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  • What is the the relation between programming and mathematics?

    - by Math Grad
    Programmers seem to think that their work is quite mathematical. I understand this when you try to optimize something in performance, find the most efficient alogithm, etc.. But it patently seems false when you look at a billing application for a shop, or a systems software riddled with I/O calls. So what is it exactly? Is computation and associated programming really mathematical? Here I have in mind particularly the words of the philosopher Schopenhauer in mind: That arithmetic is the basest of all mental activities is proved by the fact that it is the only one that can be accomplished by means of a machine. Take, for instance, the reckoning machines that are so commonly used in England at the present time, and solely for the sake of convenience. But all analysis finitorum et infinitorum is fundamentally based on calculation. Therefore we may gauge the “profound sense of the mathematician,” of whom Lichtenberg has made fun, in that he says: “These so-called professors of mathematics have taken advantage of the ingenuousness of other people, have attained the credit of possessing profound sense, which strongly resembles the theologians’ profound sense of their own holiness.” I lifted the above quote from here. It seems that programmers are doing precisely the sort of mechanized base mental activity the grand old man is contemptuous about. So what exactly is the deal? Is programming really the "good" kind of mathematics, or just the baser type, or altogether something else just meant for business not to be confused with a pure discipline?

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  • (Not So) Silly Objective-C inheritance problem when using property - GCC Bug?

    - by Ben Packard
    Update 2 - Many people are insisting I need to declare an iVar for the property. Some are saying not so, as I am using Modern Runtime (64 bit). I can confirm that I have been successfully using @property without iVars for months now. Therefore, I think the 'correct' answer is an explanation as to why on 64bit I suddenly have to explicitly declare the iVar when (and only when) i'm going to access it from a child class. The only one I've seen so far is a possible GCC bug (thanks Yuji). Not so simple after all... Update - I messed up one line of the original copy and paste - corrected. The @property call was missing (nonatomic, retain) but is a red herring - STILL NEED AN ANSWER! Thanks. I've been scratching my head with this for a couple of hours - I haven't used inheritance much. Here I have set up a simple Test B class that inherits from Test A, where an ivar is declared. But I get the compilation error that the variable is undeclared. This only happens when I add the property and synthesize declarations - works fine without them. TestA Header: #import <Cocoa/Cocoa.h> @interface TestA : NSObject { NSString *testString; } @end TestA Implementation is empty: #import "TestA.h" @implementation TestA @end TestB Header: #import <Cocoa/Cocoa.h> #import "TestA.h" @interface TestB : TestA { } @property (nonatomic, retain) NSString *testProp; @end TestB Implementation (Error - 'testString' is undeclared) #import "TestB.h" @implementation TestB @synthesize testProp; - (void)testing{ NSLog(@"test ivar is %@", testString); } @end

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  • Best way to randomly select columns from random rows of SQL results.

    - by LesterDove
    A search of SO yields many results describing how to select random rows of data from a database table. My requirement is a bit different, though, in that I'd like to select individual columns from across random rows in the most efficient/random/interesting way possible. To better illustrate: I have a large Customers table, and from that I'd like to generate a bunch of fictitious demo Customer records that aren't real people. I'm thinking of just querying randomly from the Customers table, and then randomly pairing FirstNames with LastNames, Address, City, State, etc. So if this is my real Customer data (simplified): FirstName LastName State ========================== Sally Simpson SD Will Warren WI Mike Malone MN Kelly Kline KS Then I'd generate several records that look like this: FirstName LastName State ========================== Sally Warren MN Kelly Malone SD Etc. My initial approach works, but it lacks the elegance that I'm hoping the final answer will provide. (I'm particularly unhappy with the repetitiveness of the subqueries, and the fact that this solution requires a known/fixed number of fields and therefore isn't reusable.) SELECT FirstName = (SELECT TOP 1 FirstName FROM Customer ORDER BY newid()), LastName= (SELECT TOP 1 LastNameFROM Customer ORDER BY newid()), State = (SELECT TOP 1 State FROM Customer ORDER BY newid()) Thanks!

