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• Converting Source ASCII Files to JPEGs

  - by CommonsWare

  I publish technical books, in print, PDF, and Kindle/MOBI, with EPUB on the way. The Kindle does not support monospace fonts, which are kinda useful for source code listings. The only way to do monospace fonts is to convert the text (Java source, HTML, XML, etc.) into JPEG images. More specifically, due to pagination issues, a given input ASCII file needs to be split into slices of ~6 lines each, with each slice turned into a JPEG, so listings can span a screen. This is a royal pain. My current mechanism to do that involves: Running expand to set a consistent 2-space tab size, which pipes to... a2ps, which pipes to... A small Perl snippet to add a "%%LanguageLevel: 3\n" line, which pipes to... ImageMagick's convert, to take the (E)PS and make a JPEG out it, with an appropriate background, cropped to 575x148+5+28, etc. That used to work 100% of the time. It now works 95% of the time. The rest of the time, I get convert: geometry does not contain image errors, which I cannot seem to get rid of, in part because I don't understand what the problem is. Before this process, I used to use a pretty-print engine (source-highlight) to get HTML out of the source code...but then the only thing I could find to convert the HTML into JPEGs was to automate screen-grabs from an embedded Gecko engine. Reliability stank, which is why I switched to my current mechanism. So, if you were you, and you needed to turn source listings into JPEG images, in an automated fashion, how would you do it? Bonus points if it offers some sort of pretty-print process (e.g., bolded keywords)! Or, if you know what typically causes convert: geometry does not contain image, that might help. My current process is ugly, but if I could get it back to 100% reliability, that'd be just fine for now. Thanks in advance!

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• what's the performance difference between int and varchar for primary keys

  - by user568576

  I need to create a primary key scheme for a system that will need peer to peer replication. So I'm planning to combine a unique system ID and a sequential number in some way to come up with unique ID's. I want to make sure I'll never run out of ID's, so I'm thinking about using a varchar field, since I could always add another character if I start running out. But I've read that integers are better optimized for this. So I have some questions... 1) Are integers really better optimized? And if they are, how much of a performance difference is there between varchars and integers? I'm going to use firebird for now. But I may switch later. Or possibly support multiple db's. So I'm looking for generalizations, if that's possible. 2) If integers are significantly better optimized, why is that? And is it likely that varchars will catch up in the future, so eventually it won't matter anyway? My varchar keys won't have any meaning, except for the unique system ID part. But I may want to obscure that somehow. Also, I plan to efficiently use all the bits of each character. I don't, for example, plan to code the integer 123 as the character string "123". So I don't think varchars will require more space than integers.

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• What's best choice career-wise, to know a little about a lot or a lot about a little?

  - by nimo

  I work as a developer at a rather small company and we are providing a web application that is used by a big base of customers. Because we are so small everyone have to be able to do a lot of different tasks. It ranges from advanced support, developing the product (programming: c/c++, c#, php, sql, javascript, html, css), handle network configuration and network related issues and even sometimes go on sales meetings with potential customers. My concern is that I don't really specialize in any specific area. I know and learn little about a lot. I have graduated from school two years ago and this is my first real employment and when I look at other positions out there they always require so and so many years of experience in a specific area (for example 5 years of C#). For me to get that kind of specialized experience will be really hard at my current job. My question for you is what is, in your opinion, best choice career-wise, to know a little about a lot or a lot about a little? What path did you take? pros and cons that comes with that choice.

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• Freelance web hosting - what are good LAMP choices?

  - by tkotitan

  I think it's best if I ask this question with an example scenario. Let's say your mom-and-pop local hardware store has never had a website, and they want you, the freelance developer to build them a website. You have all the skills to run a LAMP setup and admin a system, so the difficult question you ask yourself is - where will I host it? As you aren't going to host it out of the machine in your apartment. Let's say you want to be able to customize your own system, install the version of PHP you want, and manage your own database. Perhaps the best kind of hosting is to get a virtual machine so you can customize the system as you see fit. But this essentially a "set it and forget it" site you make, bill by the hour for, and then are done. In other words, the hosting should not be an issue. Given the requirements of hosting a website: Unlimited growth potential needing good amounts of bandwidth to handle visitors Wide range of system and programming options allowing it to be portable Relatively cheap (not necessarily the cheapest) or reasonable scaling cost Reliable hosting with good support Hosted entirely on the host company's hardware Who would you pick to host this website? Yes I am asking for a business/company recommendation. Is there a clear answer for this scenario, or a good source that can reliably give the current answer? I know there are all kinds of schemes out there. I'm just wondering if any one company fills the bill for freelancers and stands out in such a crowded market.

