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  • Rotate using a transform, then change frame origin, and view expands??

    - by ZaBlanc
    This is quite the iPhone quandry. I am working on a library, but have narrowed down my problem to very simple code. What this code does is create a 50x50 view, applies a rotation transform of a few degrees, then shifts the frame down a few times. The result is the 50x50 view is now much larger looking. Here's the code: // a simple 50x50 view UIView *redThing = [[UIView alloc] initWithFrame:CGRectMake(50, 50, 50, 50)]; redThing.backgroundColor = [UIColor redColor]; [self.view addSubview:redThing]; // rotate a small amount (as long as it's not 90 or 180, etc.) redThing.transform = CGAffineTransformRotate(redThing.transform, 0.1234); // move the view down 2 pixels CGRect newFrame = CGRectMake(redThing.frame.origin.x, redThing.frame.origin.y + 2, redThing.frame.size.width, redThing.frame.size.height); redThing.frame = newFrame; // move the view down another 2 pixels newFrame = CGRectMake(redThing.frame.origin.x, redThing.frame.origin.y + 2, redThing.frame.size.width, redThing.frame.size.height); redThing.frame = newFrame; // move the view down another 2 pixels newFrame = CGRectMake(redThing.frame.origin.x, redThing.frame.origin.y + 2, redThing.frame.size.width, redThing.frame.size.height); redThing.frame = newFrame; // move the view down another 2 pixels newFrame = CGRectMake(redThing.frame.origin.x, redThing.frame.origin.y + 2, redThing.frame.size.width, redThing.frame.size.height); redThing.frame = newFrame; So, what the heck is going on? Now, if I move the view by applying a translation transform, it works just fine. But that's not what I want to do and this should work anyway. Any ideas?

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  • Fastest inline-assembly spinlock

    - by sigvardsen
    I'm writing a multithreaded application in c++, where performance is critical. I need to use a lot of locking while copying small structures between threads, for this I have chosen to use spinlocks. I have done some research and speed testing on this and I found that most implementations are roughly equally fast: Microsofts CRITICAL_SECTION, with SpinCount set to 1000, scores about 140 time units Implementing this algorithm with Microsofts InterlockedCompareExchange scores about 95 time units Ive also tried to use some inline assembly with __asm {} using something like this code and it scores about 70 time units, but I am not sure that a proper memory barrier has been created. Edit: The times given here are the time it takes for 2 threads to lock and unlock the spinlock 1,000,000 times. I know this isn't a lot of difference but as a spinlock is a heavily used object, one would think that programmers would have agreed on the fastest possible way to make a spinlock. Googling it leads to many different approaches however. I would think this aforementioned method would be the fastest if implemented using inline assembly and using the instruction CMPXCHG8B instead of comparing 32bit registers. Furthermore memory barriers must be taken into account, this could be done by LOCK CMPXHG8B (I think?), which guarantees "exclusive rights" to the shared memory between cores. At last [some suggests] that for busy waits should be accompanied by NOP:REP that would enable Hyper-threading processors to switch to another thread, but I am not sure whether this is true or not? From my performance-test of different spinlocks, it is seen that there is not much difference, but for purely academic purpose I would like to know which one is fastest. However as I have extremely limited experience in the assembly-language and with memory barriers, I would be happy if someone could write the assembly code for the last example I provided with LOCK CMPXCHG8B and proper memory barriers in the following template: __asm { spin_lock: ;locking code. spin_unlock: ;unlocking code. }

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  • Refactoring or Rewriting Monolithic PHP Spaghetti Codebase

    - by nategood
    I've inherited a really poorly designed PHP spaghetti code project. It's been gaining a good bit of traffic recently and is starting to have performance issues on top of the poor monolithic code base. Its maxing out performance on a chunky 16GB dedicated machine when it really shouldn't be. I'm planning on doing some performance tweaks right off the bat to help the performance issue, but this still won't really help the horrible code base. The team is small but expecting to grow very soon. I've read Joel's article on the troubles of doing a complete rewrite and see the concerns. But how bad does the code base have to be before you consider a rewrite? There is PHP handling logic interjected into what one would usually consider a "view". Even worse, in some places SQL statements are in these same files! The only real separation of presentation and logic are a few PHP scripts that serve as function libraries. These scripts do most of the ORM stuff... if you can even call it that. Trying to slowly refractor this seems like a nightmare. Open to your thoughts and opinions... however not interested in hearing, "Run away, Run away!".

