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• mystified by qr.Q(): what is an orthonormal matrix in "compact" form?

  - by gappy

  R has a qr() function, which performs QR decomposition using either LINPACK or LAPACK (in my experience, the latter is 5% faster). The main object returned is a matrix "qr" that contains in the upper triangular matrix R (i.e. R=qr[upper.tri(qr)]). So far so good. The lower triangular part of qr contains Q "in compact form". One can extract Q from the qr decomposition by using qr.Q(). I would like to find the inverse of qr.Q(). In other word, I do have Q and R, and would like to put them in a "qr" object. R is trivial but Q is not. The goal is to apply to it qr.solve(), which is much faster than solve() on large systems.

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• Bash variable kills script execusion

  - by Kyle Terry

  Sorry if this is better suited at serverfault, but I think it learns more towards the programming side of things. I have some code that's going into /etc/rc.local to detect what type of touch screen monitor is plugged in and changes out the xorg.conf before launching X. Here is a small snippet: CURRENT_MONITOR=`ls /dev/usb | grep 'egalax_touch\|quanta_touch'` case $CURRENT_MONITOR in '') CURRENT_MONITOR='none' ;; esac If one of those two touch screens is plugged in, it works just fine. If any other monitor is plugged in, it stops at the "CURRENT_MONITOR=ls /dev/usb | grep 'egalax_touch\|quanta_touch'." For testing I touched two files. One before creating CURRENT_MONITOR and one after CURRENT_MONITOR and only file touched before is created. I'm not a bash programmer so this might be something very obvious.

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• How created method with signature as List

  - by London

  Hi all, I'm very new to Java programming language so this is probably dumb question but I have to ask it because I can't figure it out on my own. Here is the deal. I want to create method which extracts certain object type from a list. So the method should receive List as argument, meaning list should contain either Object1 or Object2. I've tried like this : public Object1 extractObject(List<?>){ //some pseudo-code ... loop trough list and check if list item is instance of object one return that instance } The problem with declaring method with List<?> as method argument is that I receive compilation error from eclipse Syntax error on token ">", VariableDeclaratorId expected after this token. How do I set the method signature properly to accept object types either Object1 or Object2 ? Thank you

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• Repeating a List in Scala

  - by Ralph

  I am a Scala noob. I have decided to write a spider solitaire solver as a first exercise to learn the language and functional programming in general. I would like to generate a randomly shuffled deck of cards containing 1, 2, or 4 suits. Here is what I came up with: val numberOfSuits = 1 (List["clubs", "diamonds", "hearts", "spades"].take(numberOfSuits) * 4).take(4) which should return List["clubs", "clubs", "clubs", "clubs"] List["clubs", "diamonds", "clubs", "diamonds"] List["clubs", "diamonds", "hearts", "spades"] depending on the value of numberOfSuits, except there is no List "multiply" operation that I can find. Did I miss it? Is there a better way to generate the complete deck before shuffling? BTW, I plan on using an Enumeration for the suits, but it was easier to type my question with strings. I will take the List generated above and using a for comprehension, iterate over the suits and a similar List of card "ranks" to generate a complete deck.

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• iPhone write to file (alternative directory)

  - by strider2k

  New to iPhone 3.2, Apple introduced File-Sharing support. Details can be found at https://developer.apple.com/iphone/library/releasenotes/General/WhatsNewIniPhoneOS/Articles/iPhoneOS3_2.html#//apple_ref/doc/uid/TP40009337-SW1 . Now, most examples floating around in the web demonstrates writing to the documents directory. What if I want to write files from my app but I don't want the user to be able to see it via iTunes? I'm looking at the Files and Networking section of the iPhone OS Programming Guide and I'm unsure what would be a good alternative to the documents directory for writing files to hide from the user and not be rejected by Apple's review team.

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• How to set background image in Java?

