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  • Thread synchronization and aborting.

    - by kubal5003
    Hello, I've got a little problem with ending the work of one of my threads. First things first so here's the app "layout": Thread 1 - worker thread (C++/CLI) - runs and terminates as expected for(...) { try { if(TabuStop) return; System::Threading::Monitor::Enter("Lock1"); //some work, unmanaged code } finally { if(stop) { System::Threading::Monitor::Pulse("Lock1"); } else { System::Threading::Monitor::Pulse("Lock1"); System::Threading::Monitor::Wait("Lock1"); } } } Thread 2 - display results thread (C#) while (WorkerThread.IsAlive) { lock ("Lock1") { if (TabuEngine.TabuStop) { Monitor.Pulse("Lock1"); } else { Dispatcher.BeginInvoke(RefreshAction); Monitor.Pulse("Lock1"); Monitor.Wait("Lock1", 5000); } } // Thread.Sleep(5000); } I'm trying to shut the whole thing down from app main thread like this: TabuEngine.TabuStop = true; //terminates nicely the worker thread and if (DisplayThread.IsAlive) { DisplayThread.Abort(); } I also tried using DisplayThread.Interrupt, but it always blocks on Monitor.Wait("Lock1", 5000); and I can't get rid of it. What is wrong here? How am I supposed to perform the synchronization and let it do the work that it is supposed to do? //edit I'm not even sure now if the trick with using "Lock1" string is really working and locks are placed on the same object..

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  • #include - brackets vs quotes in XCode?

    - by Chris Becke
    In MSVC++ #include files are searched for differently depending on whether the file is enclosed in "" or <. The quoted form searches first in the local folder, then in /I specified locations, The angle bracket form avoids the local folder. This means, in MSVC++, its possible to have header files with the same name as runtime and SDK headers. So, for example, I need to wrap up the windows sdk windows.h file to undefine some macro's that cause trouble. With MSVS I can just add a (optional) windows.h file to my project as long as I include it using the quoted form :- // some .cpp file #include "windows.h" // will include my local windows.h file And in my windows.h, I can pull in the real one using the angle bracket form: // my windows.h #include <windows.h> // will load the real one #undef ConflictingSymbol Trying this trick with GCC in XCode didn't work. angle bracket #includes in system header files in fact are finding my header files with similar names in my local folder structure. The MSVC system means its quite safe to have a "String.h" header file in my own folder structre. On XCode this seems to be a major no no. Is there some way to control this search path behaviour in XCode to be more like MSVC's? Or do I just have to avoid naming any of my headers anything that might possibly conflict with a system header. Writing cross platform code and using lots of frameworks means the possibility of incidental conflicts seems large.

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  • Commenting out portions of code in Scala

    - by akauppi
    I am looking for a C(++) #if 0 -like way of being able to comment out whole pieces of Scala source code, for keeping around experimental or expired code for a while. I tried out a couple of alternatives and would like to hear what you use, and if you have come up with something better? // Simply block-marking N lines by '//' is one way... // <tags> """ anything My editor makes this easy, but it's not really The Thing. It gets easily mixed with actual one-line comments. Then I figured there's native XML support, so: <!-- ... did not work --> Wrapping in XML works, unless you have <tags> within the block: class none { val a= <ignore> ... cannot have //<tags> <here> (not even in end-of-line comments!) </ignore> } The same for multi-line strings seems kind of best, but there's an awful lot of boilerplate (not fashionable in Scala) to please the compiler (less if you're doing this within a class or an object): object none { val ignore= """ This seems like ... <truly> <anything goes> but three "'s of course """ } The 'right' way to do this might be: /*** /* ... works but not properly syntax highlighed in SubEthaEdit (or StackOverflow) */ ***/ ..but that matches the /* and */ only, not i.e. /*** to ***/. This means the comments within the block need to be balanced. And - the current Scala syntax highlighting mode for SubEthaEdit fails miserably on this. As a comparison, Lua has --[==[ matching ]==] and so forth. I think I'm spoilt? So - is there some useful trick I'm overseeing?