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  • Best practises for Magento Deployment

    - by Spongeboy
    I am looking setting up a deployment process for a highly customised Magento site, and was wondering how other people do this. I will be setting up dev, UAT and prod environments. All the Magento files will be in source control (SVN). At this stage, I can't see any requirements for changing the DB, so the 3 databases will be manually maintained. Specifically, How do you apply Magento upgrades? (Individually in each env, or on dev then roll out, or just give up on upgrades?) What files/folders do leave alone in each environment (e.g. magento/app/etc/local.xml) Do you restrict developers to editing specific files/folders? Do you restrict theme designers to editing specific files/folders? How do you manage database changes? Theme Designer Files/Folders Designers can restricted to editing the following folders- app/design/frontend/your_interface/your_theme/layout/ app/design/frontend/your_interface/your_theme/template/ app/design/frontend/your_interface/your_theme/locale/ skin/frontend/your_interface/your_theme/ Extension Developer Files/Folders Extension developers can edit the following folders/files- /app/code/local /app/etc/modules/<Namespace>_<Module>.xml Database environment management As the store's base URL is stored in the database, you cannot just copy databases between environments. Options include- Overriding the base url in php. Blog article on setting up dev and staging databases Changing the base url in the database after copying. (Where is this stored?) Doing a MySQLDump or backup, then doing a replace on the URL in the SQL file.

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  • Using Facebook Login to create a user?

    - by andbeyond
    I've read this SO post which led me to this FB policy page, which seemed to include some pertinent information, but I'd like more of a community response, maybe some experienced FB API people who know the limits. My question is if I can use Facebook's Login api to, essentially, create a new user on my website. I really would just like to allow users to easily "transfer" some data from FB in order to more easily create a new account on my site. I realize, first and foremost, that I would obviously announce to the user that by click "submit" in the form, that they are creating a separate account on my site. Pertinent blocks on the policy page state: You may cache data you receive through use of the Facebook API in order to improve your application’s user experience, but you should try to keep the data up to date. This permission does not give you any rights to such data. Which doesn't look good for me, but also this: If you stop using Platform or we disable your application, you must delete all data you have received through use of the Facebook API unless: (a) it is basic account information; or (b) you have received explicit consent from the user to retain their data. Which, in my case, I would be satisfying part B. I would be asking the user's permission to retain the data, as I am simply using Facebook as a conveience to the user when creating an account. I also realize that Facebook has a registration API, but this would require a Facebook styled login form, along with my own sites login form, and I'd rather one interface, as this makes it easier for me on the front and back end. Any thoughts?

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  • What are some good ways to store performance statistics in a database for querying later?

    - by Nathan
    Goal: Store arbitrary performance statistics of stuff that you care about (how many customers are currently logged on, how many widgets are being processed, etc.) in a database so that you can understand what how your servers are doing over time. Assumptions: A database is already available, and you already know how to gather the information you want and are capable of putting it in the database however you like. Some Ideal Attributes of a Solution Causes no noticeable performance hit on the server being monitored Has a very high precision of measurement Does not store useless or redundant information Is easy to query (lends itself to gathering/displaying useful information) Lends itself to being graphed easily Is accurate Is elegant Primary Questions 1) What is a good design/method/scheme for triggering the storing of statistics? 2) What is a good database design for how to actually store the data? Example answers...that are sort of vague and lame... 1) I could, once per [fixed time interval], store a row of data with all the performance measurements I care about in each column of one big flat table indexed by timestamp and/or server. 2) I could have a daemon monitoring performance stuff I care about, and add a row whenever something changes (instead of at fixed time intervals) to a flat table as in #1. 3) I could trigger either as in #2, but I could store information about each aspect of performance that I'm measuring in separate tables, opening up the possibility of adding tons of rows for often-changing items, and few rows for seldom-changing items. Etc. In the end, I will implement something, even if it's some super-braindead approach I make up myself, but I'm betting there are some really smart people out there willing to share their experiences and bright ideas!