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  • Problem declaring and calling internal metthods

    - by Martin
    How do I declare and use small helper functions inside my normal methods ? In on of my objective-c methods I need a function to find an item within a string -(void) Onlookjson:(id) sender{ NSString * res = getKeyValue(res, @"Birth"); } I came up with a normal C type declaration for helper function getKeyvalue like this NSString * getKeyvalue(NSString * s, NSString key){ NSString *trm = [[s substringFromIndex:2] substringToIndex:[s length]-3]; NSArray *list = [trm componentsSeparatedByString:@";"]; .... NSString res; res = [list objectAtIndex:1]; ... return res; } Input data string: { Birth = ".."; Death = "..."; ... } Anyway I get an exception "unrecognized selector sent to instance" for any of the two first lines in the helper function How do I declare helper functions that are just to be used internally and how to call them safely ? regards Martin

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  • SqlCE DB occasionally freezes on one handheld, not another

    - by Michael
    I have two types of custom handhelds which are similar, but slightly different, each running the same WinForm application and a WinCE database: Type 1: WinCE 4.2, 400 mhz, 93244 kb Type 2: WinCE 5.0, 520 mhz, 84208 kb Type 1 will happily proceed through a large batch db operation (initiated) by the app, by Type 2 will consistently begin c-r-a-w-l-i-n-g (for several to many cycles) at around the 200 cycle mark. As several points it will begin running normally and then crawl again. The app does several db op's (inserts, updates and selects, no deletes). To simplify my situation, I've built a small test app which essentially does this: command_s.CommandText = "select dvr from vr where vid = 2211250"; command_u.CommandText = "update pvr set LocationID=81 where Status='OK' and vri = 27861"; while(going) { command_s.ExecuteScalar(); command_u.ExecuteNonQuery(); } and set it off running on the two units side by side. Sure enough, the slower (400 mhz) unit is outpacing the faster (520 mhz) unit (it's about 5000 cycles ahead right now) and I can see noticable pauses on the 520 mhz unit. What is causing this?

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  • scroll bar problems in java Layered Panes

    - by vondip
    Hi all, I've been trying to build this small java app. I find it very difficult to design UI in java, tasks that seem very simple become complicated and all these strange misbehaviors occur. In my app I've created a JLayeredPane which contains two layers. One on top on the other, They both contain scrollbars. Here's an explanation of the two layers: Layer 1: A very big image inside something similar to a scrollpane. The image is scrollable. Layer 2: A graphics2d object, this object draws an image. Once the image reaches a certain length, the layer gets a scrollpane that advances with the drawing with time. I'd like to connect both layers. I want layer two to update the scrollbar on layer 1. Meaning that once it reaches a certain length, both scrollbars will advance together. When I try doing that, the two scroll bars really do advance, but ( ! ) this strange flickering occurs. I don't understand what is the reason for the flickering. Is there any other way to implement this in a simple manner? I must have the second layer on top of the first one (drawing on top of image) since I cannot open a special post for thanking the wonderful people of this forum, I'll do it here. Thank you, you are great help. I hope this problem is solvable as well.

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  • Fast way to manually mod a number

    - by Nikolai Mushegian
    I need to be able to calculate (a^b) % c for very large values of a and b (which individually are pushing limit and which cause overflow errors when you try to calculate a^b). For small enough numbers, using the identity (a^b)%c = (a%c)^b%c works, but if c is too large this doesn't really help. I wrote a loop to do the mod operation manually, one a at a time: private static long no_Overflow_Mod(ulong num_base, ulong num_exponent, ulong mod) { long answer = 1; for (int x = 0; x < num_exponent; x++) { answer = (answer * num_base) % mod; } return answer; } but this takes a very long time. Is there any simple and fast way to do this operation without actually having to take a to the power of b AND without using time-consuming loops? If all else fails, I can make a bool array to represent a huge data type and figure out how to do this with bitwise operators, but there has to be a better way.