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  • How to implement a log window in a web browser?

    - by Jeremy Friesner
    Hi all, I'm interested in adding an HTML/web-browser based "log window" to my net-enabled device. Specifically, my device has a customized web server and an event log, and I'd like to be able to leave a web browser window open to e.g. http://my.devices.ip.address/system_log and have events show up as text in the web browser window as they happen. People could then use this as a quick way to monitor what the system is doing, without needing run any special software. My question is, what is the best way to implement this? I've tried the obvious approach -- just have my device's embedded web server hold the HTTP/TCP connection open indefinitely, and write the necessary text to the TCP socket when an event occurs -- but the problem with that is that most web browsers (e.g. Safari) don't display the web page until the server has closed the TCP connection has been closed, and so the result is that the log data never appears in the web browser, it just acts as if the page is taking forever to load. Is there some trick to make this work? I could implement it as a Java applet, but I'd much prefer something more lightweight/simple, either using only HTML or possibly HTML+JavaScript. Also I'd like to avoid having the web browser 'poll' the server, since that would either introduce too much latency (if the reload delay was large) or put load on the system (if the delay was small)

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  • How do I structure my tests with Python unittest module?

    - by persepolis
    I'm trying to build a test framework for automated webtesting in selenium and unittest, and I want to structure my tests into distinct scripts. So I've organised it as following: base.py - This will contain, for now, the base selenium test case class for setting up a session. import unittest from selenium import webdriver # Base Selenium Test class from which all test cases inherit. class BaseSeleniumTest(unittest.TestCase): def setUp(self): self.browser = webdriver.Firefox() def tearDown(self): self.browser.close() main.py - I want this to be the overall test suite from which all the individual tests are run. import unittest import test_example if __name__ == "__main__": SeTestSuite = test_example.TitleSpelling() unittest.TextTestRunner(verbosity=2).run(SeTestSuite) test_example.py - An example test case, it might be nice to make these run on their own too. from base import BaseSeleniumTest # Test the spelling of the title class TitleSpelling(BaseSeleniumTest): def test_a(self): self.assertTrue(False) def test_b(self): self.assertTrue(True) The problem is that when I run main.py I get the following error: Traceback (most recent call last): File "H:\Python\testframework\main.py", line 5, in <module> SeTestSuite = test_example.TitleSpelling() File "C:\Python27\lib\unittest\case.py", line 191, in __init__ (self.__class__, methodName)) ValueError: no such test method in <class 'test_example.TitleSpelling'>: runTest I suspect this is due to the very special way in which unittest runs and I must have missed a trick on how the docs expect me to structure my tests. Any pointers?

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  • Get the src part of a string [duplicate]

    - by Kay Lakeman
    This question already has an answer here: Grabbing the href attribute of an A element 7 answers First post ever here, and i really hope you can help. I use a database where a large piece of html is stored, now i just need the src part of the image tag. I already found a thread, but i just doesn't do the trick. My code: Original string: <p><img alt=\"\" src=\"http://domain.nl/cms/ckeditor/filemanager/userfiles/background.png\" style=\"width: 80px; height: 160px;\" /></p> How i start: $image = strip_tags($row['information'], '<img>'); echo stripslashes($image); This returns: <img alt="" src="http://domain.nl/cms/ckeditor/filemanager/userfiles/background.png" style="width: 80px; height: 160px;" /> Next step: extract the src part: preg_match('/< *img[^>]*src *= *["\']?([^"\']*)/i', $image, $matches); echo $matches ; This last echo returns: Array What is going wrong? Thanks in advance for your anwser.