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  • PHP programmer wanting to learn Flash game development

    - by grokker
    Hi! I'm currently a PHP programmer and one of my childhood dreams is to create a game. A game to show my friends or my children when the time comes :) The problem is I don't know Flash. I'm not great at drawing stuff or even artistic. I could program a little with Javascript and I could consider myself intermediate with jQuery. So my question is, how do I get started? What books do I read first? What's the steps that I should take on this journey? Thank you SO friends. I hope you all could help me create something I could be proud of :) P.S. I'm just assuming that Flash is the easiest way to create and show to other people my game. Anyway I'm very open for other suggestions! My game in mind is a side scroller about an indiana jones type of character and the setting is on the jungle with trees and snakes and a lot of animals!

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  • IHttpModule not being applied to virtual directory

    - by arthurdent510
    I have a network folder that is mapped to my iis app as a virtual directory and I'm trying to do some authentication for files that are located there with an ihttpmodule. I've verified that the ihttpmodule is firing properly for anything else in my app, just not the files located in virtual directory. Most of what I've found is that the directory can't be listed as an application (which it isn't), and everything should work. The other solution that I found was to add the the module tag to the tag, but that didn't seem to help either. Everything that I've found talks about stopping this from happening. So my question is what could be set that is causing this to not work? Is there a certain execute permission that needs to be set? Any other iis settings that could cause this? It is an mvc app, and this is how my directory structure is laid out: server/app <- my application folder server/app/content/downloads <- downloads is the virtual directory Do I have to add the virtual directory directly under my app directory? Is that part of the problem? I don't have direct control of the server my code is running on, so testing things out is a bit of a pain... so I was looking for some more thoughts before starting to send emails off to my operations people. Thanks!

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  • How 'terse' is too terse? -- Practical guidelines for expressing as much intent in as few characters

    - by Christopher Altman
    First, I love writing as little code as possible. I think, and please correct me, one of the golden rules of programming is to express your code in as few of character as possible while maintaining human readability. But I can get a little carried away. I can pack three or four lines into one statement, something like $startDate = $dateTime > time() ? mktime(0,0,0,date('m',time()-86400),date('d',time()*2),2011) : time(); (Note: this is a notional example) I can comprehend the above code when reading it. I prefer 'mushing' it all together because having less lines per page is a good thing to me. So my question: When writing code and thinking about how compact or terse you can express yourself, what are some guidelines you use? Do you write multiple lines because you think it helps other people? Do you write as little as possible, but use comments? Or do you always look for the way to write as little code as possible and enjoy the rewards of compact statements? (Just one slightly off topic comment: I love the Perl one-liners, but that is not what I am talking about here)

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  • Optimization in Python - do's, don'ts and rules of thumb.

    - by JV
    Well I was reading this post and then I came across a code which was: jokes=range(1000000) domain=[(0,(len(jokes)*2)-i-1) for i in range(0,len(jokes)*2)] I thought wouldn't it be better to calculate the value of len(jokes) once outside the list comprehension? Well I tried it and timed three codes jv@Pioneer:~$ python -m timeit -s 'jokes=range(1000000);domain=[(0,(len(jokes)*2)-i-1) for i in range(0,len(jokes)*2)]' 10000000 loops, best of 3: 0.0352 usec per loop jv@Pioneer:~$ python -m timeit -s 'jokes=range(1000000);l=len(jokes);domain=[(0,(l*2)-i-1) for i in range(0,l*2)]' 10000000 loops, best of 3: 0.0343 usec per loop jv@Pioneer:~$ python -m timeit -s 'jokes=range(1000000);l=len(jokes)*2;domain=[(0,l-i-1) for i in range(0,l)]' 10000000 loops, best of 3: 0.0333 usec per loop Observing the marginal difference 2.55% between the first and the second made me think - is the first list comprehension domain=[(0,(len(jokes)*2)-i-1) for i in range(0,len(jokes)*2)] optimized internally by python? or is 2.55% a big enough optimization (given that the len(jokes)=1000000)? If this is - What are the other implicit/internal optimizations in Python ? What are the developer's rules of thumb for optimization in Python? Edit1: Since most of the answers are "don't optimize, do it later if its slow" and I got some tips and links from Triptych and Ali A for the do's. I will change the question a bit and request for don'ts. Can we have some experiences from people who faced the 'slowness', what was the problem and how it was corrected? Edit2: For those who haven't here is an interesting read Edit3: Incorrect usage of timeit in question please see dF's answer for correct usage and hence timings for the three codes.