  - by Dew

  I am developing a simple platform game using Java using BlueJ as the IDE. Right now I have player/enemy sprites, platforms and other items in the game drawn using polygons and simple shapes. Eventually I hope to replace them with actual images. For now I would like to know what is the simplest solution to setting an image (either URL or from local source) as the 'background' of my game window/canvas? I would appreciate it if it isn't something long or complex as my programming skills aren't very good and I want to keep my program as simple as possible. Kindly provide example codes with comments to elaborate on their function, and also if it's in its own class, how to call on relevant methods used by it on other classes. Thank you very much.

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• How to implement square root and exponentiation on arbitrary length numbers?

  - by tomp

  I'm working on new data type for arbitrary length numbers (only non-negative integers) and I got stuck at implementing square root and exponentiation functions (only for natural exponents). Please help. I store the arbitrary length number as a string, so all operations are made char by char. Please don't include advices to use different (existing) library or other way to store the number than string. It's meant to be a programming exercise, not a real-world application, so optimization and performance are not so necessary. If you include code in your answer, I would prefer it to be in either pseudo-code or in C++. The important thing is the algorithm, not the implementation itself. Thanks for the help.

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• c arrays: setting size dynamically?

  - by user336994

  Hello, I am new to C programming. I am trying to set the size of the array using a variable but I am getting an error: Storage size of 'array' isn't constant !! 01 int bound = bound*4; 02 static GLubyte vertsArray[bound]; I have noticed that when I replace bounds (within the brackets on line 02) with the number say '20', the program would run with no problems. But I am trying to set the size of the array dynamically ... Any ideas why I am getting this error ? thanks much,

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• Can't load AMD 64-bit .dll on a IA 32-bit platform

  - by Guihua

  I download the Gurobi package for linear programming. I import the corresponding gurobi.jar package. Then run the example program. Then it appears the following errors: Exception in thread "main" java.lang.UnsatisfiedLinkError: C:\gurobi460\win64\win64\bin\GurobiJni46.dll: Can't load AMD 64-bit .dll on a IA 32-bit platform Then I downloaded the window 64 bit Jre, and use the "window--preference--Installed JRE" to install this new JRE. However, it still appeared this error. Could you help me? Thank you !

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• "SQL Server does not exist or access denied." upon VB.Net Deployment

  - by JasonMHirst

  Have built a small VB.Net app in VS2010. The connection string to the SQL Server is as follows: <connectionStrings> <add name="IWSR_DataDownloadWizard.My.MySettings.sqlConnection" connectionString="Provider=SQLOLEDB.1;Data Source=SQLServer;Integrated Security=SSPI;Initial Catalog=IWSROL" providerName="System.Data.OleDb" /> </connectionStrings> Within the VS2010 environment AND on my machine, the connection works perfectly, however when I deploy to clients I get an error message of: [DBNETLIB][ConnectionOpen (Connect()).]SQL Server does not exist or access denied. I've tried to search the net for solutions, have seen a few instances of people saying to NOT use the Server Name but the IP Address instead (this doesn't work) and some saying to remove the "Provider=SQLOLEDB.1", again this doesn't work. Can anyone suggest a solution please? Further information: Development System is Windows7 using VS2010 Deployment systems are a combination of Windows XP, Windows 2000 and Windows 7 SQL Server is SQL2000 (soon to be SQL2005). TIA

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• Using a different array for vertices and normals in glDrawElements (OpenGL/VBOs)

  - by Tuxer

  I'm currently programming a .obj loader in OpenGL. I store the vertex data in a VBO, then bind it using Vertex Attribs. Same for normals. Thing is, the normal data and vertex data aren't stored in the same order. The indices I give to glDrawElements to render the mesh are used, I suppose, by OpenGL to get vertices in the vertex VBO and to get normals in the normals VBO. Is there an opengl way, besides using glBegin/glVertex/glNormal/glEnd to tell glDrawElements to use an index for vertices and an other index for normals? Thanks

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• F# books question

  - by Michiel Borkent

  I am now reading Foundations of F# by Robert Pickering and parallelly the book in progress 'Real World Functional Programming' by Tomas Petricek. My question is, what is the added value I would get from buying and reading the following books: 1) Expert F# by Don Syme and others 2) F# for Scientists by John Harrop Are those books still up to date with the current CTP version. What are things to keep notice of with respect to the recent changes in the language? Will there be reprinted updated versions? Also I want to learn more about datamining techniques with F# as a tool for this. What are good books to read next on this topic?

