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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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• 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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• 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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• 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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• 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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• Would I really want to return the minimum date?

  - by Clay Shannon

  An old work colleague used to quote his father about tools, "You have to be smarter than it." In the code below, Resharper is telling me, "Value assigned is not used in any execution path" (pointing to the first line). If I accept its offer of help, dt is not assigned a value ("today"). Is this a case where "I have to be smarter than it" and ignore their warning, or is this a case where the tool is smarter than me, and I'm just not understanding it? My take on the situation is that if the if statement fails, the current date is returned (the default value I want), but if I acquiesce to Resharper's "demands" it would return the default value for Datetime, which is the minimum date, which I assume is something like 7/4/1776 or 1/1/0000 or so. DateTime dt = DateTime.Now; if (!(DateTime.TryParse(substr, out dt))) { using (var dtpDlgForm = new ReturnDate("Please select the Date that the file was created:")) { if (dtpDlgForm.ShowDialog() == DialogResult.OK) { dt = dtpDlgForm.ReturnVal; } } } return dt;

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• What You Said: How You Set Up a Novice-Proof Computer

  - by Jason Fitzpatrick

  Earlier this week we asked you to share your tips and tricks for setting up a novice-proof computer; read on to see how your fellow readers ensure friends and relatives have a well protected computer. Image available as wallpaper here. If you only listen to a single bit of advice from your fellow readers, let that advice be the importance of separate and non-administrative user accounts. Grant writes: I have two boys, now 8 and 10, who have been using the computer since age 2. I set them up on Linux (Debian first, now Ubuntu) with a limited rights account. They can only make a mess of their own area. Worst case, empty their home directory and let them start over. I have to install software for them, but they can’t break the machine without causing physical damage (hammers, water, etc.) My wife was on Windows, and I was on Debian, and before they had their own, they knew they could only use my computer, and only logged in as themselves. All accounts were password protected, so that was easy to enforce. What Is the Purpose of the “Do Not Cover This Hole” Hole on Hard Drives? How To Log Into The Desktop, Add a Start Menu, and Disable Hot Corners in Windows 8 HTG Explains: Why You Shouldn’t Use a Task Killer On Android

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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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• 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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• Open an Application .exe window inside another application

  - by jpnavarini

  I have an application in WPF running. I would like that, when a button is clicked inside this application, another application opens, with its window maximized. However, I don't want my first application to stop and wait. I want both to be open and running independently. When the button is clicked again, in case the application is minimized, the application is maximized. In case it is not, it is open again. How is it possible using C#? I have tried the following: Process process = Process.GetProcesses().FirstOrDefault(f => f.ProcessName.Contains("Analysis")); ShowWindow((process ?? Process.Start("..\\..\\..\\MS Analysis\\bin\\Debug\\Chemtech.RT.MS.Analysis.exe")).MainWindowHandle.ToInt32(), SW_MAXIMIZE); But the window does not open, even though the process does start.

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• Prototype and jQuery concatenation failure

  - by Corey Hart

  I found something strange when trying to concatenate prototype and jQuery. It seems as though when concatenated, the $ jquery reference doesn't get overwritten by prototype. I've built two test cases to single this out, and it's failing in Chrome8 and FF 3.6. Test Case 1 - Without Concatenation jQuery and Prototype are loaded separately with different script tags. jQuery is loaded first, Prototype second. Test Case 2 - With Concatenation jQuery and Prototype are concatenated into a single file, and loaded with a single script tag. jQuery is first in the script, and prototype is added second. These should act identically, but the second test is throwing errors because the $ function in prototype doesn't overwrite the $ jquery reference. Did I set these up wrong, or are browsers rendering javascript differently when it's all in the same file?

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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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• 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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• How can my team avoid frequent errors after refactoring?

  - by SDD64

  to give you a little background: I work for a company with roughly twelve Ruby on Rails developers (+/- interns). Remote work is common. Our product is made out of two parts: a rather fat core, and thin up to big customer projects built upon it. Customer projects usually expand the core. Overwriting of key features does not happen. I might add that the core has some rather bad parts that are in urgent need of refactorings. There are specs, but mostly for the customer projects. The worst part of the core are untested (as it should be...). The developers are split into two teams, working with one or two PO for each sprint. Usually, one customer project is strictly associated with one of the teams and POs. Now our problem: Rather frequently, we break each others stuff. Some one from Team A expands or refactors the core feature Y, causing unexpected errors for one of Team B's customer projects. Mostly, the changes are not announced over the teams, so the bugs hit almost always unexpected. Team B, including the PO, thought about feature Y to be stable and did not test it before releasing, unaware of the changes. How to get rid of those problems? What kind of 'announcement technique' can you recommend me?

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• Android: heavy traffic on server causes app to force close

  - by user522559

  I have developed an app to communicate with my own server and published it. However, sometimes the app force closes. I know there is no bug in the code because the app works properly most of the time, but sometimes it is waiting for an answer from the server forever. I think this is due to the fact that so many people are using the app, and the app refreshes every 1 second or so, so this heavy traffic causes the server to take a large amount of time to respond. So how do you take care of such a use case? should I have a use case where if the server does not respond after some time you just stop the app and throw a message saying that the server is not responding or something like that?