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  • How does CDI injection work in MDBs and @Scheduled beans?

    - by Nils-Petter Nilsen
    I'm working on a large Java EE 6 application that is deployed on JBoss 6 Final. My current tasks involve using @Inject consistently instead of @EJB, but I'm running into some problems on some types of beans, specifically @MessageDriven beans and beans with @Scheduled methods. What happens is that if I'm unlucky with the timing (for @Schedule) or if there are messages in the MDBs' queues at startup, instantiation of the beans will fail because the injected resources (which are EJBs themselves) are not bound yet. Because I use @Inject, I'm guessing that the EJB container considers my beans to be ready, since the container itself does not care about @Inject; it probably simply assumes that since there are no @EJB injections, the beans are ready for use. The injected CDI proxies will then fail because the resources to inject aren't actually bound yet. Tiny example: @Stateless @LocalBean public class MySupportingBean { public void doSomething() { ... } } @Singleton public class MyScheduledBean { @Inject private MySupportingBean supportingBean; @Schedule(second = "*/1", hour = "*", minute = "*", persistent = false) public void onTimeout() { supportingBean.doSomething(); } } The above example will probably not fail often because there are only two beans, but the project I'm working on binds lots of EJBs, which will amplify the problem. But it might fail because there is no guarantee that MySupportingBean is bound first, and if onTimeout is invoked before MySupportingBean is bound, then instantiation of MyScheduledBean will fail. If I used @EJB instead, MyScheduledBean wouldn't be bound until the dependency to MySupportingBean was satisfied. Note that the example will not fail in onTimeout itself, but when CDI attempts to inject MySupportingBean. I've read a lot of posts on different forums where many people argue that @Inject is always better. Generally, I agree, but how do they handle @Schedule or @MessageDriven combined with @Inject? In my experience, it comes down to dumb luck whether the beans will work or not in those cases, and the beans will fail arbitrarily, depending on which order the EJBs are deployed in, and when @Schedule or onMessage are invoked.

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  • ASP.NET MVC: Returning a view with querystring intact

    - by ajbeaven
    I'm creating a messaging web app in ASP.NET and are having some problems when displaying an error message to the user if they go to send a message and there is something wrong. A user can look through profiles of people and then click, 'send a message'. The following action is called (url is /message/create?to=username) and shows them a page where they can enter their message and send it: public ActionResult Create(string to) { ViewData["recipientUsername"] = to; return View(); } On the page that is displayed, the username is entered in to a hidden input field. When the user clicks 'send': [AcceptVerbs(HttpVerbs.Post)] public ActionResult Create(FormCollection collection, string message) { try { //do message stuff that errors out } catch { ModelState.AddModelErrors(message.GetRuleViolations()); //adding errors to modelstate } return View(); } So now the error message is displayed to the user fine, however the url is changed in that it no longer has the querystring (/message/create). Again, this would be fine except that when the user clicks the refresh button, the page errors out as the Create action no longer has the 'to' parameter. So I'm guessing that I need to maintain my querystring somehow. Is there any way to do this or do I need to use a different method altogether?

