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• Entity Framework POCO objects

  - by Dan

  I'm struggling with understanding Entity Framework and POCO objects. Here's what I'm trying to achieve. 1) Separate the DAL from the Business Layer by having my business layer use an interface to my DAL. Maybe use Unity to create my context. 2) Use Entity Framework inside my DAL. I have a Domain model with objects that reside in my business layer. I also have a database full of tables that doesn't really represent my domain model. I setup Entity Framework and generated POCO objects by using the ADO.NET POCO Generator extension. This gave me an object for each table in my database. Now I want to be able to say context.GetAll<User>(); and have it return a list of my User objects. The User object is in my business layer. Is that possible? Does that make sense or am I totally off and should start over? I'm guessing I need to use the repository pattern to achieve this, but I'm not sure. Can anyone help?

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• mysql query using global variables

  - by Carlos

  I am trying run a query to active the users account. I am not sure if I am having problem with the query itself or if there's something else that I dont know about. here is the code: if($_SESSION['lastid']&&$_SESSION['random']) { $check= mysql_query('SELECT * FROM members WHERE id= "$_SESSION[lastid]" AND random = " $_SESSION[random]"'); $checknum = mysql_num_rows($check); //$checknum = mysql_query($check) or die("Error: ". mysql_error(). " with query ". $check); if($checknum != 0) // run query to activate the account { $acti= mysql_query('UPDATE members SET activation = "1" WHERE id= "$_SESSION[lastid]"'); die('Your account has been activated. You may now log in!'); }else{ echo('Invalid id or activation code.') . ' lastid: ' .$_SESSION['lastid'] . ' random: ' .$_SESSION['random'] ; // die ('Invalid id or activation code.'); } }else{ die('Could not either find id or random number!'); } this is the warning I am getting from mysql: Warning: mysql_num_rows(): supplied argument is not a valid MySQL result resource in /hermes/bosweb26b/b2501/servername/folder/file.php on line 30 but when I echo the variables out, I get the same values that are stored in the database.... Invalid id or activation code. lastid: 2 and random: 36308075 could someone please give me a hint? thank you.

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• Appropriate uses of Monad `fail` vs. MonadPlus `mzero`

  - by jberryman

  This is a question that has come up several times for me in the design code, especially libraries. There seems to be some interest in it so I thought it might make a good community wiki. The fail method in Monad is considered by some to be a wart; a somewhat arbitrary addition to the class that does not come from the original category theory. But of course in the current state of things, many Monad types have logical and useful fail instances. The MonadPlus class is a sub-class of Monad that provides an mzero method which logically encapsulates the idea of failure in a monad. So a library designer who wants to write some monadic code that does some sort of failure handling can choose to make his code use the fail method in Monad or restrict his code to the MonadPlus class, just so that he can feel good about using mzero, even though he doesn't care about the monoidal combining mplus operation at all. Some discussions on this subject are in this wiki page about proposals to reform the MonadPlus class. So I guess I have one specific question: What monad instances, if any, have a natural fail method, but cannot be instances of MonadPlus because they have no logical implementation for mplus? But I'm mostly interested in a discussion about this subject. Thanks! EDIT: One final thought occured to me. I recently learned (even though it's right there in the docs for fail) that monadic "do" notation is desugared in such a way that pattern match failures, as in (x:xs) <- return [] call the monad's fail. It seems like the language designers must have been strongly influenced by the prospect of some automatic failure handling built in to haskell's syntax in their inclusion of fail in Monad.

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• On the search for my next great .Net Read

  - by user127954

  Just got done with "The art of unit testing". It was a great read and i think everyone should go buy a copy. With that said i think the next book I'm like to read would be a architecture / Design type book that would focus heavily on building your objects / software in such a way that it would be: Low Coupling High Cohesion Easily Maintainable / Extended Easy to test Easy to Navigate / Debug The above characteristcs are the most important ones but also maybe it would also include (but not necessary) designing for: Performance - Don't want to design a system at at the end find out its dog slow :) Scalability - Again don't want to design something at the end find out it won't scale. I'd also prefer (but not necessary again): Something newer - Architectural principles seem to gradually evolve / improve over time and id like something with current thinking. .Net as illustrating language - like i said above its not mandatory but since its what i use every day id prefer it to be in .net. Doesn't really matter if its in vb.net or c# Some of the topics that would be talked about its how to minimize dependencies and using interfaces throughout your solution rather than concrete classes. Maybe it would constract /compare some of the newest design principles like DDD, Repository Pattern, Ect... I already have "Clean Code" (don't know if its this type of book or not) and "Working effectively with legacy code" on my radar but id like to read a book based upon the topic i talked about above first. Is there such a book?

