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  • When is it appropriate to use C++ exceptions?

    - by krebstar
    I'm trying to design a class that needs to dynamically allocate some memory.. I had planned to allocate the memory it needs during construction, but how do I handle failed memory allocations? Should I throw an exception? I read somewhere that exceptions should only be used for "exceptional" cases, and running out of memory doesn't seem like an exceptional case to me.. Should I allocate memory in a separate initialization routine instead and check for failures and then destroy the class instance gracefully? Or should I use exceptions instead? The class won't have anything useful to do if these memory allocations should fail.. EDIT: The consensus seems to be that running out of memory IS an exceptional case. Will see how to go about this.. Thanks.. :)

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  • Element point map for html5 canvas element, need algorithm

    - by Artiom Chilaru
    I'm currently working on a pure html 5 canvas implementation of the "flying tag cloud sphere", which many of you have undoubtedly seen as a flash object in some pages. The tags are drawn fine, and the performance is satisfactory, but there's one thing in the canvas element that's kind of breaking this idea: you can't identify the objects that you've drawn on a canvas, as it's just a simple flat "image".. What I have to do in this case is catch the click event, and try to "guess" which element was clicked. So I have to have some kind of matrix, which stores a link to a tag object for each pixel on the canvas, AND I have to update this matrix on every redraw. Now this sounds incredibly inefficient, and before I even start trying to implement this, I want to ask the community - is there some "well known" algorithm that would help me in this case? Or maybe I'm just missing something, and the answer is right behind the corner? :)

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  • Feature categories for a social network

    - by mafutrct
    Not sure if this question belongs on SO. Anyway, please let me try to clarify the issue. I'm currently planning a social program. It's basically a chat server with the major additional ability to play games. I'd like to create categories of features that are offered to users. My question is, are there any useful standard feature categories? Does not have to be specific to my case, I'm interested in the general case as well. Just to give you an idea of what I'm thinking: functional e.g. play games social e.g. chatting operational e.g. 24/7 service availability I'm entirely unsure if this is the right place to ask, if you know of any better site to ask please don't hesitate to add a comment.

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  • How to null a translation in gettext system?

    - by Evgeny
    Suppose a simple phrase "In" in English needs to be interpreted as "" - empty string in Russian. Is is possible to specify that in the .po file? What normally happens if you set msgstr "" - you'll get the untranslated key, but I want to get nothing in that specific case. Here is a use case: I have underneath a giant search bar a set of buttons to select questions (for a Q&A site) from particular scopes - like so: (in English) In: [all] [unanswered] [my own] (in Russian I want) [???] [??? ???????] [???] It just sounds more natural. Yes I can leave out In for english, but I don't want to and I do not want to put button (things in [] are buttons) html into the 'po' file. Thanks!

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  • iPhone memory management

    - by Prazi
    I am newbie to iPhone programming. I am not using Interface Builder in my programming. I have some doubt about memory management, @property topics in iPhone. Consider the following code @interface LoadFlag : UIViewController { UIImage *flag; UIImageView *preview; } @property (nonatomic, retain) UIImageView *preview; @property (nonatomic, retain) UIImage *flag; @implementation @synthesize preview; @synthesize flag; - (void)viewDidLoad { flag = [UIImage imageNamed:@"myImage.png"]]; NSLog(@"Preview: %d\n",[preview retainCount]); //Count: 0 but shouldn't it be 1 as I am retaining it in @property in interface file preview=[[UIImageView alloc]init]; NSLog(@"Count: %d\n",[preview retainCount]); //Count: 1 preview.frame=CGRectMake(0.0f, 0.0f, 100.0f, 100.0f); preview.image = flag; [self.view addSubview:preview]; NSLog(@"Count: %d\n",[preview retainCount]); //Count: 2 [preview release]; NSLog(@"Count: %d\n",[preview retainCount]); //Count: 1 } When & Why(what is the need) do I have to set @property with retain (in above case for UIImage & UIImageView) ? I saw this statement in many sample programs but didn't understood the need of it. When I declare @property (nonatomic, retain) UIImageView *preview; statement the retain Count is 0. Why doesn't it increase by 1 inspite of retaining it in @property. Also when I declare [self.view addSubview:preview]; then retain Count increments by 1 again. In this case does the "Autorelease pool" releases for us later or we have to take care of releasing it. I am not sure but I think that the Autorelease should handle it as we didn't explicitly retained it so why should we worry of releasing it. Now, after the [preview release]; statement my count is 1. Now I don't need UIImageView anymore in my program so when and where should I release it so that the count becomes 0 and the memory gets deallocated. Again, I am not sure but I think that the Autorelease should handle it as we didn't explicitly retained it so why should we worry of releasing it. What will happen if I release it in -(void) dealloc method In the statement - flag = [UIImage imageNamed:@"myImage.png"]]; I haven't allocated any memory to flag but how can I still use it in my program. In this case if I do not allocate memory then who allocates & deallocates memory to it or is the "flag" just a reference pointing to - [UIImage imageNamed:@"myImage.png"]];. If it is a reference only then do i need to release it. Thanks in advance.