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• New to javascript, why is jQuery such a beast?

  - by gnucom

  Hey Everyone, I'm new to javascript (functional programming is okay for me, though) and I am wondering how jQuery got away with some of the design decisions they made. Is it just too much work to fix now or what? For instance, there seems use of strange symbols in strings when accessing elements in the DOM or weird function definitions for $, that are forcing me to check references every other time I want to get some basic data. Can someone point me to a learning source where I can learn all of these nuances of jQuery (jQuery's examples just don't cut it, they're too spread out)? Maybe someone has a super good reference site/pdf for jQuery? Thanks

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• How to print an isosceles triangle

  - by Steve

  Hello, I'm trying to learn programming by myself, I'm working from a book that has the following problem which I can't solve: Allow the user to input two values: a character to be used for printing an isosceles triangle and the size of the peak for the triangle. For example, if the user inputs # for the character and 6 for the peak, you should produce the following display: # ## ### #### ##### ###### ##### #### ### ## # This is the code I've got so far: char character; int peak; InputValues(out character, out peak); for (int row = 1; row < peak * 2; row++) { for (int col = 1; col <= row; col++) { Console.Write(character); } Console.WriteLine(); } Console.Read() // hold console open Thanks in advance.

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• How can I enable/disable network connection options programmatically

  - by nikie

  When I open the properties on a network connnection on windows, I see this dialog: In this dialog, in the check-listbox I can enable or disable options like "File or printer sharing", "client for microsoft networks" or network filter drivers. My question is: How can I enable/disable these options programatically? I didn't find anything that looks like this in the WMI documentation and I couldn't find any other Win32 API for this. I would prefer a C Win32 API or WMI interface, but a solution using any programming language is welcome. The question is language-agnostic.

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• Crystal Reports and WMF image

  - by Eve

  I have a problem with inserting a vector graphics (WMF) into report (Crystal Reports v10.5 from Visual Studio 2008). The image is static, inserted by choosing "Insert Picture" during report design in VS. The problem is that it displays differently (size and aspect ratio) on machines with different operating systems and screen resolutions. Converting to bitmap isn't possible beacause loss of the quality of print isn't acceptable. I thought about dynamic loading of the image, but in this version of CR. I don't see a possibility to set dynamic graphic location in picture properties. Is there any way to solve this problem?

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• MD5 hash differences between Python and other file hashers

  - by Sam

  I have been doing a bit of programming in Python (still a n00b at it) and came across something odd. I made a small program to find the MD5 hash of a filename passed to it on the command line. I used a function I found here on SO. When I ran it against a file, I got a hash "58a...113". But when I ran Microsoft's FCIV or the md5sum.py in \Python26\Tools\Scripts\, I get a different hash, "591...ae6". The actual hashing part of the md5sum.py in Scripts is m = md5.new() while 1: data = fp.read(bufsize) if not data: break m.update(data) out.write('%s %s\n' % (m.hexdigest(), filename)) This looks functionally identical to the code in the function given in the other answer... What am I missing? (This is my first time posting to stackoverflow, please let me know if I am doing it wrong.)

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• How do you design a database to allow fast multicolumn searching?

