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• Provide me with recources on Greibach & Chomsky Normal Form

  - by kristian Roger

  Hi, first please (bare with me)... :-( Im having a course at University ( Theory of Computation ) at first it was easy and simple BUT then we reach the context free grammer specialy the part where we should convert a grammer to Normal forms (Greibach & Chomsky) the thing that I couldnt understand so as usual I went to google and start searching for tutorials or videos I found many(tutorials not videos) but the problem that in tutorials they always explain things as if Im an expert or aware of every thing ... so can anyone please provide me with docs or links where they explaine the methods step by step ... (Please dont tell me to go back to my instructor because if he is useful I wont be asking your help ) thanx in advance

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• Opening MS Excel worksheet in C#

  - by topgun_ivard

  I know we can open a particular worksheet of MS Excel using C# by providing the sheet number (1,2,3..) or name (sheet1, sheet2, sheet3...) I have a excel file which has 2 sheets, 1. Values, 2. Results Is there a way to open a sheet giving the sheet name ,i.e, "Values" instead of 1 or [s|S]heet1 in C# ?? I looked thru the old posts but didnt find anything useful... so again, what I am trying to do is, open a Excel worksheet by using its user defined name (Values) instead of the system defined name(1 or [s|S]heet1) any inputs would be greatly appreciated!

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• Suggestions: Anti-Pattern counter-examples

  - by Tom W

  It doesn't seem that this exact question has been asked before, so I'll fire away: Most of us are familiar with the concept of an anti-pattern. However, avoiding implementation of anti-patterns can in principle swing too far the other way and cause problems itself. As an example, "Design by Committee" has a counter-example that I'd call "Design by Maverick" - wherein the design of an important feature is handed off to an individual to do what they think best, with the intention of reviewing their work later and deciding whether it should be finalised or go through another iteration. This takes much longer in practice as the rest of the team are occupied by other things, and can end up with a feature that's useful to nobody, particularly if the Maverick is not themselves an experienced end-user. Does anyone have any more examples of anti-pattern counter-examples?

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• [WM6] Owner of a component. What exactly is this for?

  - by kornelijepetak

  I am developing an app for Windows Mobile 6 and there is a CameraCaptureDialog class that enables me to call a camera app from my own application. The class has an Owner property that most examples on the internet set to "this". cam.Owner = this; What exactly does this do? I've seen a similar scenario with Windows Forms components/controls by setting the Parent control. In that case I guess it's used only for layout algorithms, but other than that, is there any useful purpose? I don't see how setting an owner of the CameraCaptureDialog can (and actually does not) make any difference (at least not a visible one). Any insight would be appreciated.

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• Merge overlapping date intervals

  - by leoinfo

  Is there a better way of merging overlapping date intervals? The solution I came up with is so simple that now I wonder if someone else has a better idea of how this could be done. /***** DATA EXAMPLE *****/ DECLARE @T TABLE (d1 DATETIME, d2 DATETIME) INSERT INTO @T (d1, d2) SELECT '2010-01-01','2010-03-31' UNION SELECT '2010-04-01','2010-05-31' UNION SELECT '2010-06-15','2010-06-25' UNION SELECT '2010-06-26','2010-07-10' UNION SELECT '2010-08-01','2010-08-05' UNION SELECT '2010-08-01','2010-08-09' UNION SELECT '2010-08-02','2010-08-07' UNION SELECT '2010-08-08','2010-08-08' UNION SELECT '2010-08-09','2010-08-12' UNION SELECT '2010-07-04','2010-08-16' UNION SELECT '2010-11-01','2010-12-31' UNION SELECT '2010-03-01','2010-06-13' /***** INTERVAL ANALYSIS *****/ WHILE (1=1) BEGIN UPDATE t1 SET t1.d2 = t2.d2 FROM @T AS t1 INNER JOIN @T AS t2 ON DATEADD(day, 1, t1.d2) BETWEEN t2.d1 AND t2.d2 -- AND t1.d2 <= t2.d2 /***** this condition is useless *****/ IF @@ROWCOUNT = 0 BREAK END /***** RESULT *****/ SELECT StartDate = MIN(d1) , EndDate = d2 FROM @T GROUP BY d2 ORDER BY StartDate, EndDate /***** OUTPUT *****/ /***** StartDate EndDate 2010-01-01 2010-06-13 2010-06-15 2010-08-16 2010-11-01 2010-12-31 *****/ EDIT: I realized that the t1.d2 <= t2.d2 condition is not really useful.