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  • Haskell: variant of `show` that doesn't wrap String and Char in quotes

    - by Joey Adams
    I'd like a variant of show (let's call it label) that acts just like show, except that it doesn't wrap Strings in " " or Chars in ' '. Examples: > label 5 "5" > label "hello" "hello" > label 'c' "c" I tried implementing this manually, but I ran into some walls. Here is what I tried: {-# LANGUAGE FlexibleInstances #-} {-# LANGUAGE UndecidableInstances #-} module Label where class (Show a) => Label a where label :: a -> String instance Label [Char] where label str = str instance Label Char where label c = [c] -- Default case instance Show a => Label a where label x = show x However, because the default case's class overlaps instance Label [Char] and instance Label Char, those types don't work with the label function. Is there a library function that provides this functionality? If not, is there a workaround to get the above code to work?

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  • Typical text encoding and EOL behavior on mobile devices

    - by Dan W
    Typical things to worry about when dealing with text are the BOM/signature, encoding, and the end of line (EOL) char/chars. I know that Windows often favours \r\n (CR+LF) and Mac/Linux favours \n (LF), but how about popular mobile devices such as the iPhone and Android? Do typical apps on those platforms favour one or the other (or maybe even \r for iOS)? I'll supply both types to the user just in case, but I'd like to choose one as default. Also, which text encodings are mobiles most likely to use - UTF-8, iso-8859-1, Windows 1252 (or other default codepage) or maybe even UTF-16? And if they use UTF-8/16, are they likely to need (or require not having) a BOM/signature? What is the typical behavior here? Once again, I'll supply a range of encodings to the user just in case, but I'd like to prioritize or use certain encodings as default if it's appropriate.

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  • open iphone Mail from Actionsheet..

    - by totato
    hi .. I want to open Mail app from my app when the one button in actionsheet is pressed, I know this way : -(IBAtion)openClick:(id)sender { [[UIApplication sharedApplication] openURL:[NSURL URLWithString:@”mailto:[email protected]”]]; } but can I write this method inside if statement or switch case?(in ControlView class NOT NSObject class , because I use actionsheet for this propose) like this: - (void)actionSheet:(UIActionSheet *)modalView clickedButtonAtIndex:(NSInteger)buttonIndex { switch (buttonIndex) { case 0: { [[UIApplication sharedApplication] openURL:[NSURL URLWithString:@”mailto:[email protected]”]]; break; } I can't test my code because simulator doesn't have the Mail app.. So I need to know is this will work in controlView or must write it in NSObject class ? + seconde question : I want to open Mail app from my app and copy the content in the view to mail body,then the user choice the contact from his contacts list ! Is this way achieve my goal?

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  • Facing problem in VB6.0 Activex Controls design.

