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  • What Does an OS Actually Do?

    - by Ell
    What exactly does an operating system do? I know that operating systems can be programmed, in, for example, C++, but I previously believed that C++ programs must be run under an operating system? Can somebody please explain and give links? thanks in advance, ell

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  • Which programming language to choose? (for a specific problem/domain, details inside)

    - by Bijan
    I am building a trading portfolio management system that is responsible for production, optimization, and simulation of non-high frequency trading portfolios (dealing with 1min or 3min bars of data, not tick data). I plan on employing Amazon web services to take on the entire load of the application. I have four choices that I am considering as language. a) Java b) C++ c) C# d) Python Here is the scope of the extremes of the project scope. This isn't how it will be, maybe ever, but it's within the scope of the requirements: Weekly simulation of 10,000,000 trading systems. (Each trading system is expected to have its own data mining methods, including feature selection algorithms which are extremely computationally-expensive. Imagine 500-5000 features using wrappers. These are not run often by any means, but it's still a consideration) Real-time production of portfolio w/ 100,000 trading strategies Taking in 1 min or 3 min data from every stock/futures market around the globe (approx 100,000) Portfolio optimization of portfolios with up to 100,000 strategies. (rather intensive algorithm) Speed is a concern, but I believe that Java can handle the load. I just want to make sure that Java CAN handle the above requirements comfortably. I don't want to do the project in C++, but I will if it's required. The reason C# is on there is because I thought it was a good alternative to Java, even though I don't like Windows at all and would prefer Java if all things are the same. Python - I've read somethings on PyPy and pyscho that claim python can be optimized with JIT compiling to run at near C-like speeds.... That's pretty much the only reason it is on this list, besides that fact that Python is a great language and would probably be the most enjoyable language to code in, which is not a factor at all for this project, but a perk. To sum up: - real time production - weekly simulations of a large number of systems - weekly/monthly optimizations of portfolios - large numbers of connections to collect data from There is no dealing with millisecond or even second based trades. The only consideration is if Java can possibly deal with this kind of load when spread out of a necessary amount of EC2 servers. Thank you guys so much for your wisdom.

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  • Performance of fopen vs stat

    - by Alex Marshall
    Hello, I'm writing several C programs for an embedded system where every bit of performance we can squeeze out will matter. Part of that is accessing log files. When determining if a file exists, is there any performance difference between using open / fopen, and stat ? I've been using stat on the assumption that it only has to do a quick check against the file system, whereas fopen would have to actually gain access to a file and manipulate internal data structures before returning. Is there any merit to this ?

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  • Rating mechanisms

    - by Jasie
    Is there any place that showcases a bunch of different types of rating systems (like using multiple sliders, star ratings, up/down votes)? I'm trying to get ideas for a better rating system than just up/down (more criteria). (I'm not interested in the backend, but the human/computer interaction part of it).

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  • Chrome Extension contenteditable get and set caret position

    - by jwize
    I am creating an extension where I need to insert a link into the gmail window. I am able to create a simple extension button in the top of the window and execute code that does replaces all the links. Now, I want to do add links in the contenteditable section as I type. It seems like there should be a simple way to replace text with a link in the document object model. If this is not true I need to do three things. Insert text from the current caret position Capture the caret position. Set the caret position by its offset. I have tried using window.getSelection within the gmail context(that is a body element that is set to contenteditable and embedded inside an iframe in the gmail tab) to get the current range and position. The selection is always empty and contains no ranges regardless of whether text is selected or not.

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  • What's the best way to access Neo4j from Django?

    - by abdel
    it seems that i found something that let me confused; i've found two Neo4j to download to python, the first one is: http://pypi.python.org/pypi/neo4j-embedded and the second one is: https://svn.neo4j.org/components/neo4j.py/trunk/ what's the difference between the two? the first one seems to be big (size), so does this mean that if i use it i'll not need the neo4j community release (milestone)? when i've installed the first one, and tried to test a django example, it seems that the directory named "model" https://svn.neo4j.org/components/neo4j.py/trunk/src/main/python/neo4j/model/ is missing? so what's the difference, and who will be better to use with Django? and what about that one? http://pypi.python.org/pypi/neo4django/

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  • Add xcode-select to PATH vs. Install Xcode Command Line Tools?