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• List of fundamental data structures - what am I missing?

  - by jboxer

  I've been studying my fundamental data structures a bunch recently, trying to make sure I've got them down cold. By "fundamental", I mean the real basic ones. Fancy ones like Red-Black Trees and Bloom Filters are clearly worth knowing, but they're usually either enhancements of fundamental ones (Red-Black Trees are binary search trees with special properties to keep them balanced) or they're only useful in very specific situations (Bloom Filters). So far, I'm "fluent" in the following data structures: Arrays Linked Lists Stacks/Queues Binary Search Trees Heaps/Priority Queues Hash Tables However, I feel like I'm missing something. Are there any fundamental ones that I'm forgetting about? EDIT: Added these after posting the question Strings (suggested by catchmeifyoutry) Sets (suggested by Peter) Graphs (suggested by Nick D and aJ) B-Trees (Suggested by tloach) I'm a little on-the-fence about whether these are too fancy or not, but I think they're different enough from the fundamental structures (and important enough) to be worth studying as fundamental.

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• How can I make Ruby rake display the full backtrace on uncaught exception

  - by Martinos

  As you may know rake swallows the full backtrace on uncaught exception. If I want to have a full backtrace, I need to add the --trace option. I find this very annoying because some of my tasks take long time to run (up to 6 hours), when it crashes I don't have any debugging info. I need to run it again with the --trace. On top of that, the system may not be in the same state as when the error occurred, so it may not show afterward. I always have to add --trace on any tasks. This displasy stuff that I don't want to see when the task is executed. Is there a way to change this default behaviour? (which I don't think is useful at all)

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• Change page layout in the middle of a LaTeX document

  - by David

  I'm looking for a way to change some page layout dimensions in the middle of a LaTeX document. The reason is, I'd like to have smaller margins and longer lines in the "References" section of my report document (basically because short lines aren't so important there and I can save space). In my preamble I have (works fine): \setlength\textwidth{130mm} \setlength\oddsidemargin{14.6mm} In the document I simply try to re-set them at the right point but they're ignored. ... last paragraph ends here. \newpage \setlength\textwidth{150mm} % +20mm text width \setlength\oddsidemargin{13.6mm} % -10mm left margin (so it stays centered) References ... The geometry package is useful but only for global adjustments in the preamble, so I can't use it here. Is it not possible to change the page layout at some point in the document?

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• Using WCF HttpBindings on a LAN

  - by dcw

  We have a WCF-based client server that operates over a LAN. We've been getting along ok by using the NetTcpBinding, chosen because we couldn't get either HttpBinding to work between hosts. (Within a single host works fine, but is not useful for the production environment.) We're now back at the point where we want to explore using either BasicHttpBinding or WsHttpBinding, but we simply can't see the server from the client: even putting in the path to the endpoint into IE fails to see the server. Is there something simple we've overlooked? We're not specifying any security settings (or anything else, for that matter). Should we be doing so (e.g. explicitly setting security settings to None)?

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• An analog of String.Join(string, string[]) for IEnumerable<T>

  - by abatishchev

  class String contains very useful method - String.Join(string, string[]). It creates a string from an array, separating each element of array with a symbol given. But general - it doesn't add a separator after the last element! I uses it for ASP.NET coding for separating with "<br />" or Environment.NewLine. So I want to add an empty row after each row in asp:Table. What method of IEnumerable<TableRow> can I use for the same functionality?

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• What programming language is used to design google algorithm?

  - by AKN

  It is known that google has best searching & indexing algorithm. The also have good relevancy. They are also quicker in getting down the latest results. All that's fine. What programming language (c, c++, java, etc...) & database (oracle, MySQL, etc...) they have used in achieving this. Since they have to manipulate with volume of data quickly and effectively. Though I'm not looking for their indepth architecture (if in case violates their company policies) an overview of all such things could be useful. Anybody please add you valuable suggestions and insight on this?

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• Where are the really high quality and complex Swing components?

  - by jouhni

  Looking at Swing, I have the feeling that it comes with many useful and reasonable atomic components in its core. And when I look at the Web there are hundrets of quickly plugged together components (among them many date/time pickers, pimped lists and tables), which have in common that I could easily write them on my own, if I needed them. When I build big software and come to the point where I need a domain-specific component which is really big, I mostly come to the point where I have to write it on my own, which, due to the point that they are not just plugged together lists and tables, isn't done qickly. So, the question is, why are there no Swing component galleries which contain more than just customized date/time pickers or lists with added tree support. Where are the components which really raise the level of abstraction, or are in best case domain-specific?