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• How strict should I be in the "do the simplest thing that could possible work" while doing TDD

  - by Support - multilanguage SO

  For TDD you have to Create a test that fail Do the simplest thing that could possible work to pass the test Add more variants of the test and repeat Refactor when a pattern emerge With this approach you're supposing to cover all the cases ( that comes to my mind at least) but I'm wonder if am I being too strict here and if it is possible to "think ahead" some scenarios instead of simple discover them. For instance, I'm processing a file and if it doesn't conform to a certain format I am to throw an InvalidFormatException So my first test was: @Test void testFormat(){ // empty doesn't do anything... processor.validate("empty.txt"); try { processor.validate("invalid.txt"); assert false: "Should have thrown InvalidFormatException"; } catch( InvalidFormatException ife ) { assert "Invalid format".equals( ife.getMessage() ); } } I run it and it fails because it doesn't throw an exception. So the next thing that comes to my mind is: "Do the simplest thing that could possible work", so I : public void validate( String fileName ) throws InvalidFormatException { if(fileName.equals("invalid.txt") { throw new InvalidFormatException("Invalid format"); } } Doh!! ( although the real code is a bit more complicated, I found my self doing something like this several times ) I know that I have to eventually add another file name and other test that would make this approach impractical and that would force me to refactor to something that makes sense ( which if I understood correctly is the point of TDD, to discover the patterns the usage unveils ) but: Q: am I taking too literal the "Do the simplest thing..." stuff?

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• Refactoring an ASP.NET 2.0 app to be more "modern"

  - by Wayne M

  This is a hypothetical scenario. Let's say you've just been hired at a company with a small development team. The company uses an internal CRM/ERP type system written in .NET 2.0 to manage all of it's day to day things (let's simplify and say customer accounts and records). The app was written a couple of years ago when .NET 2.0 was just out and uses the following architectural designs: Webforms Data layer is a thin wrapper around SqlCommand that calls stored procedures Rudimentary DTO-style business objects that are populated via the sprocs A "business logic" layer that acts as a gateway between the webform and database (i.e. code behind calls that layer) Let's say that as there are more changes and requirements added to the application, you start to feel that the old architecture is showing its age, and changes are increasingly more difficult to make. How would you go about introducing refactoring steps to A) Modernize the app (i.e. proper separation of concerns) and B) Make sure that the app can readily adapt to change in the organization? IMO the changes would involve: Introduce an ORM like Linq to Sql and get rid of the sprocs for CRUD Assuming that you can't just throw out Webforms, introduce the M-V-P pattern to the forms Make sure the gateway classes conform to SRP and the other SOLID principles. Change the logic that is re-used to be web service methods instead of having to reuse code What are your thoughts? Again this is a totally hypothetical scenario that many of us have faced in the past, or may end up facing.

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• Why does this Haskell code produce the "infinite type" error?

  - by Charlie Flowers

  I am new to Haskell and facing a "cannot construct infinite type" error that I cannot make sense of. In fact, beyond that, I have not been able to find a good explanation of what this error even means, so if you could go beyond my basic question and explain the "infinite type" error, I'd really appreciate it. Here's the code: intersperse :: a -> [[a]] -> [a] -- intersperse '*' ["foo","bar","baz","quux"] -- should produce the following: -- "foo*bar*baz*quux" -- intersperse -99 [ [1,2,3],[4,5,6],[7,8,9]] -- should produce the following: -- [1,2,3,-99,4,5,6,-99,7,8,9] intersperse _ [] = [] intersperse _ [x] = x intersperse s (x:y:xs) = x:s:y:intersperse s xs And here's the error trying to load it into the interpreter: Prelude :load ./chapter.3.ending.real.world.haskell.exercises.hs [1 of 1] Compiling Main ( chapter.3.ending.real.world.haskell.exercises.hs, interpreted ) chapter.3.ending.real.world.haskell.exercises.hs:147:0: Occurs check: cannot construct the infinite type: a = [a] When generalising the type(s) for `intersperse' Failed, modules loaded: none. Thanks. EDIT: Thanks to the responses, I have corrected the code and I also have a general guideline for dealing with the "infinite type" error in Haskell: Corrected code intersperse _ [] = [] intersperse _ [x] = x intersperse s (x:xs) = x ++ s:intersperse s xs What the problem was: My type signature states that the second parameter to intersperse is a list of lists. Therefore, when I pattern matched against "s (x:y:xs)", x and y became lists. And yet I was treating x and y as elements, not lists. Guideline for dealing with the "infinite type" error: Most of the time, when you get this error, you have forgotten the types of the various variables you're dealing with, and you have attempted to use a variable as if it were some other type than what it is. Look carefully at what type everything is versus how you're using it, and this will usually uncover the problem.

