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  • Nested parsers in happy / infinite loop?

    - by McManiaC
    I'm trying to write a parser for a simple markup language with happy. Currently, I'm having some issues with infinit loops and nested elements. My markup language basicly consists of two elements, one for "normal" text and one for bold/emphasized text. data Markup = MarkupText String | MarkupEmph [Markup] For example, a text like Foo *bar* should get parsed as [MarkupText "Foo ", MarkupEmph [MarkupText "bar"]]. Lexing of that example works fine, but the parsing it results in an infinite loop - and I can't see why. This is my current approach: -- The main parser: Parsing a list of "Markup" Markups :: { [Markup] } : Markups Markup { $1 ++ [$2] } | Markup { [$1] } -- One single markup element Markup :: { Markup } : '*' Markups1 '*' { MarkupEmph $2 } | Markup1 { $1 } -- The nested list inside *..* Markups1 :: { [Markup] } : Markups1 Markup1 { $1 ++ [$2] } | Markup1 { [$1] } -- Markup which is always available: Markup1 :: { Markup } : String { MarkupText $1 } What's wrong with that approach? How could the be resolved? Update: Sorry. Lexing wasn't working as expected. The infinit loop was inside the lexer. Sorry. :) Update 2: On request, I'm using this as lexer: lexer :: String -> [Token] lexer [] = [] lexer str@(c:cs) | c == '*' = TokenSymbol "*" : lexer cs -- ...more rules... | otherwise = TokenString val : lexer rest where (val, rest) = span isValidChar str isValidChar = (/= '*') The infinit recursion occured because I had lexer str instead of lexer cs in that first rule for '*'. Didn't see it because my actual code was a bit more complex. :)

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  • Special technology needed for browser based chat?

    - by orokusaki
    On this post, I read about the usage of XMPP. Is this sort of thing necessary, and more importantly, my main question expanded: Can a chat server and client be built efficiently using only standard HTTP and browser technologies (such as PHP and JS, or RoR and JS, etc)? Or, is it best to stick with old protocols like XMPP find a way to integrate them with my application? I looked into CampFire via LiveHTTPHeaders and Firebug for about 5 minutes, and it appears to use Ajax to send a request which is never answered until another chat happens. Is this just CampFire opening a new thread on the server to listen for an update and then returning a response to the request when the thread hears an update? I noticed that they're requesting on a specific port (8043 if memory serves me) which makes me think that they're doing something more complex than just what I mentioned. Also, the URL requested started with /tcp/ which I found interesting. Note: I don't expect to ever have more than 150 users live-chatting in all the rooms combined at the same time. I understand that if I was building a hosted pay for chat service like CampFire with thousands of concurrent users, it would behoove me to invest time in researching special technologies vs trying to reinvent the wheel in a simple way in my app. Also, if you're going to do it with server polling, how often would you personally poll to maximize response without slamming the server?

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  • Web application architecture, and application servers?

    - by seanieb
    Hi, I'm building a web application, and I need to use an architecture that allows me to run it on two servers. The application scrapes information from other sites periodically, and on input from the end user. To do this I'm using Php+curl to scrape the information, Php or python to parse it and store the results in a MySQLDB. Then I will use Python to run some algorithms on the data, this will happen both periodically and on input from the end user. I'm going to cache some of the results in the MySQL DB and sometimes if it is specific to the user, skip storing the data and serve it to the user. I'm think of using Php for the website front end on a separate web server, running the Php spider, MySQL DB and python on another server. As you can see I'm fairly clueless. I'm familiar with using Php, MySQL and the basics of Python, but bringing this all together using something more complex than a cron job is new to me. How do go about implementing this? What frame work(s) should I use? Is MVC a good architecture for this? (I'm new to MVC, architectures etc.) Is Cakephp a good solution? If so will I be able to control and monitor the Python code using it?

