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  • TCP sequence number question

    - by Meta
    This is more of a theoretical question than an actual problem I have. If I understand correctly, the sequence number in the TCP header of a packet is the index of the first byte in the packet in the whole stream, correct? If that is the case, since the sequence number is an unsigned 32-bit integer, then what happens after more than FFFFFFFF = 4294967295 bytes are transferred? Will the sequence number wrap around, or will the sender send a SYN packet to restart at 0?

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  • Can an algorithmic process ever give true random numbers ?

    - by Arkapravo
    I have worked with random functions in python,ruby, MATLAB, Bash and Java. Nearly every programming language has a function to generate Random numbers. However, these apparently random sequences are termed as pseudo-random number sequences as the generation follows a deterministic approach, and the sequence seems to repeat (usually with a very large period). My question, can an algorithmic/programming process ever yield true random numbers ? The questions probably is more of theoretical computer science than just programming !

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  • Object responsibilities - list and item

    - by Mark Tyler
    My question is more like a theoretical. Say you have an object, that represents the list of something (articles, pages, accounts etc.) class ObjCollection You have a class, that represents a specific item in collection: class objItem I have a problem thinking of a basic responsibilities of each object. Which class is responsible for creating a new objItem? Which class is responsible for deleting a objItem? Should it delete itself as a method?

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  • Which data structures and algorithms book should I buy?

    - by Hei
    I know C and C++ and I have some experience with Java, but I don't know too much about Algorithms and Data Structures. I did a search on Amazon, but I don't know what book should I choose. I don't want a book which put its basis only on the theoretic part; I want the practical part too (probably more than the theoretical one :) ). I don't want the code to be implemented in a certain language, but if is in Java, probably I would happier. :)

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  • Does iPhone SDK Objective C support functions inside of functions?

    - by Moshe
    I know that javascript, for example supports functions inside of functions, like so: function doSomething(){ function doAnothingThing(){ //this function is redefined every time doSomething() is called and only exists inside doSomething() } //you can also stick it inside of conditions if(yes){ function doSomethingElse(){ //this function only exists if yes is true } } } Does objective-c support this? Theoretical example: -(void) doSomething:(id) sender{ -(void) respondToEvent: (id) sender{ //theoretically? ... please? } } BONUS: What is the proper term for a "local" function?

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  • Filtering constant noise out of a sound stream

    - by tur1ng
    After watching the first game of the FIFA worldcup I was very annoyed by the sound of the Vuvuzelas. A theoretical question came up about filtering that noise out of the sound stream. What algorithms are needed to remove such a "constant" noise and is it possible to keep the quality of other background sounds?

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  • Base Case in a recursive method

    - by Shaza
    Hey all, About my question, I'm asking a theoretical question here about Base case or the halting case in a recursive method, what's its standards? I mean, is it standard not to have body in it, just a return statement? Is it always like the following: If(input operation value) return sth; Do you have different thoughts about it??

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  • Inspiration and influence of the else clause of loop statements in Python?

    - by Aristide
    Python offers an optional else clause in loop statements, which is executed if and only if the loop is not terminated by a break. For an interesting discussion about this neglected commodity, see this question. Here, I just wanted to know: if the very concept of this loop-else construct originates from another language (either theoretical or actually implemented), conversely, if it was taken up in any newer language. May be I should ask the former to Guido, but he surely is a too busy guy for such a futile inquiry. ;-)

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  • is there a proper way to handle multiple errors/exceptions?

    - by toPeerOrNotToPeer
    in OO programming, is there some conceptual pattern, ideas, about handling multiple errors? for example, i have a method that performs some checks and should return an error message for each error found ['name is too short', 'name contains invalid unicode sequences', 'name is too long'] now, should i use an array of exceptions (not thrown exceptions)? or something like this is better: class MyExceptionList extends Exception{ public Void addException(Exception e){} public Array getExceptions(){} } any theory behind this argument will be appreciated! (this isn't a request about a specific programming language, but a pure theoretical one) thank you in advance

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  • Floating point computer - Trouble with getting back correct results

    - by Francisco P.
    Having trouble with a challenge. Let's say I have a theoretical, base 10, floating point calculator with the following characteristics Only 3 digits for mantissa 1 digit for exponent Sign for mantissa and exponent How would this machine compute the following? 300 + \sum_{i=1}^{100} 0.2 The correct result is 320. The machine's result is 300. But why? Can't get where the 20 goes goes missing... Thanks for your time.