    - by Dharmaraju
    Hi, This is dharmaraju, I am facing some problem in Activex Controls design. Kindly help me to resolve the issue. Problem Description: I have created a property mentioned below for a textbox. Public Property Let DataControl_Value(ByVal Value As Variant) Public Property Get DataControl_Value() As Variant This property is editable at design time if i use it VB6.0 Applications. Same thing is read only in case if i use it in vc++ MFC applications. I have defined one more property like below. Public Property Let DataControl_DataItemDef(ByVal Value As DTMDATACONTROLLib.IXMLDOMNode) Public Property Get DataControl_DataItemDef() As DTMDATACONTROLLib.IXMLDOMNode In this case the "DataControl_DataItemDef" property will not be available at design time.[not displaying in control's property window.] Kindly help me to resolve the issue.

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  • Delete old map markers and load new ones?

    - by pufAmuf
    I'm trying to delete the old markers and load new ones. Here is the code I have that loads certain markers on page load - no issues here: (function() { var customIcons = { 1: { icon: 'redmarker.png', shadow: 'markershadow.png' }, 2: { icon: 'purplemarker.png', shadow: 'markershadow.png' }, 3: { icon: 'silvermarker.png', shadow: 'markershadow.png' }, 4: { icon: 'goldmarker.png', shadow: 'markershadow.png' } }; window.onload = function(){ var MY_MAPTYPE_ID = 'custom'; var stylez = [ { "stylers": [ { "hue": "#00ccff" }, { "saturation": -100 }, { "lightness": 5 } ] },{ } ]; var latlng = new google.maps.LatLng(10, 10); var options = { zoom: 16, center: latlng, panControl: false, zoomControl: false, scaleControl: true, mapTypeControlOptions: { mapTypeIds: [MY_MAPTYPE_ID,google.maps.MapTypeId.SATELLITE] }, mapTypeId: MY_MAPTYPE_ID }; var map = new google.maps.Map(document.getElementById('map'), options); var styledMapOptions = { name: 'Map' }; var jayzMapType = new google.maps.StyledMapType(stylez, styledMapOptions); map.mapTypes.set(MY_MAPTYPE_ID, jayzMapType); var infoWindow = new google.maps.InfoWindow; // Change this depending on the name of your PHP file downloadUrl("getxml.php", function(data) { var xml = data.responseXML; var markers = xml.documentElement.getElementsByTagName("marker"); for (var i = 0; i < markers.length; i++) { var name = markers[i].getAttribute("id"); var address = markers[i].getAttribute("id"); var type = markers[i].getAttribute("venue_type"); var point = new google.maps.LatLng( parseFloat(markers[i].getAttribute("lat")), parseFloat(markers[i].getAttribute("lng"))); var html = "<b>" + name + "</b> <br/>" + address; var icon = customIcons[type] || {}; var marker = new google.maps.Marker({ map: map, position: point, icon: icon.icon, shadow: icon.shadow }); bindInfoWindow(marker, map, infoWindow, html); } }); //BUTTON SWITCHING //////////////////////////////////////////////////////////// //BUTTON SWITCHING //////////////////////////////////////////////////////////// //BUTTON SWITCHING //////////////////////////////////////////////////////////// //BUTTON SWITCHING //////////////////////////////////////////////////////////// //BUTTON SWITCHING //////////////////////////////////////////////////////////// //BUTTON SWITCHING //////////////////////////////////////////////////////////// //BUTTON SWITCHING //////////////////////////////////////////////////////////// jQuery(document).delegate(".topCanBeActive", "click", function( e ) { e.preventDefault(); jQuery(".topCanBeActive").removeClass("topActive"); jQuery(this).addClass("topActive"); switch( this.id ){ case 'all_activity_button': alert("search"); break; case 'events_button': downloadUrl("getxml2.php", function(data) { var xml = data.responseXML; var markers = xml.documentElement.getElementsByTagName("marker"); for (var i = 0; i < markers.length; i++) { var name = markers[i].getAttribute("id"); var address = markers[i].getAttribute("id"); var type = markers[i].getAttribute("venue_type"); var point = new google.maps.LatLng( parseFloat(markers[i].getAttribute("lat")), parseFloat(markers[i].getAttribute("lng"))); var html = "<b>" + name + "</b> <br/>" + address; var icon = customIcons[type] || {}; var marker = new google.maps.Marker({ map: map, position: point, icon: icon.icon, shadow: icon.shadow }); bindInfoWindow(marker, map, infoWindow, html); } }); break; case 'venues_button': alert("venues"); break; case 'search_button': alert("search"); break; } }); //END //////////////////////////////////////////////////////////// //END //////////////////////////////////////////////////////////// //END //////////////////////////////////////////////////////////// //END //////////////////////////////////////////////////////////// //END //////////////////////////////////////////////////////////// //END //////////////////////////////////////////////////////////// //END //////////////////////////////////////////////////////////// //END //////////////////////////////////////////////////////////// } function bindInfoWindow(marker, map, infoWindow, html) { google.maps.event.addListener(marker, 'click', function() { infoWindow.setContent(html); infoWindow.open(map, marker); }); } function downloadUrl(url, callback) { var request = window.ActiveXObject ? new ActiveXObject('Microsoft.XMLHTTP') : new XMLHttpRequest; request.onreadystatechange = function() { if (request.readyState == 4) { request.onreadystatechange = doNothing; callback(request, request.status); } }; request.open('GET', url, true); request.send(null); } function doNothing() {} })(); Now, I created a button section where if you press one button, a different xml file is loaded. Notice the section with the ////////////////////// However, upon clicking the button, nothing happens. The xml file itself is okay and loads the desired data. I also receive no errors in firebug. Any ideas why this happens? Thanks!