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• C# & SQL Server Authentication

  - by Peter

  Hello, I'm currently developing a C# app with an SQL Server DB back-end. I'm approaching the point of deployment and hitting a problem. The applicaiton will be deployed within an active directory network. As far as SQL authentication goes, I understand that I have 2 options - Windows Authenticaiton or Server Authenticaiton. If I use Server Authentication, I'm concerned that the username and password for the account will be stored in plain text in the app.config file, and therefore leave the database vulnerable. Using Windows Authenticaiton will avoid this issue, however it would mean giving every member of staff within our organisation read/write access to the database in order to run the app correctly. Whilst this is ok, it also means that they can easily connect to the database themselves via other means and directly alter the data outside of the app. I'm guessing there is someting really obvious I'm missing here, but I've been googling all evening to no avail. Any advice/guidance would be much appreciated! Peter Addition - my project is Windows Form based not ASP.NET - is encrypting the app.config file still the right answer? If it is, does anyone have any examples that are not ASP.NET based?

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• Custom Navigation Bar (html/css) for a website

  - by MikeStardust

  I am making a website and though of a cool navigation bar that is suppose to look like this: And using css code: #navigation ul { list-style: none; text-align: center; } #navigation li { display: inline; } #navigation li a { text-indent: -5000px; display: inline-block; height: 40px; } #navigation li a.profile { width: 240px; background: url("http://i.imgur.com/pphPRAA.png"); text-decoration: none; } #navigation li a.profile:hover { background: url("http://i.imgur.com/bDwcbXd.png"); background-position: -240px; text-decoration: none; } #navigation li a.profile:current { background: url("http://i.imgur.com/bDwcbXd.png"); background-position: -240px; background-repeat: no-repeat; text-decoration: none; } I managed to make it look like this: http://pokemasters.freeiz.com/bare.html I just ran out of ideas.... i got the images that i made seperatly, a navbar: & buttons: I'm looking for a full width navbar that adjusts itself to different screens, is located at the bottom of the screen, red buttons while active or hovered and white buttons while normal, with that pokeball line right on top of it and overlaying the buttons Can someone point me in the right direction please?? thank you:)

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• How can I use a meter-style progress bar?

  - by Yadyn

  In Vista/7, the Windows Explorer shell window makes use of a special kind of static progress bar to display hard drive space. With default styles, this bar is blue colored and non-animated. It also turns red colored when it gets close to being full (low disk space). Using messaging, I can tell the Windows Forms ProgressBar control to update its state to Paused and Error (yellow and red colored, respectively), which works fine, but these are still specific to progress. In the Windows User Experience Guidelines, it specifically points out this "meter" variant of the Progress Bar: This pattern isn't a progress bar, but it is implemented using the progress bar control. Meters have a distinct look to differentiate them from true progress bars. They say it "is implemented using the progress bar control", so... how? What message could I send to the control to have it behave this way? I've seen that you can send messages for setting the bar color, but the documentation says these calls are ignored when visual styles are enabled. Nothing else in the Windows API documentation for raw ProgressBar controls seemed to suggest a way to do this. Am I just stuck making a custom drawn bar? I'd really like to utilize the OS whenever possible so that the application will appear consistent throughout different OS versions. I realize that pre-Vista versions probably won't support this, though. I'm looking for a Windows Forms solution, but I wonder if it is even exposed at all via Win32 API.

