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  • Convert an exception into HTTP 404 response in the Application_Error

    - by Dmitriy Nagirnyak
    Hi, First of all, quickly what exactly I want to achieve: translate particular exception into the HTTP 404 so the ASP.NET can handle it further. I am handling exceptions in the ASP.NET (MVC2) this way: protected void Application_Error(object sender, EventArgs e) { var err = Server.GetLastError(); if (err == null) return; err = err.GetBaseException(); var noObject = err as ObjectNotFoundException; if (noObject != null) HandleObjectNotFound(); var handled = noObject != null; if (!handled) Logger.Fatal("Unhandled exception has occured in application.", err); } private void HandleObjectNotFound() { Server.ClearError(); Response.Clear(); // new HttpExcepton(404, "Not Found"); // Throw or not to throw? Response.StatusCode = 404; Response.StatusDescription = "Not Found"; Response.StatusDescription = "Not Found"; Response.Write("The whole HTML body explaining whata 404 is??"); } The problem is that I cannot configure default customErrors to work with it. When it is on then it never redirects to the page specified in customErrors: <error statusCode="404" redirect="404.html"/>. I also tried to raise new HttpExcepton(404, "Not Found") from the handler but then the response code is 200 which I don't understand why. So the questions are: What is the proper way of translating AnException into HTTP 404 response? How does customErrors section work when handling exceptions in Application_Error? Why throwing HttpException(404) renders (blank) page with success (200) status? Thanks, Dmitriy.

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  • Improving long-polling Ajax performance

    - by Bears will eat you
    I'm writing a webapp (Firefox-compatible only) which uses long polling (via jQuery's ajax abilities) to send more-or-less constant updates from the server to the client. I'm concerned about the effects of leaving this running for long periods of time, say, all day or overnight. The basic code skeleton is this: function processResults(xml) { // do stuff with the xml from the server } function fetch() { setTimeout(function () { $.ajax({ type: 'GET', url: 'foo/bar/baz', dataType: 'xml', success: function (xml) { processResults(xml); fetch(); }, error: function (xhr, type, exception) { if (xhr.status === 0) { console.log('XMLHttpRequest cancelled'); } else { console.debug(xhr); fetch(); } } }); }, 500); } (The half-second "sleep" is so that the client doesn't hammer the server if the updates are coming back to the client quickly - which they usually are.) After leaving this running overnight, it tends to make Firefox crawl. I'd been thinking that this could be partially caused by a large stack depth since I've basically written an infinitely recursive function. However, if I use Firebug and throw a breakpoint into fetch, it looks like this is not the case. The stack that Firebug shows me is only about 4 or 5 frames deep, even after an hour. One of the solutions I'm considering is changing my recursive function to an iterative one, but I can't figure out how I would insert the delay in between Ajax requests without spinning. I've looked at the JS 1.7 "yield" keyword but I can't quite wrap my head around it, to figure out if it's what I need here. Is the best solution just to do a hard refresh on the page periodically, say, once every hour? Is there a better/leaner long-polling design pattern that won't put a hurt on the browser even after running for 8 or 12 hours? Or should I just skip the long polling altogether and use a different "constant update" pattern since I usually know how frequently the server will have a response for me?

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  • Determining the maximum stack depth

    - by Joa Ebert
    Imagine I have a stack-based toy language that comes with the operations Push, Pop, Jump and If. I have a program and its input is the toy language. For instance I get the sequence Push 1 Push 1 Pop Pop In that case the maximum stack would be 2. A more complicated example would use branches. Push 1 Push true If .success Pop Jump .continue .success: Push 1 Push 1 Pop Pop Pop .continue: In this case the maximum stack would be 3. However it is not possible to get the maximum stack by walking top to bottom as shown in this case since it would result in a stack-underflow error actually. CFGs to the rescue you can build a graph and walk every possible path of the basic blocks you have. However since the number of paths can grow quickly for n vertices you get (n-1)! possible paths. My current approach is to simplify the graph as much as possible and to have less possible paths. This works but I would consider it ugly. Is there a better (read: faster) way to attack this problem? I am fine if the algorithm produces a stack depth that is not optimal. If the correct stack size is m then my only constraint is that the result n is n = m. Is there maybe a greedy algorithm available that would produce a good result here?