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• How do I fix the alpha value after calling GDI text functions?

  - by Daniel Stutzbach

  I have a application that uses the Aero glass effect, so each pixel has an alpha value in addition to red, green, and blue values. I have one custom-draw control that has a solid white background (alpha = 255). I would like to draw solid text on the control using the GDI text functions. However, these functions set the alpha value to an arbitrary value, causing the text to translucently show whatever window is beneath my application's. After calling rendering the text, I would like to go through all of the pixels in the control and set their alpha value back to 255. What's the best way to do that? I haven't had any luck with the BitBlt, GetPixel, and SetPixel functions. They appear to be oblivious to the alpha value. Here are other solutions that I have considered and rejected: Draw to a bitmap, then copy the bitmap to the device: With this approach, the text rendering does not make use of the characteristics of the monitor (e.g., ClearText). Use GDI+ for text rendering: This application originally used GDI+ for text rendering (before I started working on Aero support). I switched to GDI because of difficulties I encountered trying to accurately measure strings with GDI+. I'd rather not switch back. Set the Aero region to avoid the control in question: My application's window is actually a child window of a different application running in a different process. I don't have direct control over the Aero settings on the top-level window. The application is written in C# using Windows Forms, though I'm not above using Interop to call Win32 API functions.

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• R: building a simple command line plotting tool/Capturing window close events

  - by user275455

  I am trying to use R within a script that will act as a simple command line plot tool. I.e. user pipes in a csv file and they get a plot. I can get to R fine and get the plot to display through various temp file machinations, but I have hit a roadblock. I cannot figure out how to get R to keep running until the users closes the window. If I plot and exit, the plot disappears immediately. If I plot and use some kind of infinite loop, the user cannot close the plot; he must exit by using an interrupt which I don't like. I see there is a getGraphicsEvent function, but it claims that the device is not supported (X11). Anyway, it doesn't appear to actually support an onClose event, only onMouseDown. Any ideas on how to solve this? edit: Thanks to Dirk for the advice to check out the tk interface. Here is the test code that works: require(tcltk) library(tkrplot) ##function to display plot, called by tkrplot and embedded in a window plotIt<-function(){ plot(x=1:10, y=1:10) } ##create top level window tt<-tktoplevel() ##variable to wait on like a condition variable, to be set by event handler done <- tclVar(0) ##bind to the window destroy event, set done variable when destroyed tkbind(tt,"",function() tclvalue(done) <- 1) ##Have tkrplot embed the plot window, then realize it with tkgrid tkgrid(tkrplot(tt,plotIt)) ##wait until done is true tkwait.variable(done)

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• Compilig + testing an Android library with the JDK?

  - by Jarle Hansen

  Hi all, I am creating a library for Android that others can include in their own project. So far I have been working on it as a normal Java project with JDK 1.6 setup as system library. This works just fine in Eclipse when I add the android.jar. The issue comes when I try to my build script. I am running Gradle and doing a normal compile and test build cycle. My thoughts were that it does not matter if I compile it with a normal JDK, since this is not a standalone application. The benefits by creating a normal Java project is that Gradle does support this much better. My project also does not contain any UI at all. However, the problem is that of course android.jar and the JDK contains lots of the same classes and I think that this is what messes up my build script. Everything crashes when running the tests (the tests are in the same project under src/test/java). My question is, how should I create this project that is meant to be included in Android projects as a third party library? Should I create it as an Android project in Eclipse even though I am only creating a library that does not use any of the UI features? Also, should the tests be in a separate project? Thanks for all responses!