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  • Simplest way to automatically alter "const" value in Java during compile time

    - by Michael Mao
    Hi all: This is a question corresponds to my uni assignment so I am very sorry to say I cannot adopt any one of the following best practices in a short time -- you know -- assignment is due tomorrow :( link to Best way to alter const in Java on StackOverflow Basically the only task (I hope so) left for me is the performance tuning. I've got a bunch of predefined "const" values in my single-class agent source code like this: //static final values private static final long FT_THRESHOLD = 400; private static final long FT_THRESHOLD_MARGIN = 50; private static final long FT_SMOOTH_PRICE_IDICATOR = 20; private static final long FT_BUY_PRICE_MODIFIER = 0; private static final long FT_LAST_ROUNDS_STARTTIME = 90; private static final long FT_AMOUNT_ADJUST_MODIFIER = 5; private static final long FT_HISTORY_PIRCES_LENGTH = 10; private static final long FT_TRACK_DURATION = 5; private static final int MAX_BED_BID_NUM_PER_AUC = 12; I can definitely alter the values manually and then compile the code to give it another go around. But the execution time for a thorough "statistic analysis" usually requires over 2000 times of execution, which will typically lasts more than half an hour on my own laptop... So I hope there is a way to alter values using other ways than dig into the source code to change the "const" values there, so I can automatically distributed compiled code to other people's PC and let them run the statistic analysis instead. One other reason for a automatically value adjustment is that I can try using my own agent to defeat itself by choosing different "const" values. Although my values are derived from previous history and statistical results, they are far from the most optimized values. I hope there is a easy way so I can quickly adopt that so to have a good sleep tonight while the computer does everything for me... :) Any hints on this sort of stuff? Any suggestion is welcomed and much appreciated.

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  • SQL select row into a string variable without knowing columns

    - by Brandi
    Hello, I am new to writing SQL and would greatly appreciate help on this problem. :) I am trying to select an entire row into a string, preferably separated by a space or a comma. I would like to accomplish this in a generic way, without having to know specifics about the columns in the tables. What I would love to do is this: DECLARE @MyStringVar NVARCHAR(MAX) = '' @MyStringVar = SELECT * FROM MyTable WHERE ID = @ID AS STRING But what I ended up doing was this: DECLARE @MyStringVar = '' DECLARE @SecificField1 INT DECLARE @SpecificField2 NVARCHAR(255) DECLARE @SpecificField3 NVARCHAR(1000) ... SELECT @SpecificField1 = Field1, @SpecificField2 = Field2, @SpecificField3 = Field3 FROM MyTable WHERE ID = @ID SELECT @StringBuilder = @StringBuilder + CONVERT(nvarchar(10), @Field1) + ' ' + @Field2 + ' ' + @Field3 Yuck. :( I have seen some people post stuff about the COALESCE function, but again, I haven't seen anyone use it without specific column names. Also, I was thinking, perhaps there is a way to use the column names dynamically getting them by: SELECT [COLUMN_NAME] FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_NAME = 'MyTable' It really doesn't seem like this should be so complicated. :( What I did works for now, but thanks ahead of time to anyone who can point me to a better solution. :) EDIT: Got it fixed, thanks to everyone who answered. :)

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  • What are the worst examples of moral failure in the history of software engineering?

    - by Amanda S
    Many computer science curricula include a class or at least a lecture on disasters caused by software bugs, such as the Therac-25 incidents or Ariane 5 Flight 501. Indeed, Wikipedia has a list of software bugs with serious consequences, and a question on StackOverflow addresses some of them too. We study the failures of the past so that we don't repeat them, and I believe that rather than ignoring them or excusing them, it's important to look at these failures squarely and remind ourselves exactly how the mistakes made by people in our profession cost real money and real lives. By studying failures caused by uncaught bugs and bad process, we learn certain lessons about rigorous testing and accountability, and we make sure that our innocent mistakes are caught before they cause major problems. There are kinds of less innocent failure in software engineering, however, and I think it's just as important to study the serious consequences caused by programmers motivated by malice, greed, or just plain amorality. Thus we can learn about the ethical questions that arise in our profession, and how to respond when we are faced with them ourselves. Unfortunately, it's much harder to find lists of these failures--the only one I can come up with is that apocryphal "DOS ain't done 'til Lotus won't run" story. What are the worst examples of moral failure in the history of software engineering?