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  • Stuck on Object scope in Java

    - by ivor
    Hello, I'm working my way through an exercise to understand Java, and basically I need to merge the functionality of two classes into one app. I'm stuck on one area though - the referencing of objects across classes. What I have done is set up a gui in one class (test1), and this has a textfield in ie. chatLine = new JTextField(); in another class(test2), I was planning on leaving all the functionality in there and referencing the various gui elements set up in test1 - like this test1.chatLine I understand this level of referencing, I tested this by setting up a test method in the test2 class public static void testpass() { test1.testfield.setText("hello"); } I'm trying to understand how to implement the more complex functionality in test2 class though, specifically this existing code; test1.chatLine.addActionListener(new ActionAdapter() { public void actionPerformed(ActionEvent e) { String s = Game.chatLine.getText(); if (!s.equals("")) { appendToChatBox("OUTGOING: " + s + "\n"); Game.chatLine.selectAll(); // Send the string sendString(s); } } }); This is the bit I'm stuck on, if I should be able to do this - as it's failing on the compile, can I add the actionadapter stuff to the gui element thats sat in test1, but do this from test2 - I'm wondering if I'm trying to do something that's not possible. Hope this makes sense, I'm pretty confused over this - I'm trying to understand how the scope and referencing works. Ideally what i'm trying to achieve is one class that has all the main stuff in, the gui etc, then all the related functionality in the other class, and target the first class's gui elements with the results etc. Any thoughts greatly appreciated.

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  • Sharing storage between servers

    - by El Yobo
    I have a PHP based web application which is currently only using one webserver but will shortly be scaling up to another. In most regards this is pretty straightforward, but the application also stores a lot of files on the filesystem. It seems that there are many approaches to sharing the files between the two servers, from the very simple to the reasonably complex. These are the options that I'm aware of Simple network storage NFS SMB/CIFS Clustered filesystems Lustre GFS/GFS2 GlusterFS Hadoop DFS MogileFS What I want is for a file uploaded via one webserver be immediately available if accessed through the other. The data is extremely important and absolutely cannot be lost, so whatever is implemented needs to a) never lose data and b) have very high availability (as good as, or better, than a local filesystem). It seems like the clustered filesystems will also provide faster data access than local storage (for large files) but that isn't of vita importance at the moment. What would you recommend? Do you have any suggestions to add or anything specifically to look out for with the above options? Any suggestions on how to manage backup of data on the clustered filesystems?

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  • _dl_runtime_resolve -- When do the shared objects get loaded in to memory?

    - by windfinder
    We have a message processing system with high performance demands. Recently we have noticed that the first message takes many times longer then subsequent messages. A bunch of transformation and message augmentation happens as this goes through our system, much of it done by way of external lib. I just profiled this issue (using callgrind), comparing a "run" of just one message with a "run" of many messages (providing a baseline of comparison). The main difference I see is the function "do_lookup_x" taking up a huge amount of time. Looking at the various calls to this function, they all seem to be called by the common function: _dl_runtime_resolve. Not sure what this function does, but to me this looks like the first time the various shared libraries are being used, and are then being loaded in to memory by the ld. Is this a correct assumption? That the binary will not load the shared libraries in to memory until they are being prepped for use, therefore we will see a massive slowdown on the first message, but on none of the subsequent? How do we go about avoiding this? Note: We operate on the microsecond scale.

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  • setting default value of superglobal

    - by Prasoon Saurav
    I have been working on a Timesheet Management website. I have my home page as index.php //index.php <?php session_start(); if($_SESSION['logged']=='set') { $x=$_SESSION['username']; echo '<div align="right">'; echo 'Welcome ' .$x.'<br/>'; echo'<a href="logout.php" class="links">&nbsp;<b><u>Logout</u></b></a>' ; } else if($_SESSION['logged']='unset') { echo'<form id="searchform" method="post" action="processing.php"> <div> <div align="right"> Username&nbsp;<input type="text" name="username" id="s" size="15" value="" /> &nbsp;Password&nbsp;<input type="password" name="pass" id="s" size="15" value="" /> <input type="submit" name="submit" value="submit" /> </div> <br /> </div> </form> '; } ?> The problem I am facing is that during the first run of this script I get an error Notice: Undefined index: logged in C:\wamp\www\ps\index.php but after refreshing the page the error vanishes. How can I correct this problem? logged is a variable which helps determine whether the user is logged in or not. When the user is logged in $_SESSION['logged'] is set, otherwise unset. I want the default value of $_SESSION['logged'] to be unset prior to the execution of the script. How can I solve this problem?