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  • SQL query to translate a list of numbers matched against several ranges, to a list of values

    - by Claes Mogren
    I need to convert a list of numbers that fall within certain ranges into a list of values, ordered by a priority column. The table has the following values: | YEAR | R_MIN | R_MAX | VAL | PRIO | ------------------------------------ 2010 18000 90100 52 6 2010 240000 240099 82 3 2010 250000 259999 50 5 2010 260000 260010 92 1 2010 330000 330010 73 4 2010 330011 370020 50 5 2010 380000 380050 84 2 The ranges will be different for different years. The ranges within one year will never overlap. The input will be a year and a list of numbers that might fall within one these ranges. The list of input number will be small, 1 to 10 numbers. Example of input numbers: (20000, 240004, 375000, 255000) With that input I would like to get a list ordered by the priority column, or a single value: 82 50 52 The only value I'm interested in here is 82, so UNIQUE and MAX_RESULTS=1 would do. It can easily be done with one query per number, and then sorting it in the Java code, but I would prefer to do it in a single SQL query. What SQL query, to be run in an Oracle database, would give me the desired result?

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  • Open a dialog box in same window on selectOneMenu change

    - by Pravingate
    I have a jsf page where I have a selectOneMenu and , I want to open a dialog box on selectOneMenu changes. As a example if user selects a value ="passive" from jsf selectOneMenu it should open a dialog box or a light box on same page where I want to display a small jsf form like as here done. http://www.primefaces.org/showcase-labs/ui/dialogLogin.jsf and I also want save that submitted data in my backing bean somewhere so I can store it in to database later. I dont know how to open a dialog box or light box from backing bean in same window,as we will identify value change using valueChangeListener event or by using ajax event. I am able to identify which value is selected from selectOneMenu(DropdownMenu), but dont know how to open a dialog box on selecting particular value. <h:outputLabel value="* Country: "/> <h:selectOneMenu id="someSelect" value="#{testController.countryName}" required="true"> <f:selectItem itemLabel="Select Country" itemValue=""/> <f:selectItems value="#{testController.countryNamesSelectItems}"/> </h:selectOneMenu> Supoose we have 2 options in selectItems as India and Austrlia, then If a user choose India a dialog box should open on same page where a user need to fill some information and need to submit if he is from india (like here in example http://www.primefaces.org/showcase-labs/ui/dialogLogin.jsf user will put his username and password and submits data) Hope this helps How can I achieve that by using jsf or javascript or ajax or by any else way?

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  • Unable to create a breakpoint in Eclipse and Tomcat

    - by Traroth
    Since yesterday, I get a strange error message when I start my Tomcat (6.0.35) under Eclipse Juno (build 20120614-1722): Among the things I tried in order to get rid of the error: Check in Preferences - Java - Compiler if all "Classfile Generation" checkboxes where checked. I did that for both general preferences and project preference Uncheck them, build, check them build again (found on another question) Add org.eclipse.jdt.core.compiler.debug.lineNumber=generate to my .settings/org.eclipse.jdt.core.prefs file Use a new CVS checkout (same symptoms) And now, I don't know what to do anymore. The problem is really stopping me from get anything done. I can't work anymore. Crazy is: the problem doesn't happen on every class, only on some of them. Neither does it happen on my other Eclipse projects. And it didn't happen before yesterday, even if I can't remeber having done anything weird. Actually, I have never seen a problem like this in almost 10 years I'm using Eclipse... If you have any idea, I would be really grateful... Edit: I also tried to ignore the message and go on with my tests: If I create another breakpoint upstream from my problematic class, when I enter this problematic class, it tries to open a $Proxy132 class, which means it actually opens an empty page, with a source not found message

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  • IntelliJ Doesn't Notice Changes in Interface

    - by yar
    [I've decided to give IntelliJ another go (to replace Eclipse), since its Groovy support is supposed to be the best. But back to Java...] I have an Interface that defines a constant public static final int CHANNEL_IN = 1; and about 20 classes in my Module that implement that interface. I've decided that this constant was a bad idea so I did what I do in Eclipse: I deleted the entire line. This should cause the Project tree to light up like a Christmas tree and all classes that implement that interface and use that constant to break. Instead, this is not happening. If I don't actually double-click on the relevant classes -- which I find using grep -- the module even builds correctly (using Build - Make Module). If I double-click on a relevant class, the error is shown both in the Project Tree and in the Editor. I am not able to replicate this behavior in small tests, but in large modules it works (incorrectly) this way. Is there some relevant setting in IntelliJ for this?