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• How many users are sufficient to make a heavy load for web application

  - by galymzhan

  I have a web application, which has been suffering high load recent days. The application runs on single server which has 8-core Intel CPU and 4gb of RAM. Software: Drupal 5 (Apache 2, PHP5, MySQL5) running on Debian. After reaching 500 authenticated and 200 anonymous users (simultaneous), the application drastically decreases its performance up to total failure. The biggest load comes from authenticated users, who perform activities, causing insert/update/deletes on db. I think mysql is a bottleneck. Is it normal to slow down on such number of users? EDIT: I forgot to mention that I did some kind of profiling. I runned commands top, htop and they showed me that all memory was being used by MySQL! After some time MySQL starts to perform terribly slow, site goes down, and we have to restart/stop apache to reduce load. Administrators said that there was about 200 active mysql connections at that moment. The worst point is that we need to solve this ASAP, I can't do deep profiling analysis/code refactoring, so I'm considering 2 ways: my tables are MyIsam, I heard they use table-level locking which is very slow, is it right? could I change it to Innodb without worry? what if I take MySQL, and move it to dedicated machine with a lot of RAM?

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• Testing When Correctness is Poorly Defined?

  - by dsimcha

  I generally try to use unit tests for any code that has easily defined correct behavior given some reasonably small, well-defined set of inputs. This works quite well for catching bugs, and I do it all the time in my personal library of generic functions. However, a lot of the code I write is data mining code that basically looks for significant patterns in large datasets. Correct behavior in this case is often not well defined and depends on a lot of different inputs in ways that are not easy for a human to predict (i.e. the math can't reasonably be done by hand, which is why I'm using a computer to solve the problem in the first place). These inputs can be very complex, to the point where coming up with a reasonable test case is near impossible. Identifying the edge cases that are worth testing is extremely difficult. Sometimes the algorithm isn't even deterministic. Usually, I do the best I can by using asserts for sanity checks and creating a small toy test case with a known pattern and informally seeing if the answer at least "looks reasonable", without it necessarily being objectively correct. Is there any better way to test these kinds of cases?

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• How to detect whether an EventWaitHandle is waiting?

  - by AngryHacker

  I have a fairly well multi-threaded winforms app that employs the EventWaitHandle in a number of places to synchronize access. So I have code similar to this: List<int> _revTypes; EventWaitHandle _ewh = new EventWaitHandle(false, EventResetMode.ManualReset); void StartBackgroundTask() { _ewh.Reset(); Thread t = new Thread(new ThreadStart(LoadStuff)); t.Start(); } void LoadStuff() { _revTypes = WebServiceCall.GetRevTypes() // ...bunch of other calls fetching data from all over the place // using the same pattern _ewh.Set(); } List<int> RevTypes { get { _ewh.WaitOne(); return _revTypes; } } Then I just call .RevTypes somewehre from the UI and it will return data to me when LoadStuff has finished executing. All this works perfectly correctly, however RevTypes is just one property - there are actually several dozens of these. And one or several of these properties are holding up the UI from loading in a fast manner. Short of placing benchmark code into each property, is there a way to see which property is holding the UI from loading? Is there a way to see whether the EventWaitHandle is forced to actually wait?

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• Automating Excel 2010 using F#

  - by Clive Norman

  I have been searching for a FAQ to tell me how to open a Excel Workbook/Worksheet and also how to Save the File once I have finished. I notice that in most FAQ and all the books I have purchased on F# one is show how to create a new Workbook/Worksheet but is never shown how to either open or Save it. Being a newbie to F# I would very much appreciate it if anyone could kindly provide me with either an answer or perhaps a few pointers? Update As for why F# and not C# or VB? I am pleased to say that inspite of being a newbie (with the exception of Forth, VBA & Excel 2003, 2007 & 2010 and Visual Basic) I can do this in both VB, VBA & C# and since I've been retired on medical grounds, with plenty of time unfortunately on my hands, I like to continually set myself challenges to keep my little grey cells active and being a sucker for trying new languages....well! F# is now an intergral part of Visual Studio 2010 so I thought - why not. Consider this - if we are not willing to use or at least try a new languages - I would always be wonder if I might have prefer it to VBA, VB, C# ..... and if you look at it from another point of view, if no one is going to use it - why create it in the first place? I suppose you can say if cave men hadn't experimented and made fire by rubbing two sticks together - where would we be now and would matches have been invented? Although an complete answer would be good, I prefer a few pointers, to keep my challenge going. And lastly but not least - thank you for taking the trouble to respond!