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  • 500 Worker Threads, what kind of thread pool?

    - by Submerged
    I am wondering if this is the best way to do this. I have about 500 threads that run indefinitely, but Thread.sleep for a minute when done one cycle of processing. ExecutorService es = Executors.newFixedThreadPool(list.size()+1); for (int i = 0; i < list.size(); i++) { es.execute(coreAppVector.elementAt(i)); //coreAppVector is a vector of extends thread objects } The code that is executing is really simple and basically just this class aThread extends Thread { public void run(){ while(true){ Thread.sleep(ONE_MINUTE); //Lots of computation every minute } } } I do need a separate threads for each running task, so changing the architecture isn't an option. I tried making my threadPool size equal to Runtime.getRuntime().availableProcessors() which attempted to run all 500 threads, but only let 8 (4xhyperthreading) of them execute. The other threads wouldn't surrender and let other threads have their turn. I tried putting in a wait() and notify(), but still no luck. If anyone has a simple example or some tips, I would be grateful! Well, the design is arguably flawed. The threads implement Genetic-Programming or GP, a type of learning algorithm. Each thread analyzes advanced trends makes predictions. If the thread ever completes, the learning is lost. That said, I was hoping that sleep() would allow me to share some of the resources while one thread isn't "learning"

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  • Creating Emulated iSCSI Target in a Lab/Testing Environment using Windows Server 2008 R2

    - by Brian McCleary
    We have a single server running Windows Server 2008 with Hyper-V installed running 5 virtual machines. I have purchased a second DELL R805 Server so that we can create a fail-over cluster to our current R805 that is currently in production. Right now, our R805 connects via iSCSI to a MD3000i iSCSI SAN. Before we try to roll out the second server and clustering to our production environment, I want to be able to test and "play with" the clustering features in our lab before rolling it out. The problem is that I don't want to spend a couple thousand dollars on another iSCSI SAN server just for testing. I already have two servers in my lab that are installed with Windows Server 2008 R2 64bit (one is the R805 and another spare desktop that was laying around) and with the Hyper-V roll enabled that should be ready to test with, but I don't have an iSCSI target to use as the Cluster Shared Volume. Is there anyway to install, either on a Hyper-V image or on a external spare computer that we have some sort of emulated iSCSI target? In our lab, we obviously don't need a real SAN, just something that we can test out how to setup the clustering properly outside of our production environment. Any advise is appreciated. FYI - I have read Jose Barret's blog on WUDSS at http://blogs.technet.com/josebda/archive/2008/01/07/installing-the-evaluation-version-of-wudss-2003-refresh-and-the-microsoft-iscsi-software-target-version-3-1-on-a-vm.aspx, but it seems awfully complex. I'm hoping for an easier solution.

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  • SQL to CodeIgniter Array Missing Data Issue

    - by SamD
    $query = $this->db->query("SELECT t1.numberofbets, t1.profit, t2.seven_profit, t3.28profit, user.user_id, username, password, email, balance, user.date_added, activation_code, activated FROM user LEFT JOIN (SELECT user_id, SUM(amount_won) AS profit, count(tip_id) AS numberofbets FROM tip GROUP BY user_id) as t1 ON user.user_id = t1.user_id LEFT JOIN (SELECT user_id, SUM(amount_won) AS seven_profit FROM tip WHERE date_settled > '$seven_daystime' GROUP BY user_id) as t2 ON user.user_id = t2.user_id LEFT JOIN (SELECT user_id, SUM(amount_won) AS 28profit FROM tip WHERE date_settled > '$twoeight_daystime' GROUP BY user_id) as t3 ON user.user_id = t3.user_id where activated = 1 GROUP BY user.user_id ORDER BY user.date_added DESC"); return $query->result_array(); The query works fine running it in phpMyAdmin and returns complete results (in image attached). However, printing the array in CodeIgniter, it has no value for one field ,seven_profit, where it is there in the SQL query ran in phpMyAdmin, just the discrepancy in this one field, from sql to php array... I just can’t see why, when printing the array, that one field, which should have value of 26, contains nothing? Any ideas? I changed the field name from starting with a number in attempt to fix it, but no difference. I know this is complex and looks horrible, any help or just people coming across something similar would be great to know about, thanks. Sam

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  • jQuery AJAX request (Rails 3) gets redirected and returns empty message body!

