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• Apache + Passenger not passing on custom status codes

  - by harm

  I'm currently building an API. This API communicates with the client via status codes. I created several custom status codes (as per http://www.w3.org/Protocols/rfc2616/rfc2616-sec6.html#sec6) in order to inform the client on certain things. For example I introduced the 481 status code to signify a specific client error. The Rails app I wrote works like a charm. But when Apache and Passenger are serving it things run aground. When I provoke a 481 error the response header looks like this: HTTP/1.1 500 Internal Server Error Date: Wed, 19 May 2010 06:37:05 GMT Server: Apache/2.2.9 (Debian) Phusion_Passenger/2.2.5 mod_ssl/2.2.9 OpenSSL/0.9.8g X-Powered-By: Phusion Passenger (mod_rails/mod_rack) 2.2.5 Cache-Control: no-cache X-Runtime: 1938 Set-Cookie: _session_id=32bc259dc763193ad57ae7dc19d5f57e; path=/; HttpOnly Content-Length: 62 Status: 481 Content-Type: application/json; charset=utf-8 As you can see the original Status header is still there almost a the end. But the 'true' status header (the very first line) is quiet different. It seems that Apache doesn't like Status headers it has no knowledge of and thus assumes an error. Is there anyway to fix this? Maybe via the mod_headers ( http://httpd.apache.org/docs/2.2/mod/mod_headers.html) module? I don't know enough of Apache to figure this out on my own. Thanks,

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• Which pdf elements could cause crashes?

  - by Felixyz

  This is a very general question but it's based on a specific problem. I've created a pdf reader app for the iPad and it works fine except for certain pdf pages which always crash the app. We now found out that the very same pages cause Safari to crash as well, so as I had started to suspect the problem is somewhere in Apple's pdf rendering code. From what I have been able to see, the crashing pages cause the rendering libraries to start allocating memory like mad until the app is killed. I have nothing else to help me pinpoint what triggers this process. It doesn't necessarily happen with the largest documents, or the ones with the most shapes. In fact, we haven't found any parameter that helps us predict which pages will crash and which not. Now we just discovered that running the pages through a consumer program that lets you merge docs gets rid of the problem, but I haven't been able to detect which attribute or element it is that is the key. Changing documents by hand is also not an option for us in the long run. We need to run an automated process on our server. I'm hoping someone with deeper knowledge about the pdf file format would be able to point me in a reasonable direction to look for document features that could cause this kind of behavior. All I've found so far is something about JBIG2 images, and I don't think we have any of those.

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• Vehicle License Plate Detection

  - by Ash

  Hey all Basically for my final project at university, I'm developing a vehicle license plate detection application. Now I consider myself an intermediate programmer, however my mathematics knowledge lacks anything above secondary school, therefore producing detection formulae is basically impossible. I've spend a good amount of time looking up academic papers such as: http://www.scribd.com/doc/266575/Detecting-Vehicle-License-Plates-in-Images http://www.cic.unb.br/~mylene/PI_2010_2/ICIP10/pdfs/0003945.pdf http://www.eurasip.org/Proceedings/Eusipco/Eusipco2007/Papers/d3l-b05.pdf When it comes to the maths, I'm lost. Due to this testing various graphic images proved productive, for example: to However this approach is only catered to that particular image, and if the techniques were applied to different images, I'm sure a different, most likely poorer conversion would occur. I've read about a formula called the bottom hat morphology transform, which according to the first does the following: "Basically, the trans- formation keeps all the dark details of the picture, and eliminates everything else (including bigger dark regions and light regions)." Sadly I can't find much information on this, however the image within the documentation near the end of the report shows it's effectiveness. I'm aware this is complicated and vast, I'd just appreciate a little advice, even in terms of what transformation techniques I should focus on developing, or algorithm regarding edge detection or pixel detection. Few things I need to add Developing in C Sharp Confining the project to UK registration plates only I can basically choose the images to convert as a demonstration Thanks

