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• Minimalistic tools for developer documentation

  - by Pekka

  I am currently working on a large PHP CMS / Framework and documenting it extensively as I go along. In addition to phpdoc-style inline comments, I need to document XML structures, details on concepts and practices, write HOWTOs and so on. At the moment, I am using simple OpenOffice documents for that, but I'm unhappy with it and looking for a "real" documentation system. So, I am looking for recommendations for robust, minimalistic, easy-to-use documentation software. I have tried a number of Wikis, most prominently Dokuwiki. I like the open-minded approach, the freedom in editing, and the simplicity, but they provide little support in structuring a multi-chapter documentation, and make basic reorganisation tasks very difficult (e.g. moving pages to a different namespace). Working with the plugins is Cumbersome, and they are not really easy to use. Open Source would be a plus but is not a requirement. Thanks for all the suggestions. I have not had time to look into each one in detail. I will be trying Sphinx, especially because it provides so much support for a good structure. I may update this post later when I'm done and report how it worked out. The suggestions Trac's built-in wiki which is great but for my taste provides too little support for keeping a structure - it's perfect though for "normal", smaller size project documentation Markdown my current favourite because of its minimalism, however not sure yet whether maintaining a structure will be easy enough. A Markdown-Based system would of course be very easy to extend, e.g. to look up cross references from the project's code base. Of course it would be great to find something that already has that out of the box. The DocBook format and to edit, the commercial Oxygen XML Editor - a great standard for building documentation, no doubt. Maybe too "technical" for my purposes as I need something to open quickly, write into and go on coding. Still always worth a mention. Sphinx an Open Source, Python based documentation generator, promising structured documentation and extensive cross-referencing. Interesting and will take a look. Confluence a commercial but very affordable Wiki. XWiki, an Open Source playing in Confluence's league with numerous extensions and connectors to Eclipse and Microsoft Office. TiddlyWiki an open-source Wiki.

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• Miller-rabin exception number?

  - by nightcracker

  Hey everyone. This question is about the number 169716931325235658326303. According to http://www.alpertron.com.ar/ECM.HTM it is prime. According to my miller-rabin implementation in python with 7 repetitions is is composite. With 50 repetitions it is still composite. With 5000 repetitions it is STILL composite. I thought, this might be a problem of my implementation. So I tried GNU MP bignum library, which has a miller-rabin primality test built-in. I tested with 1000000 repetitions. Still composite. This is my implementation of the miller-rabin primality test: def isprime(n, precision=7): if n == 1 or n % 2 == 0: return False elif n < 1: raise ValueError("Out of bounds, first argument must be > 0") d = n - 1 s = 0 while d % 2 == 0: d //= 2 s += 1 for repeat in range(precision): a = random.randrange(2, n - 2) x = pow(a, d, n) if x == 1 or x == n - 1: continue for r in range(s - 1): x = pow(x, 2, n) if x == 1: return False if x == n - 1: break else: return False return True And the code for the GMP test: #include <gmp.h> #include <stdio.h> int main(int argc, char* argv[]) { mpz_t test; mpz_init_set_str(test, "169716931325235658326303", 10); printf("%d\n", mpz_probab_prime_p(test, 1000000)); mpz_clear(test); return 0; } As far as I know there are no "exceptions" (which return false positives for any amount of repetitions) to the miller-rabin primality test. Have I stumpled upon one? Is my computer broken? Is the Elliptic Curve Method wrong? What is happening here? EDIT I found the issue, which is http://www.alpertron.com.ar/ECM.HTM. I trusted this applet, I'll contact the author his applet's implementation of the ECM is faulty for this number. Thanks. EDIT2 Hah, the shame! In the end it was something that went wrong with copy/pasting on my side. NOR the applet NOR the miller-rabin algorithm NOR my implementation NOR gmp's implementation of it is wrong, the only thing that's wrong is me. I'm sorry.

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• Am I "wasting" my time learning C and other low level stuff ?

  - by Andreas Grech

  I have just recently started learning C and the reason I did that was because frankly, I consider myself to be of a "less-developer" than the people who know and work with C. Thus I planned to start learning ASM, C, C++ and bought the K&R book and started pushing myself to learn the C Programming Language and up till now I'm doing great...learning about arrays the low level way (ie the pointer + offset thing), pointers and all that and obviously asking questions on stackoverflow for guidance. My problem is that sometimes I get thinking if instead of learning this low level stuff, maybe I should maybe spend more time learning newer, more widely used technologies...basically, more web stuff. Now I am well versed with both C# and ASP.Net and currently that's what I do for a living, but still there exists Microsoft technologies that I haven't quite touched upon...such as ASP.Net MVC, The Entity Framework etc... And those are only Microsoft Technologies...obviously there are other stuff that I would like to touch upon...stuff like Ruby, which would lead me to Ruby on Rails, or Python for Django or even Java and J2EE, or maybe even PHP; ie, basically mainly Web Stuff. Mind you, I did touch upon some of the stuff I mentioned earlier on, such as PHP and Java but I am still not quite versed in them as I am in C# and ASP.Net...but still, I think that by learning other languages that are used in the web environment will broaden my horizons...both as a developer who loves learning, and also Career wise. My point is, am I really using up my time correctly by learning older, lower level stuff? Stuff that for my current line of work, will most probably never use, but still is interesting to know ? To be frankly honest, I am also learning C so that I could, maybe someday, get into Electronics and Micro-controller programming but that is a whole new world for me and, if I choose to go there, will take some time to get adjusted to. And even then, I don't know if I can get a career in working in that line of work. ...but I still wonder about this question over and over...Am I doing the right thing by learning C instead of something (Web-stuff) that will most probably be more useful for me career-wise? I'm sorry for such asking such a long and most probably a boring question, but I feel as if this is the only place where I can ask such a question and get an honest answer from experts in the field. Thank you for your time.