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  • Using items in a list as arguments

    - by Travis Brown
    Suppose I have a function with the following type signature: g :: a -> a -> a -> b I also have a list of as—let's call it xs—that I know will contain at least three items. I'd like to apply g to the first three items of xs. I know I could define a combinator like the following: ($$$) :: (a -> a -> a -> b) -> [a] -> b f $$$ (x:y:z:_) = f x y z Then I could just use g $$$ xs. This makes $$$ a bit like uncurry, but for a function with three arguments of the same type and a list instead of a tuple. Is there a way to do this idiomatically using standard combinators? Or rather, what's the most idiomatic way to do this in Haskell? I thought trying pointfree on a non-infix version of $$$ might give me some idea of where to start, but the output was an abomination with 10 flips, a handful of heads and tails and aps, and 28 parentheses. (NB: I know this isn't a terribly Haskelly thing to do in the first place, but I've come across a couple of situations where it seems like a reasonable solution, especially when using Parsec. I'll certainly accept "don't ever do this in real code" if that's the best answer, but I'd prefer to see some clever trick involving the ((->) r) monad or whatever.)

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  • Factorial function - design and test.

    - by lukas
    I'm trying to nail down some interview questions, so I stared with a simple one. Design the factorial function. This function is a leaf (no dependencies - easly testable), so I made it static inside the helper class. public static class MathHelper { public static int Factorial(int n) { Debug.Assert(n >= 0); if (n < 0) { throw new ArgumentException("n cannot be lower that 0"); } Debug.Assert(n <= 12); if (n > 12) { throw new OverflowException("Overflow occurs above 12 factorial"); } //by definition if (n == 0) { return 1; } int factorialOfN = 1; for (int i = 1; i <= n; ++i) { //checked //{ factorialOfN *= i; //} } return factorialOfN; } } Testing: [TestMethod] [ExpectedException(typeof(OverflowException))] public void Overflow() { int temp = FactorialHelper.MathHelper.Factorial(40); } [TestMethod] public void ZeroTest() { int factorialOfZero = FactorialHelper.MathHelper.Factorial(0); Assert.AreEqual(1, factorialOfZero); } [TestMethod] public void FactorialOf5() { int factOf5 = FactorialHelper.MathHelper.Factorial(5); Assert.AreEqual(120,factOf5); } [TestMethod] [ExpectedException(typeof(ArgumentException))] public void NegativeTest() { int factOfMinus5 = FactorialHelper.MathHelper.Factorial(-5); } I have a few questions: Is it correct? (I hope so ;) ) Does it throw right exceptions? Should I use checked context or this trick ( n 12 ) is ok? Is it better to use uint istead of checking for negative values? Future improving: Overload for long, decimal, BigInteger or maybe generic method? Thank you

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  • entity framework navigation property further filter without loading into memory

    - by cellik
    Hi, I've two entities with 1 to N relation in between. Let's say Books and Pages. Book has a navigation property as Pages. Book has BookId as an identifier and Page has an auto generated id and a scalar property named PageNo. LazyLoading is set to true. I've generated this using VS2010 & .net 4.0 and created a database from that. In the partial class of Book, I need a GetPage function like below public Page GetPage(int PageNumber) { //checking whether it exist etc are not included for simplicity return Pages.Where(p=>p.PageNo==PageNumber).First(); } This works. However, since Pages property in the Book is an EntityCollection it has to load all Pages of a book in memory in order to get the one page (this slows down the app when this function is hit for the first time for a given book). i.e. Framework does not merge the queries and run them at once. It loads the Pages in memory and then uses LINQ to objects to do the second part To overcome this I've changed the code as follows public Page GetPage(int PageNumber) { MyContainer container = new MyContainer(); return container.Pages.Where(p=>p.PageNo==PageNumber && p.Book.BookId==BookId).First(); } This works considerably faster however it doesn't take into account the pages that have not been serialized to the db. So, both options has its cons. Is there any trick in the framework to overcome this situation. This must be a common scenario where you don't want all of the objects of a Navigation property loaded in memory when you don't need them.