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  • Insert into a generic dictionary with possibility of duplicate keys?

    - by Chris Clark
    Is there any reason to favor one of these approaches over the other when inserting into a generic dictionary with the possibility of a key conflict? I'm building an in-memory version of a static collection so in the case of a conflict it doesn't matter whether the old or new value is used. If Not mySettings.ContainsKey(key) Then mySettings.Add(key, Value) End If Versus mySettings(key) = Value And then of course there is this, which is obviously not the right approach: Try mySettings.Add(key, Value) Catch End Try Clearly the big difference here is that the first and second approaches actually do different things, but in my case it doesn't matter. It seems that the second approach is cleaner, but I'm curious if any of you .net gurus have any deeper insight. Thanks!

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  • What are the advantages to use StringBuilder versus XmlDocument or related to create XML documetns?

    - by Rob
    This might be a bit of a code smell, but I have seen it is some production code, namely the use of StringBuilder as opposed to XmlDocument when creating XML documents. In some cases these are write once operations (e.g. create the document and save it to disk) where as others are passing the built string to an XmlDocument to preform an XslTransform to a document that is returned to the client. So obvious question: is there merit to doing things this way, is it something that should be done on a case-by-case basis, or is this the wrong way of doing things?

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  • Is there a name for the technique of using base-2 numbers to encode a list of unique options?

    - by Lunatik
    Apologies for the rather vague nature of this question, I've never been taught programming and Google is rather useless to a self-help guy like me in this case as the key words are pretty ambiguous. I am writing a couple of functions that encode and decode a list of options into a Long so they can easily be passed around the application, you know this kind of thing: 1 - Apple 2 - Orange 4 - Banana 8 - Plum etc. In this case the number 11 would represent Apple, Orange & Plum. I've got it working but I see this used all the time so assume there is a common name for the technique, and no doubt all sorts of best practice and clever algorithms that are at the moment just out of my reach.

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  • Should class IOException in Java have been an unchecked RuntimeException?

    - by Derek Mahar
    Do you agree that the designers of Java class java.io.IOException should have made it an unchecked run-time exception derived from java.lang.RuntimeException instead of a checked exception derived only from java.lang.Exception? I think that class IOException should have been an unchecked exception because there is little that an application can do to resolve problems like file system errors. However, in When You Can't Throw An Exception, Elliotte Rusty Harold claims that most I/O errors are transient and so you can retry an I/O operation several times before giving up: For instance, an IOComparator might not take an I/O error lying down, but — because many I/O problems are transient — you can retry a few times, as shown in Listing 7: Is this generally the case? Can a Java application correct I/O errors or wait for the system to recover? If so, then it is reasonable for IOException to be checked, but if it is not the case, then IOException should be unchecked so that business logic can delegate handling of this exception to a separate system error handler.