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  • What areas of computer science are particularly relevant to mobile development?

    - by MalcomTucker
    This isn't a platform specific question - rather I'm interested in the general platform independent areas of computer science that are particularly relevant to mobile applications development. For example, things like compression techniques, distributed synchronisation algorithims etc.. what theoretical concepts have you found relevant, useful or enabling when building mobile apps?

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  • Make FalseClass behave like TrueClass with meta programming

    - by Edvinas Bartkus
    This is theoretical question: is it possible to change FalseClass behavior to act like TrueClass? It is possible to override to_s, xor, &, | behavior but that is not enough. If you like Test Driven Development, follow my colleague's suggestion: puts "false is new true!" if false puts "never happens" if true Asserts won't work, would it? Is it possible to pass the test successfully?

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  • purpose of php consutructor

    - by Bharanikumar
    Hi , Am working in the classes and object class structure , but not extream level , Just class and function , then in one place instantiation . that's it , not much big functions like __construct etc , Please tell me very simply , 1.what is th purpose of constructor ad destructor , But i know theoretical explanation school level , But i am expecting something like in real time , which situation we have to use, and is there any example for that please tell me, Regards

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  • Purpose of PHP constructors

    - by Bharanikumar
    Hi, I am working with classes and object class structure, but not at a complex level – just classes and functions, then, in one place, instantiation. As to __construct and __destruct, please tell me very simply: what is the purpose of constructors and destructors? I know the school level theoretical explanation, but i am expecting something like in real world, as in which situations we have to use them. Provide also an example, please. Regards

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  • Is Your ASP.NET Development Server Not Working?

    - by Paulo Morgado
    Since Visual Studio 2005, Visual Studio comes with a development web server: the ASP.NET Development Server. I’ve been using this web server for simple test projects since than with Visual Studio 2005 and Visual Studio 2008 in Windows XP Professional on my work laptop and Windows XP Professional, Windows Vista 64bit Ultimate and Windows 7 64bit Ultimate at my home desktop without any problems (apart the known custom identity problem, that is). When I received my new work laptop, I installed Windows Vista 64bit Enterprise and Visual Studio 2008 and, for my surprise, the ASP.NET Development Server wasn’t working. I started looking for differences between the laptop environment and the desktop environment and the most notorious differences were: System Laptop Desktop SKU Windows Vista 64bit Enterprise Windows Vista 64bit Ultimate Joined to a Domain Yes No Anti-Virus McAffe ESET After asserting that no domain policies were being applied to my laptop and domain user and nothing was being logged by the ant-virus, my suspicions turned to the fact that the laptop was running an Enterprise SKU and the desktop was running an Ultimate SKU. After having problems with other applications I was sure that problem was the Enterprise SKU, but never found a solution to the problem. Because I wasn’t doing any web development at the time, I left it alone. After upgrading to Windows 7, the problem persisted but, because I wasn’t doing any web development at the time, once again, I left it alone. Now that I installed Visual Studio 2010 I had to solve this. After searching around forums and blogs that either didn’t offer an answer or offered very complicated workarounds that, sometimes, involved messing with the registry, I came to the conclusion that the solution is, in fact, very simple. When Windows Vista is installed, hosts file, according to this contains this definition: 127.0.0.1 localhost ::1 localhost This was not what I had on my laptop hosts file. What I had was this: #127.0.0.1 localhost #::1 localhost I might have changed it myself, but from the amount of people that I found complaining about this problem on Windows Vista, this was probably the way it was. The installation of Windows 7 leaves the hosts file like this: #127.0.0.1 localhost #::1 localhost And although the ASP.NET Development Server works fine on Windows 7 64bit Ultimate, on Windows 7 64bit Enterprise it needs to be change to this: 127.0.0.1 localhost ::1 localhost And I suspect it’s the same with Windows Vista 64bit Enterprise.

