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• Looking for calculator source code, BSD-licensed

  - by Horace Ho

  I have an urgent project which need many functions of a calculator (plus a few in-house business rule formulas). As I won't have time to re-invent the wheel so I am looking for source code directly. Requirements: BSD licensed (GPL won't help) in c/c++ programming language 32-bit CPU minimum dependency on platform API/data structure best with both RPN and prefix notation supported emulator/simulator code also acceptable (if not impossible to add custom formula) with following functions (from wikipedia) Scientific notation for calculating large numbers floating point arithmetic logarithmic functions, using both base 10 and base e trigonometry functions (some including hyperbolic trigonometry) exponents and roots beyond the square root quick access to constants such as pi and e plus hexadecimal, binary, and octal calculations, including basic Boolean math fractions optional statistics and probability calculations complex numbers programmability equation solving

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• Roadblocks in creating a custom operating system

  - by Dinah

  It seems to me that the most common overly ambitious project that programmers (esp. Comp. Sci. grads) try to tackle is building your own operating system. (Trying to create your own programming language + compiler is probably even more common but not nearly as ambitious.) For those (like myself) foolish enough to try: aside from the sheer size, what are the biggest *gotcha*s or unexpected roadblocks you've encountered in trying to create your own OS from the ground up? Edit: A great OS question: http://stackoverflow.com/questions/43180/how-to-get-started-in-operating-system-development/

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• Clojure editor/IDE recommendations on OS X

  - by Julien Chastang

  I am starting to learn the Clojure programming language. Are there any recommendations for Clojure editors/IDEs on OS X? Update 2009-9-23: The clojure space has changed tremendously since I originally posted this question. Many of the links below, especially those that refer to clojure-mode with emacs, are out-of-date. The best clojure IDE I found was the enclojure Netbeans plugin which was recently released (2009-08-25). Update 2010-4-30: Here is another very good link on this subject by Lau B. Jensen. Also, for my own clojure development, I have actually moved to emacs / swank-clojure.

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• Asynchronous operations performance

  - by LicenseQ

  One of the features of asynchronous programming in .NET is saving threads during long running operation execution. The FileStream class can be setup to allow asynchronous operations, that allows running (e.g.) a copy operation without virtually using any threads. To my surprise, I found that running asynchronous stream copy performs not only slower, but also uses more processing power than synchronous stream copy equivalent. Is there any benchmark tests were done to compare a synchronous vs asynchronous operation execution (file, network, etc.)? Does it really make sense to perform an asynchronous operation instead of spanning separate thread and perform synchronous operation in server environment if the asynchronous operation is times slower than the synchronous one?

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• Language Design: Combining Gotos and Functions

  - by sub

  I'm designing and currently rethinking a low-level interpreted programming language with similarities to assembler. I very soon came across the functions/loops/gotos decision problem and thought that while loops like while and for would be too high-level and unfitting, gotos would be too low level, unmaintainable and generally evil again. Functions like you know them from most languages that have return values and arguments aren't fitting in the language's concept either. So I tried to figure out something between a function and a goto which is capable of Recursion Efficient loops After some thinking I came up with the idea of subroutines: They have a beginning and an end like a function They have a name but no arguments like a goto You can go into one with jump and go out of it again before its end with return (doesn't give back any result, only stops the subroutine) Handled just like normal code - Global scope like goto So I wanted to know: Is the idea above good? What are the (dis)advantages? Would there be a better combination of function and goto or even a completely new idea?

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• String Formatting Tricks/Docs

  - by Meltemi

  Was reading the response by Shaggy Frog to this post and was intrigued by the following line of code: NSLog(@"%@", [NSString stringWithFormat:@"%@:%*s%5.2f", key, padding, " ", [object floatValue]]); I know string formatting is an age old art but I'm kinda doing the end around into Cocoa/Obj-C programming and skipped a few grades along the way. Where is a good (best) place to learn all the string formatting tricks allowed in NSString's stringWithFormat? I'm familiar with Apple's String Format Specifiers page but from what I can tell it doesn't shed light on whatever is happening with %*s or the %5.2f (not to mention the 3 apparent placeholders followed by 4 arguments) above?!?