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• Bulletin board - Database optimisation

  - by andrew

  This question is a follow on from this Question The project and problem The project I am currently working on is a bulletin board for a large non-profit organisation. The bulletin board will be used to allow inter-office communication within the organisation. I am building the application and have been having trouble extracting the results that I need from my database because I don't think it is properly normalized and because of limitations in my knowledge of relational database theory and mysql. I would appreciate input into the design of the board in general and in particular, ways that the database structure can be improved to facilitate efficient queries and help me develop this application and future application faster Business Logic The bulletin board will be used in the following way Posting bulletins and responses to bulletins Employees or 'users' in offices around the country will be able to post messages to the bulletin board.Bulletins must be posted to a location and categorised- i'll call these "bulletins". Users will be able to post any number of replies to any one bulletin and users will be able to reply to their own bulletin - i'll call these 'replies'. Rating bulletins and replies Users will be able to either 'like' or 'dislike' a bulletin or a reply and the total number of likes or dislikes will be shown for each bulletin or reply. Viewing the bulletin board and responses Bulletins can be displayed chronologically. Users can sort bulletins chronologically or chronologically by the latest reply to that bulletin(let me know if you need more explanation) When a particular bulletin is selected, replies to that bulletin will be displayed chronologically @PerformanceDBA - edited 10:34 est 28/12/10I have begun implementing the data model. I assume that the 6th data model is the physical model because it contains the associative tables. I am going to post any questions that I have below. I will put up a database dump once I am done. I will then put up a list of all the queries that I need to run on the database and begin writing them. I hope you had a good Christmas. I'm in Canada and there's snow! Implementation of Physical model

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• How can a SVN::Error callback identify the context from which it was called

  - by Colin Fine

  I've written some fairly extensive Perl modules and scripts using the Perl bindings SVN::Client etc. Since the calls to SVN::Client are all deep in a module, I have overridden the default error handling. So far I have done so by setting $SVN::Error::handler = undef as described in [1], but this makes the individual calls a bit messy because you have to remember to make each call to SVN::Client in list context and test the first value for errors. I would like to switch to using an error handler I would write; but $SVN::Error::handler is global, so I can't see any way that my callback can determine where the error came from, and what object to set an error code in. I wondered if I could use a pool for this purpose: so far I have ignored pools as irrelevant to working in Perl, but if I call a SVN::Client method with a pool I have created, will any SVN::Error object be created in the same pool? Has anybody any knowledge or experience which bears on this? [1]: http://search.cpan.org/~mschwern/Alien-SVN-1.4.6.0/src/subversion/subversion/bindings/swig/perl/native/Core.pm#svn_error_t_-_SVN::Error SVN::Core POD

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• PHP array value becomes blank. What is going on?

  - by Michael Bruce

  I have written a web page that works fine expect for some weird behavior. The code below gets all expected values and populates them correctly except for $v-data["quick_phone_id"] and $v-data["quick_email_id"] which are integers. Those values come out blank in the string I am creating. The value for $v-data["id"] is another integer and works as expected. My only clue is that when I uncomment the commented out line, the code works properly. So I'm guessing this has to do with referencing getting broken for the array. Any ideas? I'd like to fix my code and my PHP knowledge. $contacts = ContactInfo::loadMyContacts($userId); $sb = new StringBuilder(); $idx = 0; //$vals = "vals: ".$contacts[0]->data["quick_phone_id"]; $sb->append(' dataRows = ['); foreach($contacts as $k => $v) { $sb->append('{ id:"'.strval($v->data["id"]).'",'); $sb->append('url:"edit_contact.php?id='.$v->data["id"].'",'); $sb->append('gname:"'.$v->data["given_name"].'",'); $sb->append('fname:"'.$v->data["family_name"].'",'); $sb->append('phone1id2:"'.strval($v->data["quick_phone_id"]).'",'); $sb->append('phone1type:"'.$v->data["quick_phone_type"].'",'); $sb->append('phone1:"'.$v->data["quick_phone"].'",'); $sb->append("email1id2:'".strval($v->data["quick_email_id"])."',"); $sb->append('email1type:"'.$v->data["quick_email_type"].'",'); $sb->append("email1:'".$v->data["quick_email"]."',"); $sb->append("dirty:false },\n"); } $sb->append('];');

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• Should not a tail-recursive function also be faster?