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  • UIKeyBoard resize on orientation change to landscape

    - by Dave
    This is very rookie question. I have a UIToolBar at the bottom which is supposed to animatedly move up and down with key board when the UIKeyBoard is displayed. I got that working with the help of UIKeyBoard Notifications. The view we are talking about has split view enabled. When device orientation is landscape, both the views as columns are shown [hope that makes sense]. When key board is shown, i do this CGSize keyBoardSize = [[notificationInfo objectForKey:UIKeyboardFrameEndUserInfoKey]CGRectValue].size; CGRect toolbarFrame= [BottomToolBar frame]; toolbarFrame.origin.y -= keyBoardSize.height; [UIView beginAnimations:nil context:nil]; [UIView setAnimationDuration:0.3]; BottomToolBar .frame = viewFrame; [UIView commitAnimations]; when key board is hiiden i do this toolbarFrame.origin.y += keyBoardSize.height; My Problem is when device orientation changes to landscape, when the key board is visible the bottom tool bar is gone. I see it move up quickly. I am not sure how to fix this. Can anyone help please? Also, is there a way to NOT make the key board span across both the views in the split view?

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  • Python progression path - From apprentice to guru

    - by Morlock
    Hi all, I've been learning, working, and playing with Python for a year and a half now. As a biologist slowly making the turn to bio-informatics, this language has been a the very core of all the major contributions I have made in the lab. (bash and R scripts have helped some too. My C++ capabilities are very not functional yet). I more or less fell in love with the way Python permits me to express beautiful solutions and also with the semantics of the language that allows such a natural flow from thoughts to workable code. What I would like to know from you is your answer to a kind of question I have seldom seen in this or other forums. Let me sum up what I do NOT want to ask first ;) I don't want to know how to QUICKLY learn Python Nor do I want to find out the best way to get acquainted with the language Finally, I don't want to know a 'one trick that does it all' approach. What I do want to know your opinion about, is: What are the steps YOU would recommend to a Python journeyman, from apprenticeship to guru status (feel free to stop wherever your expertise dictates it), in order that one IMPROVES CONSTANTLY, becoming a better and better Python coder, one step at a time. The kind of answers I would enjoy (but feel free to surprise the readership :P ), is formatted more or less like this: Read this (eg: python tutorial), pay attention to that kind of details Code for so manytime/problems/lines of code Then, read this (eg: this or that book), but this time, pay attention to this Tackle a few real-life problems Then, proceed to reading Y. Be sure to grasp these concepts Code for X time Come back to such and such basics or move further to... (you get the point :) This process depicts an iterative Learn/Code cycle, and I really care about knowing your opinion on what exactly one should pay attention to, at various stages, in order to progress CONSTANTLY (with due efforts, of course). If you come from a specific field of expertise, discuss the path you see as appropriate in this field. Thanks a lot for sharing your opinions and good Python coding!

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  • Python: some newbie questions on sys.stderr and using function as argument

    - by Cawas
    I'm just starting on Python and maybe I'm worrying too much too soon, but anyways... log = "/tmp/trefnoc.log" def logThis (text, display=""): msg = str(now.strftime("%Y-%m-%d %H:%M")) + " TREfNOC: " + text if display != None: print msg + display logfile = open(log, "a") logfile.write(msg + "\n") logfile.close() return msg def logThisAndExit (text, display=""): msg = logThis(text, display=None) sys.exit(msg + display) That is working, but I don't like how it looks. Is there a better way to write this (maybe with just 1 function) and is there any other thing I should be concerned under exiting? Now to some background... Sometimes I will call logThis just to log and display. Other times I want to call it and exit. Initially I was doing this: logThis ("ERROR. EXITING") sys.exit() Then I figured that wouldn't properly set the stderr, thus the current code shown on the top. My first idea was actually passing "sys.exit" as an argument, and defining just logThis ("ERROR. EXITING", call=sys.exit) defined as following (showing just the relevant differenced part): def logThis (text, display="", call=print): msg = str(now.strftime("%Y-%m-%d %H:%M")) + " TREfNOC: " + text call msg + display But that obviously didn't work. I think Python doesn't store functions inside variables. I couldn't (quickly) find anywhere if Python can have variables taking functions or not! Maybe using an eval function? I really always try to avoid them, tho. Sure I thought of using if instead of another def, but that wouldn't be any better or worst. Anyway, any thoughts?