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• What was your the most impressive technical programming achievement performed to impress a romantic

  - by DVK

  OK, so the archetypal human story is for a guy to go out and impress the girl with some wonderful achievement like slaying a dragon or building a monument or conquering neighboring tribe. This being enlightened 21st century on SO, let's morph this into a: StackOverflower performing a feat of programming to impress a romantic interest. There are two ways to do this: Technical achievement: Impressing a person with suitable background/understanding of programming with actual coding powerss you displayed. A dumb movie example would be that kid in "Hackers" move showing off his hacking skills in front of Angeline Jolie. Artistic achievement: Impressing a person with a result of running said code, whether they understand just how incredible the code itself is. An example is the animated ANSI rose (for a guy who actually wrote the ANSI code) This question is only about the first kind (technical achievements) - e.g. the person of interest was presented with impressive code/design that (s)he was able to properly appreciate. Rules (what doesn't qualify): The target audience must have been a person of romantic interest (prospective or present significant other or random hook-up). E.g. showing your program to your sister who's also a software developer doesn't count. The achievement must have been done specifically with the goal to impress such a person. However, it is OK if the achievement was done to impress a generic qualifying person, not someone specific. Although... if you write code to impress girls in general, I'd say "get a better idea of the opposite sex" The achievement must have been done with the goal of impressing the person. In other words, if you would have done it without romantic interest's knowledge anyway, it doesn't count. As examples, the following does not count: programming for your job. Programming for a coding contest. Open Source program that you'd have done anyway. The precise nature of the awesomeness of the achievement is somewhat irrelevant - from learning entire J2EE in 2 days to writing fancy game engine to implementing Python compiler in LOGO. As long as it's programming/software development related. The achievement should preferably be something other people would rank highly as well. If your date was impressed with your skill at calculating Fibonacci sequence without recursive function calls, it doesn't mean most developers will be. But it does mean you need to start finding better things to do on dates ;)

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• Is it possible to programatically catch JavaScript SyntaxErrors?

  - by Matty

  I don't think that this is doable, but wanted to throw it out to the community to confirm my suspicions. Let's say you're writing a program in another language like Python, PHP, or ASP. This program is intended to build another program written in JavaScript. However, the first program is unfortunately not immune to errors. So, occasionally, the program which builds the JavaScript program does some funky stuff and outputs a syntax error in the JavaScript source. Now some user goes and loads the program and it essentially halts, because the web browser running it can't properly parse the JavaScript. This user is probably not going to be happy. I wouldn't be. This brings me to my question. Is it possible to write an error handler that would catch these kind of syntax problems allowing the application to fail gracefully? Here's an example: <html> <head> <script type="text/javascript" charset="utf-8"> window.onerror = errorHandler; function errorHandler(a,b,c) { alert('horray! No wait, Booo!'); } vara jfs; </script> </head> <body> Can this be done? </body> </html> or <html> <head> <script type="text/javascript" charset="utf-8"> try { vara jfs; } catch (e) { alert('horray! No wait, Booo!'); } </script> </head> <body> Can this be done? </body> </html>

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• Do you still limit line length in code?

  - by Noldorin

  This is a matter on which I would like to gauge the opinion of the community: Do you still limit the length of lines of code to a fixed maximum? This was certainly a convention of the past for many languages; one would typically cap the number of characters per line to a value such as 80 (and more recnetly 100 or 120 I believe). As far as I understand, the primary reasons for limiting line length are: Readability - You don't have to scroll over horizontally when you want to see the end of some lines. Printing - Admittedly (at least in my experience), most code that you are working on does not get printed out on paper, but by limiting the number of characters you can insure that formatting doesn't get messed up when printed. Past editors (?) - Not sure about this one, but I suspect that at some point in the distant past of programming, (at least some) text editors may have been based on a fixed-width buffer. I'm sure there are points that I am still missing out, so feel free to add to these... Now, when I tend to observe C or C# code nowadays, I often see a number of different styles, the main ones being: Line length capped to 80, 100, or even 120 characters. As far as I understand, 80 is the traditional length, but the longer ones of 100 and 120 have appeared because of the widespread use of high resolutions and widescreen monitors nowadays. No line length capping at all. This tends to be pretty horrible to read, and I don't see it too often, though it's certainly not too rare either. Inconsistent capping of line length. The length of some lines are limited to a fixed maximum (or even a maximum that changes depending on the file/location in code), while others (possibly comments) are not at all. My personal preference here (at least recently) has been to cap the line length to 100 in the Visual Studio editor. This means that in a decently sized window (on a non-widescreen monitor), the ends of lines are still fully visible. I can however see a few disadvantages in this, especially when you end up writing code that's indented 3 or 4 levels and then having to include a long string literal - though I often take this as a sign to refactor my code! In particular, I am curious what the C and C# coders (or anyone who uses Visual Studio for that matter) think about this point, though I would be interested in hearing anyone's thoughts on the subject. Edit Thanks for the all answers - I appreciate the variety of opinions here, all presenting sound reasons. Consensus does seem to be tipping in the direction of always (or almost always) limit the line length. Interestingly, it seems to be in various coding standards to limit the line length. Judging by some of the answers, both the Python and Google CPP guidelines set the limit at 80 chars. I haven't seen anything similar regarding C# or VB.NET, but I would be curious to see if there are ones anywhere.

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• Implement Semi-Round-Robin file which can be expanded and saved on demand

  - by ircmaxell

  Ok, that title is going to be a little bit confusing. Let me try to explain it a little bit better. I am building a logging program. The program will have 3 main states: Write to a round-robin buffer file, keeping only the last 10 minutes of data. Write to a buffer file, ignoring the time (record all data). Rename entire buffer file, and start a new one with the past 10 minutes of data (and change state to 1). Now, the use case is this. I have been experiencing some network bottlenecks from time to time in our network. So I want to build a system to record TCP traffic when it detects the bottleneck (detection via Nagios). However by the time it detects the bottlenecking, most of the useful data has already been transmitted. So, what I'd like is to have a deamon that runs something like dumpcap all the time. In normal mode, it'll only keep the past 10 minutes of data (Since there's no point in keeping a boat load of data if it's not needed). But when Nagios alerts, I will send a signal in the deamon to store everything. Then, when Naigos recovers it will send another signal to stop storing and flush the buffer to a save file. Now, the problem is that I can't see how to cleanly store a rotating 10 minutes of data. I could store a new file every 10 minutes and delete the old ones if in mode 1. But that seems a bit dirty to me (especially when it comes to figuring out when the alert happened in the file). Ideally, the file that was saved should be such that the alert is always at the 10:00 mark in the file. While that is possible with new files every 10 minutes, it seems like a bit dirty to "repair" the files to that point. Any ideas? Should I just do a rotating file system and combine them into 1 at the end (doing quite a bit of post-processing)? Is there a way to implement the semi-round-robin file cleanly so that there is no need for any post-processing? Thanks Oh, and the language doesn't matter as much at this stage (I'm leaning towards Python, but have no objection to any other language. It's less of an issue than the overall design)...