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• Launch a new page in Zend/php on button click

  - by BlueMonster

  PHP & Zend Noob here I've downloaded the skeleton project from here: https://github.com/zendframework/ZendSkeletonApplication Say i want to open a new page that simply displays "hello world" text if click on the "ZF2 Development Portal" button(bottom left green button) on the page that launches --- how do i do this? See image: I've read through this tutorial, but i'm not sure how the model, view, or controller are actually launched? See tutorial: http://blog.wilgucki.pl/2012/07/tworzenie-modulw-w-zend-framework-2.html From looking at the code, i know that i will have to change this line of code: <div class="span4"> <h2><?php echo $this->translate('Follow Development') ?></h2> <p><?php echo sprintf($this->translate('Zend Framework 2 is under active development. If you are interested in following the development of ZF2, there is a special ZF2 portal on the official Zend Framework website which provides links to the ZF2 %swiki%s, %sdev blog%s, %sissue tracker%s, and much more. This is a great resource for staying up to date with the latest developments!'), '<a href="http://framework.zend.com/wiki/display/ZFDEV2/Home">', '</a>', '<a href="http://framework.zend.com/zf2/blog">', '</a>', '<a href="http://framework.zend.com/issues/browse/ZF2">', '</a>') ?></p> <p><a class="btn btn-success" href="http://framework.zend.com/zf2" target="_blank"><?php echo $this->translate('ZF2 Development Portal') ?> &raquo;</a></p> </div> More specifically this line: <p><a class="btn btn-success" href="http://framework.zend.com/zf2" target="_blank"><?php echo $this->translate('ZF2 Development Portal') ?> &raquo;</a></p> but i'm really confused as to what i'm supposed to change it to in order to launch a new page. Any ideas? Thanks in advance!

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• Questions about the Backpropogation Algorithm

  - by Colemangrill

  I have a few questions concerning backpropogation. I'm trying to learn the fundamentals behind neural network theory and wanted to start small, building a simple XOR classifier. I've read a lot of articles and skimmed multiple textbooks - but I can't seem to teach this thing the pattern for XOR. Firstly, I am unclear about the learning model for backpropogation. Here is some pseudo-code to represent how I am trying to train the network. [Lets assume my network is setup properly (ie: multiple inputs connect to a hidden layer connect to an output layer and all wired up properly)]. SET guess = getNetworkOutput() // Note this is using a sigmoid activation function. SET error = desiredOutput - guess SET delta = learningConstant * error * sigmoidDerivative(guess) For Each Node in inputNodes For Each Weight in inputNodes[n] inputNodes[n].weight[j] += delta; // At this point, I am assuming the first layer has been trained. // Then I recurse a similar function over the hidden layer and output layer. // The prime difference being that it further divi's up the adjustment delta. I realize this is probably not enough to go off of, and I will gladly expound on any part of my implementation. Using the above algorithm, my neural network does get trained, kind of. But not properly. The output is always XOR 1 1 [smallest number] XOR 0 0 [largest number] XOR 1 0 [medium number] XOR 0 1 [medium number] I can never train the [1,1] [0,0] to be the same value. If you have any suggestions, additional resources, articles, blogs, etc for me to look at I am very interested in learning more about this topic. Thank you for your assistance, I appreciate it greatly!

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• ctrl+click or shift+click not always firing the onclick event

  - by Erik

  Hi, I recently discovered that different browsers handle the onclick event differently when the control of shift key is pressed. Same thing for following links with the middle mouse button. <a href="http://www.example.com/" onclick="alert('onclick');">go to example.com</a> Onclick browser support table Mouse Keyboard Chrome Firefox Safari Opera IE5.5 IE6 IE7 IE8 IE9 Left None yes yes yes yes yes yes yes yes yes Left Ctrl yes yes yes yes ? yes no no ? Left Shift yes yes yes yes ? yes yes yes ? Middle None yes no yes no ? N/A no no ? Can someone please fill in the question marks for me? Also; I'm wondering if the behaviour differs for each version of Chrome, Firefox, Safari and Opera. Finding a logical pattern in this behaviour would be even nicer, but I don't think there is :). Thanks a lot.