    - by elsurudo
    I'm trying to do a manual jQuery AJAX request the following way: $("#user_plan_id").change(function() { $("#plan_container").load('/plans/' + this.value); }); I have the "rails.js" file included in my header, and a "<%= csrf_meta_tag %". I see from my log that the request IS getting to the server (although without the authenticity token... does rails.js even do this?), but the response is a 302 (Found) rather than 200, and no data actually gets rendered. Any ideas? Edit: I now see that the first request redirects, and the proper partial gets rendered on the redirect. However, the 2nd response's body (on the client-side) is still empty. I'm guessing jQuery uses the first response and doesn't have a listener set up for the redirect. How do I get around this? Also, another note: the page doing the requesting is an HTTPS page. Here is what my log says: Started GET "/plans/221168073" for 127.0.0.1 at Tue Jun 15 01:24:06 -0400 2010 Processing by PlansController#show as HTML Parameters: {"id"=>"221168073"} DEPRECATION WARNING: Using #request_uri is deprecated. Use fullpath instead. (called from ensure_proper_protocol at /Users/ernestsurudo/Sites/vidfolia/vendor/plugins/ssl_requirement/lib/ssl_requirement.rb:57) Redirected to http://vidfolia.com/plans/221168073 Completed 302 Found in 1ms Perhaps it has something to do with the deprecation warning?

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  • How to hand-over a TCP listening socket with minimal downtime?

    - by Shtééf
    While this question is tagged EventMachine, generic BSD-socket solutions in any language are much appreciated too. Some background: I have an application listening on a TCP socket. It is started and shut down with a regular System V style init script. My problem is that it needs some time to start up before it is ready to service the TCP socket. It's not too long, perhaps only 5 seconds, but that's 5 seconds too long when a restart needs to be performed during a workday. It's also crucial that existing connections remain open and are finished normally. Reasons for a restart of the application are patches, upgrades, and the like. I unfortunately find myself in the position that, every once in a while, I need to do this kind of thing in production. The question: I'm looking for a way to do a neat hand-over of the TCP listening socket, from one process to another, and as a result get only a split second of downtime. I'd like existing connections / sockets to remain open and finish processing in the old process, while the new process starts servicing new connectinos. Is there some proven method of doing this using BSD-sockets? (Bonus points for an EventMachine solution.) Are there perhaps open-source libraries out there implementing this, that I can use as is, or use as a reference? (Again, non-Ruby and non-EventMachine solutions are appreciated too!)

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  • Search for a date between given ranges - Lotus

    - by Kris.Mitchell
    I have been trying to work out what is the best way to search for gather all of the documents in a database that have a certain date. Originally I was trying to use FTsearch or search to move through a document collection, but I changed over to processing a view and associated documents. My first question is what is the easiest way to spin through a set of documents and find if a date stored in the documents is greater than or less than a specified date? So, to continue working I implemented the following code. If (doc.creationDate(0) > cdat(parm1)) And (doc.creationDate(0) < CDat(parm2)) then ... end if but the results are off Included! Date:3/12/10 11:07:08 P1:3/1/10 P2: 3/5/10 Included! Date:3/13/10 9:15:09 P1:3/1/10 P2: 3/5/10 Included! Date:3/17/10 16:22:07P1:3/1/10 P2: 3/5/10 You can see that the date stored in the doc is not between P1 and P2. BUT! it does limit the documents with a date less than P1 correctly. So I won't get a result for a document with a date less than 3/1/10 If there isn't a better way than the if statement, can someone help me understand why the two examples from above are included?