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• Is the Scala 2.8 collections library a case of "the longest suicide note in history" ?

  - by oxbow_lakes

  First note the inflammatory subject title is a quotation made about the manifesto of a UK political party in the early 1980s. This question is subjective but it is a genuine question, I've made it CW and I'd like some opinions on the matter. Despite whatever my wife and coworkers keep telling me, I don't think I'm an idiot: I have a good degree in mathematics from the University of Oxford and I've been programming commercially for almost 12 years and in Scala for about a year (also commercially). I have just started to look at the Scala collections library re-implementation which is coming in the imminent 2.8 release. Those familiar with the library from 2.7 will notice that the library, from a usage perspective, has changed little. For example... > List("Paris", "London").map(_.length) res0: List[Int] List(5, 6) ...would work in either versions. The library is eminently useable: in fact it's fantastic. However, those previously unfamiliar with Scala and poking around to get a feel for the language now have to make sense of method signatures like: def map[B, That](f: A => B)(implicit bf: CanBuildFrom[Repr, B, That]): That For such simple functionality, this is a daunting signature and one which I find myself struggling to understand. Not that I think Scala was ever likely to be the next Java (or /C/C++/C#) - I don't believe its creators were aiming it at that market - but I think it is/was certainly feasible for Scala to become the next Ruby or Python (i.e. to gain a significant commercial user-base) Is this going to put people off coming to Scala? Is this going to give Scala a bad name in the commercial world as an academic plaything that only dedicated PhD students can understand? Are CTOs and heads of software going to get scared off? Was the library re-design a sensible idea? If you're using Scala commercially, are you worried about this? Are you planning to adopt 2.8 immediately or wait to see what happens? Steve Yegge once attacked Scala (mistakenly in my opinion) for what he saw as its overcomplicated type-system. I worry that someone is going to have a field day spreading fud with this API (similarly to how Josh Bloch scared the JCP out of adding closures to Java). Note - I should be clear that, whilst I believe that Josh Bloch was influential in the rejection of the BGGA closures proposal, I don't ascribe this to anything other than his honestly-held beliefs that the proposal represented a mistake.

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• Which management tools would you recommend for software development?

  - by Robert Schneider

  What would you generally recommend for software developement? Which combination do you use or would you recommend? I assume that tools are needed for Version control, issues/bugs/task, Release management, Requirement management. Tools for Test management and Project management should be accounted for as well, I guess. Did I forget anything? Maybe tools for Continous Integration. I'm not interested in a halfway combination of one ore two tools like a Subversion + Bugzilla (I know they are good but for a company they might not be sufficient). And also tools like make/ant shouldn't be taken into account. I'd like to know a combination that covers all what is important for professional software development. However, it could be a single tool of course if it covers all the management issues. What do you think would be a good combination? I assume a combination should be regardes as good if the tools itself are good but also if they have good integrations. Udate: Something like Ant is just a script not a management tool. Okay: we do already have Perforce. But this is somehow generic. We have different projects that uses C-, VS/.NET-, Python-, PHP and we will be starting new projects in Java. Plenty of languages and frameworks, though some are going to be legacy. So the tools should be generic. Obviously we don't want to use Bugzilla for one project and Jira for another. The management tools have to be generic. Further thoughts: Think of sourceforge: For each project they offer a version control system, an issue tracker, a wiki, ... totally independent of what the project is about. Those are some management tools that a project usually needs. I would say that most companies need such a set of tools. But I could imagine, if a company has several projects, they need further tools too: for Project management, Quality management, ... And I could imagine there are some recommendable combinations of tools. A not really apropiate comparison to this could be LAMP (Linux, Apache, MySQL, PHP). A combination of software that has evolved since they work very well together, and are pretty useful for a lot of applications (or rather web sites). So maybe there are some recommendable management tool combinations that also fit toghether like LAMP. The integration is important. Thank you for the incredibly fast and helpful responses!!!

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• Git/Mercurial (hg) opinion

  - by Richard

  First, let me say I'm not a professional programmer, but an engineer who had a need for it and had to learn. I was always working alone, so it was just me and my seven splitted personalities ... and we worked okey as a team :) Most of my stuff is done in C/Fortran/Matlab and so far I've been learning git to manage it all. However, although I've had no unsolvable problems with it, I've never been "that" happy with it ... for everything I cannot do, I hae to look up a book. And, for some time now I've been hearning a lot of good stuff about hg. Now, a coleague of mine will have to work with me on a project (I almost feel sorry for him) and he's started learning hg (says he likes it more), and I'm considering the switch myself. We work almost exclusivly on Windows platform (although I manage relatively ok using unix tools and things that come from that part of the world). So, I was wondering, in a described scenario, what problems could I expect with the switch. I heard that hg is rather more user friendly towards windows users, regarding the user interfaces. How does it handle repositories ? Does it create them the same way as git does (just one subdirectory in a working directory) and can I just copy the whole project directory (including git repo) and just carry them somewhere with no extra thinking ? (I really liked that when I was choosing over git/svn). Are there any good books on it that you can recommend (something like Pro Git, only for Hg). What are good ways to implement hg into Visual Studio/GVim for Windows, or into Windows Explorer so I can work relatively easily (I would like to avoid using the command line for everything regarding it, like in git shell). Is there something else I should be aware of (please, on this don't point me to other questions ... they just give me a ton of info, and I'm not sure what is it that I should take as important, and what to disregard). I'm trying to cut some time, since I cannot spend all that time relearning hg, like I did for git. I've also heard git is c project, while mercurial is python ... is there any noticeable difference in speed. git was pretty speedy ... will I encounter some waiting while working. Notice: All my projects are of let's say, middle size ... mostly numerical simulations ... 10-15000 lines (medium size?)