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• asp.net mvc 2 - return JavaScript with View

  - by Tomaszewski

  Hi, using ASP.NET MVC 2 I have a navigation menu inside my Master Page. In the navigation menu, I am trying add a class to the that the current page relates to (i.e., home page will add class="active" to the Home button). I'm trying to consider scalability and the fact that I don't want to change individual pages if the navigation changes later. The only way I can think of doing this is: Add JavaScript to each individual View that will add the class when the DOM is ready Return JavaScript when return View() occurs on point (2), I am unsure how to do. Thusfar I have been doing the following in my controller: public ActionResult Index() { ViewData["messege"] = JavaScript("<script type='text/javascript' language='javascript'> $(document).ready(function () { console.log('hi hi hi'); }); </script>"); return View(); } but in my view, when I call: <%: ViewData["messege"] %> I get: System.Web.Mvc.JavaScriptResult as the result Would you guys have any ideas on How to solve the navigation menu probelem, other than the solutions I've listed return JavaScript along with your view from the Controller Thanks, in advanced!

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• How to maintain form state after Post-Redirect-Get in ASP.net?

  - by Ian Boyd

  Imagine a page with a form input: Search Criteria: crackers                   From: [email protected]           To: [email protected]       Subject: How to maintain form state with PRG? Message: Imagine a page with form input:                         Send After the user clicks Send, the server will instruct to client to Redirect, as part of the Post-Redirect-Get pattern. POST /mail/u/compose HTTP/1.1 303 See Other Location: http://stackoverflow.com/mail/u/compose And the client will issue a GET of the new page. The problem is that some elements of the existing form are lost: Search Criteria:                    It gets worse when there are a few drop-downs, and checkboxes. How can i maintain form state in using Post-Redirect-Get in ASP.net, given that the viewstate is then non-existent. Bonus Reading ASP.NET: How to redirect, prefilling form data?

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• How do I check to see if a scalar has a compiled regex in it with Perl?

  - by Robert P

  Let's say I have a subroutine/method that a user can call to test some data that (as an example) might look like this: sub test_output { my ($self, $test) = @_; my $output = $self->long_process_to_get_data(); if ($output =~ /\Q$test/) { $self->assert_something(); } else { $self->do_something_else(); } } Normally, $test is a string, which we're looking for anywhere in the output. This was an interface put together to make calling it very easy. However, we've found that sometimes, a straight string is problematic - for example, a large, possibly varying number of spaces...a pattern, if you will. Thus, I'd like to let them pass in a regex as an option. I could just do: $output =~ $test if I could assume that it's always a regex, but ah, but the backwards compatibility! If they pass in a string, it still needs to test it like a raw string. So in that case, I'll need to test to see if $test is a regex. Is there any good facility for detecting whether or not a scalar has a compiled regex in it?

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• How much is too much memory allocation in NDK?

  - by Maximus

  The NDK download page notes that, "Typical good candidates for the NDK are self-contained, CPU-intensive operations that don't allocate much memory, such as signal processing, physics simulation, and so on." I came from a C background and was excited to try to use the NDK to operate most of my OpenGL ES functions and any native functions related to physics, animation of vertices, etc... I'm finding that I'm relying quite a bit on Native code and wondering if I may be making some mistakes. I've had no trouble with testing at this point, but I'm curious if I may run into problems in the future. For example, I have game struct defined (somewhat like is seen in the San-Angeles example). I'm loading vertex information for objects dynamically (just what is needed for an active game area) so there's quite a bit of memory allocation happening for vertices, normals, texture coordinates, indices and texture graphic data... just to name the essentials. I'm quite careful about freeing what is allocated between game areas. Would I be safer setting some caps on array sizes or should I charge bravely forward as I'm going now?

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• Bash PATH: How long is too long?

  - by ajwood

  Hi, I'm currently designing a software quarantine pattern to use on Ubuntu. I'm not sure how standard "quarantine" is in this context, so here is what I hope to accomplish... Inside a particular quarantine is all of the stuff one needs to run an application (bin, share, lib, etc.). Ideally, the quarantine has no leaks, which means it's not relying on any code outside of itself on the system. A quarantine can be defined as a set of executables (and some environment settings needed to make them run). I think it will be beneficial to separate the built packages enough such that upgrading to a newer version of the quarantine won't require rebuilding the whole thing. I'll be able to update just a few packages, and then the new quarantine can use some of old parts and some of the new parts. One issue I'm wondering about is the environment variables I'll be setting up to use a particular quarantines. Is there a hard limit on how big PATH can be? (either in number of characters, or in the number of directories it contains) Might a path be so long that it affects performance? Thanks very much, Andrew p.s. Any other wisdom that might help my design would be greatly appreciated :)