  - by Balint Erdi

  I have the following Clojure code to calculate a number with a certain "factorable" property. (what exactly the code does is secondary). (defn factor-9 ([] (let [digits (take 9 (iterate #(inc %) 1)) nums (map (fn [x] ,(Integer. (apply str x))) (permutations digits))] (some (fn [x] (and (factor-9 x) x)) nums))) ([n] (or (= 1 (count (str n))) (and (divisible-by-length n) (factor-9 (quot n 10)))))) Now, I'm into TCO and realize that Clojure can only provide tail-recursion if explicitly told so using the recur keyword. So I've rewritten the code to do that (replacing factor-9 with recur being the only difference): (defn factor-9 ([] (let [digits (take 9 (iterate #(inc %) 1)) nums (map (fn [x] ,(Integer. (apply str x))) (permutations digits))] (some (fn [x] (and (factor-9 x) x)) nums))) ([n] (or (= 1 (count (str n))) (and (divisible-by-length n) (recur (quot n 10)))))) To my knowledge, TCO has a double benefit. The first one is that it does not use the stack as heavily as a non tail-recursive call and thus does not blow it on larger recursions. The second, I think is that consequently it's faster since it can be converted to a loop. Now, I've made a very rough benchmark and have not seen any difference between the two implementations although. Am I wrong in my second assumption or does this have something to do with running on the JVM (which does not have automatic TCO) and recur using a trick to achieve it? Thank you.

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• How to catch YouTube embed code and turn into URL

  - by Jonathan Vanasco

  I need to strip YouTube embed codes down to their URL only. This is the exact opposite of all but one question on StackOverflow. Most people want to turn the URL into an embed code. This question addresses the usage patttern I want, but is tied to a specific embed code's regex ( Strip YouTube Embed Code Down to URL Only ) I'm not familiar with how YouTube has offered embeds over the years - or how the sizes differ. According to their current site, there are 2 possible embed templates and a variety of options. If that's it, I can handle a regex myself -- but I was hoping someone had more knowledge they could share, so I could write a proper regex pattern that matches them all and not run into endless edge-cases. The full use case scenario : user enters content in web based wysiwig editor backend cleans out youtube & other embed codes; reformats approved embeds into an internal format as the text is all converted to markdown. on display, appropriate current template/code display for youtube or other 3rd party site is generated At a previous company, our tech-team devised a plan where YouTube videos were embedded by listing the URL only. That worked great , but it was in a CMS where everyone was trained. I'm trying to create a similar storage, but for user-generated-content.

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• How can I generate an "unlimited" world?

  - by snowlord

  I would like to create a game with an endless (in reality an extremely large) world in which the player can move about. Whether or not I will ever get around to implement the game is one matter, but I find the idea interesting and would like some input on how to do it. The point is to have a world where all data is generated randomly on-demand, but in a deterministic way. Currently I focus on a large 2D map from which it should be possible to display any part without knowledge about the surrounding parts. I have implemented a prototype by writing a function that gives a random-looking, but deterministic, integer given the x and y of a pixel on the map (see my recent question about this function). Using this function I populate the map with "random" values, and then I smooth the map using a simple filter based on the surrounding pixels. This makes the map dependent on a few pixels outside its edge, but that's not a big problem. The final result is something that at least looks like a map (especially with a good altitude color map). Given this, one could maybe first generate a coarser map which is used to generate bigger differences in altitude to create mountain ranges and seas. Anyway, that was my idea, but I am sure that there exist ways to do this already and I also believe that given the specification, many of you can come up with better ideas. EDIT: Forgot the link to my question.