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• Drupal Ubercart: error in passing values back to the Content Type after checkout

  - by user512826

  I am trying to set up event registration in a drupal site using Ubercart + the UC Node Checkout Module. I have followed the instructions provided in http://drupaleasy.com/blogs/ultimike/2009/03/event-registration-ubercart. However I seem to be unable to pass the Order ID and Payment Status back to the node. I have created a conditional action that on node checkout executes the following PHP code: I am using the following code to update the node on checkout - but nothing happens: if (isset($order)) { foreach ($order->products as $product) { if (isset($product->data['node_checkout_nid'])) { $node = node_load($product->data['node_checkout_nid']); $node->field_status['0']['value'] = 1; $node->field_orderid['0']['value'] = $order->order_id; node_save($node); } } } I know the conditional action is working because it prints dsm('hello world') messages on node checkout - however when I include a dsm($node) or dsm($product) in the PHP code, they return blank. Also when I go back to my product and click the 'Devel' tab, the 'data' string contains the following characters: a:1:{s:13:"form_build_id";s:37:"form-3ccc03345f4832c69666a89c560de940";} In this link http://www.ubercart.org/forum/support/10951/node_checkout_issue I found someone else with the same issue, but I have been unable to replicate his solution. Can anybody please help? Thanks so much!

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• Custom View Engine in ASP.NET MVC 2 does not work with Areas

  - by mare

  I used the code below so far with ASP.NET MVC v1 and v2 but when I added an Area today to my application, the controller for the area couldn't find any views in my Areas/Views/controllerView folder. It issued the very well known exception that it searched those 4 standard folders but it did not look under Areas.. How can I change the code so that it will work with Areas? Maybe an example of custom view engine under ASP.NET MVC 2 with Areas support? The information about it on the net is very scarse.. Here's the code: public class PendingViewEngine : VirtualPathProviderViewEngine { public PendingViewEngine() { // This is where we tell MVC where to look for our files. /* {0} = view name or master page name * {1} = controller name */ MasterLocationFormats = new[] {"~/Views/Shared/{0}.master", "~/Views/{0}.master"}; ViewLocationFormats = new[] { "~/Views/{1}/{0}.aspx", "~/Views/Shared/{0}.aspx", "~/Views/Shared/{0}.ascx", "~/Views/{1}/{0}.ascx" }; PartialViewLocationFormats = new[] {"~/Views/{1}/{0}.ascx", "~/Views/Shared/{0}.ascx"}; } protected override IView CreatePartialView(ControllerContext controllerContext, string partialPath) { return new WebFormView(partialPath, ""); } protected override IView CreateView(ControllerContext controllerContext, string viewPath, string masterPath) { return new WebFormView(viewPath, masterPath); } }

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• NHibernate - Retrieving Lots of Data Becomes Exponentially Slow

  - by nfplee

  Hi, I have an issue when I retrieve lots of data in NHibernate (such as when producing a report) the page becomes exponentially slower the more data it has to retrieve. I found the following article: http://nhforge.org/blogs/nhibernate/archive/2008/10/30/bulk-data-operations-with-nhibernate-s-stateless-sessions.aspx It explains how doing bulk data operations in NHibernate is slow since the first level cache grows too large and how you should use the IStatelessSession instead. The trouble I have is that I don't wish to tie my application to NHibernate so I've added a wrapper around ISession. I then use Linq as my query mechanism but IStatelessSession does not support Linq (it may do in NHibernate 3 but the Linq provider is not stable as it stands at the moment). I then read that you could do a clear after so many iterations to clear out the first level cache. The problem now is that you can't use lazy loading. The linq provider doesn't allow you to override the mapping defined (or eagerly fetch the additional data) so whenever I grab data which is lazy loaded after I have cleared the session an exception is thrown. I'm completely lost on what do now. I like the ease of producing reports with linq but the limitations of the inbuilt linq provider in NHibernate seem to be holding me back. I'd really appreciate it if someone could show me an alternative approach. Thanks

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• Can I have the gcc linker create a static libary?