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• A strong case for WF

  - by Pita.O

  Hi guys, I have struggled for so long to find a compelling use case for workflow (ie: WF) as against regular imperative programming. Each time I fall back to the conclusion that I should just leave WF out or defer getting into it until later. But I keep having this nagging feeling that there's something am missing. Does anyone know any book that truly makes a strong case for the Workflow way? The book has to (i) teach WF well, and (ii) show using appropriate use cases that WF made an implementation easy to do than if we just did our regular straight coding. I will appreciate it.

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• Resizing screenshots/screen captures for inclusion in Beamer

  - by Stephen

  Sorry, this may or may not be a programming question directly, but I am trying to resize screenshots with Imagemagick and Gimp to include in a Beamer presentation, but it comes out even blurrier than the resizing done by LaTeX. For instance, in Beamer I might have a command to rescale the image \includegraphics[width=.5\textwidth]{fig.png}. Using something like \begin{frame} \message{width = \the\textwidth} \message{height = \the\textheight} \end{frame} I have gotten the \textwidth and \textheight parameters in points (345.69548, 261.92444). So I have a script (in Python) that sends a system call to Imagemagick: 'convert %s -resize %.6f@ resized_%s' % (f,a,f) where a is calculated as \textwidth*\textheight*0.5**2. When I then go back into my Beamer presentation and include the resized figure, \includegraphics{resized_fig.png}, the size looks approximately correct but it's super-blurry. I also tried resizing in Gimp (using the GUI) but no luck either... help? Thanks...

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• Aaron Hillegass Chapter 18 Challenge Question

  - by jasonbogd

  I am working through Aaron Hillegass' Cocoa Programming for Mac OS X and am doing the challenge for Chapter 18. Basically, the challenge is to write an app that can draw ovals using your mouse, and then additionally, add saving/loading and undo support. I'm trying to think of a good class design for this app that follows MVC. Here's what I had in mind: Have a NSView-subclass that represents an oval (say JBOval) that I can use to easily draw an oval. Have a main view (JBDrawingView) that holds JBOvals and draws them. The thing is that I wasn't sure how to add archiving. Should I archive each JBOval? I think this would work, but archiving an NSView doesn't seem very efficient. Any ideas on a better class design? Thanks.

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• iPhone Foundation - performance implications of mutable and xxxWithCapacity:0

  - by Adam Eberbach

  All of the collection classes have two versions - mutable and immutable, such as NSArray and NSMutableArray. Is the distinction merely to promote careful programming by providing a const collection or is there some performance hit when using a mutable object as opposed to immutable? Similarly each of the collection classes has a method xxxxWithCapacity, like [NSMutableArray arrayWithCapacity:0]. I often use zero as the argument because it seems a better choice than guessing wrongly how many objects might be added. Is there some performance advantage to creating a collection with capacity for enough objects in advance? If not why isn't the function something like + (id)emptyArray?

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• Android WakeLock and KeyGuard

  - by KimAMartinsen

  Hi! I'm just wondering if I do this correctly; I'm programming a notification app which can display a notification when the phone is sleeping Disable keyguard lock Aquire a wake lock show notification Set alarm for timeout and reenabling keyguard and release wakelock is the user dont touches the screen. 4.1 User touches the screen, and I disable the timer. Do nothing more. Done and done 4.2 User dont touch the screen, so reenable keyguard and release wakelock. Phone sleeps again Basically I'm wondering about point 4.1 the most. cancel the pendingintent for the alarm, and do nothing more? or should the keyguard and wakelock that are set be dealt with in some way?

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• Reading multiple Emacs info files simultaneously

  - by pajato0

  For reading programming (and other) documentation, the Emacs INFO mode is outstanding. So outstanding that I would like to be able to read say, the Emacs Lisp info file and the org-mode info files simultaneously without traversing back up to the beginning of the info tree. Either I've missed something obvious or I will need to hack some Emacs Lisp to achieve the goal. And yet again, someone may have already cracked this nut. So I guess my question is: what is the state of the practice for reading mulitple INFO files in Emacs simultaneously?

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• Career advice for a frustrated newbie programmer.