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• mysql row locking via php

  - by deezee

  I am helping a friend with a web based form that is for their business. I am trying to get it ready to handle multiple users. I have set it up so that just before the record is displayed for editing I am locking the record with the following code. $query = "START TRANSACTION;"; mysql_query($query); $query = "SELECT field FROM table WHERE ID = \"$value\" FOR UPDATE;"; mysql_query($query); (okay that is greatly simplified but that is the essence of the mysql) It does not appear to be working. However, when I go directly to mysql from the command line, logging in with the same user and execute START TRANSACTION; SELECT field FROM table WHERE ID = "40" FOR UPDATE; I can effectively block the web form from accessing record "40" and get the timeout warning. I have tried using BEGIN instead of START TRANSACTION. I have tried doing SET AUTOCOMMIT=0 first and starting the transaction after locking but I cannot seem to lock the row from the PHP code. Since I can lock the row from the command line I do not think there is a problem with how the database is set up. I am really hoping that there is some simple something that I have missed in my reading. FYI, I am developing on XAMPP version 1.7.3 which has Apache 2.2.14, MySQL 5.1.41 and PHP 5.3.1. Thanks in advance. This is my first time posting but I have gleaned alot of knowledge from this site in the past.

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• How can someone with no experience learn how to program?

  - by Mugatu

  A friend and I have been coming up with website ideas for a couple years, mostly just jotting them down whenever we come up with a good, useful idea when browsing the web. For the past 6 months we've hired a couple different programmers to make a couple of the sites for us, but have been disappointed with how it's gone. Been too slow and too many miscommunications for our liking. So like the saying goes if you want something done right do it yourself, we're going to do it ourselves. I know nothing about programming, I've never written a line of code in my life. I consider myself very good with math and about as logical as you can get, but I have zero real-life programming knowledge. The sites we want to make are all pretty 'Web 2.0'ish', meaning user-generated content, commenting on posts, pages that change on the fly, etc. So here are some of my questions for anyone who's been there before: Is there a language you'd recommend learning first? Something that is a good indicator how most other languages work? What web programming languages do you recommend learning first based on popularity both now and the future. I don't want to learn a language that's going to be outdated by the time I'm an expert at it. Any specific books you'd recommend? Any general advice you'd give to someone literally starting at square zero for coding who plans on being in it for the long haul?

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• Reversible numerical calculations in Prolog

  - by user8472

  While reading SICP I came across logic programming chapter 4.4. Then I started looking into the Prolog programming language and tried to understand some simple assignments in Prolog. I found that Prolog seems to have troubles with numerical calculations. Here is the computation of a factorial in standard Prolog: f(0, 1). f(A, B) :- A > 0, C is A-1, f(C, D), B is A*D. The issues I find is that I need to introduce two auxiliary variables (C and D), a new syntax (is) and that the problem is non-reversible (i.e., f(5,X) works as expected, but f(X,120) does not). Naively, I expect that at the very least C is A-1, f(C, D) above may be replaced by f(A-1,D), but even that does not work. My question is: Why do I need to do this extra "stuff" in numerical calculations but not in other queries? I do understand (and SICP is quite clear about it) that in general information on "what to do" is insufficient to answer the question of "how to do it". So the declarative knowledge in (at least some) math problems is insufficient to actually solve these problems. But that begs the next question: How does this extra "stuff" in Prolog help me to restrict the formulation to just those problems where "what to do" is sufficient to answer "how to do it"?

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• PHP static function self:: in joomla JFactory class explanation?