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  • Ajax heavy JS apps using excessive amounts of memory over time.

    - by Shane Reustle
    I seem to have some pretty large memory leaks in an app that I am working on. The app itself is not very complex. Every 15 seconds, the page requests approx 40kb of JSON from the server, and draws a table on the page using it. It is cheaper to draw the table over because the data is usually always new. I am attaching a few events to the table, approx 5 per line, 30 lines in the table. I used jQuery's .html() method to put the new html into the container and overwrite the existing. I do this specifically so that jQuery's special cleanup functions go in and attempt to detach all events on the elements in the element that it is overwriting. I then also delete the large variables of html once they are sent to the DOM using delete my_var. I have checked for circular references and attached events that are never cleared a few times, but never REALLY dug into it. I was wondering if someone could give me a few pointers on how to optimize a very heavy app like this. I just picked up "High Performance Javascript" by Nicholas Zakas, but didn't have much time to get into it yet. To give an idea on how much memory this is using, after 4~ hours, it is using about 420,000k on chrome, and much more on Firefox or IE. Thanks!

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  • How to keep your unit test Arrange step simple and still guarantee DDD invariants ?

    - by ian31
    DDD recommends that the domain objects should be in a valid state at any time. Aggregate roots are responsible for guaranteeing the invariants and Factories for assembling objects with all the required parts so that they are initialized in a valid state. However this seems to complicate the task of creating simple, isolated unit tests a lot. Let's assume we have a BookRepository that contains Books. A Book has : an Author a Category a list of Bookstores you can find the book in These are required attributes : a book has to have an author, a category and at least a book store you can buy the book from. There's likely to be a BookFactory since it is quite a complex object, and the Factory will initialize the Book with at least all the mentioned attributes. Now we want to unit test a method of the BookRepository that returns all the Books. To test if the method returns the books, we have to set up a test context (the Arrange step in AAA terms) where some Books are already in the Repository. If the only tool at our disposal to create Book objects is the Factory, the unit test now also uses and is dependent on the Factory and inderectly on Category, Author and Store since we need those objects to build up a Book and then place it in the test context. Would you consider this is a dependency in the same way that in a Service unit test we would be dependent on, say, a Repository that the Service would call ? How would you solve the problem of having to re-create a whole cluster of objects in order to be able to test a simple thing ? How would you break that dependency and get rid of all these attributes we don't need in our test ? By using mocks or stubs ? If you mock up things a Repository contains, what kind of mock/stubs would you use as opposed to when you mock up something the object under test talks to or consumes ?

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  • Does a CS PhD Help for Software Engineering Career?

    - by SiLent SoNG
    I would like to seek advice on whether or not to take a PhD offer from a good university. My only concern is the PhD will take at least 4 year's commitment. During the period I won't have good monetary income. I am also concerned whether the PhD will help my future career development. My career goal is software engineering only. Some of the PhD info: The PhD is CS related. The research area is Information Retrieval, Machine Learning, and Nature Language Processing. More specifically, the research topic is Deep Web search. Some of backgrounds: I worked in Oracle for 3 years in database development after obtained a CS degree from some good university. In last year I received an email telling an interesting project from a professor and thereafter I was lured into his research team. The team consists of 4 PhD students; those students have little or no industry experiences and their coding skills are really really bad. By saying bad I mean they do not know some common patterns and they do not know pitfalls of the programming languages as well as idioms for doing things right. I guess a at least 4 year commitment is worth of serious consideration. I am 27 at this moment. If I take the offer, that implies I will be 31+ upon graduation. Wah... becoming.. what to say, no longer young. Hence, here I am seeking advice on whether it is good or not to take the PhD offer, and whether a CS PhD is good for my future career growth as a software engineer? I do not intent to go for academia.