    - by MattDiPasquale
    Now with Xcode 4.5, is it OK to just add the following line to my ~/.bash_profile rather than installing the Xcode Command Line Tools? export PATH="$PATH:`xcode-select -print-path`/usr/bin:`xcode-select -print-path`/Toolchains/XcodeDefault.xctoolchain/usr/bin" Note: Xcode says the following about Command Line Tools: Before installing, note that from within Terminal you can use the XCRUN tool to launch compilers and other tools embedded within the Xcode application. Use the XCODE-SELECT tool to define which version of Xcode is active. Type "man xcrun" from within Terminal to find out more.

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  • Is being a programmer a younger person's job?

    - by Saobi
    After you get old, say past 30 or 40. Can you still keep up with the young coders from your company, those fresh out of school, who can code for 15+ hours on 10 cans of redbulls (most people in Google, Facebook, etc) ? And given the lightning speed with which today's programming frameworks and architectures evolve, can you keep up with the most up to date stuff and be as proficient at them as the next college grad? I know for jobs like unix/c/embedded programming, it might be that the older the better. But for programming jobs in say web development, social media, search engine technology, etc. Do you become less and less competitive career-wise versus youngsters? For example, most coders in Google and Facebook, I believe are under 25 years old. In other words, once you reach a certain age, would it be unwise to continue to be a coder, and is it better to try becoming a project manager or architect?

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  • Super Cam iphone app how do they make it possible?

    - by Silent
    there is an iphone app called supercam and you can get it through the app store free. This app features a way to connect your webcam or dv cam that is connected on the internet, you could set up the ip address and enter the data on the app and it will connect to your online camera. the thing is that they have the video stream and it looks like they embedded the video in a uiview or webview at the bottom they have buttons to choose from all the cameras you have set up. so this is different from other video streaming apps because it does not play the video from the full screen mode (MPMediaPlayer API) would there be any tutorials about this or somehow take reverse engineer this?

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  • Publish to Facebook Stream in as3

    - by Kid Adiran
    Hi, I am trying to publish to a users stream when they click a share button in my flash app that i have living in a tab on a fan fan. I basically have my swf embedded on a page that has a java script function that calls the facebook share dialogue. Here is what i got so far: // flash embedd <fb:fbjs-bridge/> // share function <script> function publishfeed() { var attachment = {'media':[{'type':'image','src':'http://bit.ly/AJTnf','href':'http://bit.ly/hifZk'}]}; Facebook.streamPublish('', attachment); } In my flash file, I try using this code to get it to pull the javascript funtion, but no luck. function jspopupWindow(event:MouseEvent):void { var request:URLRequest = new URLRequest("javascript:publishfeed()"); navigateToURL(request,"_blank"); } share_btn.addEventListener(MouseEvent.CLICK, jspopupWindow); Can anyone help me, what am i missing? thanks a

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  • What messaging technologies in windows-ce for gauranteed msg delivery?

    - by Aidanapword
    All, We are building a windows-ce (6.0R3) based device that requires guaranteed and audit-ready message delivery (including store & forward) up to and down from the cloud. I have been looking for choices beyond: MSMQ a proprietary solution (what our prototype device is using) AMQP (research on using this in our context is now starting) ... are there any others? We will be transporting sensitive data (who isn't?!?!) over a public network, and large scale options are required. Anything running on an embedded device will be performance sensitive too. Thanks! Aidanapword

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  • Java - How to set focus the already running application ?

    - by Brad
    I am using a ServerSocket port to run one instance only of my Java Swing application, so if a user tries to open another instance of the program, i show him a warning that "Another instance is already open". This works fine, but instead of showing this message i want to set focus on the running application itself, like some programs does (MSN Messenger), even if it was minimized. Is there a solution for this for various operating systems ?

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  • NSString simple pattern matching

    - by SirRatty
    Hi all, Mac OS 10.6, Cocoa project, 10.4 compatibility required. (Please note: my knowledge of regex is quite slight) I need to parse NSStrings, for matching cases where the string contains an embedded tag, where the tag format is: [xxxx] Where xxxx are random characters. e.g. "The quick brown [foxy] fox likes sox". In the above case, I need to grab the string "foxy". (Or nil if no tag is found.) Each string will only have one tag, and the tag can appear anywhere within the string, or may not appear at all. Could someone please help with a way to do that, preferably without having to include another library such as RegexKit. Thank you for any help.