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  • Has anyone setup tomcat to run virtual hosts using mod_jk

    - by Adam
    I work in OSX primarily with mostly PHP. Normally I work locally using MAMP and virtual hosts setup in my httpd.conf so that I can point a browser to http://some-project and have as many projects as I need setup. We have a project coming up where we need to serve JSP pages and I would like to set up my local apache server to serve only JSP files to Tomcat and everything else to MAMP using the same virtual hosts setup in: ~/applications/MAMP/conf/apache/httpd.conf So far I have: Successfully installed Tomcat Placed mod_jd.so in ~/applications/MAMP/Library/modules/mod_jk.so Added the module by placing: LoadModule jk_module modules/mod_jk.so in ~/applications/MAMP/conf/apache/httpd.conf Created /Library/Tomcat/Home/conf/jk/workers.properties and added the following lines: workers.tomcat_home=/Library/Tomcat workers.java_home=/System/Library/Frameworks/JavaVM.framework/Versions/1.5.0/Home ps=/ worker.list=ajp12, ajp13 worker.ajp13.port=8009 worker.ajp13.host=localhost worker.ajp12.type=ajp13 worker.ajp13.mount=/*.jsp added the following lines: JkWorkersFile /Library/Tomcat/Home/conf/workers.properties JkLogFile /Library/Tomcat/Home/logs/mod_jk.log JkLogLevel debug to ~/applications/MAMP/conf/apache/httpd.conf I cannot start my MAMP however when these last two lines are present in my httpd.conf. Does anyone work like this? Any tips? Any clear ideas of what I'm doing wrong?

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  • Hide Image Title in Slimbox

    - by Stephen
    My issue is a lot like this solved thread, except I'm using Slimbox 2: http://stackoverflow.com/questions/940994/hide-image-title-tool-tip-popup-on-mouse-rollover-or-hover When you hover over an image, the "Title" attribute pops up. I need HTML in my image title in Slimbox. So, of course, when you're hovering, the "Title" attribute shows all the HTML code. The code works perfectly when you're viewing the image in Slimbox so no problems there. I just need the Title attribute to be hidden/modified not to show this HTML code. I tried to change Q.title in slimbox.js to something else (like captionname). Then changed the HTML to call for: <a href="images/team/large.jpg" title="Joe Smith" captionname="URL" rel="lightbox-team"><img src="images/team/small.jpg" class ="headline" border="1" hspace="2" /></a> "Joe Smith" displays as the Title but when you view the image in Slimbox, captionname does not come up at all and neither does the Title. It's just blank where it should be. What do I need to modify in slimbox2.js to make this work?

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  • Castle windsor security exception

    - by Sunil
    I developed a small WCF service that uses Castle Windsor IoC container and it works fine on my PC. When I deploy it onto a Win 2008 R2 server and host the WCF service in IIS 7 it fails with the following error. I checked the server level web.config and the trust level is set to "Full". What do I need to do to get this to work. As a test I deployed the same service as it is onto a Windows 2003 server with the trust level set to "Full" and it works fine. I am unable to figure out what setting/configuration I am missing on the 2008 server that is making the service fail. Stack Trace: [SecurityException: That assembly does not allow partially trusted callers.] Castle.Windsor.WindsorContainer..ctor() +0 WMS.ServiceContractImplementation.IoC.IoCInstanceProvider..ctor(Type serviceType) in D:\WCF\WCFProofOfConcept\WMSServices \WMS.ServiceContractImplementation\IoC\IoCInstanceProvider.cs:19 WMS.ServiceContractImplementation.IoC.IoCServiceBehavior.ApplyDispatchBehav­ior(ServiceDescription serviceDescription, ServiceHostBase serviceHostBase) in D:\WCF \WCFProofOfConcept\WMSServices\WMS.ServiceContractImplementation\IoC \IoCServiceBehavior.cs:24 System.ServiceModel.Description.DispatcherBuilder.InitializeServiceHost(Ser­viceDescription description, ServiceHostBase serviceHost) +377 System.ServiceModel.ServiceHostBase.InitializeRuntime() +37 System.ServiceModel.ServiceHostBase.OnBeginOpen() +27 System.ServiceModel.ServiceHostBase.OnOpen(TimeSpan timeout) +49 System.ServiceModel.Channels.CommunicationObject.Open(TimeSpan timeout) +261 System.ServiceModel.HostingManager.ActivateService(String normalizedVirtualPath) +121 System.ServiceModel.HostingManager.EnsureServiceAvailable(String normalizedVirtualPath) +479

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  • When to drop an IT job

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

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  • Same session and session ID for different subdomains in Grails project - How can I do that?