  - by Lucas Meijer

  I have a library consisting of some 300 c++ files. The program that consumes the library does not want to dynamically link to it. (For various reasons, but the best one is that some of the supported platforms do not support dynamic linking) Then I use g++ and ar to create a static library (.a), this file contains all symbols of all those files, including ones that the library doesn't want to export. I suspect linking the consuming program with this library takes an unnecessary long time, as all the .o files inside the .a still need to have their references resolved, and the linker has more symbols to process. When creating a dynamic library (.dylib / .so) you can actually use a linker, which can resolve all intra-lib symbols, and export only those that the library wants to export. The result however can only be "linked" into the consuming program at runtime. I would like to somehow get the benefits of dynamic linking, but use a static library. If my google searches are correct in thinking this is indeed not possible, I would love to understand why this is not possible, as it seems like something that many c and c++ programs could benefit from.

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• Hopping from a C++ to a Perl Unix profile?

  - by rocknroll

  Hi all, I have been a C++,Linux Developer till now and I am adept in this stack. Off late I have been getting opportunities that require Perl,Unix (with knowledge of C++,shell scripting) expertise. Organisations are showing interest even thought I don't have much scripting experience to boast off. The roll is more in a Support,maintenance project involving SQL as well. Off late I am in a fix whether to forgo these offers or not. I don't know the dynamics of an IT organisation and thus on one hand I fear that my C++ experience will be nullified and on the positive side I am getting to work on a new technology stack which will only add to my skill set. I am sure, most of you at some point of time have encountered such dilemmas and would have taken some decision. I want you to share your perspectives on such a scenario where a person is required to change his/her technology stack when changing his/her job. What are the merits and demerits in going with either of the choices? Also I know that C++ isn't going anywhere in the near future. What about perl? I have no clue as to what the future holds for perl developer? Whether there are enough opportunities for a perl developer? I am asking this question here because most of my fellow programmers face this career choice dilemma. Thanks.

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• How does PHP interface with Apache?

  - by Sbm007

  Hi, I've almost finished writing a HTTP/1.0 compliant web server under Java (no commercial usage as such, this is just for fun) and basically I want to include PHP support. I realize that this is no easy task at all, but I think it'll be a nice accomplishment. So I want to know how PHP exactly interfaces with the Apache web server (or any other web server really), so I can learn from it and write my own PHP wrapper. It doesn't necessarily have to be mod_php, I don't mind writing a FastCGI wrapper - which to my knowledge is capable of running PHP as well. I would've thought that all that PHP needs is the output that goes to client (so it can interpret the PHP parts), the full HTTP request from client (so it can extract POST variables and such) and the client's host name. And then you simply take the parsed PHP code and write that to the output stream. There will probably be more things, but in essence that's how I would have thought it works. From what I've gathered so far, apache2handler provides an API which PHP makes use of to 'connect' to Apache. I guess it's an idea to look at the source code for apache2handler and php5apache2.dll or so, but before I do that I thought I'd ask SO first. If anyone has more information, experience, or some sort of specification that is relevant to this then please let me know. Thanks in advance!

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• Setting WCF service for multiple client calls

  - by user348255

  Hi all, I have made a WCF service which is defined like this: [ServiceBehavior(InstanceContextMode = InstanceContextMode.Single, ConcurrencyMode = ConcurrencyMode.Multiple)] binding is done using netTcpBinding. We support 50+ clients that call the server from time to time. Each client opens a channel using channelfactory once it is loaded and uses that channel for all calls (creates the channel and proxy only once). we have built a small load tester that imitates the client by calling the server by 50 different threads at once (using 50 different channels). when we run this tester, after the 10th client tries to connect, all other client fail connecting. We have set throttling to 100. My questions are: 1. is it correct for each client to create a channel and use it through the client life time? or, do i need to use a using statement for each call to the server (create and distroy a new channel for each call). 2. does the service have a limit of channel connections to it? other then throttling? thanks alot, Guy.

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• When is a try catch not a try catch?