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  • Recommended textbook for machine-level programming?

    - by Norman Ramsey
    I'm looking at textbooks for an undergraduate course in machine-level programming. If the perfect book existed, this is what it would look like: Uses examples written in C or assembly language, or both. Covers machine-level operations such as two's-complement integer arithmetic, bitwise operations, and floating-point arithmetic. Explains how caches work and how they affect performance. Explains machine instructions or assembly instructions. Bonus if the example assembly language includes x86; triple bonus if it includes x86-64 (aka AMD64). Explains how C values and data structures are represented using hardware registers and memory. Explains how C control structures are translated into assembly language using conditional and unconditional branch instructions. Explains something about procedure calling conventions and how procedure calls are implemented at the machine level. Books I might be interested in would probably have the words "machine organization" or "computer architecture" in the title. Here are some books I'm considering but am not quite happy with: Computer Systems: A Programmer's Perspective by Randy Bryant and Dave O'Hallaron. This is quite a nice book, but it's a book for a broad, shallow course in systems programming, and it contains a great deal of material my students don't need. Also, it is just out in a second edition, which will make it expensive. Computer Organization and Design: The Hardware/Software Interface by Dave Patterson and John Hennessy. This is also a very nice book, but it contains way more information about how the hardware works than my students need. Also, the exercises look boring. Finally, it has a show-stopping bug: it is based very heavily on MIPS hardware and the use of a MIPS simulator. My students need to learn how to use DDD, and I can't see getting this to work on a simulator. Not to mention that I can't see them cross-compiling their code for the simulator, and so on and so forth. Another flaw is that the book mentions the x86 architecture only to sneer at it. I am entirely sympathetic to this point of view, but news flash! You guys lost! Write Great Code Vol I: Understanding the Machine by Randall Hyde. I haven't evaluated this book as thoroughly as the other two. It has a lot of what I need, but the translation from high-level language to assembler is deferred to Volume Two, which has mixed reviews. My students will be annoyed if I make them buy a two-volume series, even if the price of those two volumes is smaller than the price of other books. I would really welcome other suggestions of books that would help students in a class where they are to learn how C-language data structures and code are translated to machine-level data structures and code and where they learn how to think about performance, with an emphasis on the cache.

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  • How to assign fine grained permission on shared mailboxes?

    - by sudhirc
    Typically you can assign either Full and Sendas permissions to mailboxes using Powershell. In our organization we have a need to assign other fine grained permissions like editor, reader , author to the shared mailboxes. We are using a third party tool to achieve this. I am pretty happy with the tool except for that fact that it is a GUI only tool. I am trying to automate the entire process of shared mailbox creation by using a combination of embedded powershell in C# program. All other steps are easy to automate but because this tool is GUI only, I am really struck. Is there an API method available to to achieve this? I guess EWS API can provide some answer but I really do not know where to start.

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  • match at the beginning of any line, including the first

    - by JoelFan
    According the the Perl documentation on regexes: By default, the "^" character is guaranteed to match only the beginning of the string ... Embedded newlines will not be matched by "^" ... You may, however, wish to treat a string as a multi-line buffer, such that the "^" will match after any newline within the string ... you can do this by using the /m modifier on the pattern match operator. The "after any newline" part means that it will only match at the beginning of the 2nd and subsequent lines. What if I want to match at the beginning of any line (1st, 2nd, etc.)?

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  • Do I have to create a static library to test my application?

    - by Christopher Gateley
    I'm just getting started with TDD and am curious as to what approaches others take to run their tests. For reference, I am using the google testing framework, but I believe the question is applicable to most other testing frameworks and to languages other than C/C++. My general approach so far has been to do either one of three things: Write the majority of the application in a static library, then create two executables. One executable is the application itself, while the other is the test runner with all of the tests. Both link to the static library. Embed the testing code directly into the application itself, and enable or disable the testing code using compiler flags. This is probably the best approach I've used so far, but clutters up the code a bit. Embed the testing code directly into the application itself, and, given certain command-line switches either run the application itself or run the tests embedded in the application. None of these solutions are particularly elegant... How do you do it?