  - by Carbon6

  Hi I'm looking at the code of Joomla and trying to figure out what exactly happends in this function. index.php makes a call to function $app = JFactory::getApplication('site'); jfactory.php code public static function getApplication($id = null, $config = array(), $prefix='J') { if (!self::$application) { jimport('joomla.application.application'); self::$application = JApplication::getInstance($id, $config, $prefix); } return self::$application; } application.php code.. public static function getInstance($client, $config = array(), $prefix = 'J') { static $instances; if (!isset($instances)) { $instances = array(); } ....... more code ........ return $instances[$client]; } Now I cannot figure out in function getApplication why is self:$application used. self::$application = JApplication::getInstance($id, $config, $prefix); $application is always null, what is the purpose of using this approach. I tryied modifying it to $var = JApplication::getInstance($id, $config, $prefix); and returnig it but it doesn't work. I would be very glad if someone with more knowledge could explain what is happening here detailed as possible. Many thanks.

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• When to drop an IT job

  - by Nippysaurus

  In my career I have had two programming jobs. Both these jobs were in a field that I am most familiar with (C# / MSSQL) but I have quit both jobs for the same reason: unmanageable code and bad (loose) company structure. There was something in common with both these jobs: small companies (in one I was the only developer). Currently I am in the following position: being given written instructions which are almost impossible to follow (somewhat of a fools errand). we are given short time constraints, but seldom asked how long work will take, and when we do it is always too long and needs to be shorter (and when it ends up taking longer than they need it to take, it's always our fault). there is no time for proper documenting, but we get blamed for not documenting (see previous point). Management is constantly screwing me around, saying I'm underperforming on a given task (which is not true, and switching me to a task which is much more confusing). So I must ask my fellow developers: how bad does a job need to be before you would consider jumping ship? And what to look out for when considering taking a job. In future I will be asking about documented procedures, release control, bug management and adoption of new technologies. EDIT: Let me add some more fuel to the fire ... I have been in my current job for just over a year, and the work I am doing almost never uses any of the knowledge I have gained from the other work I have been doing here. Everything is a giant learning curve. Because of this about 30% of my time is learning what is going on with this new product (who's owner / original developer has left the company), 30% trying to find the relevant documentation that helps the whole thing make sense, 30% actually finding where to make the change, 10% actually making the change.

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• What should i do for accomodating large scale data storage and retrieval?

  - by kailashbuki

  There's two columns in the table inside mysql database. First column contains the fingerprint while the second one contains the list of documents which have that fingerprint. It's much like an inverted index built by search engines. An instance of a record inside the table is shown below; 34 "doc1, doc2, doc45" The number of fingerprints is very large(can range up to trillions). There are basically following operations in the database: inserting/updating the record & retrieving the record accoring to the match in fingerprint. The table definition python snippet is: self.cursor.execute("CREATE TABLE IF NOT EXISTS `fingerprint` (fp BIGINT, documents TEXT)") And the snippet for insert/update operation is: if self.cursor.execute("UPDATE `fingerprint` SET documents=CONCAT(documents,%s) WHERE fp=%s",(","+newDocId, thisFP))== 0L: self.cursor.execute("INSERT INTO `fingerprint` VALUES (%s, %s)", (thisFP,newDocId)) The only bottleneck i have observed so far is the query time in mysql. My whole application is web based. So time is a critical factor. I have also thought of using cassandra but have less knowledge of it. Please suggest me a better way to tackle this problem.

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• Perl - Using hashes in classes