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  • Consuming WCF Web Service

    - by Debby
    Hi, I have a simple web service running and I have a console application client consuming the service. I did have issues getting this running and I had been helped by some wonderful people in this community. I have another problem: if I want to call the service from the client in a loop, it doesn't work. It works only for the first time and then it just keeps waiting. Why is this happening and how can I resolve it. The code: namespace WebService { [ServiceContract] public interface IService { [OperationContract(Name="Result")] [WebGet(UriTemplate = "/")] Stream Result(); } public class Service:IService { public Stream Result() { // read a file from the server and return it as stream } } } The client: namespace WebServiceClient { [ServiceContract] public interface IService { [OperationContract(Name="Result")] [WebGet(UriTemplate = "/")] Stream Result(); } } static void Main() { Console.WriteLine("Press enter when the service is available"); Console.ReadLine(); // creating factory HttpChunkingBinding binding = new HttpChunkingBinding(); binding.MaxReceivedMessageSize = 0x7fffffffL; ChannelFactory<WebServiceClient.IService> factory = new ChannelFactory<WebServiceClient.IService> (binding, new EndpointAddress("http://localhost/WebService/Service")); WebServiceClient.IService service = factory.CreateChannel(); for(int i = 0; i < 10; i++) { Stream s = service.Result(); // write this stream to a file and close the stream } //Closing our channel. ((IClientChannel)service).Close(); } Thanks,

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  • C#'s equivalent to VB.Net's DirectCast?

    - by Collin Sauve
    This has probably been asked before, but if it has, I can't find it. Does C# have an equivalent to VB.Net's DirectCast? I am aware that it has () casts and the 'as' keyword, but those line up to CType and TryCast. To be clear, these keywords do the following; CType/() casts: If it is already the correct type, cast it, otherwise look for a type converter and invoke it. If no type converter is found, throw an InvalidCastException. TryCast/"as" keyword: If it is the correct type, cast it, otherwise return null. DirectCast: If it is the correct type, cast it, otherwise throw an InvalidCastException. EDIT: After I have spelled out the above, some people have still responded that () is equivalent, so I will expand further upon why this is not true. DirectCast only allows for either Narrowing or Widening conversions on inheritance tree, it does not support conversions across different branches like () does. ie: C#, this compiles and runs: //This code uses a type converter to go across an inheritance tree double d = 10; int i = (int)d; VB.Net, this does NOT COMPILE 'Direct cast can only go up or down a branch, never across to a different one. Dim d as Double= 10 Dim i as Integer = DirectCast(d, Integer) The equivalent in VB.Net to my C# code is CType: 'This compiles and runs Dim d as Double= 10 Dim i as Integer = CType(d, Integer) (Edit again, I was originally using strings, I changed it to double... sorry)

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  • SQL Server database change workflow best practices

    - by kubi
    The Background My group has 4 SQL Server Databases: Production UAT Test Dev I work in the Dev environment. When the time comes to promote the objects I've been working on (tables, views, functions, stored procs) I make a request of my manager, who promotes to Test. After testing, she submits a request to an Admin who promotes to UAT. After successful user testing, the same Admin promotes to Production. The Problem The entire process is awkward for a few reasons. Each person must manually track their changes. If I update, add, remove any objects I need to track them so that my promotion request contains everything I've done. In theory, if I miss something testing or UAT should catch it, but this isn't certain and it's a waste of the tester's time, anyway. Lots of changes I make are iterative and done in a GUI, which means there's no record of what changes I made, only the end result (at least as far as I know). We're in the fairly early stages of building out a data mart, so the majority of the changes made, at least count-wise, are minor things: changing the data type for a column, altering the names of tables as we crystallize what they'll be used for, tweaking functions and stored procs, etc. The Question People have been doing this kind of work for decades, so I imagine there have got to be a much better way to manage the process. What I would love is if I could run a diff between two databases to see how the structure was different, use that diff to generate a change script, use that change script as my promotion request. Is this possible? If not, are there any other ways to organize this process? For the record, we're a 100% Microsoft shop, just now updating everything to SQL Server 2008, so any tools available in that package would be fair game.