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  • Trying to get django app to work with mod_wsgi on CentOS 5

    - by David
    I'm running CentOS 5, and am trying to get a django application working with mod_wsgi. I'm using .wsgi settings I got working on Ubuntu. Here is the error: [Thu Mar 04 10:52:15 2010] [error] [client 10.1.0.251] SystemError: dynamic module not initialized properly [Thu Mar 04 10:52:15 2010] [error] [client 10.1.0.251] mod_wsgi (pid=23630): Target WSGI script '/data/hosting/cubedev/apache/django.wsgi' cannot be loaded as Python module. [Thu Mar 04 10:52:15 2010] [error] [client 10.1.0.251] mod_wsgi (pid=23630): Exception occurred processing WSGI script '/data/hosting/cubedev/apache/django.wsgi'. [Thu Mar 04 10:52:15 2010] [error] [client 10.1.0.251] Traceback (most recent call last): [Thu Mar 04 10:52:15 2010] [error] [client 10.1.0.251] File "/data/hosting/cubedev/apache/django.wsgi", line 8, in [Thu Mar 04 10:52:15 2010] [error] [client 10.1.0.251] import django.core.handlers.wsgi [Thu Mar 04 10:52:15 2010] [error] [client 10.1.0.251] File "/opt/python2.6/lib/python2.6/site-packages/django/core/handlers/wsgi.py", line 1, in [Thu Mar 04 10:52:15 2010] [error] [client 10.1.0.251] from threading import Lock [Thu Mar 04 10:52:15 2010] [error] [client 10.1.0.251] File "/opt/python2.6/lib/python2.6/threading.py", line 13, in [Thu Mar 04 10:52:15 2010] [error] [client 10.1.0.251] from functools import wraps [Thu Mar 04 10:52:15 2010] [error] [client 10.1.0.251] File "/opt/python2.6/lib/python2.6/functools.py", line 10, in [Thu Mar 04 10:52:15 2010] [error] [client 10.1.0.251] from _functools import partial, reduce [Thu Mar 04 10:52:15 2010] [error] [client 10.1.0.251] SystemError: dynamic module not initialized properly And here is my .wsgi file import os import sys os.environ['PYTHON_EGG_CACHE'] = '/tmp/django/' os.environ['DJANGO_SETTINGS_MODULE'] = 'cube.settings' sys.path.append('/data/hosting/cubedev') import django.core.handlers.wsgi application = django.core.handlers.wsgi.WSGIHandler()

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  • Is my objective possible using WCF (and is it the right way to do things?)

    - by David
    I'm writing some software that modifies a Windows Server's configuration (things like MS-DNS, IIS, parts of the filesystem). My design has a server process that builds an in-memory object graph of the server configuration state and a client which requests this object graph. The server would then serialize the graph, send it to the client (presumably using WCF), the server then makes changes to this graph and sends it back to the server. The server receives the graph and proceeds to make modifications to the server. However I've learned that object-graph serialisation in WCF isn't as simple as I first thought. My objects have a hierarchy and many have parametrised-constructors and immutable properties/fields. There are also numerous collections, arrays, and dictionaries. My understanding of WCF serialisation is that it requires use of either the XmlSerializer or DataContractSerializer, but DCS places restrictions on the design of my object-graph (immutable data seems right-out, it also requires parameter-less constructors). I understand XmlSerializer lets me use my own classes provided they implement ISerializable and have the de-serializer constructor. That is fine by me. I spoke to a friend of mine about this, and he advocates going for a Data Transport Object-only route, where I'd have to maintain a separate DataContract object-graph for the transport of data and re-implement my server objects on the client. Another friend of mine said that because my service only has two operations ("GetServerConfiguration" and "PutServerConfiguration") it might be worthwhile just skipping WCF entirely and implementing my own server that uses Sockets. So my questions are: Has anyone faced a similar problem before and if so, are there better approaches? Is it wise to send an entire object graph to the client for processing? Should I instead break it down so that the client requests a part of the object graph as it needs it and sends only bits that have changed (thus reducing concurrency-related risks?)? If sending the object-graph down is the right way, is WCF the right tool? And if WCF is right, what's the best way to get WCF to serialise my object graph?