  - by brydgesk

  I have a class with several variables, one of which is a hash (_runs): sub new { my ($class, $name) = @_; my $self = { _name => $name, ... _runs => (), _times => [], ... }; bless ($self, $class); return $self; } Now, all I'm trying to do is create an accessor/mutator, as well as another subroutine that pushes new data into the hash. But I'm having a hell of a time getting all the referencing/dereferencing/$self calls working together. I've about burned my eyes out with "Can't use string ("blah") as a HASH ref etc etc" errors. For the accessor, what is 'best practice' for returning hashes? Which one of these options should I be using (if any)?: return $self->{_runs}; return %{ $self->{_runs} }; return \$self->{_runs}; Further, when I'm using the hash within other subroutines in the class, what syntax do I use to copy it? my @runs = $self->{_runs}; my @runs = %{ $self->{_runs} }; my @runs = $%{ $self->{_runs} }; my @runs = $$self->{_runs}; Same goes for iterating over the keys: foreach my $dt (keys $self->{_runs}) foreach my $dt (keys %{ $self->{_runs} }) And how about actually adding the data? $self->{_runs}{$dt} = $duration; %{ $self->{_runs} }{$dt} = $duration; $$self->{_runs}{$dt} = $duration; You get the point. I've been reading articles about using classes, and articles about referencing and dereferencing, but I can't seem to get my brain to combine the knowledge and use both at the same time. I got my _times array working finally, but mimicking my array syntax over to hashes didn't work.

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• Numerical calculations in Prolog

  - by user8472

  While reading SICP I came across logic programming chapter 4.4. Then I started looking into the Prolog programming language and tried to understand some simple assignments in Prolog. I found that Prolog seems to have troubles with numerical calculations. Here is the computation of a factorial in standard Prolog: f(0, 1). f(A, B) :- A > 0, C is A-1, f(C, D), B is A*D. The issues I find is that I need to introduce two auxiliary variables (C and D), a new syntax (is) and that the problem is non-reversible (i.e., f(5,X) works as expected, but f(X,120) does not). Naively, I expect that at the very least C is A-1, f(C, D) above may be replaced by f(A-1,D), but even that does not work. My question is: Why do I need to do this extra "stuff" in numerical calculations but not in other queries? I do understand (and SICP is quite clear about it) that in general information on "what to do" is insufficient to answer the question of "how to do it". So the declarative knowledge in (at least some) math problems is insufficient to actually solve these problems. But that begs the next question: How does this extra "stuff" in Prolog help me to restrict the formulation to just those problems where "what to do" is sufficient to answer "how to do it"?

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• UIImageView Centering Problem.

  - by sagar

  To understand my problem let's follow this steps. Open - XCode - New Project - View based application. Open View Controller.xib file. Drag an image-view into viewController's view. Place that image view on center of viewController's view. Apply size of 125x125 to image-view. Take any image with dimension of 320 width & 460 height. Drag that image into your application resources directory. Now, Again back to .xib File & select image-view Set image (which is in your resources) to image-view Set Image-view Mode to - Center Ok. Let me explain the situation now. after performing all above steps - image-view has an image which is larger than image-view's size. However, Image-view places that image on center & in View controller image-view is looking proper ( not scaled ). But When you run your application, image-view will be displayed in size of 320x460. ( but it is not actually scaled. ) Now, I can't find the reason, why interface builder is displaying something else & simulator/iphone is displaying something else ? My Query. I want the image's center portion within image-view no matter what image size is. Thanks in advance for sharing your knowledge. Sagar.

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• Ajax with Jsf 1.1 implementation

  - by Rohan Ved

  I am using JSF1.1 in that, have this code_ <%@ taglib uri="http://java.sun.com/jsf/html" prefix="h"%> <%@ taglib uri="http://java.sun.com/jsf/core" prefix="f"%> <%@ taglib uri="http://www.azureworlds.org" prefix="azure"%> <%@ taglib uri="http://myfaces.apache.org/tomahawk" prefix="x"%> <%@ taglib uri="http://www.asifqamar.com/jsf/asif" prefix="a"%> ... <x:selectOneMenu value="#{hotelBean.state}"> <f:selectItem itemLabel="Select One" itemValue="" /> <f:selectItem value="#{hotelBean.mapStates }" /> <x:ajax update="city" listener="#{hotelBean.handleCityChange}" /> </x:selectOneMenu> <h:outputText value="City* " /> <x:selectOneMenu id="city" value="#{hotelBean.city}"> <f:selectItem itemLabel="Select One" itemValue="" /> <f:selectItem value="#{hotelBean.mapCities }" /> </x:selectOneMenu> line x:ajax update="city" listener="#{hotelBean.handleCityChange}" is not working , i searched but got JSF1.1 not support for Ajax. then what can i do for this? and i have less knowledge of JS. Thanx

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• What's the next steps for moving from appengine to full django?