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  • Omit Properties from WebControl Serialization

    - by Laramie
    I have to serialize several objects inheriting from WebControl for database storage. These include several unecessary (to me) properties that I would prefer to omit from serialization. For example BackColor, BorderColor, etc. Here is an example of an XML serialization of one of my controls inheriting from WebControl. <Control xsi:type="SerializePanel"> <ID>grCont</ID> <Controls /> <BackColor /> <BorderColor /> <BorderWidth /> <CssClass>grActVid bwText</CssClass> <ForeColor /> <Height /> <Width /> ... </Control> I have been trying to create a common base class for my controls that inherits from WebControl and uses the "xxxSpecified" trick to selectively choose not to serialize certain properties. For example to ignore an empty BorderColor property, I'd expect [XmlIgnore] public bool BorderColorSpecified() { return !base.BorderColor.IsEmpty; } to work, but it's never called during serialization. I've also tried it in the class to be serialized as well as the base class. Since the classes themselves might change, I'd prefer not to have to create a custom serializer. Any ideas?

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  • Php string handling triks

    - by Dam
    Hi my question Need to get the 10 word before and 10 words after for the given text . i mean need to start the 10 words before the keyword and end with 10 word after the key word. Given text : "Twenty-three" The main trick : content having some html tags etc .. tags need to keep that tag with this content only . need to display the words from 10before - 10after content is bellow : <div id="hpFeatureBoxInt"><h3><a href="/go/homepage/i/int/news/world/1/-/news/1/hi/world/europe/8592190.stm">Suicide bombings hit Moscow Metro</a></h3><p>Past suicide bombings in Moscow have been blamed on Islamist rebels At least 35 people have been killed after two female suicide bombers blew themselves up on Moscow Metro trains in the morning rush hour,<h2><span class="dy">Top News Story</span></h2> officials say.<img height="150" width="201" alt="Emergency services carry a body from a Metro station in Moscow (29 March 2010)" src="http://wwwimg.bbc.co.uk/feedengine/homepage/images/_47550689_moscowap203_201x150.jpg">Twenty-three died in the first blast at 0756 (0356 GMT) as a<a href="#"> train stood </a>at the central Lubyanka station, beneath the offices of the FSB intelligence agency.About 40 minutes later, a second explosion ripped through a train at Park Kultury, leaving another 12 dead.No-one has said they carried out the worst attack in the capital since 2004. </p><p id="fbilisten"><a href="/go/homepage/i/int/news/heading/-/news/">More from BBC News</a></p></div> Thank you

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  • Is it possible, in ASP .net, to reference private assembly in a non-virtual subdirectory?

    - by Bago
    Is it possible to reference a private assembly in asp .net from a sub-folder that is not setup as a virtual directory? In other words, my page is setup in ~/subdir, I don't have access to ~/, and I am not an IIS admin. Can I reference a private assembly? How would I do this? I've tried <%@ Assembly Src="/subdir/bin/Assembly.dll % and <%@ Assembly Src="/subdir/bin/Assembly.dll % , but I get the messages "There is no build provider to match the extension .dll" or "Failed to map to path" respectively. Here is my folder structure: / | -subdir | | - Bin | | | *Assembly.dll | | *Default.aspx I've heard that in web.config might do the trick, but when I've tried it, it doesn't seem to work. Furthermore, I've read that only works in the application .config file. (i.e., the one in ~/). Anyhow, I already tried adding the following to web.config: <runtime> <assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1"> <probing privatePath="/subdir/bin" /> <dependentAssembly> <codeBase href="/subdir/bin/Assembly.dll"/> </dependentAssembly> </assemblyBinding> For more background on my problem, I am simply using a shared host, all I have is access to is that subdirectory, and I am trying to use fckeditor.

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  • Is it possible, in ASP.net, to reference private assembly in a non-virtual subdirectory?

    - by Bago
    Is it possible to reference a private assembly in asp .net from a sub-folder that is not setup as a virtual directory? In other words, my page is setup in ~/subdir, I don't have access to ~/, and I am not an IIS admin. Can I reference a private assembly? How would I do this? I've tried <%@ Assembly Src="/subdir/bin/Assembly.dll % and <%@ Assembly Src="/subdir/bin/Assembly.dll % , but I get the messages "There is no build provider to match the extension .dll" or "Failed to map to path" respectively. Here is my folder structure: / | -subdir | | - Bin | | | *Assembly.dll | | *Default.aspx I've heard that in web.config might do the trick, but when I've tried it, it doesn't seem to work. Furthermore, I've read that only works in the application .config file. (i.e., the one in ~/). Anyhow, I already tried adding the following to web.config: <runtime> <assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1"> <probing privatePath="/subdir/bin" /> <dependentAssembly> <codeBase href="/subdir/bin/Assembly.dll"/> </dependentAssembly> </assemblyBinding> For more background on my problem, I am simply using a shared host, all I have is access to is that subdirectory, and I am trying to use fckeditor.