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  • Zend_Date and Zend Locale; can't get it to work ><

    - by Rick de Graaf
    Loving Zend Framework, hating Zend_Date... I'm buidling an app where one of the functions is to track the time one spends on a certain task. This works great. My previous question was my incapability to get the sum of all the timestamps (time spent on each task). Well that works as a charm, but when I echo this value, it adds one hour. Using gmdate() (just for checking) and the value turns out exactly as it's supposed to. I thought to solve this problem easeliy with Zend_Local, but I can't get the damn thing to work! This is my bootstrap code: protected function _initLocale() { $locale = new Zend_Locale('nl_NL'); $locale->setLocale($locale); Zend_Registry::set('Zend_Locale', $locale); } This is the code in my view file: $date = new Zend_Date($this->timequery, null, $locale); echo $date->toString(Zend_Date::HOUR.':'.Zend_Date::MINUTE.':'.Zend_Date::SECOND); The timestamp I'm processing is: 2632 which equals 00:43:52. The output I get is: 01:43:52 I know the extra hour comes from the time difference, but I can seem to solve this with Zend_Local and Zend_Date.

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  • general learning methodology

    - by momo
    just wanted to hear on the different general learning paths people embark on when learning a new language/framework. the one i currently use, which is how i learned bash and am currently learning python, is: instant hacking tutorial (very short tutorial introducing the basic syntax, variable declaration, loops, data types, etc. and how they are generally used) in depth tutorial with good programming style and slightly topic-specific (e.g. Mark Pilgrim's Dive into Python), important topics for me personally are regex methods, file IO, and ways the different data types are utilized best (i wrote a very primitive bayesian spam filter using python's dictionaries to keep track of word occurrences) spaced-repition of syntax or short recipes (i use anki, with questions like 'create dictionary with filename and filesize metadata, human-readable' or simpler ones like 'match 0 - 3 occurences of the letter M in a string', or 'return/create an iterator from two sequences') the use of spaced-repitition has been invaluable, and i credit it with the ease that i can recall/create python algorithms. however, i've recently started looking into django, and i've found that spaced-repitition, at least in my case, doesn't work very well for learning a framework, it works best with short code recipes (either that or i should start looking into more basic django framework tutorials). the problem i'm encountering is that since framework programming is not only algorithms, but actually learning the API, which can be quite complex since you have to learn all the methods, modules, the places where they are stored, and the sequence of which things have to be done. for ex. in django to start a project that deals with polls (from the django tutorial), one has to create the project, edit the settings.py file, create the polls app, edit the models.py file (which requires knowing the classes that are present in the module models), edit the urls.py file, etc. i found that my spaced-repition method didn't work very well for this type of learning, so i wanted to ask you guys what method(s) you use for learning the different frameworks/APIs.

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  • How to make a wxFrame behave like a modal wxDialog object

    - by dagorym
    Is is possible to make a wxFrame object behave like a modal dialog box in that the window creating the wxFrame object stops execution until the wxFrame object exits? I'm working on a small game and have run into the following problem. I have a main program window that hosts the main application (strategic portion). Occasionally, I need to transfer control to a second window for resolution of part of the game (tactical portion). While in the second window, I want the processing in the first window to stop and wait for completion of the work being done in the second window. Normally a modal dialog would do the trick but I want the new window to have some functionality that I can't seem to get with a wxDialog, namely a status bar at the bottom and the ability to resize/maximize/minimize the window (this should be possible but doesn't work, see this question How to get the minimize and maximize buttons to appear on a wxDialog object). As an addition note, I want the second window's functionality needs to stay completely decoupled from the primary window as it will be spun off into a separate program eventually. Has anyone done this or have any suggestions?