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• shopify_app syntax error

  - by Pete171

  Edit: Debugging has got me further. Question clarified. We have installed Ruby, RubyGems and Rails and have forked the shopify_app project. We have created a new rails applications and added three items to the Gemfile: execjs, therubyracer and shopify_app. Running rails s in order to start our rails application returns this trace: root@ubuntu:/usr/local/pete-shopify/cart# rails s Faraday: you may want to install system_timer for reliable timeouts /var/lib/gems/1.8/gems/shopify_app-4.1.0/lib/shopify_app.rb:15:in `require': /var/lib /gems/1.8/gems/shopify_app-4.1.0/lib/shopify_app/login_protection.rb:5: syntax error, unexpected ':', expecting kEND (SyntaxError) ...rce::UnauthorizedAccess, with: :close_session ^ from /var/lib/gems/1.8/gems/shopify_app-4.1.0/lib/shopify_app.rb:15 from /var/lib/gems/1.8/gems/bundler-1.2.1/lib/bundler/runtime.rb:68:in `require' from /var/lib/gems/1.8/gems/bundler-1.2.1/lib/bundler/runtime.rb:68:in `require' from /var/lib/gems/1.8/gems/bundler-1.2.1/lib/bundler/runtime.rb:66:in `each' from /var/lib/gems/1.8/gems/bundler-1.2.1/lib/bundler/runtime.rb:66:in `require' from /var/lib/gems/1.8/gems/bundler-1.2.1/lib/bundler/runtime.rb:55:in `each' from /var/lib/gems/1.8/gems/bundler-1.2.1/lib/bundler/runtime.rb:55:in `require' from /var/lib/gems/1.8/gems/bundler-1.2.1/lib/bundler.rb:128:in `require' from /usr/local/pete-shopify/cart/config/application.rb:7 from /var/lib/gems/1.8/gems/railties-3.2.8/lib/rails/commands.rb:53:in `require' from /var/lib/gems/1.8/gems/railties-3.2.8/lib/rails/commands.rb:53 from /var/lib/gems/1.8/gems/railties-3.2.8/lib/rails/commands.rb:50:in `tap' from /var/lib/gems/1.8/gems/railties-3.2.8/lib/rails/commands.rb:50 from script/rails:6:in `require' from script/rails:6 I haven't modified any files since forking from Github. Lines 1 - 6 of login_protection.rb are as follows: module ShopifyApp::LoginProtection extend ActiveSupport::Concern included do rescue from ActiveResource::UnauthorizedAccess, with: :close_session end I've looked into this and it seems that the error is caused by a new-style hash syntax between Ruby 1.8 and 1.9; key : value instead of key => value. Running ruby -v from the command line returns ruby 1.9.3p0 (2011-10-30 revision 33570) [x86_64-linux]. This would seem to be OK... but I did some debugging, and inside the file /var/lib/gems/1.8/gems/shopify_app-4.1.0/lib/shopify_app.rb (at the top) by putting this: puts RUBY_VERSION exit It printed 1.8.7. **Why are ruby -v and RUBY_VERSION giving me different results? And am I correct in assuming this is the cause of my problems? Note: To upgrade Ruby I installed the later version with apt-get and then switched to it by using update-alternatives --config ruby and selecting option 2 like this: root@ubuntu:/usr/local/pete-shopify/cart# update-alternatives --config ruby There are 2 choices for the alternative ruby (providing /usr/bin/ruby). Selection Path Priority Status ------------------------------------------------------------ 0 /usr/bin/ruby1.8 50 auto mode 1 /usr/bin/ruby1.8 50 manual mode * 2 /usr/bin/ruby1.9.1 10 manual mode Also note: We're PHP/Python developers so this is all new to us! Summary: 1 - Am I right in determining the cause of the syntax error? 2 - Why does RUBY_VERSION and ruby -v give me different results?

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• Constraint Satisfaction Problem

  - by Carl Smotricz

  I'm struggling my way through Artificial Intelligence: A Modern Approach in order to alleviate my natural stupidity. In trying to solve some of the exercises, I've come up against the "Who Owns the Zebra" problem, Exercise 5.13 in Chapter 5. This has been a topic here on SO but the responses mostly addressed the question "how would you solve this if you had a free choice of problem solving software available?" I accept that Prolog is a very appropriate programming language for this kind of problem, and there are some fine packages available, e.g. in Python as shown by the top-ranked answer and also standalone. Alas, none of this is helping me "tough it out" in a way as outlined by the book. The book appears to suggest building a set of dual or perhaps global constraints, and then implementing some of the algorithms mentioned to find a solution. I'm having a lot of trouble coming up with a set of constraints suitable for modelling the problem. I'm studying this on my own so I don't have access to a professor or TA to get me over the hump - this is where I'm asking for your help. I see little similarity to the examples in the chapter. I was eager to build dual constraints and started out by creating (the logical equivalent of) 25 variables: nationality1, nationality2, nationality3, ... nationality5, pet1, pet2, pet3, ... pet5, drink1 ... drink5 and so on, where the number was indicative of the house's position. This is fine for building the unary constraints, e.g. The Norwegian lives in the first house: nationality1 = { :norway }. But most of the constraints are a combination of two such variables through a common house number, e.g. The Swede has a dog: nationality[n] = { :sweden } AND pet[n] = { :dog } where n can range from 1 to 5, obviously. Or stated another way: nationality1 = { :sweden } AND pet1 = { :dog } XOR nationality2 = { :sweden } AND pet2 = { :dog } XOR nationality3 = { :sweden } AND pet3 = { :dog } XOR nationality4 = { :sweden } AND pet4 = { :dog } XOR nationality5 = { :sweden } AND pet5 = { :dog } ...which has a decidedly different feel to it than the "list of tuples" advocated by the book: ( X1, X2, X3 = { val1, val2, val3 }, { val4, val5, val6 }, ... ) I'm not looking for a solution per se; I'm looking for a start on how to model this problem in a way that's compatible with the book's approach. Any help appreciated.