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  • Team City + Gallio runs tests, but results are not shown

    - by Twindagger
    We recently updated to Visual Studio 2010, and as part of our upgrade we started using Gallio 3.2 prerelease builds. Everything runs fine in Visual Studio (through resharper) but I'm having problems with TeamCity integration. The tests seem to run during TeamCity builds just fine (our build takes long enough to run all our tests), but the tests are not showing up in TeamCity's test area. Here is the test target from our NANT build file (this hasn't changed in our upgrade at all). Is there a trick to getting the tests to show up in TeamCity or is this something that's broken in the latest builds of Gallio? <target name="runTests"> <gallio result-property="exitCode" failonerror="false"> <runner-extension value="TeamCityExtension,Gallio.TeamCityIntegration" /> <assemblies> <include name="..\Source\Tests\${testProject}\bin\Debug\${testProject}.dll" /> </assemblies> </gallio> </target>

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  • What are your Programming Falacies/Myths?

    - by pms1969
    I recently started a new job and as is typical of all jobs, if you've left, you get blamed for everything. Not long after I started there was a change required for an app (web based) that we maintain, and it was quickly pointed out that the actual code for this site had been lost a long time ago, and the only changes we could make to the it were ones that required changes to mark-up [it was a pre-compiled site]. Being new, I needed a little help finding my way around the code, and enlisted the services of one of my colleagues. Made my changes, and then re-enlisted his help to deploy it. While prepping for the deployment (getting the app on the QA server) we discovered that there were actually 2 different, very similarly named, folders in our source repository. It transpired that for the last year or so, mark-up changes had been made to the site directly, and these were the only differences with the code in the slightly incorrectly named folder in source control. So we did have all the code, and can now properly support the site. This put me in mind of a trick we played on a junior programmer once in a previous job, where we told him he couldn't/shouldn't do a certain thing in code as this would likely bring the server to it's knees and cost the company thousands of pounds (a gag that last months :-). And another one in the first programming job I took on - the batch commission run was just going to crash once a month and there was nothing to be done about it, causing a call out, and call out compensation for the on-call guy (a bug I fixed as soon as I became the on-call guy - 2am call outs don't work for me). So I was wondering... What other programming fallacies/myths are out there that are worth sharing?

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  • MSSQL 2008 - Bit Param Evaluation alters Execution Plan

    - by Nathanial Woolls
    I have been working on migrating some of our data from Microsoft SQL Server 2000 to 2008. Among the usual hiccups and whatnot, I’ve run across something strange. Linked below is a SQL query that returns very quickly under 2000, but takes 20 minutes under 2008. I have read quite a bit on upgrading SQL server and went down the usual paths of checking indexes, statistics, etc. before coming to the conclusion that the following statement, found in the WHERE clause, causes the execution plan for the steps that follow this statement to change dramatically: And ( @bOnlyUnmatched = 0 -- offending line Or Not Exists( The SQL statements and execution plans are linked below. A coworker was able to rewrite a portion of the WHERE clause using a CASE statement, which seems to “trick” the optimizer into using a better execution plan. The version with the CASE statement is also contained in the linked archive. I’d like to see if someone has an explanation as to why this is happening and if there may be a more elegant solution than using a CASE statement. While we can work around this specific issue, I’d like to have a broader understanding of what is happening to ensure the rest of the migration is as painless as possible. Zip file with SQL statements and XML execution plans Thanks in advance!

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  • sending large data .getJSON or proxy ?