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  • Perf: Viewing thousands of images in Silverlight 3 on a 3D Wall

    - by Bob Holland
    I currently work on a very cool Silverlight app that displays photos in a 3D wall space like the Wall3D demo that is thrown in with Blend 3. The problem I am currently facing is performance. The app works like this: As you scroll right or left the 3d photo wall rotates As each movement is made, the next column of photos are downloaded, decoded into a BitmapImage and thrown into a 3D Wall Node. As you can imagine users (if you let them) will want to flip through the photos really quickly, but the problem I have is I cannot display the photos quick enough. In most cases it's a beautiful app that works really well, but when an album contains over 300 photos, you can imagine the sort of memory taken up by all the BitmapImage classes and how moving the slider can jump from photo 20 to photo 120 in a second. Of course we have algorithms in place to not download every photo in between, but I still can't work out a fast way to get the photos displayed. It may be a case that we need to throw away the 'great for show' 3D wall and go to a flat DeepZoom like wall like the Playboy archive one that Vertigo did. Still not sure, let me know your thoughts. P.S. We are using Kit3D for all the 3D work, it's using PerspectiveCamera, Model3DGroup, ModelVisual3D, RotateTransform3D & TranslateTransform3D. Cheers, Bob.

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  • Improve XPath efficiency for repeated, parameterized queries

    - by Chris Allan
    Hi, I am repeatedly performing the following XPath query (though parameterized by 'keywordText') around 40,000 times: String query = SystemGlobal.YAHOO_KEYWORDSSUBNODE + "/" + SystemGlobal.YAHOO_KEYWORDNODE + "[" + SystemGlobal.YAHOO_ATTRKEYPHRASE + "='" + keywordText + "']"; CachedXPathAPI cachedXPathAPI = new CachedXPathAPI(); NodeIterator nl = cachedXPathAPI.selectNodeIterator(doc.getElementsByTagName(SystemGlobal.YAHOO_KEYWORDSROOT).item(0), query); Node n; if ((n = nl.nextNode()) != null) { keyword.setKeywordId(Long.parseLong(cachedXPathAPI.selectSingleNode(n, SystemGlobal.YAHOO_ATTRKEYID).getTextContent())); keyword.setKeyPhrase(cachedXPathAPI.selectSingleNode(n, SystemGlobal.YAHOO_ATTRKEYPHRASE).getTextContent()); keyword.setStatus(mapStatus(cachedXPathAPI.selectSingleNode(n, SystemGlobal.YAHOO_ATTRSTATUS).getTextContent())); keyword.setCampaignId(Long.parseLong(cachedXPathAPI.selectSingleNode(n, "../../" + SystemGlobal.YAHOO_ATTRCAMPAIGNID).getTextContent())); keyword.setAdGroupId(Long.parseLong(cachedXPathAPI.selectSingleNode(n, "../" + SystemGlobal.YAHOO_ATTRADGROUPID).getTextContent())); On the first run of the script, all 40,000 runs of this piece of code will have nl.nextNode() == null, and everything runs quite quickly. However, on the following runs, when nl.nextNode() != null, then things slow down a lot - this takes around an additional 40min to run (whereas the first run takes maybe 1 minute). Oh, and the doc is constructed like so: InputSource in = new InputSource(new FileInputStream(filename)); DocumentBuilderFactory dfactory = DocumentBuilderFactory.newInstance(); dfactory.setNamespaceAware(true); doc = dfactory.newDocumentBuilder().parse(in); I tried including the following lines reportEvaluator = new XPathEvaluatorImpl(reportDoc); reportResolver = reportEvaluator.createNSResolver(reportDoc); and rather creating a NodeIterator, instead creating an XPathResult: XPathResult result = (XPathResult)reportEvaluator.evaluate(query, doc.getElementsByTagName(SystemGlobal.YAHOO_KEYWORDSROOT).item(0), reportResolver, XPathResult.UNORDERED_NODE_ITERATOR_TYPE, null); however this ran even slower Is there a way in which I can speed up the running of this script? I have seen references to precompiled queries, though I haven't seen many actual details. Also, as seen in the code, I am using CachedXPathAPI, though the benefit for this case is not so great. Any help is much appreciated! Chris Allan