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• Copying data from STDOUT to a remote machine using SFTP

  - by freddie

  In order to backup large database partitions to a remote machine using SFTP, I'd like to use the databases dump command and send it directly over using SFTP to a remote location. This is useful when needing to dump large data sets when you don't have enough local disk space to create the backup file, and then copy it to a remote location. I've tried using python + paramiko which provides this functionality, but the performance much worse than using the native openssh/sftp binary to transfer files. Does anyone have any idea on how to do this either with the native sftp client on linux, or some library like paramiko? (but one that performs close to the native sftp client)?

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• How do you access config outside of a request in CherryPy?

  - by OrganicPanda

  I've got a webapp running on CherryPy that needs to access the CherryPy config files before a user creates a request. The docs say to use: host = cherrypy.request.app.config['database']['host'] But that won't work outside of a user request. You can also use the application object when you start the app like so: ... application = cherrypy.tree.mount(root, '/', app_conf) host = application.config['database']['host'] ... But I can see no way of accessing 'application' from other classes outside of a user request. I ask because our app looks at several databases and we set them up when the app starts rather than on user request. I have a feeling this would be useful in other places too; so is there any way to store a reference to 'application' somewhere or access it through the CherryPy API?

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• How to get a count of ManagementObjects (WMI results) without enumerating through the collection in

  - by Mark

  When querying for large ammount of data through WMI (say the windows events log Win32_NTLogEvent) it is very useful to know what kind of numbers you are getting yourself into before downloading all the content. Is there a way two do this? From what i know there is no "Select Count(*) FROM Win32_NTLogEvent" in WQL. From what i know the Count property of the ManagementObjectCollection actually enumerates through all the results whether you have the Rewindable property set to true or false. If it cannot be done in .NET, can it be done by directly using the underlying IWbem objects Thanks

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• iPhone 4.0 Screen Resolution and writing robust code...

  - by Magic Bullet Dave

  Does anyone know what will happen with existing apps when they run on the iPhone 4.0 in terms of the new screen resolution? I am assuming, just like developing for the iPad that there should be no hard coded screen resolutions in your code. I'd also like advice on the best way of writing robust code to work well on any device. For instance, detecting the screen resolution is not enough - on the iPad the screen is physically bigger so you can display more items on it. On the new iPhone the screen is the same physical size but higher resolution, so the likely thing is that you wont want to display more items, just higher resolution versions of them. Any help would be useful, Regards Dave EDIT: I have read the other similar posts, I guess what I really would like to know is what is the recommended way to write code for all App Store devices in a robust way so they a) all work b) make best use of the device.

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• Dealing with HTTP content in HTTPS pages

  - by El Yobo

  We have a site which is accessed entirely over HTTPS, but sometimes display external content which is HTTP (images from RSS feeds, mainly). The vast majority of our users are also stuck on IE6. I would both of the following Prevent the IE warning message about insecure content Present something useful to users in place of the images that they can't otherwise see; if there was some JS I could run to figure out which images haven't been loaded and replace them with an image of ours instead that would be great. I suspect that the first aim is simply not possible, but the second may be sufficient. A worst case scenario is that I parse the RSS feeds when we import them, grab the images store them locally so that the users can access them that way, but it seems like a lot of pain for reasonably little gain.

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• Is there a way to hide annotations in Netbeans or Eclipse?

  - by Boden

  Maybe a dumb question, but it would be nice if there was a way to hide or collapse Java annotations when viewing source in Netbeans (or Eclipse). I'm not finding an option and a quick search didn't turn anything up. Is this one of those "you should never want to do that, code folding is a sin!" things? Personally I'd find it useful for annotated entity classes. All the hibernate / etc annotations are just fluff that I never look at once my mapping is working fine. It's similar to imports, really. (Yes, I can use XML instead of annotations, which I might start doing. But I was just wondering...)

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• vim - how am I suppose to read this command to remove all blanks at the end of a line

  - by whaley

  I happened across this page full of super useful and rather cryptic vim tips at http://rayninfo.co.uk/vimtips.html. I've tried a few of these and I understand what is happening enough to be able to parse it correctly in my head so that I can possibly recreate it later. One I'm having a hard time getting my head wrapped around though are the following two commands to remove all spaces from the end of every line :%s= *$== : delete end of line blanks :%s= \+$== : Same thing I'm interpreting %s as string replacement on every line in the file, but after that I am getting lost in what looks like some gnarly variation of :s and regex. I'm used to seeing and using :s/regex/replacement. But the above is super confusing. What do those above commands mean in english, step by step?