    - by fluxon
    I am currently working on a project that supports multiple languages. In order to be seo friendly, I am trying to redirect users subdomains corresponding to their locale (or their preferred language). I.e., my projects's url is mydomain.com and I work with the subdomains en.mydomain.com, es.mydomain.com, de.mydomain.com, fr.mydomain.com ... you get the idea. All subdomains are served by the same grails app for now. What happens is that my grails project maintains different sessions (as seen by the session ids) for every single subdomain, hence information is lost, when a user switches between languages. I had not forseen that. :( How can I explicitly set the session identifier? I would like it to be based on just mydomain.com. I got the hint that Apache Tomcat offers something like <Context sessionCookiePath="/" sessionCookieDomain=".mydomain.com"> , but that does not help for the devel environment etc. Any hints? Have you tried storing session information in the DB? This is sometimes used for load-balancing purposes and might help here as well?! Help is highly appreciated (as always)! Cheers!

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  • Iterating through Event Log Entry Collection, IndexOutOutOfBoundsException

    - by fjdumont
    Hello, in a service application I am iterating through the Windows application event log to parse Events in order react depanding on the entry message. In the case that the event log is full (Windows usually makes sure there is enough space by deleting old entries - this is configurable in the eventvwr.exe settings), the service always runs into an IndexOutOfBoundsException while iterating through the EventLog.Entries collection. No matter how I iterate (for-loop, using the collections enumerator, copying the collection into an array, ...), I can't seem to get rid of this ´bug´. Currently, I ensure that the log is not full in order to keep the service running by regularly deleting the last few item by parsing the event log file and deleting the last few nodes (Don't beat me up, I couldn't find a better alternative...). How can I iterate through the collection without trying to access already deleted entries? Is there probably a more elegant method? I am only trying to acces the logs written during the last x seconds (even LINQ failed to select those when the log is full - same exception), could this help? Thanks for any advice and hints Frank Edit: I forgot to mention that my assumption is the loops are accessing entries which are being deleted during iteration by Windows. Basically that is why I tried to clone the collection. Is there perhaps a way to lock the collection for a small amount of time for just my application?

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  • Are bad data issues that common?

    - by Water Cooler v2
    I've worked for clients that had a large number of distinct, small to mid-sized projects, each interacting with each other via properly defined interfaces to share data, but not reading and writing to the same database. Each had their own separate database, their own cache, their own file servers/system that they had dedicated access to, and so they never caused any problems. One of these clients is a mobile content vendor, so they're lucky in a way that they do not have to face the same problems that everyday business applications do. They can create all those separate compartments where their components happily live in isolation of the others. However, for many business applications, this is not possible. I've worked with a few clients, one of whose applications I am doing the production support for, where there are "bad data issues" on an hourly basis. Yeah, it's that crazy. Some data records from one of the instances (lower than production, of course) would have been run a couple of weeks ago, and caused some other user's data to get corrupted. And then, a data script will have to be written to fix this issue. And I've seen this happening so much with this client that I have to ask. I've seen this happening at a moderate rate with other clients, but this one just seems to be out of order. If you're working with business applications that share a large amount of data by reading and writing to/from the same database, are "bad data issues" that common in your environment?