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• ActiveMQ 5.2.0 + REST + HTTP POST = java.lang.OutOfMemoryError

  - by Bruce Loth

  First off, I am a newbie when it comes to JMS & ActiveMQ. I have been looking into a messaging solution to serve as middleware for a message producer that will insert XML messages into a queue via HTTP POST. The producer is an existing system written in C++ that cannot be modified (so Java and the C++ API are out). Using the "demo" examples and some trial and error, I have cobbled together a working example of what I want to do (on a windows box). The web.xml I configured in a test directory under "webapps" specifies that the HTTP POST messages received from the producer are to be handled by the MessageServlet. I added a line for the text app in "activemq.xml" ('ow' is the test app dir): I created a test script to "insert" messages into the queue which works well. The problem I am running into is that it as I continue to insert messages via REST/HTTP POST, the memory consumption and thread count used by ActiveMQ continues to rise (It happens when I have timely consumers as well as slow or non-existent consumers). When memory consumption gets around 250MB's and the thread count exceeds 5000 (as shown in windows task manager), ActiveMQ crashes and I see this in the log: Exception in thread "ActiveMQ Transport Initiator: vm://localhost#3564" java.lang.OutOfMemoryError: unable to create new native thread It is as if Jetty is spawning a new thread to handle each HTTP POST and the thread never dies. I did look at this page: http://activemq.apache.org/javalangoutofmemory.html and tried but that didn't fix the problem (although I didn't fully understand the implications of the change either). Does anyone have any ideas? Thanks! Bruce Loth PS - I included the "test message producer" python script below for what it is worth. I created batches of 100 messages and continued to run the script manually from the command line while watching the memory consumption and thread count of ActiveMQ in task manager. def foo(): import httplib, urllib body = "<?xml version='1.0' encoding='UTF-8'?>\n \ <ROOT>\n \ [snip: xml deleted to save space] </ROOT>" headers = {"content-type": "text/xml", "content-length": str(len(body))} conn = httplib.HTTPConnection("127.0.0.1:8161") conn.request("POST", "/ow/message/RDRCP_Inbox?type=queue", body, headers) response = conn.getresponse() print response.status, response.reason data = response.read() conn.close() ## end method definition ## Begin test code count = 0; while(count < 100): # Test with batches of 100 msgs count += 1 foo()

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• jquerymobile conflict with autocomplete : $this.attr("href") is undefined

  - by sweets-BlingBling

  When I use jquery ui autocomplete version 1.8.5 with jquery mobile alpha 2. I get an error when I click an item from the autocomplete list: $this.attr("href") is undefined. Does anyone know any fix for it? EDITED: <html> <head> <link rel="stylesheet" type="text/css" href="css/ui-lightness/jquery-ui-1.8.custom.css"> <link rel="stylesheet" type="text/css" href="css/autocomplete.css"> </head> <body> <div id="formWrap"> <form id="messageForm" action="#"> <fieldset> <label id="toLabel">select:</label> <div id="friends" class="ui-helper-clearfix"> <input id="to" type="text"> </div> </fieldset> </form> </div> <script type="text/javascript" src="js/jquery-1.4.2.min.js"></script> <script type="text/javascript" src="js/jquery.mobile-1.0a2.js"></script> <script type="text/javascript" src="js/jquery-ui-1.8.custom.min.js"></script> <script type="text/javascript"> $(function(){ var availableTags = [ "ActionScript", "AppleScript", "Asp", "BASIC", "C", "C++", "Clojure", "COBOL", "ColdFusion", "Erlang", "Fortran", "Groovy", "Haskell", "Java", "JavaScript", "Lisp", "Perl", "PHP", "Python", "Ruby", "Scala", "Scheme" ]; //attach autocomplete $("#to").autocomplete({ source:availableTags , //define select handler select: function(e, ui) { var contact = ui.item.value; createSpan(contact); $("#to").val("").css("top", 2); return false; } }); }); function createSpan(contact){ //create formatted friend span = $("<span>").text(contact) //add contact to contact div span.insertBefore("#to"); } </script> </body> </html>

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• PL/SQL pre-compile and Code Quality checks in an automatted build environment?

  - by Lars Corneliussen

  We build software using Hudson and Maven. We have C#, java and last, but not least PL/SQL sources (sprocs, packages, DDL, crud) For C# and Java we do unit tests and code analysis, but we don't really know the health of our PL/SQL sources before we actually publish them to the target database. Requirements There are a couple of things we wan't to test in the following priority: Are the sources valid, hence "compilable"? For packages, with respect to a certain database, would they compile? Code Quality: Do we have code flaws like duplicates, too complex methods or other violations to a defined set of rules? Also, the tool must run head-less (commandline, ant, ...) we wan't to do analysis on a partial code base (changed sources only) Tools We did a little research and found the following tools that could potencially help: Cast Application Intelligence Platform (AIP): Seems to be a server that grasps information about "anything". Couldn't find a console version that would export in readable format. Toad for Oracle: The Professional version is said to include something called Xpert validates a set of rules against a code base. Sonar + PL/SQL-Plugin: Uses Toad for Oracle to display code-health the sonar-way. This is for browsing the current state of the code base. Semantic Designs DMSToolkit: Quite general analysis of source code base. Commandline available? Semantic Designs Clones Detector: Detects clones. But also via command line? Fortify Source Code Analyzer: Seems to be focussed on security issues. But maybe it is extensible? more... So far, Toad for Oracle together with Sonar seems to be an elegant solution. But may be we are missing something here? Any ideas? Other products? Experiences? Related Questions on SO: http://stackoverflow.com/questions/531430/any-static-code-analysis-tools-for-stored-procedures http://stackoverflow.com/questions/839707/any-code-quality-tool-for-pl-sql http://stackoverflow.com/questions/956104/is-there-a-static-analysis-tool-for-python-ruby-sql-cobol-perl-and-pl-sql