  - by Satoru.Logic

  Hi, all. This is my first year as a programmer. The programming language that I'm most familiar with is Python. I am maintaining a web2py based legacy system, alone, which means I have to grow up as an all-rounder. The original programmers on this project are nowhere to find, and there are hardly any usable documents about requirements or anything. I find it very frustrating every time I hear the users criticize the system, and I can't help explaining that "that was not my fault, those mess was there even before I entered this company." I wonder what should I do with this situation. Please give me some advice, thanks in advance.

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• Calculating determinant by hand

  - by ldigas

  Okey, this is only half programming, but let's see how you are on terms with manual calculations. I believe many of you did this on your university's while giving "linear systems" ... the problem is it's been so long I can't remember how to do it any more. I know quite a few algorithms for calculating determinants, and they all work fine ... for large systems, where one would never try to do it manually. Unfortunatelly, I'm soon going on an exam, where I do have to calculate it manually, up to the system of 5. So, I have a K(omega) matrix that looks like this: [2-(omega^2)*c -4 2 0 0] [-2 5-(omega^2)*c -4 1 0] [1 -4 6-(omega^2)*c -4 1] [0 1 -4 5-(omega^2)*c -2] [0 0 2 -4 2-(omega^2)*c] and I need all the omegas which satisfy the det[K(omega)]=0 criteria. What would be a good way to calculate it so it can be repeated in a manual process ?

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• Relating NP-Complete problems to real world problems

  - by terru

  I have a decent grasp of NP Complete problems; that's not the issue. What I don't have is a good sense of where they turn up in "real" programming. Some (like knapsack and traveling salesman) are obvious, but others don't seem obviously connected to "real" problems. I've had the experience several times of struggling with a difficult problem only to realize it is a well known NP Complete problem that has been researched extensively. If I had recognized the connection more quickly I could have saved quite a bit of time researching existing solutions to my specific problem. Are there any resources (online or print) that specifically connect NP Complete to real world instances?

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• How to create playable FLV video from part of FLV file using FFMPEG?

  - by Ole Jak

  So we had real FLV video file. we had devided it into 3 parts (more or less equal, not looking into structure orcontext). We have taken second part and forgot about first 2. Video contained audio and video track. mp3 and on vp6. Is it any how possible to play thsat second part after sending to ffmpeg some command? So how to (using any FFMPEG API (in general in any programming language) or using command line) turn bytearray into playable video? (knowing what format video was created in and some other data like used codecs )

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• Why can't I download a whole image file with urllib2.urlopen()

  - by John Gann

  When I run the following code, it only seems to be downloading the first little bit of the file and then exiting. Occassionally, I will get a 10054 error, but usually it just exits without getting the whole file. My internet connection is crappy wireless, and I often get broken downloads on larger files in firefox, but my browser has no problem getting a 200k image file. I'm new to python, and programming in general, so I'm wondering what nuance I'm missing. import urllib2 xkcdpic=urllib2.urlopen("http://imgs.xkcd.com/comics/literally.png") xkcdpicfile=open("C:\\Documents and Settings\\John Gann\\Desktop\\xkcd.png","w") while 1: chunk=xkcdpic.read(4028) if chunk: print chunk xkcdpicfile.write(chunk) else: break

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• Usng Rails ActiveRecord relationships

  - by Brian Goff

  I'm a newbie programmer, been doing shell scripting for years but have recently taken on OOP programming using Ruby and am creating a Rails application. I'm having a hard time getting my head wrapped around how to use my defined model relationships. I've tried searching Google, but all I can come up with are basically cheat sheets for what has_many, belongs_to, etc all mean. This stuff is easy to define & understand, especially since I've done a lot of work directly with SQL. What I don't understand is how to actually used those defined relationships. In my case I have 3 models: Locations Hosts Services Relationships (not actual code, just for shortening it): Services belongs_to :hosts Hosts has_many :services belongs_to :locations Locations has_many :hosts In this case I want to be able to display a column from Locations while working with Services. In SQL this is a simple join, but I want to do it the Rails/Ruby way, and also not use SQL in my code or redefine my joins.

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• Looking for programs on audio tape/cassette containing programs for Sinclair Z80 PC?

  - by DVK

  OK, so back before ice age, I recall having a Sinclair ZX80 PC (with TV as a display, and a cassette tape player as storage device). Obviously, the programs on cassette tapes made a very distinct sound (er... noise) when playing the tape... I was wondering if someone still had those tapes? The reason (and the reason this Q is programming related) is that IIRC different languages made somewhat different pitched noises, but I would like to run the tape and listen myself to confirm if that was really the case...