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  • Configuring TeamCity + NUnit unit tests so files can be loaded properly

    - by Dave
    In a nutshell, I have a solution that builds fine in the IDE, and the unit tests all run fine with the NUnit GUI (via the NUnitit VS2008 plugin). However, when I execute my TeamCity build runner, all unit tests that require file access (e.g. for running tests against specific XML files), I just get System.IO.DirectoryNotFoundExceptions. The reason for this is clear: it's looking for those supporting XML files loaded by various unit tests in the wrong folder. The way my unit tests are structured looks like this: +-- project folder +-- unit tests folder +-- test.xml +-- test.cs +-- project file.xaml +-- project file.xaml.cs All of my projects own their own UnitTests folder, which contains the .cs file and any XML files, XML Schemas, etc that are necessary to run the tests. So when I write my test.cs, I have it look for "test.xml" in the code because they are in the same folder (actually, I do something like ....\unit tests\test.xml, but that's kind of silly). As I said before, the tests run great in NUnit. But that's because the unit tests are part of the project. When running the unit tests from TeamCity, I am executing them against the assemblies that get copied to the main app's output folder. These unit test XML files should not be copied willy-nilly to the output folder just to make the tests pass. Can anyone suggest a better method of organizing my unit tests in each project (which are dependencies for the main app), such that I can execute the unit tests from NUnit and from the TeamCity build runner? The only other option I can come up with is to just put the testing XML data in code, rather than loading it from a file. I would rather not do this.

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  • Travelling Visual Studio developers

    - by Graphain
    Hi, I am about to travel to Europe (I'm Australian but imagine this is a similar circumstance for US users and simply flipped for European users). However, there is the slim possibility I will need to do some Visual Studio work while I'm travelling. As I see it I have three options: Leave a desktop PC on at home, access remotely via net cafes. Carry a laptop with me on the trip, upload files as required using public wifi. Option 2 but instead buy cheap light netbook that is miraculously capable of running VS. Does anyone have any experience or advice to shed on any of these options? For reference, this existing post suggests that VS remotely for short distances is okay, but over longer distances could be more problematic. I've used VS via RDP to a US server before and it was pretty laggy but for small changes I could get by. Concerns I have that you may have some experience with: Weight of luggage (ideally like to travel light) Security of laptop (imagine it'll be too heavy to carry around all the time so have to leave it at hotel/hostel etc. and hope for the best) Security of data (don't want someone stealing RDP access to my home PC) Security of FTP (don't want someone stealing FTP passwords over wireless)

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  • Behavior of <- NULL on lists versus data.frames for removing data

    - by Ananda Mahto
    Many R users eventually figure out lots of ways to remove elements from their data. One way is to use NULL, particularly when you want to do something like drop a column from a data.frame or drop an element from a list. Eventually, a user comes across a situation where they want to drop several columns from a data.frame at once, and they hit upon <- list(NULL) as the solution (since using <- NULL will result in an error). A data.frame is a special type of list, so it wouldn't be too tough to imagine that the approaches for removing items from a list should be the same as removing columns from a data.frame. However, they produce different results, as can be seen in the example below. ## Make some small data--two data.frames and two lists cars1 <- cars2 <- head(mtcars)[1:4] cars3 <- cars4 <- as.list(cars2) ## Demonstration that the `list(NULL)` approach works cars1[c("mpg", "cyl")] <- list(NULL) cars1 # disp hp # Mazda RX4 160 110 # Mazda RX4 Wag 160 110 # Datsun 710 108 93 # Hornet 4 Drive 258 110 # Hornet Sportabout 360 175 # Valiant 225 105 ## Demonstration that simply using `NULL` does not work cars2[c("mpg", "cyl")] <- NULL # Error in `[<-.data.frame`(`*tmp*`, c("mpg", "cyl"), value = NULL) : # replacement has 0 items, need 12 Switch to applying the same concept to a list, and compare the difference in behavior. ## Does not fully drop the items, but sets them to `NULL` cars3[c("mpg", "cyl")] <- list(NULL) # $mpg # NULL # # $cyl # NULL # # $disp # [1] 160 160 108 258 360 225 # # $hp # [1] 110 110 93 110 175 105 ## *Does* drop the `list` items while this would ## have produced an error with a `data.frame` cars4[c("mpg", "cyl")] <- NULL # $disp # [1] 160 160 108 258 360 225 # # $hp # [1] 110 110 93 110 175 105 The main questions I have are, if a data.frame is a list, why does it behave so differently in this scenario? Is there a foolproof way of knowing when an element will be dropped, when it will produce an error, and when it will simply be given a NULL value? Or do we depend on trial-and-error for this?

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  • Do ORMs normally allow circular relations? If so, how would they handle it?