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• what do i need to do so that mod_wsgi will find libmysqlclient.16.dylib? (osx 10.7 with apache mod_wsgi)

  - by compound eye

  I am trying to run django on osx 10.7 (lion) with apache mod_wsgi and virtualenv. My site works if I use the django testing server: (baseline)otter:hello mathew$ python manage.py runserver but it doesn't work when I run apache. The core of the error seems to be Library not loaded: libmysqlclient.16.dylib I think its to do with the path apache is using to locate libmysqlclient.16.dylib when I run otool in the lib directory it looks good otter:lib mathew$ pwd /usr/local/mysql/lib otter:lib mathew$ otool -L libmysqlclient.16.dylib libmysqlclient.16.dylib: libmysqlclient.16.dylib (compatibility version 16.0.0, current version 16.0.0) /usr/lib/libSystem.B.dylib (compatibility version 1.0.0, current version 125.0.1) but from outside it can't find it otter:lib mathew$ cd / otter:/ mathew$ otool -L libmysqlclient.16.dylib otool: can't open file: libmysqlclient.16.dylib (No such file or directory) if i manually set DYLD_LIBRARY_PATH otool works otter:lib mathew$ DYLD_LIBRARY_PATH=/usr/local/mysql/lib otter:lib mathew$ otool -L libmysqlclient.16.dylib libmysqlclient.16.dylib: libmysqlclient.16.dylib (compatibility version 16.0.0, current version 16.0.0) /usr/lib/libSystem.B.dylib (compatibility version 1.0.0, current version 125.0.1) When I run the django testing server, my .bash_profile sets up the virtualenv and the path to the mysql dynamic library export DYLD_LIBRARY_PATH=/usr/local/mysql/lib/:$DYLD_LIBRARY_PATH export PATH When i run apache it finds my virtualenv paths, but it doesn't seem to find the dynamic library path. I tried adding this path to /usr/sbin/envvars DYLD_LIBRARY_PATH="/usr/lib:/usr/local/mysql/lib:$DYLD_LIBRARY_PATH" export DYLD_LIBRARY_PATH and to /private/etc/paths.d/libmysql /usr/local/mysql/lib then restarted the machine but that has not changed the error message. Error loading MySQLdb module: dlopen(/usr/local/python_virtualenv/baseline/lib/python2.7/site-packages/_mysql.so, 2): Library not loaded: libmysqlclient.16.dylib I don't think is a permissions issue: -rwxr-xr-x 1 root wheel 3787328 4 Dec 2010 libmysqlclient.16.dylib drwxr-xr-x 39 root wheel 1394 18 Nov 21:07 / drwxr-xr-x@ 15 root wheel 510 24 Oct 22:10 /usr drwxrwxr-x 20 root admin 680 2 Nov 20:22 /usr/local drwxr-xr-x 20 mathew admin 680 9 Nov 21:58 /usr/local/python_virtualenv drwxr-xr-x 6 mathew admin 204 2 Nov 21:36 /usr/local/python_virtualenv/baseline drwxr-xr-x 4 mathew admin 136 2 Nov 21:26 /usr/local/python_virtualenv/baseline/lib drwxr-xr-x 52 mathew admin 1768 2 Nov 21:26 /usr/local/python_virtualenv/baseline/lib/python2.7 drwxr-xr-x 18 mathew admin 612 4 Nov 21:20 /usr/local/python_virtualenv/baseline/lib/python2.7/site-packages -rwxr-xr-x 1 mathew admin 66076 2 Nov 21:18 /usr/local/python_virtualenv/baseline/lib/python2.7/site-packages/_mysql.so What do i need to do so that mod_wsgi will find libmysqlclient.16.dylib? apache and mysql are both 64 bit: otter:lib mathew$ file /usr/sbin/httpd /usr/sbin/httpd: Mach-O universal binary with 2 architectures /usr/sbin/httpd (for architecture x86_64): Mach-O 64-bit executable x86_64 /usr/sbin/httpd (for architecture i386): Mach-O executable i386 otter:lib mathew$ otter:lib mathew$ file /usr/local/mysql/lib/libmysqlclient.16.dylib /usr/local/mysql/lib/libmysqlclient.16.dylib: Mach-O 64-bit dynamically linked shared library x86_64

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• Classifying captured data in unknown format?

  - by monch1962

  I've got a large set of captured data (potentially hundreds of thousands of records), and I need to be able to break it down so I can both classify it and also produce "typical" data myself. Let me explain further... If I have the following strings of data: 132T339G1P112S 164T897F5A498S 144T989B9B223T 155T928X9Z554T ... you might start to infer the following: possibly all strings are 14 characters long the 4th, 8th, 10th and 14th characters may always be alphas, while the rest are numeric the first character may always be a '1' the 4th character may always be the letter 'T' the 14th character may be limited to only being 'S' or 'T' and so on... As you get more and more samples of real data, some of these "rules" might disappear; if you see a 15 character long string, then you have evidence that the 1st "rule" is incorrect. However, given a sufficiently large sample of strings that are exactly 14 characters long, you can start to assume that "all strings are 14 characters long" and assign a numeric figure to your degree of confidence (with an appropriate set of assumptions around the fact that you're seeing a suitably random set of all possible captured data). As you can probably tell, a human can do a lot of this classification by eye, but I'm not aware of libraries or algorithms that would allow a computer to do it. Given a set of captured data (significantly more complex than the above...), are there libraries that I can apply in my code to do this sort of classification for me, that will identify "rules" with a given degree of confidence? As a next step, I need to be able to take those rules, and use them to create my own data that conforms to these rules. I assume this is a significantly easier step than the classification, but I've never had to perform a task like this before so I'm really not sure how complex it is. At a guess, Python or Java (or possibly Perl or R) are possibly the "common" languages most likely to have these sorts of libraries, and maybe some of the bioinformatic libraries do this sort of thing. I really don't care which language I have to use; I need to solve the problem in whatever way I can. Any sort of pointer to information would be very useful. As you can probably tell, I'm struggling to describe this problem clearly, and there may be a set of appropriate keywords I can plug into Google that will point me towards the solution. Thanks in advance

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• What would I use to remove escaped html from large sets of data.