  - by Dearmash

  I have a fun issue where during application shutdown, try / catch blocks are being seemingly ignored in the stack. I don't have a working test project (yet due to deadline, otherwise I'd totally try to repro this), but consider the following code snippet. public static string RunAndPossiblyThrow(int index, bool doThrow) { try { return Run(index); } catch(ApplicationException e) { if(doThrow) throw; } return ""; } public static string Run(int index) { if(_store.Contains(index)) return _store[index]; throw new ApplicationException("index not found"); } public static string RunAndIgnoreThrow(int index) { try { return Run(index); } catch(ApplicationException e) { } return ""; } During runtime this pattern works famously. We get legacy support for code that relies on exceptions for program control (bad) and we get to move forward and slowly remove exceptions used for program control. However, when shutting down our UI, we see an exception thrown from "Run" even though "doThrow" is false for ALL current uses of "RunAndPossiblyThrow". I've even gone so far as to verify this by modifying code to look like "RunAndIgnoreThrow" and I'll still get a crash post UI shutdown. Mr. Eric Lippert, I read your blog daily, I'd sure love to hear it's some known bug and I'm not going crazy. EDIT This is multi-threaded, and I've verified all objects are not modified while being accessed

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• Void* array casting to float, int32, int16, etc.

  - by Griffin

  Hey guys, I've got an array of PCM data, it could be 16 bit, 24 bit packed, 32 bit, etc.. It could be signed, or unsigned, and it could be 32 or 64 bit floating point. It is currently stored as a "void**" matrix, indexed by channel, then by frame. The goal is to allow my library to take in any PCM format and buffer it, without requiring manipulation of the data to fit a designated structure. If the A/D converter spits out 24 bit packed arrays of interleaved PCM, I need to accept it gracefully. I also need to support 16 bit non interleaved, as well as any permutation of the above formats. I know the bit depth and other information at runtime, and I'm trying to code efficiently while not duplicating code. What I need is an effective way to cast the matrix, put PCM data into the matrix, and then pull it out later. I can cast the matrix to int32_t, or int16_t for the 32 and 16 bit signed PCM respectively, I'll probably have to store the 24 bit PCM in an int32_t for 32 bit, 8 bit byte systems as well. Can anyone recommend a good way to put data into this array, and pull it out later? I'd like to avoid large sections of code which look like: switch( mFormat ) { case 1: // unsigned 8 bit for( int i = 0; i < mChannels; i++ ) framesArray = (uint8_t*)pcm[i]; break; case 2: // signed 8 bit for( int i = 0; i < mChannels; i++ ) framesArray = (int8_t*)pcm[i]; break; case 3: // unsigned 16 bit ... Limitations: I'm working in C/C++, no templates, no RTTI, no STL. Think embedded. Things get trickier when I have to port this to a DSP with 16 bit bytes. Does anybody have any useful macros they might be willing to share? Thanks, -Griff

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• Client Side Only Cookies

  - by Mike Jones

  I need something like a cookie, but I specifically don't want it going back to the server. I call it a "client side session cookie" but any reasonable mechanism would be great. Basically, I want to store some data encrypted on the server, and have the user type a password into the browser. The browser decrypts the data with the password (or creates and encrypts the data with the password) and the server stores only encrypted data. To keep the data secure on the server, the server should not store and should never receive the password. Ideally there should be a cookie session expiration to clean up. Of course I need it be available on multiple pages as the user walks through the web site. The best I can come up with is some sort of iframe mechanism to store the data in javascript variables, but that is ugly. Does anyone have any ideas how to implement something like this? FWIW, the platform is ASP.NET, but I don't suppose that matters. It needs to support a broad range of browsers, including mobile. In response to one answer below, let me clarify. My question is not how to achieve the crypto, that isn't a problem. The question is where to store the password so that it is persistent from page to page, but not beyond a session, and in such a way that the server doesn't see it.

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• How to provide i18n service for developer and end user

  - by user247245

  Many android applications have quite poor i18n-support, and for an understandable reason, as it adds much work for the developer. From a both intuitive and cultural point of view it would be a good thing if end-users could translate the apps themself, and OTA share the translation, without reinstalling the app itself. In concept; as wikipedia, some add content easily, others only use what's there. It's of course important that the service is as easy as possible to use, both for app-developers, and people willing to transcribe. To keep it simple, this is the solution I'm concidering; Developer perspective: Developer uses a customized setContentView when open activities/layouts that will seach for thanslations of xml-entries. (below) The customized version is provided as a free downloadable library/class..., turning the i18n feature to more or less a one liner. User perspective: User downloads app without any translation As app launches, it checks locale running at phone, and will look for a translated xml-file at shared space in SD. If no or old transcribed xml (above), try to download new from internet-service (ansync). This is all done by library above, no need for intents. Translator perspective: Separate app to provide translations for any app using the i18n service above. (Could be just a webapp), with some form of QA on translators/input. QUESTION: Now, for this to work efficiently, it has to be AeasyAP for the developer to even bother, and the most fluent solution would be a customized version of setContentView, that simply loads the translated values from external xml, instead of the ones in the apk. Is this possible at all, and if not, what's your suggested solutions? (And of course, Happy New Year, feliz ano novo, blwyddyn newydd dda, Gott Nytt År, kontan ane nouvo, szczesliwego nowego roku ...) Regards, /T

