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• Wastage of resources in Virtualization

  - by Sabeen Malik

  I am not sure if this is the write place to ask the question. However i hope it is. When looking for a VPS earlier today, I was trying to understand how each container would work in the background. Keeping in mind the fact that the operating system uses most of the power and power on a system, wouldn't having multiple operating systems in the same machine mean more wastage of resources. For instance if i was running centOS on a dedicated box and it was running lets say 20 background OS level processes. Then i go and install a virtualization platform and install 5 more centOS virtual machines in the same system which are exactly the same as the host operating system. Doesn't this mean duplication of those 20 processes 6 times? So internally the context switching is happening between 120 processes instead of 20?

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• why am i getting an error SyntaxError : invalid syntax for this code

  - by eragon1189

  This is a code in python which calculates f (x) =? ((-1)*x)/(x*x+n*n) n from 1 to infinite.... correct to 0.0001, for the range 1 < x < 100 in steps of 0.1.But i am getting an syntax error,as i am new to programming in python... from scipy import * from matplotlib.pyplot import * x=arange(0.1,100,0.1) f=zeros(len(x)) s=-1 for n in range (1,10000): t=s*x/(x*x+n*n) f +=t s =-s if max(abs(t))< 1e-4 break for xx in c_[x,f]: print "%f %f" % (xx[0],xx[1])

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• Brief Explanation of C Supersets?

  - by Ben Hooper

  I'm getting more and more confused in regards to C's supersets the further I venture into the programming world. There's just so many versions.. C, C++, C#, Objective-C, Objective-C++ and God knows what else. I only know tidbits about these languages (some are object-oriented, some are procedural, C was originally developed for UNIX, C++ started as an extension and is used primarily on the Windows OS, Objective-C is primarily used on Linux and Mac OS/iOS, etc), but I'm not even sure that what I know is correct. I would just like someone to shed some light on what I "know" - a little bit more information about which are successive versions, which platforms each are generally used on, which are the best versions to learn, etc if anyone is feeling generous. :) Thanks. :)

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• Trust metrics and related algorithms

  - by Nick Gerakines

  I'm trying to learn more about trust metrics (including related algorithms) and how user voting, ranking and rating systems can be wired to stiffle abuse. I've read abstract articles and papers describing trust metrics but haven't seen any actual implementations. My goal is to create a system that allows users to vote on other users and the content of other users and with those votes and related meta-data, determine if those votes can be applied to a users level or popularity. Have you used or seen some sort of trust system within a social graph? How did it work and what were its areas of strength and weaknesses?

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• How to create an iPad directory view like animation?

  - by mahes25

  In the recent iOS 4.2 update, Apple introduced a nice animation for creating one level directories. I am trying to figure out how to implement a similar animation in my project. I would deeply appreciate it if anyone could give me any pointers to do this efficiently. From my investigation, I believe this animation or effect could be done very efficiently using Core Image which would allow me to write a custom filter. Unfortunately, Core Image is not available in iPhone. So how can do it? I read a blog post that explained a core animation scheme to create an iPad flip clock. The problem I have is similar but has important differences. Besides, I not excited about saving the subimage combinations, which I believe can cause a memory issue. Please enlighten me on the possible ways of doing this animation. I am relatively new to iOS programming, so I might have missed obvious ways of doing this animation or effect.

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• T4 Template Interception

  - by JeffN825

  I'm wondering if anyone out there knows of any T4 template based method interception systems? We are beginning to write mobile applications (currently with MonoTouch for IOS). We have a very nice core set of DI/IoC functionality and I'd like to leverage this in development for the new platform. Since runtime code generation Reflection.Emit is not supported, I'm hoping to use T4 templates to implement the dynamic interception functionality (+ TinyIoC as a container for resolution). We are currently using Castle Windsor (and intend to continue doing so for our SL and full .NET development), but all of the Windsor specific ties are completely encapsulated, so given a suitable T4 solution, it shouldn't be hard to implement an adapter that uses a T4 based implementation instead of Windsor.

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• Best approach to creating a database driven Java website?