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  • Force-directed graphing

    - by David
    Hello, I'm trying to write a force-directed or force-atlas code base for a graphing application I'm building for myself. Here is an example of what I'm attempting: http://sawamuland.com/flash/graph.html I managed to find some pseudo code to accomplish what I'd like on the Wiki Force-atlas article. I've converted this into ActionScript 3.0 code since it's a Flash application. Here is my source: var timestep:int = 0; var damping:int = 0; var total_kinetic_engery:int = 0; for (var node in list) { var net_force:int = 0; for (var other_node in list) { net_force += coulombRepulsion(node, other_node, nodeList); } for (var spring in list[node].relations) { net_force += hookeAttraction(node, spring, nodeList); } list[node].velocity += (timestep * net_force) * damping; list[node].position += timestep * list[node].velocity; total_kinetic_engery += list[node].mass * (list[node].velocity) ^ 2; } The problem now is finding pseudo code or a function to perform the the coulomb repulsion and hooke attraction code. I'm not exactly sure how to accomplish this. Does anyone know of a good reference I can look at...understand and implement quickly? Best.

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  • Reinforcement learning toy project

    - by Betamoo
    My toy project to learn & apply Reinforcement Learning is: - An agent tries to reach a goal state "safely" & "quickly".... - But there are projectiles and rockets that are launched upon the agent in the way. - The agent can determine rockets position -with some noise- only if they are "near" - The agent then must learn to avoid crashing into these rockets.. - The agent has -rechargable with time- fuel which is consumed in agent motion - Continuous Actions: Accelerating forward - Turning with angle I need some hints and names of RL algorithms that suit that case.. - I think it is POMDP , but can I model it as MDP and just ignore noise? - In case POMDP, What is the recommended way for evaluating probability? - Which is better to use in this case: Value functions or Policy Iterations? - Can I use NN to model environment dynamics instead of using explicit equations? - If yes, Is there a specific type/model of NN to be recommended? - I think Actions must be discretized, right? I know it will take time and effort to learn such a topic, but I am eager to.. You may answer some of the questions if you can not answer all... Thanks

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  • Smoothing touch-based animation in iPhone OpenGL?

    - by quixoto
    I know this is vague, but looking for general tips/help on this, as it's not an area of significant expertise for me. I have some iPhone code that's basically an EAGL view handling a single touch. The app draws (using GL) a circle via triangle fan at the touch point, and moves it when the user moves the touch point, and re-renders the view then. When dragging a finger slowly, the circle keeps up and consistent with the finger as it moves. If I scribble my finger quickly back and forth across the screen, the rendering doesn't keep up with the touch motion, so you see an optical illusion of "multiple" discrete circles on the screen "at once". (Normal persistence of vision illusion). This optical illusion is jarring. How can I make this look more natural? Can I blur the motion of the circle somehow? Is this result the evidence of some bad frame rate issue? I see this artifact even when nothing else is being rendered, so I think this might just be as fast as we can go. Any hints or suggestions? Much appreciated. Thanks.

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  • Seperating Javascript and Html, when dynamically adding html via javascript

    - by optician
    I am currently building a very dynamic table for a list application, which will basically perform basic CRUD functions via AJAX. What I would like to do is separate the visual design and javascript to the point where I can change the design side without touching the JS side. This would only work where the design stays roughly the same(i would like to use it for rapid protyping) Here is an example. <table> <tr><td>record-123</td><td>I am line 123</td><td>delete row</td></tr> <tr><td>record-124</td><td>I am line 124</td><td>delete row</td></tr> <tr><td>record-125</td><td>I am line 125</td><td>delete row</td></tr> <tr><td>add new record</td></tr> </table> Now, when I add a new record, I would like to insert a new row of html, but I would rather not put this html into the javascript file. What I am considering is creating a row like this on the page, near the table. <tr style='visble:none;' id='template-row'><td>record-id</td><td>content-area</td><td>delete row</td></tr> And when I come to add the new row, I search the page for the tags with the id=template-row , and then grab it, do a string replace on it, and then put it in the right place in the page. As long as the design doesn't shift radically, and I keep the placeholder strings the same, it means designs can be quickly modified without touching the js. Can any give any advice on a methodology like this?