  - by Fletcher Moore

  I am creating a real estate search from RETS data, but this is a general question. When you have a variety of columns that you would like the user to be able to filter their search result by, how do you optimize this? For example, http://www.charlestonrealestateguide.com/listings.php has 16 or so optional filters. Granted, he only has up to 11,000 entries (I have the same data), but I don't imagine the search is performed with just a giant WHERE AND AND AND ... clause. Or is this typically accomplished with one giant multicolumn index? Newegg, Amazon, and countless others also have cool & fast filtering systems for large amounts of data. How do they do it? And is there a database optimization reason for the tendency to provide ranges instead of empty inputs, or is that merely for user convenience?

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• Text should wrap if checkbox is selected

  - by Dainel

  i am working with android webview and inside webview i am displaying the webpage which is having css,Javascript so i want that whenever i will select the checkbox and try to zoom the page so it should wrap otherwise it should not. So for that i tried to set the property of css - w.loadUrl("javascript:(function() {" + "document.getElementByTagName('html')[0].style.whiteSpace='nowrap';})"); but i am changing these properties by programming so it is not affecting the text content so please tell me how can i make the webpage text as wrapped if the checkbox is selected and it should not wrap if the checkbox is not selected,so please provide me any suggestion?? Thanks in advance

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• Question about when and when not to raise events (C#)

  - by NoPyGod

  I am programming an instant messaging library for MSN Messenger, and I have a simple question about raising events. When logging in, should I be raising UserAdded for each user that is synchronized (already on the contact list), or should the UserAdded event be reserved for when a new user has been added to the contact list via the AddUser method? Should I perhaps use another event, UserDownloaded for when a user is downloaded? Similarly, when I call logout, should I call UserRemoved? I hope this makes sense. Thank you

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• Need help for this syntax: "#define LEDs (char *) 0x0003010"

  - by Noge

  I'm doing programming of a softcore processor, Nios II from Altera, below is the code in one of the tutorial, I manage to get the code working by testing it on the hardware (DE2 board), however, I could not understand the code. #define Switches (volatile char *) 0x0003000 #define LEDs (char *) 0x0003010 void main() { while (1) *LEDs = *Switches; } What I know about #define is that, it is either used to define a constant, or a macro, but why in the above code, there are casting like, (char *) 0x0003010, in #define? why the 2 constants, Switches and LEDs act like a variable instead of a constant? Thanks in advance !

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• What Database to distribute as part of a C# app backend

  - by jez

  I am planning on writing and commercialising a C# app which will store data in an underlying database I use MySQL on my environment for my own development and this is what I would have used to write the application for myself (no need to use FK - MyISAM engine would be fine). I am concerned about how easy it will be to distribute the app together with the database engine. Would using MySQL allow me for easy packaging of the app for a "one-click" install on the client side? (ie I do not want them to have to install MySQL by themselves) and also is it feasible from a licensing point of view? Are there other Database systems which would make the process more straight-forward

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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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• Good book(s) for MMORPG design & implementation?

  - by mawg

  I am a long time professional C/C++ programmer (mostly embedded systems) and a hobbyist windows & php hacker. Can anyone recommend a book(s) specifically aimed at designing and (hopefully) implementing an MMORPG? I don't need general how to design or how to code books. Maybe a really good generic games book, but I am not interested in 1st person shooters, I want to know what it takes to implement an MMORPG. Good books, maybe also good URLs. Thanks just searching eBay and Amazon threw up a whole slew of books. Amazon's customer reviews give me an idea of how good they are, and the overview tells me what areas they cover

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• How to write applications that modifies the Windows UI?

  - by StevenGilligan

  Hi, I have this programming question that's been bothering me for some time now. I'm wondering how is it possible to write applications that change the Windows UI? More precisely how could you write an application that modifies the Windows Taskbar or the Windows Desktop? I'm really interested in this topic but cannot find a lot of information. I've read about extending the Windows Shell but I can't seem to find anything related to modifying the Taskbar and the Desktop. I'm looking for something along the lines of Rainmeter. How did those guys create an application that lives inside the Windows Desktop? I'd like to point out that my prefered language for this would be C# but if you want to give me hints in other languages I'm fine with it and I am running on Windows 7. Thank you

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