  - by Craig Whitley

  I'm fairly new to programming and new to java, but I'd like to jump in the deep end with a little database driven website project. I've read quite a lot about requirements in the 'real world' requesting experience with Spring and Hibernate, so I have those installed on netbeans and a project created (if I hit run I get the default spring page). Now I just need a little guidance as to where to start designing my app (please tell me if I'm getting in a bit too over my head for a beginner!). Should I start off with my classes? - create all my classes as they map to my database tables and decide which attributes and methods each will require? Can anyone suggest any good books for maybe.. making a java based website from scratch (i.e. from design right through to deployment) that might be useful for a beginner? Any help appreciated thanks.

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• generating resource file (Resource Generator)

  - by syedsaleemss

  I'm new to c# programming.. I'm using windows form application c# .net I have been given a .resources file. it contains 2 columns 1) key and 2) values. I have brought the contents of this file into a datagrid using dynamic table in between and using resource manager. Now i have to edit the value column in the datagrid and if i click on a GENERATE button i should create a new resource file and it has to be stored as a file. In the same way i should create many sucj resource file. please help me.

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• Claims-based Authentication: Are strings the essence of claims?

  - by Rising Star

  I've been programming with claims-based authentication for some time now with Windows Identity Foundation. It appears to me that in Windows Identity Foundation, once a user is logged in, the claims are basically strings of information that describe the user. With the old role-based authentication, I could say that a user is or is not a member of a given group, but with claims-based authentication, I can now have strings of information that describe a user. "This user is female". This user was born on "July 6, 1975". "This user logged in using a USB key". Is it the essence of claims-based authentication,that I have strings of information about the user given to the application by the framework?

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• System.Net.Mail.SmtpClient cannot authenticate against a POP3 server, right?

  - by Herchu

  One of our customer seems to have a very old email system, those that ask you to authenticate to the POP3 server before allowing you to send messages through the SMTP server. Regrettably, we have to believe in what our customer tell us for we cannot access their facilities. But as far as I remember, years ago there were mail systems that once you log into the POP3, the STMP server is kept open for a few minutes for the client IP. Our application sends messages by using System.Net.Mail.SmtpClient which seems to be unable to authenticate to those kinds of servers. Is that correct? If so, what would be the simplest workaround? I was thinking of a minimal POP3 implementation (just the login part of the protocol). Would that work? Thanks in advance.

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• Retrieving content of a txt file from URL to Android

  - by eightx2

  I would like to be able to retrieve contents of a .txt file from the internet, and load it in an EditText. I tried using the code on this page: Reading Text File From Server on Android It didn't work, as you might have guessed. I've read on numerous sites about this type of problem, but I can't get anything to work. Someone suggested AndroidHttpClient (http://developer.android.com/reference/android/net/http/AndroidHttpClient.html), but I simply can't find any examples with this. As I'm a newbie in Android programming, I would love if someone could please give me a small example.

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• Crowdsourcing translation for mobile developers?

  - by superg

  I am developing applications for mobile phones with different operating systems (Android, Symbian, iPhone). Applications are sold internationally so they need to be translated to different languages in addition to english version. I assume most mobile developers do the translations using some paid external service each time. This approach does not look very cost-effective to me. Would it make sense to have a website where simple translations would be done using crowdsourcing (other developers)? Most strings in mobile applications are very simple and short, for example "OK, "Cancel", "Are you sure?", "Please enter your password". Also the same strings are used in hundreds of applications. Instead of paying for translating all strings, developers could save money by only buying their difficult application specific translations. Does anyone agree with this idea? I have seen many opensource projects doing the translations succesfully using volunteers.

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• Tabbed application troubles in xcode

  - by trludt

  I am working with my first tabbed application in xcode. I am just testing with some stuff since I'm relatively new to programming. I am just using the 2 views already put into the template. I am putting a slider into the first view and am going to attach it to a text box with numbers. But that isn't the problem! This is probably really stupid and simple, but when i run the application just to see the stuff on the simulator, it is just showing a black screen. NO CLUE WHY! But its killing me and would love some help!

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• After tar extract, Changing Permissions

  - by Moe

  Just a Question Regarding unix and PHP today. What I am doing on my PHP is using the Unix system to untar a tarred file. exec("tar -xzf foo.tar.gz"); Generally everything works fine until I run into this particular foo.tar.gz, which has a file system as follows: Applications/ Library/ Systems/ After running the tar command, it seems that the file permissions get changed to 644 (instead of 755). This causes Permission denied (errno 13) and therefore disabling most of my code. (I'm guessing from lack of privileges) Any way I can stop this tar command completely ruining my permissions? Thanks. Oh and this seems to only happen when I have a foo.tar.gz file that Has this particular file system. Anything else and I'm good.