    - by numerical25
    Hey guys. I was told that the only trick to sending data to a external server (i.e x-domain) is to use getJSON. Well my problem is that the data I am sending exceeds the getJSON data limit. I am tracking mouse movements on a screen for analytics. Another option is I could also send a little data at a time. probably every time the mouse moves. but that seems as if it would slow things down. I could setup a proxy server. My question is which would be better? Setting up a proxy server ? or Just sending bits of information via javascript or JQUERY. What do the professionals use (Google and other company's that build mash-ups that send a lot of data to x-domain sites.) I need to know the best practices. Thanx!! Also the data is put into JSON.

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  • How can one enforce calling a base class function after derived class constructor?

    - by Mike Elkins
    I'm looking for a clean C++ idiom for the following situation: class SomeLibraryClass { public: SomeLibraryClass() { /* start initialization */ } void addFoo() { /* we are a collection of foos */ } void funcToCallAfterAllAddFoos() { /* Making sure this is called is the issue */ } }; class SomeUserClass : public SomeLibraryClass { public: SomeUserClass() { addFoo(); addFoo(); addFoo(); // SomeUserClass has three foos. } }; class SomeUserDerrivedClass : public SomeUserClass { public: SomeUserDerrivedClass() { addFoo(); // This one has four foos. } }; So, what I really want is for SomeLibraryClass to enforce the calling of funcToCallAfterAllAddFoos at the end of the construction process. The user can't put it at the end of SomeUserClass::SomeUserClass(), that would mess up SomeUserDerrivedClass. If he puts it at the end of SomeUserDerrivedClass, then it never gets called for SomeUserClass. To further clarify what I need, imagine that /* start initialization */ acquires a lock, and funcToCallAfterAllAddFoos() releases a lock. The compiler knows when all the initializations for an object are done, but can I get at that information by some nice trick?

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  • DIV inside TD to make it appear correctly

    - by Daniel Svensson
    Hi, I have a <table> generated from code-behind and now facing a problem. In one of the TD i need to have a DIV that is setup with JQuery so that when i click a link the DIV slideToggles. Now i need the TD belonging to that TR not to expand the TR. To solve this i have used an old trick that is to place the JQuery DIV inside another surrounding DIV with height 1px and make the TR not expanding with the heigth of the DIV that slides out. In IE the sliding DIV is partially under the table and in Firefox the DIV appears over the table but it's trasparent, the text from the data in the table shows thru. I have tried to alter the Z-index in various ways but it's no good. Anyone that has an idea or alternatively solution that has worked for them. HtmlGenericControl containerDiv = new HtmlGenericControl("div"); containerDiv.ID = "containerDiv"; containerDiv.Style.Add(System.Web.UI.HtmlTextWriterStyle.Width, "100%"); containerDiv.Style.Add(System.Web.UI.HtmlTextWriterStyle.Height, "1px"); containerDiv.Style.Add(System.Web.UI.HtmlTextWriterStyle.ZIndex, "999"); HtmlGenericControl innerDiv = new HtmlGenericControl("div"); innerDiv.ID = System.Guid.NewGuid().ToString() + "_annualDiv"; inner.Style.Add(System.Web.UI.HtmlTextWriterStyle.Width, "100%"); innerDiv.Style.Add(System.Web.UI.HtmlTextWriterStyle.Height, "300px"); innerDiv.Style.Add(System.Web.UI.HtmlTextWriterStyle.ZIndex, "1000"); innerDiv.Style.Add(System.Web.UI.HtmlTextWriterStyle.BorderStyle, "solid"); innerDiv.Style.Add(System.Web.UI.HtmlTextWriterStyle.BorderColor, "Black"); innerDiv.Style.Add(System.Web.UI.HtmlTextWriterStyle.BorderWidth, "1px"); innerDiv.Style.Add(System.Web.UI.HtmlTextWriterStyle.BackgroundColor, "white"); innerDiv.InnerHtml = "Here is a list of links coming later"; conDiv.Controls.Add(innerDiv);