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• What web-development platform should I use considering Time-To-Market?

  - by Jonas

  I have been looking at a few differend platforms for my coming web-development project. I would like to hear what web-development platform is recommended when considering Time-To-Maket. Suppose that I already know the programming language well, but not the web-framework. The OS will be Linux. My requirements and priorities: Time-To-Market RESTful Maintainable code Scales-up (not dog-slow) The one I have looked at but never used are: Java and Play! Framework or GWT Python and Django PHP and Zend Framework Ruby and Ruby on Rails Erlang and Nitrogen and Webmachine Scala and Lift C++ and Wt C# and ASP.NET Mono It's a bonus if the framework has support for making sites for mobile phones.

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• displaying web pages over web views in collection view using cocoa bindings

  - by Miraaj

  Hi all, I tried sample example given at this link - Collection View Programming Guide It is simple and it worked. Considering it as a reference I tried a simple application which will show a collection view of web views with some web page displayed over each web view. The model class has two properties: NSString *pageName, and NSURL *pageURL. I then followed each and every step written in tutorial above with required modifications but I was caught in the step - How to bind web view to collection view item? In binding tab it shows three possibilities : Editable, Hidden, Tool tip but none of these is working. Can anyone suggest me way to accomplish my requirement? Thanks, Miraaj

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• Touchscreen using sound input?

  - by ricardowong

  Hi, i don't really know if it is actually possible, but i believe that it can be made. How possible is it to make a program that recognizes different sound bouncing from the screen and turn it into a position that will obviously be later fed to the mouse. I know that it sounds kind of dumb, but lately i've been noticing that a very dull, strong sound is made when touching the screen, and that sound varies when doing so at different positions. Probably the microphone "hears" differently because the screen acts as a drum with the casing. Anyways, what do you think, anyone has any experience programming with sound?

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• Distributing APNS providers

  - by Sam

  I'm writing a business-focused iPhone app which includes a self-hosted server component. I'd like to include push notification functionality in the server; reading through the programming guide it looks as if this would involve either: Distributing the provider certificate with the server component - this doesn't sound like a terribly good idea (even if Apple permits it?) Hosting a shared notification provider and forwarding notifications to APNS from the servers. For an ongoing, high-availability service, this is likely to require including a subscription pricing component, which I would prefer to avoid. Require customers to apply for their own provider certificate. However, it's not clear whether multiple organisations are allowed to apply for provider certificates with a single bundle ID, and it would significantly increase the barrier to adoption. APNS looks to me as if it's specifically geared for centrally hosted services. Is anyone distributing self-hosted notification providers? Are there any other options?

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• help installing odfWeave

  - by Andreas

  This is not a programming question per se - but I hope someone can help: I can't install odfWeave - it looks like the problem is with the package XML - which i can't install either. checking for xml2-config... no Cannot find xml2-config ERROR: configuration failed for package ‘XML’ * removing ‘/home/andreas/R/i486-pc-linux-gnu-library/2.10/XML’ * installing source package ‘odfWeave’ ... ** R ** inst ** preparing package for lazy loading Warning in library(pkg, character.only = TRUE, logical.return = TRUE, lib.loc = lib.loc) : there is no package called 'XML' Error : package 'XML' could not be loaded ERROR: lazy loading failed for package ‘odfWeave’ * removing ‘/home/andreas/R/i486-pc-linux-gnu-library/2.10/odfWeave’ Any help much appreciated System: ubuntu 9.04

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• What way to use the CGContext to draw is suitable?

  - by Tattat

  I know that the CGContext cannot call it to draw directly, and it needs to fill the drawing logic in the drawInContext, and call the CGContext to draw using "setNeedsDisplay", so, I designed a cmd to execute, but it cause some problems... like this : http://stackoverflow.com/questions/2617827/why-i-cant-draw-in-a-loop-using-uiview-in-iphone I think the CGContext is very different from my previous programming experience....(I used HTML5 canvas, that allow me add more details, after I draw, so do the Java Swing) Actually, I want to know what is the suitable to implement these kind of thing in Apples' programmer mind. Thz.

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