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• Custom Message Box: Windows' "Move Cursor to Default Button" Feature

  - by Andreas Rejbrand

  In Microsoft Windows, there is a (highly useful) feature that automatically moves the cursor to the default button of a modal dialog box (activated in Win+R, "control mouse"). Now I have created a custom dialog box in Delphi (basically a TForm), see below. But, quite naturally, the cursor does not automatically move to the default button ("Yes" in this case), even though the feature is turned on in "control mouse". How to implement this feature using Windows API? I guess it would be sufficient to obtain the settings as a boolean (true if feature activated, false if not), and then simply move the cursor programmatically using SetCursorPos if true. But how to obtain this setting?

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• How do you use data binding in C# development ?

  - by MemoryLeak

  Recently I use data binding to speed up my development of C# winforms application. But I found that data binding is just useful when the control is Textbox or textare and text kind of controls. If things come to be radio button, image control or datagridview, it's hard for me to use data binding. For example, it's hard for me to bind a group of radio button to a database field. It's hard for me to pre-process the data in database and then bind to datagridview control(I know I can use view to do this, but it is not that convenient) So I really want to know, most of you guys when will use data binding? And how will you use it ?

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• What is better for a student programming in C++ to learn for writing GUI: C# vs QT?

  - by flashnik

  I'm a teacher(instructor) of CS in the university. The course is based on Cormen and Knuth and students program algorithms in C++. But sometimes it is good to show how an algorithm works or just a result of task through GUI. Also in my opinion it's very imporant to be able to write full programs. They will have courses concerning GUI but a three years, later, in fact, before graduatuion. I think that they should be able to write simple GUI applications earlier. So I want to teach them it. How do you think, what is more useful for them to learn: programming GUI with QT or writing GUI in C# and calling unmanaged C++ library?

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• Why do open source projects cling on 0.x versions for too long?

  - by ssg

  I see many open source projects insist on staying in 0.xxx version for a very long time despite that the product has been proven useful and very stable. Trac is one example. They even risked switching from 0.9 to 0.10 which might confuse a lot of users about which is more recent. I wonder if this is a cultural paradigm, an honor code in open source community or simply a strict interpretation of release cycle management? Would a person who releases first version as "1.0 beta" be banished from open source world, or more realistically appeal less number of contributors? For some projects it even looks like they will never switch to 1.0 ever but only approximating only half way each time, like Zeno's paradox.

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• AbsoluteTime with numeric argument behaves strangely.

  - by dreeves

  This is strange: DateList@AbsoluteTime[596523] returns {2078, 7, 2, 2, 42, 9.7849} But DateList@AbsoluteTime[596524] returns {1942, 5, 26, 20, 28, 39.5596} The question: What's going on? Note that AbsoluteTime with a numeric argument is undocumented. (I think I now know what it's doing but figured this is useful to have as a StackOverflow question for future reference; and I'm curious if there's some reason for that magic 596523 number.) PS: I encountered this when writing these utility functions for converting to and from unix time in Mathematica: (* Using Unix time (an integer) instead of Mathematica's AbsoluteTime... *) tm[x___] := AbsoluteTime[x] (* tm is an alias for AbsoluteTime. *) uepoch = tm[{1970}, TimeZone->0]; (* unixtm works analogously to tm. *) unixtm[x___] := Round[tm[x]-uepoch] (* tm & unixtm convert between unix & *) unixtm[x_?NumericQ] := Round[x-uepoch] (* mma epoch time when given numeric *) tm[t_?NumericQ] := t+uepoch (* args. Ie, they're inverses. *)

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• Linux issues on setting a timer function

  - by laura

  I am creating a process with 2 children, 1 of the children is responsible to read questions (line by line from a file), output every question and reading the answer, and the other one is responsable to measure the time elapsed and notify the user at each past 1 minute about the remaining time. My problem is that i couldn't find any useful example of how i can make this set time function to work. Here is what i have tried so far. The problem is that it outputs the same elapsed time every time and never gets out from the loop. #include<time.h> #define T 600000 int main(){ clock_t start, end; double elapsed; start = clock(); end = start + T; while(clock() < end){ elapsed = (double) (end - clock()) / CLOCKS_PER_SEC; printf("you have %f seconds left\n", elapsed); sleep(60); } return 0; }

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