  - by Elizabeth Buckwalter

  Our database is filled with articles retrieved from RSS feeds. I was unsure of what data I would be getting, and how much filtering was already setup (WP-O-Matic Wordpress plugin using the SimplePie library). This plugin does some basic encoding before insertion using Wordpress's built in post insert function which also does some filtering. I've figured out most of the filters before insertion, but now I have whacko data that I need to remove. This is an example of whacko data that I have data in one field which the content I want in the front, but this part removed which is at the end: <img src="http://feeds.feedburner.com/~ff/SoundOnTheSound?i=xFxEpT2Add0:xFbIkwGc-fk:V_sGLiPBpWU" border="0"></img> <img src="http://feeds.feedburner.com/~ff/SoundOnTheSound?d=qj6IDK7rITs" border="0"></img> &lt;img src=&quot;http://feeds.feedburner.com/~ff/SoundOnTheSound?i=xFxEpT2Add0:xFbIkwGc-fk:D7DqB2pKExk&quot; Notice how some of the images are escape and some aren't. I believe this has to do with the last part being cut off so as to be unrecognizable as an html tag, which then caused it to be html endcoded. Another field has only this which is now filtered before insertion, but I have to get rid of the others: &lt;img src=&quot;http://farm3.static.flickr.com/2183/2289902369_1d95bcdb85.jpg&quot; alt=&quot;post_img&quot; width=&quot;80&quot; (all examples are on one line, but broken up for readability) Question: What is the best way to work with the above escaped html (or portion of an html tag)? I can do it in Perl, PHP, SQL, Ruby, and even Python. I believe Perl to be the best at text parsing, so that's why I used the Perl tag. And PHP times out on large database operations, so that's pretty much out unless I wanted to do batch processing and what not. PS One of the nice things about using Wordpress's insert post function, is that if you use php's strip_tags function to strip out all html, insert post function will insert <p> at the paragraph points. Let me know if there's anything more that I can answer. Some article that didn't quite answer my questions. (http://stackoverflow.com/questions/2016751/remove-text-from-within-a-database-text-field) (http://stackoverflow.com/questions/462831/regular-expression-to-escape-html-ampersands-while-respecting-cdata)

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• Accidental Complexity in OpenSSL HMAC functions

  - by Hassan Syed

  SSL Documentation Analaysis This question is pertaining the usage of the HMAC routines in OpenSSL. Since Openssl documentation is a tad on the weak side in certain areas, profiling has revealed that using the: unsigned char *HMAC(const EVP_MD *evp_md, const void *key, int key_len, const unsigned char *d, int n, unsigned char *md, unsigned int *md_len); From here, shows 40% of my library runtime is devoted to creating and taking down **HMAC_CTX's behind the scenes. There are also two additional function to create and destroy a HMAC_CTX explicetly: HMAC_CTX_init() initialises a HMAC_CTX before first use. It must be called. HMAC_CTX_cleanup() erases the key and other data from the HMAC_CTX and releases any associated resources. It must be called when an HMAC_CTX is no longer required. These two function calls are prefixed with: The following functions may be used if the message is not completely stored in memory My data fits entirely in memory, so I choose the HMAC function -- the one whose signature is shown above. The context, as described by the man page, is made use of by using the following two functions: HMAC_Update() can be called repeatedly with chunks of the message to be authenticated (len bytes at data). HMAC_Final() places the message authentication code in md, which must have space for the hash function output. The Scope of the Application My application generates a authentic (HMAC, which is also used a nonce), CBC-BF encrypted protocol buffer string. The code will be interfaced with various web-servers and frameworks Windows / Linux as OS, nginx, Apache and IIS as webservers and Python / .NET and C++ web-server filters. The description above should clarify that the library needs to be thread safe, and potentially have resumeable processing state -- i.e., lightweight threads sharing a OS thread (which might leave thread local memory out of the picture). The Question How do I get rid of the 40% overhead on each invocation in a (1) thread-safe / (2) resume-able state way ? (2) is optional since I have all of the source-data present in one go, and can make sure a digest is created in place without relinquishing control of the thread mid-digest-creation. So, (1) can probably be done using thread local memory -- but how do I resuse the CTX's ? does the HMAC_final() call make the CTX reusable ?. (2) optional: in this case I would have to create a pool of CTX's. (3) how does the HMAC function do this ? does it create a CTX in the scope of the function call and destroy it ? Psuedocode and commentary will be useful.

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• SET game odds simulation (MATLAB)

  - by yuk

  Here is an interesting problem for your weekend. :) I recently find the great card came - SET. Briefly, there are 81 cards with the four features: symbol (oval, squiggle or diamond), color (red, purple or green), number (one, two or three) or shading (solid, striped or open). The task is to find (from selected 12 cards) a SET of 3 cards, in which each of the four features is either all the same on each card or all different on each card (no 2+1 combination). In my free time I've decided to code it in MATLAB to find a solution and to estimate odds of having a set in randomly selected cards. Here is the code: %% initialization K = 12; % cards to draw NF = 4; % number of features (usually 3 or 4) setallcards = unique(nchoosek(repmat(1:3,1,NF),NF),'rows'); % all cards: rows - cards, columns - features setallcomb = nchoosek(1:K,3); % index of all combinations of K cards by 3 %% test tic NIter=1e2; % number of test iterations setexists = 0; % test results holder % C = progress('init'); % if you have progress function from FileExchange for d = 1:NIter % C = progress(C,d/NIter); % cards for current test setdrawncardidx = randi(size(setallcards,1),K,1); setdrawncards = setallcards(setdrawncardidx,:); % find all sets in current test iteration for setcombidx = 1:size(setallcomb,1) setcomb = setdrawncards(setallcomb(setcombidx,:),:); if all(arrayfun(@(x) numel(unique(setcomb(:,x))), 1:NF)~=2) % test one combination setexists = setexists + 1; break % to find only the first set end end end fprintf('Set:NoSet = %g:%g = %g:1\n', setexists, NIter-setexists, setexists/(NIter-setexists)) toc 100-1000 iterations are fast, but be careful with more. One million iterations takes about 15 hours on my home computer. Anyway, with 12 cards and 4 features I've got around 13:1 of having a set. This is actually a problem. The instruction book said this number should be 33:1. And it was recently confirmed by Peter Norvig. He provides the Python code, but I didn't test it. So can you find an error?