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  • Wine is no longer able to initialize OpenGL

    - by nebukadnezzar
    Since a while, wine is no longer able to initialize OpenGL on my 64bit Linux. This is by no means a unique problem to me- Lots of people with nvidia cards running 64bit linux seem to have this problem with wine on oneiric: http://forum.winehq.org/viewtopic.php?p=66856&sid=9d6e5ad628ee6fb6e5ef04577275daed http://forum.pinguyos.com/Thread-Wine-OpenGl-Problem https://bbs.archlinux.org/viewtopic.php?id=137696 And while some launchpad bug reports say one should use this workaround: LD_PRELOAD=/usr/lib32/nvidia-current/libGL.so.1 wine <app> It unfortunately does not solve the problem at all for me; That is, if i'd run CS:S, the game will run just fine for a while, but will abort after some time, including a range of GLSL-related errors. Here the startup errors from simply running steam: + wine steam.exe fixme:process:GetLogicalProcessorInformation ((nil),0x33e488): stub [.. snip ...] fixme:dwmapi:DwmSetWindowAttribute (0x1009a, 3, 0x33d384, 4) stub fixme:dwmapi:DwmSetWindowAttribute (0x1009a, 4, 0x33d374, 4) stub err:wgl:is_extension_supported No OpenGL extensions found, check if your OpenGL setup is correct! err:wgl:is_extension_supported No OpenGL extensions found, check if your OpenGL setup is correct! err:wgl:is_extension_supported No OpenGL extensions found, check if your OpenGL setup is correct! [... this error is being reported a few dozen times, so snip again ...] err:wgl:is_extension_supported No OpenGL extensions found, check if your OpenGL setup is correct! err:wgl:is_extension_supported No OpenGL extensions found, check if your OpenGL setup is correct! err:wgl:is_extension_supported No OpenGL extensions found, check if your OpenGL setup is correct! err:wgl:is_extension_supported No OpenGL extensions found, check if your OpenGL setup is correct! fixme:iphlpapi:NotifyAddrChange (Handle 0x47cdba8, overlapped 0x45dba80): stub fixme:winsock:WSALookupServiceBeginW (0x47cdbc8 0x00000ff0 0x47cdbc4) Stub! [... snip ...] Here are the errors reported while running, and after running (because the log is huge-ish, it's pasted elsewhere): http://paste.ubuntu.com/901925/ Now, 32bit OpenGL works just fine; The 32bit executables of Nexuiz, for example, work just fine. That being said, I'm suspecting that this is a problem of wine itself. I've already manually built the git version of wine, to no avail. So what's going on? Is something broken? How do I check (correctly) whether something is broken? How do I solve this?

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  • Shutdown Hangs for 5 Minutes on Kubuntu 14.04