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  • Working with a large data object between ruby processes

    - by Gdeglin
    I have a Ruby hash that reaches approximately 10 megabytes if written to a file using Marshal.dump. After gzip compression it is approximately 500 kilobytes. Iterating through and altering this hash is very fast in ruby (fractions of a millisecond). Even copying it is extremely fast. The problem is that I need to share the data in this hash between Ruby on Rails processes. In order to do this using the Rails cache (file_store or memcached) I need to Marshal.dump the file first, however this incurs a 1000 millisecond delay when serializing the file and a 400 millisecond delay when serializing it. Ideally I would want to be able to save and load this hash from each process in under 100 milliseconds. One idea is to spawn a new Ruby process to hold this hash that provides an API to the other processes to modify or process the data within it, but I want to avoid doing this unless I'm certain that there are no other ways to share this object quickly. Is there a way I can more directly share this hash between processes without needing to serialize or deserialize it? Here is the code I'm using to generate a hash similar to the one I'm working with: @a = [] 0.upto(500) do |r| @a[r] = [] 0.upto(10_000) do |c| if rand(10) == 0 @a[r][c] = 1 # 10% chance of being 1 else @a[r][c] = 0 end end end @c = Marshal.dump(@a) # 1000 milliseconds Marshal.load(@c) # 400 milliseconds Update: Since my original question did not receive many responses, I'm assuming there's no solution as easy as I would have hoped. Presently I'm considering two options: Create a Sinatra application to store this hash with an API to modify/access it. Create a C application to do the same as #1, but a lot faster. The scope of my problem has increased such that the hash may be larger than my original example. So #2 may be necessary. But I have no idea where to start in terms of writing a C application that exposes an appropriate API. A good walkthrough through how best to implement #1 or #2 may receive best answer credit.

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  • Separating Javascript and Html, when dynamically adding html via javascript

    - by optician
    I am currently building a very dynamic table for a list application, which will basically perform basic CRUD functions via AJAX. What I would like to do is separate the visual design and javascript to the point where I can change the design side without touching the JS side. This would only work where the design stays roughly the same(i would like to use it for rapid protyping) Here is an example. <table> <tr><td>record-123</td><td>I am line 123</td><td>delete row</td></tr> <tr><td>record-124</td><td>I am line 124</td><td>delete row</td></tr> <tr><td>record-125</td><td>I am line 125</td><td>delete row</td></tr> <tr><td>add new record</td></tr> </table> Now, when I add a new record, I would like to insert a new row of html, but I would rather not put this html into the javascript file. What I am considering is creating a row like this on the page, near the table. <tr style='visble:none;' id='template-row'><td>record-id</td><td>content-area</td><td>delete row</td></tr> And when I come to add the new row, I search the page for the tags with the id=template-row , and then grab it, do a string replace on it, and then put it in the right place in the page. As long as the design doesn't shift radically, and I keep the placeholder strings the same, it means designs can be quickly modified without touching the js. Can any give any advice on a methodology like this?

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  • Java NoClassDefFoundError when calling own class from instrumented method

    - by lethal_possum
    Hello, I am working on a kit of simple Java agents to help me (and hopefully others) troubleshoot Java applications. One of the agents I would like to create instruments the JComponent.getToolTipText() method to quickly identify any GUI class by just hovering the mouse cursor over it. You can find the code of my transformer and the rest of the project here: http://sfn.cvs.sourceforge.net/viewvc/sfn/core/src/main/java/org/leplus/sfn/transformer/JComponentTransformer.java?view=markup I launch my test GUI with the agent attached as follow: $ java -javaagent:target/jars/sfn-0.1-agent.jar=JComponent -cp lib/jars/bcel-5.2.jar:target/jars/sfn-0.1-test.jar:target/jars/sfn-0.1-agent.jar org.leplus.sfn.test.Main sfn-0.1-agent.jar contains the org.leplus.sfn.transformer.JComponentTransformer class. sfn-0.1-test.jar contains the org.leplus.sfn.test.Main class. Here is what the application prints when I launch it and I put the mouse over it: Loading agent: JComponent Instrumentation ready! Exception in thread "AWT-EventQueue-0" java.lang.NoClassDefFoundError: org/leplus/sfn/tracer/ComponentTracer at javax.swing.JComponent.getToolTipText(JComponent.java) at javax.swing.ToolTipManager$insideTimerAction.actionPerformed(ToolTipManager.java:662) ... What is surprising to me is that if I change my transformer to call any class from the JRE, it works. But it doesn't work when I call my own class org.leplus.sfn.tracer.ComponentTracer. My first guess was a classpath issue but the ComponentTracer is both in the classpath and in the agent's jar. So I am lost. If any of you see where I am missing something. Cheers, Tom