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• What exactly does "adopt a protocol" mean in the Objective-C / Cocoa documentation ?

  - by driis

  I am a C# developer getting started on Objective-C / Cocoa Touch programming. I think I might have gotten some terms wrong because I keep thinking about them "the C# way". Specifically, I have come around the term "protocol" in various documentation and tutorials. In Objective-C, what exactly is a protocol ? Can it be compared to a C# interface ? Is the following declaration the same as saying "The class is implementing the protocol UITextFieldDelegate" ? Or is UITextFieldDelegate to be compared with a generic type parameter in C# ? @interface MyViewController : UIViewController <UITextFieldDelegate> { }

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• What's the deal with rubygems on Debian? It's different and strange.

  - by JSW

  I've noticed at least the following oddities around rubygems on Debian (5.0 lenny in my case): Packages go into a different installation location: /var/lib/gems vs /usr/lib/ruby/gems The debian package is rubygems 1.3.6, and updating rubygems to the latest version (1.3.7) doesn't work: $ sudo gem update --system ERROR: While executing gem ... (RuntimeError) gem update --system is disabled on Debian. RubyGems can be updated using the official Debian repositories by aptitude or apt-get. Not all gems appear to work like they do on other systems. For instance, when installing Phusion Passenger, it did not detect the "rack" gem even though it was definitely installed. Manually installing rubygems using the source tarball and reinstalling all my gems (to /usr/lib/ruby/gems) made my problems go away. What's the deal? Why is debian's package different?

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• What books help one to learn to read code?

  - by Daniel

  Lion's Commentary on Unix Sixth Edition with Source Code is a wonderful book to learn how to read code. Reading code is important -- how does one learn how to write excellent code without having read excellent code? But, sadly, while great writers, of fiction and non-fiction, all spend a great deal of time reading stuff, we, programmers, seem to avoid it like the plague. Worse still, programming books usually go the same way. They might show a pattern or a style, but they often avoid showing good, complex code, and helping one go through it. There are exceptions, of course. I hope. So, with that in mind, what books are to be found which help one learn how to read code?

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• How does compiling circular dependencies work?

  - by Fabio F.

  I've made the example in Java but I think (not tested) that it works in other (all?) languages. You have 2 files. First, M.java: public class MType { XType x; MType() {x = null;} } Second, another file (in the same directory), XType.java: public class XType { MType m; public XType(MType m) {this.m = m;} } Ok it's bad programming, but if you run javac XType it compiles: compiles even MType because XType needs it. But ... MType needs XType ... how does that work? How does the compiler know what is happening? Probably this is a stupid question, but I would like to know how the compiler (javac or any other compilers you know) manages that situation, not how to avoid it. I'm asking because i'm writing a precompiler and I would like to manage that situation.

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• Manipulating both unicode and ASCII character set in C#

  - by Murlex

  I have this mapping in my C# application string [,] unicode2Ascii = { { "&#3001;", "\x86" } }; ஹ - is the unicode value for a tamil literal "ஹ". This is the raw hex literal for the unicode value saved by MS Word as a byte sequence. I am trying to map these unicode value "strings" to a hex value under 255 (so as to accommodate non-unicode supported systems). I trying to use string.replace like this: S = S.replace(unicode2Ascii[0,0], unicode2Ascii[0,1]); However the resultant ouput has a ? instead of the actual hex 0x86 stored. Any pointer on how I could set the encoding for the second element of that array to something like windows-1252? Or is there a better way to do this conversion? thanks in advance

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• Python editor/IDE for OS X

  - by TheJuice

  As a (reasonably) new Python programmer, what IDEs or editors would you recommend for Python programming on OS X and why (i.e. what features/capabilities/workflow techniques really help)? I've used Xcode and played a bit with TextMate but I can't really say that either have really hit the spot for me (although TextMate's code completion is pretty neat, I think i've been spoilt with code-completion facilities provided by editors for statically-typed languages so maybe i'm subconsciously comparing apples and oranges) I'm looking to increase my efficacy with Python and any tips would be appreciated. I know people have asked similar questions for Python IDEs in general but I am specifically concentrating on OS X and the 'Mac way'. If Xcode or TextMate are thought highly of, perhaps some suggestions as to how I could get the most benefit from the tools would help.