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• database change after pressing 'X' button

  - by Anup Prakash

  What i know:- We can use Ajax to change database from javascript. So whenever we press the 'X' button on title bar it calls "onbeforeunload" event. And by this event we can change the database. But in my case, i want to change the status of user only when user click on 'X' button. Not in case of changing the page. As because changing the page is unloading the page. and closing the page is also unloading the page(As much i know). Is there any way to differentiate between closing the page and moving from one page to other page? I want to use it for changing the status of user(i.e. login/logout), whenever he presses cross button. I don't want to set status "logout" when user changes the page. I want to set status "logout" when user 'X' the button. Plese help me.

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• The pros and cons of use JSON for WCF service

  - by brz dot net

  What are the pros and cons of the following 2 cases: Case I: Traditional way: Add service reference in project. Create object and Get data from service on server side and bind to asp.net grid. Case II: Update Service for JSON behavior. Add service reference in project. Call service from javascript to get data. Bind data to jquery grid. Which one is the best approach and why?(Not developer point of view) If there is another approach which is more optimized, please explain it.

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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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• Using switch and enumerations as substitute for named methods

  - by MatthewMartin

  This pattern pops up a lot. It looks like a very verbose way to move what would otherwise be separate named methods into a single method and then distinguished by a parameter. Is there any good reason to have this pattern over just having two methods Method1() and Method2() ? The real kicker is that this pattern tends to be invoked only with constants at runtime-- i.e. the arguments are all known before compiling is done. public enum Commands { Method1, Method2 } public void ClientCode() { //Always invoked with constants! Never user input. RunCommands(Commands.Method1); RunCommands(Commands.Method2); } public void RunCommands(Commands currentCommand) { switch (currentCommand) { case Commands.Method1: // Stuff happens break; case Commands.Method2: // Other stuff happens break; default: throw new ArgumentOutOfRangeException("currentCommand"); } }

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• C# how to dynamically cast an object?

  - by JL

  I am building a helper object that has a property called Mailer. In reality Mailer can be either a System.Net.Mail.MailMessage or a Mono.System.Net.Mail.MailMessage. So I would preferably only want 1 declaration of mailer. For example I don't want: private Mono.Mailing.MailMessage MonoMessage = new Mono.Mailing.MailMessage(); private System.Net.Mail.MailMessage MailMessage = new System.Net.Mail.MailMessage(); I would prefer object mailer; Then in constructor switch (software) { case EnunInternalMailingSoftware.dotnet: this.mailer = new System.Net.Mail.MailMessage(); break; case EnunInternalMailingSoftware.mono: this.mailer = new Mono.Mailing.MailMessage(); break; } The problem is that mailer has no properties at design time. So I can't compile my code. How can this be fixed, am I taking the right approach. Thanks in advance

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• Windows Phone7 Development: Selecting target SDK(OS) version

  - by JibW

  I am a bit confusing in selecting the target version in Windows phone7 Application development. In my Windows phone7 app I need to use a light weight relational DB Which didn't introduce with version 7.0 but SQL CE with 7.1 version. The problem is if I select the target version as 7.1, then the devices which came up with windows phone7 OS 7.0 will not be able to install this. But I heard that all the devices that came with windows phone7 OS version 7.0 is upgradable for windows OS version 7.1 for free. If this is the case then if I select the development SDK version as 7.1, then will all the windows phone7 devices be able to install this? Like to know which will be the best Target version in this case to select, before I start developing. Any guidance/ Idea is highly appreciated. Thanks...

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• Detecting regular expression in content during parse

  - by sonofdelphi

  I am writing a parser for C. I was just running it with some other language files (for fun, to see the extent C-likeness). It breaks down if the code being parsed contains regular expressions... Case 1: For example, while parsing the JavaScript code snippet, var phone="(304)434-5454" phone=phone.replace(/[\(\)-]/g, "") //Returns "3044345454" (removes "(", ")", and "-") The '(', '[' etc get matched as starters of new scopes, which may never be closed. Case 2: And, for the Perl code snippet, # Replace backslashes with two forward slashes # Any character can be used to delimit the regex $FILE_PATH =~ s@\\@//@g; The // gets matched as a comment... How can I detect a regular expression within the content text of a "C-like" program-file?

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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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• 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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• C# How to create objects without class definitions?

  - by JL

  Is it possible to create objects at designtime without having to have hard coded class definitions, then populate properties with primitives or even strongly typed data types? This might sound confusing, so I will attempt to give you a use case scenario. Use case: You have an XML config file that could hold configuration values for connecting to various systems in an SOA application. In C# the XML file is read, but for each system the configuration properties are different (e.g: SQL might have a connection string, while SharePoint might need a username + password + domain + url, while yet an smtp server would need username + password + port + url) So instead of creating static classes as follows public class SharePointConfiguration or public class SQLConfiguration, then have each class with custom properties (this is cumbersome) or using a 1990's method, an arrayList or some named collection Is there not a more preferred way to achieve this? Taking advantage of new language features, that can still offer design time intellisense, which would make the code easier to maintain and less prone to error. Thanks

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