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  • how to delete in Mysql

    - by Ian Moss
    i want to delete a element in mysql. the problem is that my connection not succesfully open and they give me error unable to connect even same connectionstring work elsewhere in current project. well when my code open the connection they work fine. but a small function try to delete a row in Mysql. i am confused what is goes wrong because :- same connectionstring work elsewhere in project i trying but a function only have a project [unable to connect] the [unable to connect] problem come when my code trying to delete the rows in mysql. i use sqlyog to open the connection and they work fine as other code work and their is no problem i got when i run the command on sqlyog. conclusion:- why connection not open if they work elsewhere in the project and in also in sqlyog. any reason for unable to connect. because connection can not open offcourse command never run so what is reason upon the connection unable to connect. well any suggestion , thing you feel and trick you have to solve this issue i have. thanks

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  • Using list() to extract a data.table inside of a function

    - by Nathan VanHoudnos
    I must admit that the data.table J syntax confuses me. I am attempting to use list() to extract a subset of a data.table as a data.table object as described in Section 1.4 of the data.table FAQ, but I can't get this behavior to work inside of a function. An example: require(data.table) ## Setup some test data set.seed(1) test.data <- data.table( X = rnorm(10), Y = rnorm(10), Z = rnorm(10) ) setkey(test.data, X) ## Notice that I can subset the data table easily with literal names test.data[, list(X,Y)] ## X Y ## 1: -0.8356286 -0.62124058 ## 2: -0.8204684 -0.04493361 ## 3: -0.6264538 1.51178117 ## 4: -0.3053884 0.59390132 ## 5: 0.1836433 0.38984324 ## 6: 0.3295078 1.12493092 ## 7: 0.4874291 -0.01619026 ## 8: 0.5757814 0.82122120 ## 9: 0.7383247 0.94383621 ## 10: 1.5952808 -2.21469989 I can even write a function that will return a column of the data.table as a vector when passed the name of a column as a character vector: get.a.vector <- function( my.dt, my.column ) { ## Step 1: Convert my.column to an expression column.exp <- parse(text=my.column) ## Step 2: Return the vector return( my.dt[, eval(column.exp)] ) } get.a.vector( test.data, 'X') ## [1] -0.8356286 -0.8204684 -0.6264538 -0.3053884 0.1836433 0.3295078 ## [7] 0.4874291 0.5757814 0.7383247 1.5952808 But I cannot pull a similar trick for list(). The inline comments are the output from the interactive browser() session. get.a.dt <- function( my.dt, my.column ) { ## Step 1: Convert my.column to an expression column.exp <- parse(text=my.column) ## Step 2: Enter the browser to play around browser() ## Step 3: Verity that a literal X works: my.dt[, list(X)] ## << not shown >> ## Step 4: Attempt to evaluate the parsed experssion my.dt[, list( eval(column.exp)] ## Error in `rownames<-`(`*tmp*`, value = paste(format(rn, right = TRUE), (from data.table.example.R@1032mCJ#7) : ## length of 'dimnames' [1] not equal to array extent return( my.dt[, list(eval(column.exp))] ) } get.a.dt( test.data, "X" ) What am I missing? Update: Due to some confusion as to why I would want to do this I wanted to clarify. My use case is when I need to access a data.table column when when I generate the name. Something like this: set.seed(2) test.data[, X.1 := rnorm(10)] which.column <- 'X' new.column <- paste(which.column, '.1', sep="") get.a.dt( test.data, new.column ) Hopefully that helps.

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  • Excel - Variable number of leading zeros in variable length numbers?

    - by daltec
    The format of our member numbers has changed several times over the years, such that 00008, 9538, 746, 0746, 00746, 100125, and various other permutations are valid, unique and need to be retained. Exporting from our database into the custom Excel template needed for a mass update strips the leading zeros, such that 00746 and 0746 are all truncated to 746. Inserting the apostrophe trick, or formatting as text, does not work in our case, since the data seems to be already altered by the time we open it in Excel. Formatting as zip won't work since we have valid numbers less than five digits in length that cannot have zeros added to them. And I am not having any luck with "custom" formatting as that seems to require either adding the same number of leading zeros to a number, or adding enough zeros to every number to make them all the same length. Any clues? I wish there was some way to set Excel to just take what it's given and leave it alone, but that does not seem to be the case! I would appreciate any suggestions or advice. Thank you all very much in advance!