    - by Augustinus
    I've had persistent problems with a 5 minute hang at shutdown for the last three versions of Kubuntu (13.04, 13.10, and now 14.04). I suspect this is not a KDE-specific problem. Recently, I performed a fresh installation of Kubuntu 14.04 from a live-USB, and shutdown worked normally for about a week. The hang-up is now happening again, and I can't figure out why. A brief description of the problem: The hang-up occurs with all methods of initiating a normal shutdown: Clicking the shutdown or restart button in KDE, sudo shutdown -h now, sudo reboot The shutdown splash screen appears. Using the down-arrow to access verbose messages, I see "Asking all remaining processes to terminate." This message remains for 5 minutes with no disk activity. Finally, a rapid series of messages flurries to the screen: * All processes ended within 300 seconds... [ OK ] nm-dispatcher.action: Caught signal 15, shutting down... ModemManager[852]: <warn> Could not acquire the 'org.freedesktop.ModemManager1' service name ModemManager[852]: <info> ModemManager is shut down * Deactivating swap... [ OK ] * Unmounting local filesystems... [ OK ] * Will now restart` Possible Sources of the Problem: Before the problem re-appeared, I have mainly been doing routine computing. I have kept the system up-to-date using apt-get upgrade and apt-get dist-upgrade. The only other notable incident was a power failure. I do not have the computer connected to a UPS, so the power failure resulted in an immediate shutdown. Could this have corrupted an important file which must be accessed at shutdown? Is there any way that could cause a 5-minute hang-up? Here is a list of packages that have been updated before the problem appeared: bash iotop dpkg dpkg-dev python3-software-properties libdpkg-perl software-properties-kde software-properties-common akonadi-backend-mysql libakonadiprotocolinternals1 akonadi-server firefox-locale-en firefox flashplugin-installer libqapt2 libqapt2-runtime thunderbird openjdk-7-jre-headless thunderbird-locale-en kubuntu-driver-manager qapt-deb-installer openjdk-7-jre qapt-batch icedtea-7-jre-jamvm libelf1 dpkg dpkg-dev libdpkg-perl libjbig0 gettext-base libgettextpo-dev libssl1.0.0 libgettextpo0 libasprintf-dev linux-headers-3.13.0-24 gettext libasprintf0c2 linux-headers-3.13.0-24-generic openssl linux-libc-dev gstreamer0.10-qapt kubuntu-desktop linux-image-extra-3.13.0-24-generic linux-image-3.13.0-24-generic I would appreciate any help with this.

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  • How to share two keyboard on the same laptop, french iso layout and usa ansi layout keyboard with usb?

    - by reyman64
    I recently buy a "noppoo choc mini" with this specific ANSI US-INTERNATIONAL pc84 layout. This specific keyboard have only 84 key , a 60% (compact tenkeyless) reduced layout My problem is simple, there is no keyboard layout into Ubuntu 12.04 which correspond to this usa normal ansi layout ... so it's the same problem with reduced version and only 84 key .. I search a template of normal ANSI US-INTERNATIONAL for xmodmap/xkb, and after i can try to manually map the other key. I search on google, and i don't find any other user which have same problem, so it's seem i have not the good keywoard to search this information.. Edit 1 : Here you can see there is probably a bug in ubuntu, because the layout for USA with dead key is not correct ! I have this : http://minus.com/lEdKMrsNAwkVA And other users have this for the same layout : http://i.stack.imgur.com/p52XG.png EDIT 2 It seems after a "sudo dpkg-reconfigure keyboard-configuration" : french standard keyboard pc105 + precision M65 keyboard from dell laptop Now i can see the good us layout in parameters, but i cannot have the iso layout for french usage... EDIT 3 Ok, after reboot i understand the probleme, i explain. I have one laptop with integrated french keyboard, and i want to use my usb keyboard which use a usa ANSI layout. It seem it's impossible in ubuntu and "dpkg-reconfigure keyboard-configuration" to share two different physical layout (ANSI and EU ISO) on the same computer ... EDIT4 Ok, it seems i can switch the physical layout (ISO <- ANSI) with this command in terminal : setxkbmap -layout us setxkbmap -layout us -variant alt-intl an setxkbmap -layout fr It's very complicated qnd it seem ubuntu 12.04 have big problem with keyboard manager ... because all works great with these two commands, without ANY change into the system parameters keyboard !!! Second bug ? The image of the layout for fr is buggy, the layout is not ISO, but i can press on the letter "< " at the left of right shift without any problem ! You can see the image here (french alternative with ANSI layout ? it's crazy ?) : http: //minus.com/lXsDJwoeyWAfF Can you help me on this point ? I'm lost with xkb, and manual mapping is very complicated ... Thanks a lot, SR

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  • Inside Red Gate - Ricky Leeks

