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• What lessons can you learn from software maintanence?

  - by Vasil Remeniuk

  Hello everyone, In the perfect world, all the software developers would work with the cutting edge technologies, creating systems from the scratch. In the real life, almost all of us have to maintain software from time to time (unlucky ones do it on a regular basis). Personally I first 2 years of my career was fixing bugs in the company that no longer exists (it has been taken up by Oracle). And probably the biggest lesson I've learned that time - despite of the pressure, always try to get as much information about the domain as possible (even if it's irrelevant to fixing a specific bug or adding a feature) - abstract domain knowledge doesn't lose value as fast as knowledge about trendy frameworks or methodologies. What lessons have you learned from maintenance?

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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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• Are today's young programmers getting wrapped around the axle with patterns and practices?

  - by Robert Harvey

  Recently I have noticed a number of questions on SO that look something like this: I am writing a small program to keep a list of the songs that I keep on my ipod. I'm thinking about writing it as a 3-tier MVC Ruby on Rails web application with TDD, DDD and IOC, using a factory pattern to create the classes and a singleton to store my application settings. Do you think I'm taking the right approach? Do you think that we're handing novice programmers a very sharp knife and telling them, "Don't cut yourself with this"? NOTE: Despite the humorous tone, this is a serious (and programming-related) question.

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• setNeedsDisplayInRect: paints a white rectangle only

  - by Ion Tichy

  Hi, I'm still a little fresh to CoreGraphics programming, so please bear with me. I'm trying to write an application, which allows the user to rub stuff off an image with the finger. I have the basic functionality nailed down, but the result is sluggish since the screen is redrawn completely every time a touch is rendered. I did some research and found out that I can refresh only a portion of the screen using UIView's setNeedsDisplayInRect: method. This does call drawRect: as expected, however everything I draw in the drawRect: following the setNeedsDisplayInRect: is ignored. Instead, the area in the rect parameter is simply filled with white. No matter what I draw inside, all I end up with is a white rectangle. In essence, this is what I do: 1) when user touches screen, this touch is rendered into a mask 2) when the drawRect: is called, the image is masked with that mask There must be something simple I'm overlooking, surely?

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• resetting the image in an NSView

  - by Josan

  I think this is a very simple question, but I’m new to programming so I may be going about it in a wrong-headed way. I have a basic understanding of Objective-C writing terminal applications and am teaching myself how to use the Cocoa GUI. I understand how to use IBOutlet and IBAction to connect a simple button to a method that will repeatedly send random numbers to a textfield . I understand how to add a NSView file, connect it to a custom view in interface builder and draw a path through random points in the view when the application launches. (I’ve been putting this code inside the - (void)drawRect:(NSRect)dirtyRect method that is declared when the file is created). What I can’t seem to figure out is how to connect a button to an action that will then ‘refresh’ the view – in this case repopulate it with another set of random points connected with a path. Looking at the documentation, I think I should somehow be using – (void) setNeedsDisplay(BOOL)flag but nothing I have tried so far had worked. Please tell me, what am I missing here?

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• Straight Java/Groovy versus ETL tool (Talend/etc) - what libraries would you use?

  - by Alex R

  Assume you have a small project which on the surface looks like a good match for an ETL tool like Talend. But assume further, that you have never used Talend and furthermore, you do not trust "visual programming" tools in general and would rather code everything the old fashioned way (text on a nice IDE!) with the help of an appropriate language & support libraries. What are some language patterns & support libraries that could help you stay away from the ETL tool temptation/trap?

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• How do you invoke a web service from another web service using php?

  - by hello nottellingmyname

  So, I'm new to web programming, and for my homework I have to write some web services using PHP. Some of the web services have to use other web services, though, and we didn't learn how to do that. My professor said we should look up how to do that online. I think to call a web service using a GET parameter I just need to do file_get_contents(url), but I have no idea how to make a web service call using POST. So, how do I make a web service call from a web service using POST?

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• Style of if: to nest or not to nest

  - by Marco

  A colleague of mine and me had a discussion about the following best-practice issue. Most functions/methods start with some parameter checking. I advocate the following style, which avoids nesting. if (parameter one is ugly) return ERROR; if (parameter two is nonsense || it is raining) return ERROR; // do the useful stuff return result; He, who comes from a more functional/logic programming background, prefers the following, because it reduces the number of exit points from the function. if (parameter one is ok) { if (parameter two is ok && the sun is shining) { // do the useful stuff return result } } return ERROR; Which one would you prefer and why?

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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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• 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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• 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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• For what programs are Objective C and Ruby ideal on the Mac?

  - by Kurt

  Hi, as a Mac outsider it seems that two popular programming languages on the Mac appear to be Objective C and Ruby. From what I understand the main API Cocoa seems to be written in and optimized for Objective C, but it is also possible to use Ruby for that. Are there different areas where each language is ideal, for example, I could imagine Objective C could be ideal for a GUI layer, or standalone desktop app, and Ruby could be good for web services etc. What about classic business logic, or data access layers? What language would be a good choice for a library of services for example? Can we write a library in one language and link to it from a main program written in the other language? If I wanted to write a layered enterprise application using domain driven design and dependency injection which languages could support each concerns? Are things like DDD and DI common amongst Mac devs? Just a curious outsider.

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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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• 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 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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• 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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• 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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• Bash variable kills script execution

  - 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 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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• 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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• Is there a Chrome extension to add mailto links to email addresses?

  - by Martin Burch

  Wait, wait, this is a programming question! I want to build an extension if none exists. Imagine this: you come across a webpage that says "Just send a message to [email protected]" but to actually send the email, you need to highlight the address and then cut and paste it into the recipient field of a new compose window of your email client of choice. Obviously life would be easier if it were simply a mailto: link, so you could click on it and have a new message created automatically. (Or if the page designer had used a form, perhaps ...) I was originally going to ask if there was an extension to enable similar functionality for unlinked twitter @username mentions but I thought this email address problem would be a simpler situation. If you think it would be useless, perhaps I should look at the twitter username problem instead. Thanks for your feedback.

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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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• The shortest way to convert infix expressions to postfix (RPN) in C

  - by kuszi

  Original formulation is given here (you can try also your program for correctness) . Additional rules: 1. The program should read from standard input and write do standard output. 2. The program should return zero to the calling system/program. 3. The program should compile and run with gcc -O2 -lm -s -fomit-frame-pointer. The challenge has some history: the call for short implementations has been announced at the Polish programming contest blog in September 2009. After the contest, the shortest code was 81 chars long. Later on the second call has been made for even shorter code and after the year matix2267 published his solution in 78 bytes: main(c){read(0,&c,1)?c-41&&main(c-40&&(c%96<27||main(c),putchar(c))):exit(0);} Anyone to make it even shorter or prove this is impossible?

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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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• 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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