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  • Creating serializeable unique compile-time identifiers for arbitrary UDT's.

    - by Endiannes
    I would like a generic way to create unique compile-time identifiers for any C++ user defined types. for example: unique_id<my_type>::value == 0 // true unique_id<other_type>::value == 1 // true I've managed to implement something like this using preprocessor meta programming, the problem is, serialization is not consistent. For instance if the class template unique_id is instantiated with other_type first, then any serialization in previous revisions of my program will be invalidated. I've searched for solutions to this problem, and found several ways to implement this with non-consistent serialization if the unique values are compile-time constants. If RTTI or similar methods, like boost::sp_typeinfo are used, then the unique values are obviously not compile-time constants and extra overhead is present. An ad-hoc solution to this problem would be, instantiating all of the unique_id's in a separate header in the correct order, but this causes additional maintenance and boilerplate code, which is not different than using an enum unique_id{my_type, other_type};. A good solution to this problem would be using user-defined literals, unfortunately, as far as I know, no compiler supports them at this moment. The syntax would be 'my_type'_id; 'other_type'_id; with udl's. I'm hoping somebody knows a trick that allows implementing serialize-able unique identifiers in C++ with the current standard (C++03/C++0x), I would be happy if it works with the latest stable MSVC and GNU-G++ compilers, although I expect if there is a solution, it's not portable.

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  • EF 4.0 Guid or Int as A primary Key

    - by bigb
    I am Implementing custom ASPNetMembership using EF 4.0 Is there any reason why i should use Guid as a primary key in User tables? As far as i know Int as a PK on SQL Server more performanced than strings. And Int is easier to iterate. Also, for security purpose if i need to pass this it id somewhere in url i may encrypt it somehow and pass it like a strings with no probs. But if i want to use auto generated Guid on SQL Server side using EF 4.0 i need to do this trick http://leedumond.com/blog/using-a-guid-as-an-entitykey-in-entity-framework-4/ I can't see any cases why i should use Guid as PK, may be only one if system going to have millions ans millions users, but also, theoretically, Guid could be duplicated sometime isn't so? Anyway Int32 size is 2,147.483.647 it is pretty much even for very-very big system, but if this number is still not enough I may go with Int64, in that cases I may have 9,223.372.036.854.775.807 rows. Pretty much huh? From another hand, M$ using Guids as PK in their ASPNetMembership implementation. [aspnetdb].[aspnet_Users] - PK UserId Type uniqueidentifier, should be some reasons/explanation why the did it?! May be some one has any ideas/experience about that?

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  • Rails RESTful routs without #new, rspec trouble

    - by pdkl95
    I'm currently writing a Rails app, and hit a somewhat strange quirk. I have a controller PermissionsController, which is mainly for display purposes at the moment. So my routing is locked down: map.resources :permissions, :only => [:index, :show] Unfortunately, when writing the tests, one of the routing tests fails: it "does not recognize #new" do { :get => "/permissions/new" }.should_not be_routable end with the error: Expected 'GET /permissions/new' to fail, but it routed to {"action"=>"show", "id"=>"new", "controller"=>"permissions"} instead Obviously, the #show action's route is matching with /permissions/:id, which also gives the expected error Couldn't find Permission with ID=new if you actually browse to that URL. This is not a serious error, as it is correctly raising an exception with the bad :id parameter, but it's kind of ugly. Is there any way to actually make Rails reject that route? Some trick in the routing options that I'm missing? I suppose I should just leave that test out and ignore it, or maybe remove the whole RESTful idea altogether and go back to a simpler map.connect 'permissions/:id' style. I strongly suspect I'll be expanding this in the future, though, and kind of wanted to keep my controllers consistent with each other. Just having to add occasional :only or :except rules made routes.rb nice and clean...

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