    - by Simon Cooper
    So, one of our profilers has a problem. Red Gate produces two .NET profilers - ANTS Performance Profiler (APP) and ANTS Memory Profiler (AMP). Both products help .NET developers solve problems they are virtually guaranteed to encounter at some point in their careers - slow code, and high memory usage, respectively. Everyone understands slow code - the symptoms are very obvious (an operation takes 2 hours when it should take 10 seconds), you know when you've solved it (the same operation now takes 15 seconds), and everyone understands how you can use a profiler like APP to help solve your particular problem. High memory usage is a much more subtle and misunderstood concept. How can .NET have memory leaks? The garbage collector, and how the CLR uses and frees memory, is one of the most misunderstood concepts in .NET. There's hundreds of blog posts out there covering various aspects of the GC and .NET memory, some of them helpful, some of them confusing, and some of them are just plain wrong. There's a lot of misconceptions out there. And, if you have got an application that uses far too much memory, it can be hard to wade through all the contradictory information available to even get an idea as to what's going on, let alone trying to solve it. That's where a memory profiler, like AMP, comes into play. Unfortunately, that's not the end of the issue. .NET memory management is a large, complicated, and misunderstood problem. Even armed with a profiler, you need to understand what .NET is doing with your objects, how it processes them, and how it frees them, to be able to use the profiler effectively to solve your particular problem. And that's what's wrong with AMP - even with all the thought, designs, UX sessions, and research we've put into AMP itself, some users simply don't have the knowledge required to be able to understand what AMP is telling them about how their application uses memory, and so they have problems understanding & solving their memory problem. Ricky Leeks This is where Ricky Leeks comes in. Created by one of the many...colourful...people in Red Gate, he headlines and promotes several tutorials, pages, and articles all with information on how .NET memory management actually works, with the goal to help educate developers on .NET memory management. And educating us all on how far you can push various vegetable-based puns. This, in turn, not only helps them understand and solve any memory issues they may be having, but helps them proactively code against such memory issues in their existing code. Ricky's latest outing is an interview on .NET Rocks, providing information on the Top 5 .NET Memory Management Gotchas, along with information on a free ebook on .NET Memory Management. Don't worry, there's loads more vegetable-based jokes where those came from...

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  • Unable to update/ install any files [closed]

    - by Surya
    Possible Duplicate: “Problem with MergeList” error when trying to do an update Just now I installed ubuntu 12.04 on my Lenovo G570 laptop. First I got an error at the time of installation (don't know about it) and I restarted the system and next time, it went well. So, after installing problems started.. There was a error with "Language recognition" and I tried to fix it but didn't work. I tried to install powerTop to check the status of power management. at terminal: sudo apt-get install powertop This is the error I got surya@surya-Lenovo-G570:~$ sudo apt-get powertop install [sudo] password for surya: E: Invalid operation powertop surya@surya-Lenovo-G570:~$ sudo apt-get install powertop Reading package lists... Error! E: Encountered a section with no Package: header E: Problem with MergeList /var/lib/apt/lists/extras.ubuntu.com_ubuntu_dists_precise_main_binary-i386_Packages E: The package lists or status file could not be parsed or opened. surya@surya-Lenovo-G570:~$ ^C surya@surya-Lenovo-G570:~$ ^C surya@surya-Lenovo-G570:~$ ^C surya@surya-Lenovo-G570:~$ I downloaded Google Chrome .deb one and tried to install but its not working. Software center is opened and its not loading. There was a notification on the status bar which says: An error occurred please run the package manager from the right-click menu ... .... ... E: Encountered a section with no Package: header E: Problem with MergeList /var/lib/apt/lists/extras.ubuntu.com_ubuntu_dists_precise_main_binary-i386_Packages "Copy & Paste" from terminal is not really working... When I press Ctrl + C; its showing ^C on terminal but its not working.. The most important error: I am unable to see a "chip" icon on the status bar so as to install proprietary drivers for my ATI drivers... The interesting part is, powertop worked will on live cd and it even detected my ATI card. Update When I opened "Software Up to Date", this showed a error: Could not initialize the package information An unresolvable problem occurred while initializing the package information. Please report this bug against the 'update-manager' package and include the following error message: 'E:Encountered a section with no Package: header, E:Problem with MergeList /var/lib/apt/lists/extras.ubuntu.com_ubuntu_dists_precise_main_binary-i386_Packages, E:The package lists or status file could not be parsed or opened.' : My laptop details Lenovo G570; Intel 2nd Gen i5 processor 4GB DDR3 RAM Intel in-build graphics + AMD Radeon HD 6370M 1GB graphics. I need help ASAP.

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