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  • How do the size standard libraries compare for different languages

    - by Roman A. Taycher
    Someone was recently raving about how great jQuery was and how it made javascript into a pleasure and also how the whole source code was so small(and one file). I looked it up on www.ohloh.net/ and it said it was about 30,000 lines of javascript, when I tired curl piped to wc it said about 5000 lines(strange discrepancy that, maybe test suites, ect?). I thought well it isn't that strange since javascript from what I've heard has a lot of fun dynamic tricks, so you can probably get away with a small library. But then I thought what about other high level languages, the ones with large standard libraries and wondered how big the standard are for python/ruby/haskell/pharo(smalltalk)/*ml/ect. (libraries not vm stuff to the degree its possible to separate it) Anybody know? Any details (comment/blank/code lines , test code lines, lines in language vs lines in ffi/byte-code) are appreciated! edit: ps. since it started this me asking about jQuery as a bonus if you could please list the size of mega frameworks, a megaframewok provides so much that people using an x megaframework in language y might sometimes refer to programming in xy or even x rather then in y (ie. : qt, jQuery, etc.).

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  • MySql too many connections

    - by MichaelMcCabe
    I hate to bring up a question which is widely asked on the web, but I cant seem to solve it. I started a project a while back and after a month of testing, I hit a "Too many connections" error. I looked into it, and "Solved" it by increasing the max_connections. This then worked. Since then more and more people started to use it, and it hit again. When I am the only user on the site, i type "show processlist" and it comes up with about 50 connections which are still open (saying "Sleep" in the command). Now, I dont know enough to speculate why these are open, but in my code I tripple checked and every connection I open, I close. ie. public int getSiteIdFromName(String name, String company)throws DataAccessException,java.sql.SQLException{ Connection conn = this.getSession().connection(); Statement smt = conn.createStatement(); ResultSet rs=null; String query="SELECT id FROM site WHERE name='"+name+"' and company_id='"+company+"'"; rs=smt.executeQuery(query); rs.next(); int id=rs.getInt("id"); rs.close(); smt.close(); conn.close(); return id; } Every time I do something else on the site, another load of connections are opened and not closed. Is there something wrong with my code? and if not, what could be the problem?

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  • Need guidelines for optimizing WebGL performance by minimizing shader changes

    - by brainjam
    I'm trying to get an idea of the practicality of WebGL for rendering large architectural interior scenes, consisting of 100K's of triangles. These triangles are distributed over many objects, and there are many materials in the scene. On the other hand, there are no moving parts. And the materials tend to be fairly simple, mostly based on texture maps. There is a lot of texture map sharing .. for example all the chairs in scene will share a common map. There is also some multitexturing - up to three textures overlaid in a material. I've been doing a little experimentation and reading, and gather that frequently switching materials during a rendering pass will slow things down. For example, a scene with 200K triangles will have significant performance differences, depending on whether there are 10 or 1000 objects, assuming that each time an object is displayed a new material is set up. So it seems that if performance is important the scene should be sorted by materials so as to minimize material switching. What I'm looking for is guidelines on how to think of the overhead of various state changes, and where do I get the biggest bang for the buck. For example, what are the relative performance costs of, say, gl.useProgram(), gl.uniformMatrix4fv(), gl.drawElements() should I try to write ubershaders to minimize shader switching? should I try to aggregate geometry to minimize the number of gl.drawElements() calls I realize that mileage may vary depending on browser, OS, and graphics hardware. And I'm also not looking for heroic measures. Just some guidelines from people who have already had some experience in making scenes fast. I'll add that while I've had some experience with fixed-pipeline OpenGL programming in the past, I'm rather new to the WebGL/OpenGL ES 2.0 way of doing things.

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  • PHP: MVC and Model

    - by Pirkka
    Hello I`ve been wondering this one thing about creating models. If I make for example Page model. Is it the both: It can retrieve one row from the table or all the rows. Somehow Im mixing the objects and the database. I have thought it like this: I would have to make a Page-class that would represent one row in the table. It also would have all the basic CRUD-methods. Then I would have to do a Pages-class (somekind of collection) that would retrieve rows from the table and instantiate a Page object from each row. Is this kind of weird? If someone could explain to me the idea of model throughout.. Im again confused. Maybe Im thinking the whole OOP too difficult.. And by the way this forum is great. Hopefully people will just understand my problems. Heh. I was a long time procedural style programmer and now in 3 months I have dived into OOP and MVC and PHP frameworks and I just get more excited day by day when I explore this stuff!

