variable names (characters, in this case): val names = Stream('a' to 'z': _*) I want to pull a name off the top of the stream and assign it to each parenthetical expression as I parse it, and then map that name to a string representing the contents of the parentheses, with the nested parenthetical expressions (if any) replaced by their names. To make this more concrete, here's what I'd want the output to look like for the example input above: val target = Map( 'a' -> "617", 'b' -> "0", 'c' -> "32", 'd' -> "bc", 'e' -> "ad" ) There may be either a string of digits or arbitrarily many sub-expressions at a given level, but these two kinds of content won't be mixed in a single parenthetical expression. To keep things simple, we'll assume that the stream of names will never contain either duplicates or digits, and that it will always contain enough names for our input. Using parser combinators with a bit of mutable state The example above is a slightly simplified version of the parsing problem in this Stack Overflow question. I answered that question with a solution that looked roughly like this: import scala.util.parsing.combinator._ class ParenParser(names: Iterator[Char]) extends RegexParsers { def paren: Parser[List[(Char, String)]] = "(" ~> contents <~ ")" ^^ { case (s, m) => (names.next -> s) :: m } def contents: Parser[(String, List[(Char, String)])] = "\\d+".r ^^ (_ -> Nil) | rep1(paren) ^^ ( ps => ps.map(_.head._1).mkString -> ps.flatten ) def parse(s: String) = parseAll(paren, s).map(_.toMap) } It's not too bad, but I'd prefer to avoid the mutable state. What I want Haskell's Parsec library makes adding user state to a parser trivially easy: import Control.Applicative ((*>), (<$>), (<*)) import Data.Map (fromList) import Text.Parsec paren = do (s, m) <- char '(' *> contents <* char ')' h : t <- getState putState t return $ (h, s) : m where contents = flip (,) [] <$> many1 digit <|> (\ps -> (map (fst . head) ps, concat ps)) <$> many1 paren main = print $ runParser (fromList <$> paren) ['a'..'z'] "example" "((617)((0)(32)))" This is a fairly straightforward translation of my Scala parser above, but without mutable state. What I've tried I'm trying to get as close to the Parsec solution as I can using Scalaz's state monad transformer, so instead of Parser[A] I'm working with StateT[Parser, Stream[Char], A]. I have a "solution" that allows me to write the following: import scala.util.parsing.combinator._ import scalaz._, Scalaz._ object ParenParser extends ExtraStateParsers[Stream[Char]] with RegexParsers { protected implicit def monadInstance = parserMonad(this) def paren: ESP[List[(Char, String)]] = (lift("(" ) ~> contents <~ lift(")")).flatMap { case (s, m) => get.flatMap( names => put(names.tail).map(_ => (names.head -> s) :: m) ) } def contents: ESP[(String, List[(Char, String)])] = lift("\\d+".r ^^ (_ -> Nil)) | rep1(paren).map( ps => ps.map(_.head._1).mkString -> ps.flatten ) def parse(s: String, names: Stream[Char]) = parseAll(paren.eval(names), s).map(_.toMap) } This works, and it's not that much less concise than either the mutable state version or the Parsec version. But my ExtraStateParsers is ugly as sin—I don't want to try your patience more than I already have, so I won't include it here (although here's a link, if you really want it). I've had to write new versions of every Parser and Parsers method I use above for my ExtraStateParsers and ESP types (rep1, ~>, <~, and |, in case you're counting). If I had needed to use other combinators, I'd have had to write new state transformer-level versions of them as well. Is there a cleaner way to do this? I'd love to see an example of a Scalaz 7's state monad transformer being used to thread state through a parser, but Scala 6 or Haskell examples would also be useful.

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• How to modularize a b2b webservice transformation application

  - by hstoerr

  How would you modularize a large application that has some incoming (SOAP) webservices, some outgoing webservices, transformations between them and internal formats, internal logging services, accesses external archiving webservices, delays stuff and works on this asynchronously and so forth? One way is to split the functionality into a collection of WAR, deploy all of them on one application server and have them communicate with internal webservices. This has some overhead, especially if the messages are large, and you might run into performance problems due to thread count restrictions and so forth. Another way would be to put everything into a giant WAR, such that you can communicate directly. Not exactly modularization. What would you do?

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• Can I append to a preprocessor macro?

  - by JCSalomon

  Is there any way in standard C—or with GNU extensions—to append stuff to a macro definition? E.g., given a macro defined as #define quux_list X(foo) X(bar) can I append X(bas) so that it now expands as if I’d defined it #define quux_list X(foo) X(bar) X(bas)? I’m playing with discriminated/tagged unions along these lines: struct quux_foo { int x; }; struct quux_bar { char *s; }; struct quux_bas { void *p; }; enum quux_type {quux_foo, quux_bar, quux_bas}; struct quux { enum quux_type type; union { struct quux_foo foo; struct quux_bar bar; struct quux_bas bas; } t; }; I figure this is a good place for the X-macro. If I define a macro #define quux_table X(foo) X(bar) X(bas) the enumeration & structure can be defined thus, and never get out of sync: #define X(t) quux_ ## t, enum quux_type {quux_table}; #undef X #define X(t) struct quux_ ## t t; struct quux { enum quux_type type; union {quux_table} t; }; #undef X Of course, the quux_* structures can get out of sync, so I’d like to do something like this, only legally: struct quux_foo { int x; }; #define quux_table quux_table X(foo) struct quux_bar { char *s; }; #define quux_table quux_table X(bar) struct quux_bas { void *p; }; #define quux_table quux_table X(bas) (Well, what I really want to be able to do is something like member_struct(quux, foo) { int x; }; but I’m well aware that macros cannot be (re)defined from within macros.) Anyhow, that’s my motivating example. Is there a way to accomplish this? Boost.Preprocessor examples are fine, if you can show me how to make the X-macro technique work with that library.

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• Variable for the field name of mysql row result

  - by ana

  I'm retrieving a row with php from mysql and it has fields like: name_en, name_es, name_de... I want to retrieve the right field base on my $lang variable (en, es, de...). If the $lang variable is 'es', I'd need to get $row['name_es']. I've tried this (based on this thread), but it's not working: $name = $row->{'name_'.$lang}; Any idea how can I use a variable as the name of the field of a row? Thanks in advance for your help!

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• RaisePropertyChanged for Windows Phone

  - by chief7

  I'm starting to use the MVVMLight framework and have a question about binding to properties in the ViewModel. I found that I have to call the RaisePropertyChanged method in the setter for the property in order for the View to be updated. And I have to call RaisePropertyChanged from through the dispatcher otherwise I get a thread access error. public string Lat { get { return _lat; } set { _lat = value; Deployment.Current.Dispatcher.BeginInvoke(() => RaisePropertyChanged("Lat")); } } This works but its a lot of code to get auto binding properties. Is there a helper to handle this more cleanly?

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• Demystifying gcc under lpthreads

  - by Berkay

  in these i'm playing with thread library and trying to implement some functions. One of the tutorial says that to run the program use : gcc -lpthread -lrt -lc -lm project1.c scheduler.c -o out first of all i need deep understanding of what is gcc doing in each line, lpthread is used for what? what are the contributions of lrt -lc -lm ? project1.c and scheduler.c is compiled together so what should i understand? i checked the code and any of them not included in project1.c or scheduler.c. as an output clearly it gives "out". secondly the author states that to run the program you have to use ./out number filename (For example, ./out 2 sample.txt) To make these clear as far as i understand the main function gets number and sample.txt as an input.(?) thanks for your answers and making me clear.

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