    - by SeanJA
    I was hacking around trying to make a basic orm that has support for the one => one and one => many relationships. I think I succeeded somewhat, but I am curious about how to handle circular relationships. Say you had something like this: user::hasOne('car'); car::hasMany('wheels'); car::property('type'); wheel::hasOne('car'); You could then do this (theoretically): $u = new user(); echo $u->car->wheels[0]->car->wheels[1]->car->wheels[2]->car->wheels[3]->type; #=> "monster truck" Now, I am not sure why you would want to do this. It seems like it wastes a whole pile of memory and time just to get to something that could have been done in a much shorter way. In my small ORM, I now have 4 copies of the wheel class, and 4 copies of the car class in memory, which causes a problem if I update one of them and save it back to the database, the rest get out of date, and could overwrite the changes that were already made. How do other ORMs handle circular references? Do they even allow it? Do they go back up the tree and create a pointer to one of the parents? DO they let the coder shoot themselves in the foot if they are silly enough to go around in circles?

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  • git rebse onto remote updates

    - by Blake Chambers
    I work with a small team that uses git for source cod management. Recently, we have been doing topic branches to keep track of features then merging them into master locally then pushing them to a central git repository on a remote server. This works great when no changes have been made in master: I create my topic branch, commit it, merge it into master, then push. Hooray. However, if someone has pushed to origin before i do, my commits are not fast-forward. Thus a merge commit ensues. This also happens when a topic branch needs to merge with master locally to ensure my changes work with the code as of now. So, we end up with merge commits everywhere and a git log rivaling a friendship bracelet. So, rebasing is the obvious choice. What I would like is to: create topic branches holding several commits checkout master and pull (fast-forward because i haven't committed to master) rebase topic branches onto the new head of master rebase topics against master(so the topics start at masters head), bringing master up to my topic head My way of doing this currently is listed below: git checkout master git rebase master topic_1 git rebase topic_1 topic_2 git checkout master git rebase topic_2 git branch -d topic_1 topic_2 Is there a faster way to do this?

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  • What is the performance impact of CSS's universal selector?

    - by Bungle
    I'm trying to find some simple client-side performance tweaks in a page that receives millions of monthly pageviews. One concern that I have is the use of the CSS universal selector (*). As an example, consider a very simple HTML document like the following: <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8"/> <title>Example</title> <style type="text/css"> * { margin: 0; padding: 0; } </head> <body> <h1>This is a heading</h1> <p>This is a paragraph of text.</p> </body> </html> The universal selector will apply the above declaration to the body, h1 and p elements, since those are the only ones in the document. In general, would I see better performance from a rule such as: body, h1, p { margin: 0; padding: 0; } Or would this have exactly the same net effect? Essentially, what I'm asking is if these rules are effectively equivalent in this case, or if the universal selector has to perform more unnecessary work that I may not be aware of. I realize that the performance impact in this example may be very small, but I'm hoping to learn something that may lead to more significant performance improvements in real-world situations. Thanks for any help!

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  • ASP.NET MVC Viewmodel trouble...

    - by ile
    I've already started similar topic, but still didn't find final solution... So here I am with new one :) ... I'm developing NerdDinner from scratch and now I came to point where I define DinnerViewModel. Following these instructions (starting from Listing 5) I came to this: namespace Nerd.Controllers { // View Model Classes public class DinnerViewModel { public DinnerViewModel(List<Dinner> dinners) { this.Dinners = dinners; } public List<Dinner> Dinners { get; private set; } } public class DinnerController : Controller { private DinnerRepository dinnerRepository = new DinnerRepository(); .... public ActionResult NewDinners() { // Create list of products var dinners = new List<Dinner>(); dinners.Add(new Dinner(/*Something to add*/)); // Return view return View(new DinnerViewModel(dinners)); } } } Also, the Dinner table in this new version of NerdDinner is a bit shortened (it contains of DinnerID, Title, EventDate and Description fields). No matter what I try to add here dinners.Add(new Dinner(/*Something to add*/)); I always get following error Error 1 'Nerd.Model.Dinner' does not contain a constructor that takes '1' arguments C:\Documents and Settings\ilija\My Documents\Visual Studio 2008\Projects\Nerd\Nerd\Controllers\DinnerController.cs 150 25 Nerd Because I'm total beginner in C# and generally OOP, I have no idea what to do here... I suppose I need to declare a constructor, but how and where exactly? Thanks, Ile

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