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• Set service dependencies after install

  - by Dennis

  I have an application that runs as a Windows service. It stores various things settings in a database that are looked up when the service starts. I built the service to support various types of databases (SQL Server, Oracle, MySQL, etc). Often times end users choose to configure the software to use SQL Server (they can simply modify a config file with the connection string and restart the service). The problem is that when their machine boots up, often times SQL Server is started after my service so my service errors out on start up because it can't connect to the database. I know that I can specify dependencies for my service to help guide the Windows service manager to start the appropriate services before mine. However, I don't know what services to depend upon at install time (when my service is registered) since the user can change databases later on. So my question is: is there a way for the user to manually indicate the service dependencies based on the database that they are using? If not, what is the proper design approach that I should be taking? I've thought about trying to do something like wait 30 seconds after my service starts up before connecting to the database but this seems really flaky for various reasons. I've also considered trying to "lazily" connect to the database; the problem is that I need a connection immediately upon start up since the database contains various pieces of vital info that my service needs when it first starts. Any ideas?

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• Catch a PHP Object Instantiation Error

  - by Rob Wilkerson

  It's really irking me that PHP considers the failure to instantiate an object a Fatal Error (which can't be caught) for the application as a whole. I have set of classes that aren't strictly necessary for my application to function--they're really a convenience. I have a factory object that attempts to instantiate the class variant that's indicated in a config file. This mechanism is being deployed for message storage and will support multiple store types: DatabaseMessageStore FileMessageStore MemcachedMessageStore etc. A MessageStoreFactory class will read the application's preference from a config file, instantiate and return an instance of the appropriate class. It might be easy enough to slap a conditional around the instantiation to ensure that class_exists(), but MemcachedMessageStore extends PHP's Memcached class. As a result, the class_exists() test will succeed--though instantiation will fail--if the memcached bindings for PHP aren't installed. Is there any other way to test whether a class can be instantiated properly? If it can't, all I need to do is tell the user which features won't be available to them, but let them continue one with the application. Thanks.

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• Scalable Full Text Search With Per User Result Ordering

  - by jeremy

  What options exist for creating a scalable, full text search with results that need to be sorted on a per user basis? This is for PHP/MySQL (Symfony/Doctrine as well, if relevant). In our case, we have a database of workouts that have been performed by users. The workouts that the user has done before should appear at the top of the results. The more frequently they've done the workout, the higher it should appear in search matches. If it helps, you can assume we know the number of times a user has done a workout in advance. Possible Solutions Sphinx - Use Sphinx to implement full text search, do all the querying and sorting in MySQL. This seems promising (and there's a Symfony Plugin!) but I don't know much about it. Lucene - Use Lucene to perform full text search and put the users' completions into the query. As is suggested in this Stack Overflow thread. Alternatively, use Lucene to retrieve the results, then reorder them in PHP. However, both solutions seem clunky and potentially unscalable as a user may have completed hundreds of workouts. Mysql - No native full text support (InnoDB), so we'd have use LIKE or REGEX, which isn't scalable.

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• Why is my JavaScript function "a" not defined?