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  • Procedural modeling of Robots?

    - by anon
    Procedural techniques is common for texture synthesis, modeling plants, and modeling terrains. However, I've seen very little work on algorithmic construction of robots, which is a bit surprising given how mechanical these systems are. Anyone have a good resource on the algorithmic construction of robots / robotic humanoids? Thanks!

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  • What parameters should I use in a Google Maps URL to go to a lat-lon?

    - by xpda
    I would like to produce a url for Google Maps that goes to a specific latitude and longitude. Now, I generate a url such as this: http://maps.google.com/maps?z=11&t=k&q=58 41.881N 152 31.324W The resulting map comes up with a round "A" balloon pointer, which seems to point to the nearest named object, and a green arrow, which points to the lat-lon. Sometimes, as in this example, the "A" pointer is centered and is far enough away that you cannot see the pointer to the lat-lon. (Zoom out to see both pointers in this example. The "A" pointer is in the center of Alaska, while the lat-long pointer is on Kodiak Island.) Are there some parameters I can use in the Google Maps URL that will produce a single pointer to a designated lat-lon? (This loads in a separate window. It is not embedded.)

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  • Does Displaytag stash the "media type" in a page or request attribute?

    - by Pointy
    When you enable "export" from Displaytag, the tag code gives you links with special magic parameters that the tag recognizes as indicators that the table contents should be exported (as CSV, Excel, whatever). Well I'm interested in detecting the media type so that (for example) I can exclude columns that make no sense in an export (embedded action buttons, for one thing, or checkboxes for row selection). I suppose I could write a table decorator and use that to stick the media type on the request, but it'd be nice to avoid that if the tag already does it. The documentation is not clear on the subject; I guess I can start digging through the source code too.

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  • WPF - copy/paste selection with custom font family

    - by summergoat
    I have a custom font family embedded in my WPF application which I can reference by specifying a base URI and font family name. new FontFamily(new Uri("pack://application:,,,/Fonts/"), "./#My Custom Font Family"); However, when I copy a selection which uses this font the xaml on the clipboard resembles the following <Run Text="Foo" FontFamily="./#My Custom Font Family" /> When I paste into the same RichTextBox I lose the font as it falls back to the system default because - When a FontFamily is specified as an attribute in markup, the base URI value is always implied—its value is the URI of the XAML page. http://msdn.microsoft.com/en-us/library/system.windows.media.fontfamily.aspx and my xaml page is not located in the same directory as the custom font family. Any ideas for a workaround?

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  • How to learn to program C the right way

    - by sfactor
    i have been programming in C/C++ for my academic courses a lot and was under the impression i had a pretty good grasp of it. but lately i had to work in a bluetooth application that had a server and client implementation in a Linux box and an embedded system. i learned bluez bluetooth API, socket/network programming and coded it. however i ran into a lot of problems with memory leaks and segmentation faults and other memory related errors along the way.as the code grew more complex i all but lost control of the pointers and threads and sockets. this got me wondering that i had a lot to learn that they didn't say in the basic C/C++ books. so i wanted to ask for the resources that are available that'll help be code better in a professional way in C/C++ .especially for the Linux/Mac environment (gcc compiler).

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  • Where/When do C# and the .NET Framework fail to be the right tool?

    - by Nate Bross
    In my non-programming life, I always attempt to use the appropriate tool for the job, and I feel that I do the same in my programming life, but I find that I am choosing C# and .NET for almost everything. I'm finding it hard to come up with (realistic business) needs that cannot be met by .NET and C#. Obviously embedded systems might require something less bloated than the .NET Micro Framework, but I'm really looking for line of business type situations where .NET is not the best tool. I'm primarly a C# and .NET guy since its what I'm the most comfertable in, but I know a fair amount of C++, php, VB, PowerShell, batch files, and Java, as well as being versed in the web technologes (JavaScript, HTML, and CSS). But I'm open minded about it my skill set and I'm looking for cases where C# and .NET are not the right tool for the job. I choose .NET and C# because I'm comfortable with it, but I'm looking for cases where it isn't appropriate.

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