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  • Problem with Java Applet <--> Javascript communication

    - by davr
    I'm having trouble getting a Java Applet to communicate with the Javascript code on the page the applet is hosted on. It works sometimes, but othertimes it throws an obscure exception, that googling for has not turned up any useful information, besides a few Java bug reports that were never resolved (thanks Sun). Here is the code I am using: JSObject win = JSObject.getWindow(this); Object[] args = new Object[1]; args[0] = "test argument"; String result = (String) win.call("testJSfunc", args); // XXX Here is the exception I get on the line marked // XXX. Note that it is intermittent. Often it works, but sometimes it does not, using the same exact code. Reloading the page repeatedly will produce the error pretty quickly. netscape.javascript.JSException: No registered plugin for applet ID 1 at sun.plugin2.main.client.MessagePassingJSObject.newJSException(Unknown Source) at sun.plugin2.main.client.MessagePassingJSObject.waitForReply(Unknown Source) at sun.plugin2.main.client.MessagePassingJSObject.call(Unknown Source) at TestApplet.testCallJS(TestApplet.java:159) at TestApplet.init(TestApplet.java:139) at sun.plugin2.applet.Plugin2Manager$AppletExecutionRunnable.run(Unknown Source) at java.lang.Thread.run(Unknown Source) Is there another more stable way of communicating between Java and Javascript that I should be using?

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  • maintaining a large list in python

    - by Oren
    I need to maintain a large list of python pickleable objects that will quickly execute the following algorithm: The list will have 4 pointers and can: Read\Write each of the 4 pointed nodes Insert new nodes before the pointed nodes Increase a pointer by 1 Pop nodes from the beginning of the list (without overlapping the pointers) Add nodes at the end of the list The list can be very large (300-400 MB), so it shouldnt be contained in the RAM. The nodes are small (100-200 bytes) but can contain various types of data. The most efficient way it can be done, in my opinion, is to implement some paging-mechanism. On the harddrive there will be some database of a linked-list of pages where in every moment up to 5 of them are loaded in the memory. On insertion, if some max-page-size was reached, the page will be splitted to 2 small pages, and on pointer increment, if a pointer is increased beyond its loaded page, the following page will be loaded instead. This is a good solution, but I don't have the time to write it, especially if I want to make it generic and implement all the python-list features. Using a SQL tables is not good either, since I'll need to implement a complex index-key mechanism. I tried ZODB and zc.blist, which implement a BTree based list that can be stored in a ZODB database file, but I don't know how to configure it so the above features will run in reasonable time. I don't need all the multi-threading\transactioning features. No one else will touch the database-file except for my single-thread program. Can anyone explain me how to configure the ZODB\zc.blist so the above features will run fast, or show me a different large-list implementation?

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  • Equivalent of typedef in C#

    - by Matthew Scharley
    Is there a typedef equivalent in C#, or someway to get some sort of similar behaviour? I've done some googling, but everywhere I look seems to be negative. Currently I have a situation similar to the following: class GenericClass<T> { public event EventHandler<EventData> MyEvent; public class EventData : EventArgs { /* snip */ } // ... snip } Now, it doesn't take a rocket scientist to figure out that this can very quickly lead to alot of typing (appologies for the horrible pun) when trying to implement a handler for that event. It'd end up being something like this: GenericClass<int> gcInt = new GenericClass<int>; gcInt.MyEvent += new EventHandler<GenericClass<int>.EventData>(gcInt_MyEvent); // ... private void gcInt_MyEvent(object sender, GenericClass<int>.EventData e) { throw new NotImplementedException(); } Except, in my case, I was already using a complex type, not just an int. It'd be nice if it was possible to simplify this a little... Edit: ie. perhaps typedefing the EventHandler instead of needing to redefine it to get similar behaviour.