  - by tomcritchlow

  Hey guys, I'm super new to programming and I've been using appengine to help me learn python and general coding. I'm getting better quickly and I'm loving it all the way :) Appengine was awesome for allowing me to just dive into writing my app and getting something live that works (see http://www.7bks.com/). But I'm realising that the longer I continue to learn on appengine the more I'm constraining myself and locking myself into a single system. I'd like to move to developing on full django (since django looks super cool!). What are my next steps? To give you a feel for my level of knowledge: I'm not a unix user I'm not familiar with command line controls (I still use appengine/python completely via the appengine SDK) I've never programmed in anything other than python, anywhere other than appengine I know the word SQL, but don't know what MySQL is really or how to use it. So, specifically: What are the skills I need to learn to get up and running with full django/python? If I'm going to host somewhere else I suppose I'll need to learn some sysadmin type skills (maybe even unix?). Is there anywhere that offers easy hosting (like appengine) but that supports django? I hear such great things about heroku I'm considering switching to RoR and going there I appreciate that I'm likely not quite ready to move away from appengine just yet but I'm a fiercely passionate learner (http://www.7bks.com/blog/179001) and would love it if I knew all the steps I needed to learn so I could set about learning them. At the moment, I don't even know what the steps are I need to learn! Thank you very much. Sorry this isn't a specific programming question but I've looked around and haven't found a good how-to for someone of my level of experience and I think others would appreciate a good roadmap for the things we need to learn to get up and running. Thanks, Tom PS - if anyone is in London and fancies showing me the ropes in person that would be super awesome :)

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• Is it a good idea to use an integer column for storing US ZIP codes in a database?

  - by Yadyn

  From first glance, it would appear I have two basic choices for storing ZIP codes in a database table: Text (probably most common), i.e. char(5) or varchar(9) to support +4 extension Numeric, i.e. 32-bit integer Both would satisfy the requirements of the data, if we assume that there are no international concerns. In the past we've generally just gone the text route, but I was wondering if anyone does the opposite? Just from brief comparison it looks like the integer method has two clear advantages: It is, by means of its nature, automatically limited to numerics only (whereas without validation the text style could store letters and such which are not, to my knowledge, ever valid in a ZIP code). This doesn't mean we could/would/should forgo validating user input as normal, though! It takes less space, being 4 bytes (which should be plenty even for 9-digit ZIP codes) instead of 5 or 9 bytes. Also, it seems like it wouldn't hurt display output much. It is trivial to slap a ToString() on a numeric value, use simple string manipulation to insert a hyphen or space or whatever for the +4 extension, and use string formatting to restore leading zeroes. Is there anything that would discourage using int as a datatype for US-only ZIP codes?

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• What does it mean to say "Instance variables are not over-rided" in java?

  - by Ankit

  I am aware of the concept called field hiding in java. But still I am having a confusion in relation to instance variable being not over-ridden. According to my present knowledge, overriding a method of super-class means that the JVM will call the sub-class's over-ridden method though the super-class's method is available to the sub-class. And I read the similar thing for field hiding via the link:- Hiding Fields So, in any case we are over-ridding the instance if we change the values of the inherited instance variable in the sub-class. I am confused please help. I am using the following super-class:- public class Animal{ File picture; String food; int hunger; int width, height; int xcoord, ycoord; public void makeNoise(){ ......... } public void eat(){ ............. } public void sleep(){ .......... } public void roam(){ ............. } } It has sub-classes like Tiger, cat, dog,hippo etc. The sub-classes over-ride the makeNoise(), eat and roam() method. But each sub-class also uses a different set of values for instance variables. So as per my confusion, I am kind-of overriding all the instance variables and 3 methods of the super-class Animal; and I still have the super-class instance variables available to the sub-class with the use of the super keyword.