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• Shortest command to calculate the sum of a column of output on Unix?

  - by Andrew

  I'm sure there is a quick and easy way to calculate the sum of a column of values on Unix systems (using something like awk or xargs perhaps), but writing a shell script to parse the rows line by line is the only thing that comes to mind at the moment. For example, what's the simplest way to modify the command below to compute and display the total for the SEGSZ column (70300)? ipcs -mb | head -6 IPC status from /dev/kmem as of Mon Nov 17 08:58:17 2008 T ID KEY MODE OWNER GROUP SEGSZ Shared Memory: m 0 0x411c322e --rw-rw-rw- root root 348 m 1 0x4e0c0002 --rw-rw-rw- root root 61760 m 2 0x412013f5 --rw-rw-rw- root root 8192

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• First and last window don't show up.

  - by SirGregg

  Hi, I'm creating a WinApi application for my programming course. The program is supposed to show an LED clock using a separate window for each 'block'. I have figured most of it out, except for one thing: when creating the two-dimensional array of windows, the first and last window never show up. Here's the piece of code from the InitInstance function: for (int x=0;x<8;x++) for (int y=0;y<7;y++) { digitWnd[x][y] = CreateWindowEx((WS_EX_LAYERED | WS_EX_TRANSPARENT | WS_EX_NOACTIVATE | WS_EX_STATICEDGE), szWindowClass, szTitle, (WS_POPUP| WS_BORDER), NULL, NULL, NULL, NULL, dummyWnd, NULL, hInstance, NULL); ShowWindow(digitWnd[x][y], nCmdShow); UpdateWindow(digitWnd[x][y]); } The same loop bounds are used everytime I interact with the windows (set position and enable/disable). All the windows seem to be working fine, except for digitWnd[0][0] and digitWnd[7][6]... Any ideas as to what is happening?

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• Best directory to store application data with read\write rights for all users?

  - by Wodzu

  Hi guys. Until Windows Vista I was saving my application data into the directory where the program was located. The most common place was "C:\Program Files\MyApplication". As we know, under Vista and later the common user does't have rights to write under "Program Files" folder. So my first idea was to save the application data under "All Useres\Application Data" folder. But it seams that this folder has writing restrictions too! So to sum up, my requirements are: Folder should exist under Windows XP and above Microsoft's systems. All useres of the system should read\write\creation rights to this folder and it subfolders and files. I want to have only one copy of file\files for all useres. Thanks for your time.

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• Debugging ASP.NET in VS

  - by negligible

  A lot of what I'm doing at the moment is figuring out other peoples code and adding or adapting functions, so currently I am debugging more than I am writing code of my own. I'm still new to this, Junior Developer, and I am always finding new ways to improve what I am doing. For example I recently found This Guide which had some excellent tips, such as overriding the ToString() method in your classes so children are readable from their parents. So I am looking for any other tips or tricks to make my debugging more efficient, as I recognise it as a big part of programming, that you more experienced programmers may have picked up or found. Anything appreciated, I can read websites just fine so no need to explain it yourself if you have a good link!

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• Making an asynchronous interface appear synchronous to mod_python users

  - by Trey

  I have a Python-driven web interface powered by Apache 2.2 with mod_python and Python 2.4. I need to make an asynchronous process appear synchronous to users of this web interface. When users access one module on this website: An external SOAP interface will be contacted with a unique identifier and will respond with a number N The external interface will respond asynchronously by contacting a SOAP server on my machine between 1 and 10 times (the number N tells us how many responses we will receive) I need to somehow aggregate these responses and pass them to the original module which will display the information back to the user. The goal is to make the process appear synchronous to the user. What is the best way to handle this synchronization issue? Is this something Twisted would be well-suited for? I am not restricting myself to Python for the solution, though it is preferred because everything else on the server is in Python. I prefer a solution that is both scalable and will take a minimal amount of programming time (though I understand that these attributes are somewhat at odds).

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