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  • Good grammar for date data type for recursive descent parser LL(1)

    - by Totophil
    I'm building a custom expression parser and evaluator for production enviroment to provide a limited DSL to the users. The parser itself as the DSL, need to be simple. The parser is going to be built in an exotic language that doesn't support dynamic expression parsing nor has any parser generator tools available. My decision is to go for recursive descent approach with LL(1) grammar, so that even programmers with no previous experience in evaluating expression could quickly learn how the code works. It has to handle mixed expressions made up of several data types: decimals, percentages, strings and dates. And dates in the format of dd/mm/yyyy are easy to confuse with a string of devision ops. Is where a good solution to this problem? My own solution that is aimed at keeping the parser simple involves prefixing dates with a special symbol, let's say apostrophe: <date> ::= <apostr><digit><digit>/<digit><digit>/<digit><digit><digit><digit> <apostr> ::= ' <digit> ::= '0'..'9'

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  • Right way to dispose Image/Bitmap and PictureBox

    - by kornelijepetak
    I am trying to develop a Windows Mobile 6 (in WF/C#) application. There is only one form and on the form there is only a PictureBox object. On it I draw all desired controls or whatever I want. There are two things I am doing. Drawing custom shapes and loading bitmaps from .png files. The next line locks the file when loading (which is an undesired scenario): Bitmap bmp = new Bitmap("file.png"); So I am using another way to load bitmap. public static Bitmap LoadBitmap(string path) { using (Bitmap original = new Bitmap(path)) { return new Bitmap(original); } } This is I guess much slower, but I don't know any better way to load an image, while quickly releasing the file lock. Now, when drawing an image there is method that I use: public void Draw() { Bitmap bmp = new Bitmap(240,320); Graphics g = Graphics.FromImage(bmp); // draw something with Graphics here. g.Clear(Color.Black); g.DrawImage(Images.CloseIcon, 16, 48); g.DrawImage(Images.RefreshIcon, 46, 48); g.FillRectangle(new SolidBrush(Color.Black), 0, 100, 240, 103); pictureBox.Image = bmp; } This however seems to be some kind of a memory leak. And if I keep doing it for too long, the application eventually crashes. Therefor, I have X questions: 1.) What is the better way for loading bitmaps from files without locking the file? 2.) What objects needs to be manually disposed in the Draw() function (and in which order) so there's no memory leak and no ObjectDisposedException throwing? 3.) If pictureBox.Image is set to bmp, like in the last line of the code, would pictureBox.Image.Dispose() dispose only resources related to maintaining the pictureBox.Image or the underlying Bitmap set to it?

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  • Named pipe blocking with user nobody

    - by dnagirl
    I have 2 short scripts. The first, an awk script, processes a large file and prints to a named pipe 'myfifo.dat'. The second, a Perl script, runs a LOAD DATA LOCAL INFILE 'myfifo.dat'... command. Both of these scripts work when run locally like so: lee.awk big.file & lee.pl However, when I call these scripts from a PHP webpage, the named pipe blocks: $awk="/path/to/lee.awk {$_FILES['uploadfile']['tmp_name']} &"; $sql="/path/to/lee.pl"; if(!exec($awk,$return,$err)) throw new ZException(print_r($err,true)); //blocks here if(!exec($sql,$return,$err)) throw new ZException(print_r($err,true)); If I modify the awk and Perl scripts so that they write and read to a normal file, everything works fine from PHP. The permissions on the fifo and the normal file are 666 (for testing purposes). These operations run much more quickly through a named pipe, so I'd prefer to use one. Any ideas how to unblock it? ps. In case you're wondering why I'm going to all this aggravation, see this SO question.

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  • Double type returns -1.#IND/NaN error when calculating pi iteratively