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  • OpenXml - How to identify whether the paragraph extends to next page

    - by K.V.
    From aspx page, I dynamically add paragraphs to a word document using OpenXml SDK. In this case, a page break within a paragraph is not allowed. So in case a paragraph starts in middle of page 1 and extends to page2 then it should actually start in Page2. However, if it ends in the same page it is okay. How to achieve this? Is there a way to set in th document that page break is not allowed within a paragraph? Any input is highly appreciated.

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  • What's the performance penalty of weak_ptr?

    - by Kornel Kisielewicz
    I'm currently designing a object structure for a game, and the most natural organization in my case became a tree. Being a great fan of smart pointers I use shared_ptr's exclusively. However, in this case, the children in the tree will need access to it's parent (example -- beings on map need to be able to access map data -- ergo the data of their parents. The direction of owning is of course that a map owns it's beings, so holds shared pointers to them. To access the map data from within a being we however need a pointer to the parent -- the smart pointer way is to use a reference, ergo a weak_ptr. However, I once read that locking a weak_ptr is a expensive operation -- maybe that's not true anymore -- but considering that the weak_ptr will be locked very often, I'm concerned that this design is doomed with poor performance. Hence the question: What is the performance penalty of locking a weak_ptr? How significant is it?

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  • C++ Long switch statement or look up with a map?

    - by Rachel
    In my C++ application, I have some values that act as codes to represent other values. To translate the codes, I've been debating between using a switch statement or an stl map. The switch would look something like this: int code; int value; switch(code) { case 1: value = 10; break; case 2: value = 15; break; } The map would be an stl::map<int, int> and translation would be a simple lookup with the code used as the key value. Which one is better/more efficient/cleaner/accepted? Why?

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  • Scala: Matching optional Regular Expression groups

    - by Brian Heylin
    I'm trying to match on an option group in Scala 2.8 (beta 1) with the following code: import scala.xml._ val StatementPattern = """([\w\.]+)\s*:\s*([+-])?(\d+)""".r def buildProperty(input: String): Node = input match { case StatementPattern(name, value) => <propertyWithoutSign /> case StatementPattern(name, sign, value) => <propertyWithSign /> } val withSign = "property.name: +10" val withoutSign = "property.name: 10" buildProperty(withSign) // <propertyWithSign></propertyWithSign> buildProperty(withoutSign) // <propertyWithSign></propertyWithSign> But this is not working. What is the correct way to match optional regex groups?

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  • why is there different id syntax in the Android docs?

    - by darren
    This page in the Android documentation defines an element id as follows: <TextView android:id="@+id/label" android:layout_width="fill_parent" android:layout_height="wrap_content" android:text="Type here:" /> However this page defines it as: <EditText id="text" xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="fill_parent" android:layout_height="fill_parent" android:textColor="@color/opaque_red" android:text="Hello, World!" /> I thought I had a decent understanding of what was going on until I saw this second example. In the first case, you need the + character so that id 'label' is added to the R file, correct? In the second case, would the EditText's id not be added to the R file because it does not contain the + character? Also, the second example does not include the android namespace on the id. Does having or not having the Android namespace affect whether that id will be added to the R file? Thanks for any clarification.

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  • Is it possible to send an automated email with dynamic content in Rails

    - by Danny McClelland
    Hi Everyone, I am looking into the best way of doing the following: I have a model called Kase, and when a user creates a new case then are taken to the show view as you would expect. I am trying to work out what the best way of sending an automated email between those two events is. I would need to include in the email the content of a couple of the fields, ideally I am looking for a way of just typing out the email and adding the same snippets that are in the show view for each of the fields I need. I am using the Base App from Github so the email sending is already setup for the user authentication and registration, but I'm not sure where to begin. The reason I want to send the email is to create a new Case in our Highrise account, and I don't have a clue how to use the API. So I think the email sending is the easier way. Thanks, Danny

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  • Transition between many Views in ViewFlipper ?