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  • Select those objects whose related objects IDs are *all* in given string

    - by Jannis
    Hi Django people, I want to build a frontend to a recipe database which enables the user to search for a list of recipes which are cookable with the ingredients the user supplies. I have the following models class Ingredient(models.Model): name = models.CharField(max_length=100, unique=True) slug = models.SlugField(max_length=100, unique=True) importancy = models.PositiveSmallIntegerField(default=4) […] class Amount(models.Model): recipe = models.ForeignKey('Recipe') ingredient = models.ForeignKey(Ingredient) […] class Rezept(models.Model): name = models.CharField(max_length=100) slug = models.SlugField() instructions = models.TextField() ingredients = models.ManyToManyField(Ingredient, through=Amount) […] and a rawquery which does exactly what I want: It gets all the recipes whose required ingredients are all contained in the list of strings that the user supplies. If he supplies more than necessary, it's fine too. query = "SELECT *, COUNT(amount.zutat_id) AS selected_count_ingredients, (SELECT COUNT(*) FROM amount WHERE amount.recipe_id = amount.id) AS count_ingredients FROM amount LEFT OUTER JOIN amount ON (recipe.id = recipe.recipe_id) WHERE amount.ingredient_id IN (%s) GROUP BY amount.id HAVING count_ingredient=selected_count_ingredient" % ",".join([str(ingredient.id) for ingredient in ingredients]) rezepte = Rezept.objects.raw(query) Now, what I'm looking for is a way that does not rely on .raw() as I would like to do it purely with Django's queryset methods. Additionally, it would be awesome if you guys knew a way of including the ingredient's importancy in the lookup so that a recipe is still shown as a result even though one of its ingredients (that has an importancy of 0) is not supplied by the user.

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  • ASP.NET MVC WAP, SharePoint Designer and SVN

    - by David Lively
    All, I'm starting a new ASP.NET MVC project which requires some content management capabilities. The people who will be managing the content prefer to use SharePoint Designer (successor to FrontPage) to modify content. I'd like to allow them to keep doing that. The issues are: Since I'd like this to be a WAP, not a website project, how can I allow them to see their changes in action without requiring them to have Visual Studio on their local machines? Can I specify a "default" action for a controller so that given a url like /products/new_view_here Can I let them save pages (views) and see them in the browser without having to go through the check-in/build/deploy process? I'd like their changes to be stored in SVN; SharePoint designer seems to only support Visual SourceSafe (ugh) directly. The ideas I've come up with so far are Write an HTTP handler that implements the FrontPage Server Extensions protocol. This sounds time consuming, but I haven't yet looked at the protocol spec. However, it would allow me to perform whatever operations I want on the server side, including checking files into SVN. Ditch the WAP in favor of a website project. I do not like having the source present on the server, however. Also, will MVC work in a website project? Surely someone has tackled this problem before?

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  • Should a setter return immediately if assigned the same value?

    - by Andrei Rinea
    In classes that implement INotifyPropertyChanged I often see this pattern : public string FirstName { get { return _customer.FirstName; } set { if (value == _customer.FirstName) return; _customer.FirstName = value; base.OnPropertyChanged("FirstName"); } } Precisely the lines if (value == _customer.FirstName) return; are bothering me. I've often did this but I am not that sure it's needed nor good. After all if a caller assigns the very same value I don't want to reassign the field and, especially, notify my subscribers that the property has changed when, semantically it didn't. Except saving some CPU/RAM/etc by freeing the UI from updating something that will probably look the same on the screen/whatever_medium what do we obtain? Could some people force a refresh by reassigning the same value on a property (NOT THAT THIS WOULD BE A GOOD PRACTICE HOWEVER)? 1. Should we do it or shouldn't we? 2. Why?

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