    - by Draak
    I am working through a problem for my MCTS certification. The program has to calculate pi until the user presses a key, at which point the thread is aborted, the result returned to the main thread and printed in the console. Simple enough, right? This exercise is really meant to be about threading, but I'm running into another problem. The procedure that calculates pi returns -1.#IND. I've read some of the material on the web about this error, but I'm still not sure how to fix it. When I change double to Decimal type, I unsurprisingly get Overflow Exception very quickly. So, the question is how do I store the numbers correctly? Do I have to create a class to somehow store parts of the number when it gets too big to be contained in a Decimal? Class PiCalculator Dim a As Double = 1 Dim b As Double = 1 / Math.Sqrt(2) Dim t As Double = 1 / 4 Dim p As Double = 1 Dim pi As Double Dim callback As DelegateResult Sub New(ByVal _callback As DelegateResult) callback = _callback End Sub Sub Calculate() Try Do While True Dim a1 = (a + b) / 2 Dim b1 = Math.Sqrt(a * b) Dim t1 = t - p * (a - a1) ^ 2 Dim p1 = 2 * p a = a1 b = b1 t = t1 p = p1 pi = ((a + b) ^ 2) / (4 * t) Loop Catch ex As ThreadAbortException Finally callback(pi) End Try End Sub End Class

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  • Problem with multiple event handling in JQuery

    - by Greg
    Hi everyone, I have a strange jquery problem with multiple event handlers. What I'm trying to achieve is this: User selects some text on the page If the selection is not empty - show a context menu If user clicks somewhere else - the context menu should disappear I'm having troubles with the above i.e. sometimes the context menu appears correctly, sometimes it appears and disappears straight after user makes a selection. Please help. See the relevant parts of my code below. Also when user selects a paragraph or a word by double clicking - context menu appears and quickly disappears again. var ContextMenu = { ... show: function(e) { var z = this; if (!this.shown) { if (this.contextMenu) { this.contextMenu.css({ left: e.pageX, top: e.pageY }).slideDown('fast'); this.shown = true; } var hideHandler = function() { z.hide(this); }; $(document.body).bind("click", hideHandler); } }, hide: function(hideHandler) { if (this.contextMenu && this.shown) { this.contextMenu.slideUp('fast'); this.shown = false; $(document.body).unbind("click", hideHandler); } } }; // Context menu display logic $(document.body).bind("mousedown mouseup", function(e) { if ((window.getSelection().toString() != "") && (!ContextMenu.shown)) { ContextMenu.show(e); } });

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  • .NET custom property attribute?

    - by ropstah
    EDIT: I'd better rephrase: How can I shift the GET-implementation of a Class property to a / using a custom attribute? (I've added instantation vars (classname, propertyname) to the attribute, however I'd rather have these automatically fetched ofcourse.) Public Class CustomClass <CustomAttributeClass(ClassName:="CustomClass", PropertyName = "SomeProperty")> _ Public Property SomeProperty() as String Get() as String //This implementation should be handled by the attribute class End Get Set(Byval value as String) Me._someProperty = value End Set End Property End Class Old question: I want to create a custom property attribute for classes. I can create a class derived from Attribute, and 'mark' the property with the attribute, but where to go from here? I have a repository where I can quickly get data based on the attributes values. I would like to generalize the behaviour of the property in the attribute but I don't know how to go from here... Any help would be greatly accepted! Public Class CustomDataAttribute : Inherits Attribute Private _name As String Public Sub New(ByVal name As String) Me.Name = name End Sub Property Name() As String Get Return _name End Get Set(ByVal value As String) Me._name = value End Set End Property End Class Public Class CustomClass <CustomDataAttribute(Name:="CustomField")> _ Public Property CustomField() End Property End Class

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  • Programmatically implementing an interface that combines some instances of the same interface in var

    - by namin
    What is the best way to implement an interface that combines some instances of the same interface in various specified ways? I need to do this for multiple interfaces and I want to minimize the boilerplate and still achieve good efficiency, because I need this for a critical production system. Here is a sketch of the problem. Abstractly, I have a generic combiner class which takes the instances and specify the various combinators: class Combiner<I> { I[] instances; <T> T combineSomeWay(InstanceMethod<I,T> method) { // ... method.call(instances[i]) ... combined in some way ... } // more combinators } Now, let's say I want to implement the following interface among many others: Interface Foo { String bar(int baz); } I want to end up with code like this: class FooCombiner implements Foo { Combiner<Foo> combiner; @Override public String bar(final int baz) { return combiner.combineSomeWay(new InstanceMethod<Foo, String> { @Override public call(Foo instance) { return instance.bar(baz); } }); } } Now, this can quickly get long and winded if the interfaces have lots of methods. I know I could use a dynamic proxy from the Java reflection API to implement such interfaces, but method access via reflection is hundred times slower. So what are the alternatives to boilerplate and reflection in this case?

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