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  • User preferences using SQL and JavaScript

    - by Shyam
    Hi, I am using Server Side JavaScript - yes, I am actually using Server Side JavaScript. To complexify things even more, I use Oracle as a backend database (10g). With some crazy XSLT and mutant-like HTML generation, I can build really fancy web forms - yes, I am aware of Rails and other likewise frameworks and I choose the path of horror instead. I have no JQuery or other fancy framework at my disposal, just plain ol' JavaScript that should be supported by the underlying engine called Mozilla Rhino. Yes, it is insane and I love it. So, I have a bunch of tables at my disposal and some of them are filled with associative keys that link to values. As I am a people pleaser, I want to add some nifty user-preference driven solutions. My users have all an unique user_id and this user_id is available during the entire session. My initial idea is to have a user preference table, where I have "three" columns: user_id, feature and pref_string. Using a delimiter, such as : or - (haven't thought about a suitable one yet), I could like store a bunch of preferences as a list and store its elements inside an array using the .split-method (similar like the PHP-explode function). The feature column could be like the table name or some identifier for the "feature" i want to link preferences too. I hate hardcoding objects, especially as I want to be able to back these up and reuse this functionality application-wide. Of course I would love better ideas, just keep in mind I cannot just add a library that easily. These preferences could be like "joined" to the table, so I can query it and use its values. I hope it doesn't sounds too complex, because well.. its basically something really simple I need. Thanks!

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  • JBoss Clustered Service that sends emails from txt file

    - by michael lucas
    I need a little push in the right direction. Here's my problem: I have to create an ultra-reliable service that sends email messages to clients whose addresses are stored in txt file on FTP server. Single txt file may contain unlimited number of entries. Most often the file contains about 300,000 entries. Service exposes interface with just two simple methods: TaskHandle sendEmails(String ftpFilePath); ProcessStatus checkProcessStatus(TaskHandle taskHandle); Method sendEmails() returns TaskHandle by which we can ask for ProcessStatus. For such a service to be reliable clustering is necessary. Processing single txt file might take a long time. Restarting one node in a cluster should have no impact on sending emails. We use JBoss AS 4.2.0 which comes with a nice HASingletonController that ensure one instance of service is running at given time. But once a fail-over happens, the second service should continue work from where the first one stopped. How can I share state between nodes in a cluster in such a way that leaves no possibility of sending some emails twice?

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  • Spring MVC 3 - How come @ResponseBody method renders a JSTLView?

    - by Ken Chen
    I have mapped one of my method in one Controller to return JSON object by @ResponseBody. @RequestMapping("/{module}/get/{docId}") public @ResponseBody Map<String, ? extends Object> get(@PathVariable String module, @PathVariable String docId) { Criteria criteria = new Criteria("_id", docId); return genericDAO.getUniqueEntity(module, true, criteria); } However, it redirects me to the JSTLView instead. Say, if the {module} is product and {docId} is 2, then in the console I found: DispatcherServlet with name 'xxx' processing POST request for [/xxx/product/get/2] Rendering view [org.springframework.web.servlet.view.JstlView: name 'product/get/2'; URL [/WEB-INF/views/jsp/product/get/2.jsp]] in DispatcherServlet with name 'xxx' How can that be happened? In the same Controller, I have another method similar to this but it's running fine: @RequestMapping("/{module}/list") public @ResponseBody Map<String, ? extends Object> list(@PathVariable String module, @RequestParam MultiValueMap<String, String> params, @RequestParam(value = "page", required = false) Integer pageNumber, @RequestParam(value = "rows", required = false) Integer recordPerPage) { ... return genericDAO.list(module, criterias, orders, pageNumber, recordPerPage); } Above do returns correctly providing me a list of objects I required. Anyone to help me solve the mystery?

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  • Catching / blocking SIGINT during system call

    - by danben
    I've written a web crawler that I'd like to be able to stop via the keyboard. I don't want the program to die when I interrupt it; it needs to flush its data to disk first. I also don't want to catch KeyboardInterruptedException, because the persistent data could be in an inconsistent state. My current solution is to define a signal handler that catches SIGINT and sets a flag; each iteration of the main loop checks this flag before processing the next url. However, I've found that if the system happens to be executing socket.recv() when I send the interrupt, I get this: ^C Interrupted; stopping... // indicates my interrupt handler ran Traceback (most recent call last): File "crawler_test.py", line 154, in <module> main() ... File "/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/socket.py", line 397, in readline data = recv(1) socket.error: [Errno 4] Interrupted system call and the process exits completely. Why does this happen? Is there a way I can prevent the interrupt from affecting the system call?

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