    - by user164589
    Hi guys, I am using "ViewFlipper" for my application. This ViewFlipper includes 5 layouts. I am trying make it that can be changed from current layout to any layout. In other words, it can be changed Layout#1 - Layout#5 or Layout#4 - Layout#1 ..etc. How to make it ? I used showNext() and showPrevious(). It is not better idea for my case. Can I use ViewSwither instead of this case ? Please advice. Can you give example code related this issue ? Thanks in advance.

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  • How to salvage SQL server 2008 query from KILLED/ROLLBACK state without waiting half a day?

    - by littlegreen
    I have a stored procedure that inserts batches of millions of rows, emerging from a certain query, into an SQL database. It has one parameter selecting the batch; when this parameter is omitted, it will gather a list of batches and recursively call itself, in order to iterate over batches. In (pseudo-)code, it looks something like this: CREATE PROCEDURE spProcedure AS BEGIN IF @code = 0 BEGIN ... WHILE @@Fetch_Status=0 BEGIN EXEC spProcedure @code FETCH NEXT ... INTO @code END END ELSE BEGIN -- Disable indexes ... INSERT INTO table SELECT (...) -- Enable indexes ... Now it can happen that this procedure is slow, for whatever reason: it can't get a lock, one of the indexes it uses is misdefined or disabled. In that case, I want to be able kill the procedure, truncate and recreate the resulting table, and try again. However, when I try and kill the procedure, the process frequently oozes into a KILLED/ROLLBACK state from which there seems to be no return. From Google I have learned to do an sp_lock, find the spid, and then kill it with KILL <spid>. But when I try to kill it, it tells me SPID 75: transaction rollback in progress. Estimated rollback completion: 0%. Estimated time remaining: 554 seconds. I did find a forum message hinting that another spid should be killed before the other one can start a rollback. But that didn't work for me either, plus I do not understand, why that would be the case... could it be because I am recursively calling my own stored procedure? (But it should be having the same spid, right?) In any case, my process is just sitting there, being dead, not responding to kills, and locking the table. This is very frustrating, as I want to go on developing my queries, not waiting hours on my server sitting dead while pretending to be finishing a supposed rollback. Is there some way in which I can tell the server not to store any rollback information for my query? Or not to allow any other queries to interfere with the rollback, so that it will not take so long? Or how to rewrite my query in a better way, or how kill the process successfully without restarting the server?

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  • JSF: attach rich:toggleControl to radio buttons or select items.

    - by arw
    Has anyone had any success attaching a rich:toggleControl component to a radio button component (h:selectOneRadio) or alternatively any of its children select items (in this case s:enumItem). Basic code example: <h:selectOneRadio value="#{backingValue}"> <s:enumItem enumValue="VAL_1" itemLabel="Value One" /> <s:enumItem enumValue="VAL_2" itemLabel="Value Two" /> <s:convertEnum /> </h:selectOneRadio> The ideal thing would be to attach the toggle control to the enumItems so I could have it switch to a particular state. However at this point I'd be happy if the toggle control can just be attached to the selectOneRadio. I've tried the toggle control as a child of the selectOneRadio and enumItems; neither works. I've also tried wrapping the toggleControl around the selectOneRadio, the toggle control works in this case but the radio buttons don't :(

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  • Why is distributed source control considered harder?

    - by Will Robertson
    It seems rather common (around here, at least) for people to recommend SVN to newcomers to source control because it's "easier" than one of the distributed options. As a very casual user of SVN before switching to Git for many of my projects, I found this to be not the case at all. It is conceptually easier to set up a DCVS repository with git init (or whichever), without the problem of having to set up an external repository in the case of SVN. And the base functionality between SVN, Git, Mercurial, Bazaar all use essentially identical commands to commit, view diffs, and so on. Which is all a newcomer is really going to be doing. The small difference in the way Git requires changes to be explicitly added before they're committed, as opposed to SVN's "commit everything" policy, is conceptually simple and, unless I'm mistaken, not even an issue when using Mercurial or Bazaar. So why is SVN considered easier? I would argue that this is simply not true.

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