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• how does Cocoa compare to Microsoft, Qt?

  - by Paperflyer

  I have done a few months of development with Qt (built GUI programatically only) and am now starting to work with Cocoa. I have to say, I love Cocoa. A lot of the things that seemed hard in Qt are easy with Cocoa. Obj-C seems to be far less complex than C++. This is probably just me, so: Ho do you feel about this? How does Cocoa compare to WPF (is that the right framework?) to Qt? How does Obj-C compare to C# to C++? How does XCode/Interface Builder compare to Visual Studio to Qt Creator? How do the Documentations compare? For example, I find Cocoa's Outlets/Actions far more useful than Qt's Signals and Slots because they actually seem to cover most GUI interactions while I had to work around Signals/Slots half the time. (Did I just use them wrong?) Also, the standard templates of XCode give me copy/paste, undo/redo, save/open and a lot of other stuff practically for free while these were rather complex tasks in Qt. Please only answer if you have actual knowledge of at least two of these development environments/frameworks/languages.

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• WPF - Transparency - Stream Desktop Content

  - by Niels Willems

  Greetings I'm in the process of making a Scoreboard for a game (Starcraft II). This scoreboard is being made as a WPF Application with a C# code-behind. I already have a version which works for 90% in WinForms but I lacked the support to easily make it look a lot nicer which are available in WPF. The point of this application will be to form a kind of overlay on top of a running game. This game is in Fulscreen(Windowed Mode) so when in WinForms I coded it so that it should always be on top. It would do so and that was no problem. Since the main look of the app in WPF is based on an image with a transparent background I have set most Background values to Transparent. However when I do this the entire application does not get registered by streaming software. For example it just shows my Desktop or the game I'm playing but not my application even though it IS there. I can see it with my own eyes but the audience on the stream cannot. Does anyone have any experience with this matter because it's really doing my head in. My entire application will be useless if it is not visible on streams. If I have to put the background on a color rather than transparent the UI will be completely demolished as well in terms of looks. I'm basically trying to make a game-overlay in C# & WPF. I have read you can do this on different ways as well but I have little to no knowledge of C++ nor do I know anything about DirectX Thank you for your time reading and your possible insights. Edit: The best solution would be an overlay similar to that one of Steam/Xfire/Dolby Axon. Edit 2: I've had no luck with all the suggestions so I basically made the transparent bits of my image non transparent and let the user decide which one to use depending on what streaming software they would be using.

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• Is there a best practice for concatenating MP3 Files, adjusting sample rates to match, while preserving original files?

  - by Scott

  Hello overflow community! Does anyone know if there is a "best practice" to concatenate mp3 files to create new files, while preserving the original files? I am working on a CentOS Linux machine, in command line. I will eventually call the command line from a PHP script. I have been doing research and I have come up with a process that I think could work. It combines general advice from different forums, blogs, and sources like this one. So here I go: Create a temporary folder Loop through files to create a new, converted copy, of file into a "raw" format (which one, I don't know. I didn't know "raw" files existed before too long ago. I could use some suggestions on this) Store the path to the temporary files, in the temporary folder, and then loop through the files to concatenate them and then put the new merged file the final "processed directory" Delete the contents of the temporary file with the temporary raw files inside. Convert the final file from "raw" to mp3 and enjoy the finished result I'm thinking that this course of action might be best because I can't necessarily control the quality of the original "source" mp3s. The only other option I could think of would be to create a script that would perform a similar process upon files being added to the system leaving only the files with the "proper" format and removing the original "erroneous" file. Hopefully you can see that I have put some thought into this and that I'm trying to leverage the collective knowledge of this community to choose the best direction. Perhaps there is a better path that I could take? By concatenate, I mean to join together in sequence to create a new audio file from the "concatenated files."

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