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• MySql Check if NOW() falls within a weekday/time range

  - by Niall

  I have a table as follows: CREATE TABLE `zonetimes` ( `id` int(11) unsigned NOT NULL AUTO_INCREMENT, `zone_id` int(10) unsigned NOT NULL, `active_from_day` tinyint(1) unsigned NOT NULL DEFAULT '2', `active_to_day` tinyint(1) unsigned NOT NULL DEFAULT '2', `active_from` time NOT NULL, `active_to` time NOT NULL PRIMARY KEY (`id`) ) ENGINE=MyISAM ; So, a user could add a time entry starting on a particular day and time and ending on a particular day and time, eg: Between Monday 08:00 and Friday 18:00 or Between Thursday 15:00 and Tuesday 15:00 (Note the crossover at the end of the week). I need to query this data and determine if a zone is currently active (NOW(), DAYOFWEEK() etc)... This is turning out to be quite tricky. If I didn't have overlaps, eg: from 'Wednesday 8pm to Tuesday 4am' or from 'Thursday 4pm to Tuesday 4pm' this would be easy with BETWEEN. Also, need to allow a user to add for the entire week, eg: Monday 8am - Monday 8am (This should be easy enough, eg: where (active_from_day=active_to_day AND active_from=active_to) OR .. Any ideas? Note: I found a similar question here Timespan - Check for weekday and time of day in mysql but it didn't get an answer. One of the suggestions was to store each day as a separate row. I would much rather store one time span for multiple days though.

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• OOP design issue: Polymorphism

  - by Graham Phillips

  I'm trying to solve a design issue using inheritance based polymorphism and dynamic binding. I have an abstract superclass and two subclasses. The superclass contains common behaviour. SubClassA and SubClassB define some different methods: SubClassA defines a method performTransform(), but SubClassB does not. So the following example 1 var v:SuperClass; 2 var b:SubClassB = new SubClassB(); 3 v = b; 4 v.performTransform(); would cause a compile error on line 4 as performTransform() is not defined in the superclass. We can get it to compile by casting... (v as SubClassA).performTransform(); however, this will cause a runtime exception to be thrown as v is actually an instance of SubClassB, which also does not define performTransform() So we can get around that by testing the type of an object before casting it: if( typeof v == SubClassA) { (cast v to SubClassA).performTransform(); } That will ensure that we only call performTransform() on v's that are instances of SubClassA. That's a pretty inelegant solution to my eyes, but at least its safe. I have used interface based polymorphism (interface meaning a type that can't be instantiated and defines the API of classes that implement it) in the past, but that also feels clunky. For the above case, if SubClassA and SubClassB implemented ISuperClass that defined performTransform, then they would both have to implement performTransform(). If SubClassB had no real need for a performTransform() you would have to implement an empty function. There must be a design pattern out there that addresses the issue.

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• re.sub emptying list

  - by jmau5

  def process_dialect_translation_rules(): # Read in lines from the text file specified in sys.argv[1], stripping away # excess whitespace and discarding comments (lines that start with '##'). f_lines = [line.strip() for line in open(sys.argv[1], 'r').readlines()] f_lines = filter(lambda line: not re.match(r'##', line), f_lines) # Remove any occurances of the pattern '\s*<=>\s*'. This leaves us with a # list of lists. Each 2nd level list has two elements: the value to be # translated from and the value to be translated to. Use the sub function # from the re module to get rid of those pesky asterisks. f_lines = [re.split(r'\s*<=>\s*', line) for line in f_lines] f_lines = [re.sub(r'"', '', elem) for elem in line for line in f_lines] This function should take the lines from a file and perform some operations on the lines, such as removing any lines that begin with ##. Another operation that I wish to perform is to remove the quotation marks around the words in the line. However, when the final line of this script runs, f_lines becomes an empty lines. What happened? Requested lines of original file: ## English-Geek Reversible Translation File #1 ## (Moderate Geek) ## Created by Todd WAreham, October 2009 "TV show" <=> "STAR TREK" "food" <=> "pizza" "drink" <=> "Red Bull" "computer" <=> "TRS 80" "girlfriend" <=> "significant other"

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