  - by 4l3x

  When I call my JavaScript function B, the javascript console in firefox said that function A is not defined, but on chrome browser if defined. And when I call function "A" in body segment: <input type="button" onclick="A()" value=" ..A.. "> , firefox said that function B is not defined? :S <html> <head> <script language="javascript" type="text/javascript"> function B(){ alert(" hi B "); document.write('<br><br><input type="button" onClick="A()" value=" ..A..">'); }; function A(){ alert(" hi A"); document.write('<br><br><input type="button" onclick="B()" value=" ..b..">'); if (window.WebCL == undefined) { alert("Unfortunately your system does not support WebCL. "); return false; } } </script> </head> <body> <input type="button" onclick="B()" value=" ..B.. "> </body> </html>

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• c++ templates and inheritance

  - by Armen Ablak

  Hey, I'm experiencing some problems with breaking my code to reusable parts using templates and inheritance. I'd like to achieve that my tree class and avltree class use the same node class and that avltree class inherits some methods from the tree class and adds some specific ones. So I came up with the code below. Compiler throws an error in tree.h as marked below and I don't really know how to overcome this. Any help appreciated! :) node.h: #ifndef NODE_H #define NODE_H #include "tree.h" template <class T> class node { T data; ... node() ... friend class tree<T>; }; #endif tree.h #ifndef DREVO_H #define DREVO_H #include "node.h" template <class T> class tree { public: //signatures tree(); ... void insert(const T&); private: node<T> *root; //missing type specifier - int assumed. Note: C++ does not support default-int }; //implementations #endif avl.h #ifndef AVL_H #define AVL_H #include "tree.h" #include "node.h" template <class T> class avl: public tree<T> { public: //specific int findMin() const; ... protected: void rotateLeft(node<T> *)const; private: node<T> *root; }; #endif avl.cpp (I tried separating headers from implementation, it worked before I started to combine avl code with tree code) #include "drevo" #include "avl.h" #include "vozlisce.h" template class avl<int>; //I know that only avl with int can be used like this, but currently this is doesn't matter :) //implementations ...

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• Can a custom MFC window/dialog be a class template instantiation?

  - by John

  There's a bunch of special macros that MFC uses when creating dialogs, and in my quick tests I'm getting weird errors trying to compile a template dialog class. Is this likely to be a big pain to achieve? Here's what I tried: MyDlg.h template <class W> class CMyDlg : public CDialog { typedef CDialog super; DECLARE_DYNAMIC(CMyDlg <W>) public: CMyDlg (CWnd* pParent); // standard constructor virtual ~CMyDlg (); // Dialog Data enum { IDD = IDD_MYDLG }; protected: virtual void DoDataExchange(CDataExchange* pDX); // DDX/DDV support DECLARE_MESSAGE_MAP() private: W *m_pWidget; //W will always be a CDialog }; IMPLEMENT_DYNAMIC(CMyDlg<W>, super) <------------------- template <class W> CMyDlg<W>::CMyDlg(CWnd* pParent) : super(CMyDlg::IDD, pParent) { m_pWidget = new W(this); } I get a whole bunch of errors but main one appears to be: error C2955: 'CMyDlg' : use of class template requires template argument list I tried using some specialised template versions of macros but it doesn't help much, other errors change but this one remains. Note my code is all in one file, since C++ templates don't like .h/.cpp like normal. I'm assuming someone must have done this in the past, possibly creating custom versions of macros, but I can't find it by searching, since 'template' has other meanings.

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• Magento products will not show in category

  - by Aaron

  I've recently been tasked with the build and deployment of a large Ecommerce site. In the past we've had to use the clients legacy X-cart installation for redevelopment (too far integrated with their existing work flow). We'd heard good things about Magento, so I've set up a test install to get to grips with it. After a couple of initial issues, there is a live development site which displays categories on the default theme. The problem we've hit now is that products don't display..! After a lot more in-depth research into this, all I've been able to discover is that quite a number of developers endorse using other solutions entirely, with the other 50% saying after the steep learning curve the platform is as wonderful as we'd initially been led to believe. Now, my test category is showing, so I know this is configured properly. I've set up three test products and associated them with this (all done following the Magento user guide), checked double checked and thrice checked the products are enabled and visible individually, yet still the front end says the category has no products in it. I've cleared the cache repeatedly, reset everything possible many times in index management - no products show up. I have to make a call tomorrow morning on whether we're going ahead with Magento. If I can't even get it to show products I'm going to have to go with something with a more established track record and more community support available. Can anybody advise what could possibly be wrong here?

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