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• Is it possible to reliably auto-decode user files to Unicode? [C#]

  - by NVRAM

  I have a web application that allows users to upload their content for processing. The processing engine expects UTF8 (and I'm composing XML from multiple users' files), so I need to ensure that I can properly decode the uploaded files. Since I'd be surprised if any of my users knew their files even were encoded, I have very little hope they'd be able to correctly specify the encoding (decoder) to use. And so, my application is left with task of detecting before decoding. This seems like such a universal problem, I'm surprised not to find either a framework capability or general recipe for the solution. Can it be I'm not searching with meaningful search terms? I've implemented BOM-aware detection (http://en.wikipedia.org/wiki/Byte_order_mark) but I'm not sure how often files will be uploaded w/o a BOM to indicate encoding, and this isn't useful for most non-UTF files. My questions boil down to: Is BOM-aware detection sufficient for the vast majority of files? In the case where BOM-detection fails, is it possible to try different decoders and determine if they are "valid"? (My attempts indicate the answer is "no.") Under what circumstances will a "valid" file fail with the C# encoder/decoder framework? Is there a repository anywhere that has a multitude of files with various encodings to use for testing? While I'm specifically asking about C#/.NET, I'd like to know the answer for Java, Python and other languages for the next time I have to do this. So far I've found: A "valid" UTF-16 file with Ctrl-S characters has caused encoding to UTF-8 to throw an exception (Illegal character?) (That was an XML encoding exception.) Decoding a valid UTF-16 file with UTF-8 succeeds but gives text with null characters. Huh? Currently, I only expect UTF-8, UTF-16 and probably ISO-8859-1 files, but I want the solution to be extensible if possible. My existing set of input files isn't nearly broad enough to uncover all the problems that will occur with live files. Although the files I'm trying to decode are "text" I think they are often created w/methods that leave garbage characters in the files. Hence "valid" files may not be "pure". Oh joy. Thanks.

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• How do we, as a community, help encourage programming in public schools? (Or state Schools for the U

  - by NoMoreZealots

  PRIMARY MOTIVATION My office gets involved with the "First Robotics" competitions and one thing that lingers year to year is the students typically have no preparation for doing even simple programming as part of the public schools system. While the science classes provide some basic grasp of mechanical and electrical concepts, by in large computer programming gets no coverage from the curriculum. (This my be different in other areas of the country/world.) What makes it worse is there is only a short period of time you have to prepare the student's and help them design the robot. Talking to some professors from local colleges, it's a problem because you can't assume even the most basic understanding for freshman CS majors. Languages like Python, Lua and BASIC are simple enough for at least high school level students, if not younger. SCOPE So how do you get public schools to support a programming, at least to the level of "Try it in BASIC" examples that used to be at the end of a chapter in my Algebra book? At least enough to prepare them for event's such as the FIRST Robotic competitions. Which the primary objectives are to teach problem solving and team work, and to possible foster an interest in Math, Science and Engineering in general. (Not force feed to them, as some people her seem to be implying.) Edit: Why teach kids: (Since 2000 CS enrollment in US colleges has decreased by 70% while college enrollment has increased, this is a PROBLEM.) Saying there is no value in teaching someone programming in Jr./High school because they might think "they know programming." Is like saying there's no value in teaching High school science and physics, because they might decide they "know physics." Leading to abuse like: "I passed a high school physics class, I'm going to develop a Unified Quantum Gravitational Theory." Better Prepared students are better students. Instead it would allows college programs to raise the bar on the entry level courses, allowing students to be weeded out based on their understanding of more advanced material. Plus people who did poorly in that in topic in High school aren't as likely to say "I think there's money in computer's so I'll computer science." Plus if people take it in high school and decide THEN that it's not for them, it's better than them wasting their money to PAY a college to figure that out. The result is that people who take the degree are more likely to succeed and be there for the RIGHT reasons. (i.e. It's what they REALLY want to do. And that's REALLY the key to being good at anything.) Programming is like anything else, the more practice and genuine interest you have the better you get. If you start them later, they get less practice. The earlier give them the opportunity to start, the more practice they will get. All other things equal, the more practice the better the programmer.

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• Job queue manager with RPC interface

  - by admr

  I need a job queue manager that I can control over the Internet. It should be able to execute and stop processes, check on their status (ideally notice and execute some code when a process exits), respond to commands and also be able to report back to a server. Background: I have a GWT application that allows to create jobs to execute on a cloud instance (currently EC2). I want to push a "job packet" (data for a process to operate on etc) to S3, start a Linux EC2 instance (or use one that's already running), and tell a job manager on the instance to execute that job (possibly parallel to other jobs). It should then pull the "job packet" from S3, run a process that operates on that data and report back to the server that is running the server part of my GWT application with some information (e.g. exit code, stdout, stderr). If I have to write e.g. stdour/err to a file from the process and read that file, that's OK too. I would really like the manager to be "close" to the processes it runs, meaning I want to avoid using something like Runtime.exec from the JDK. It seems like I would have to do that if I used Quartz for example. I'm fine with the calls in both directions being asynchronous. I'm fine with any reasonable technology for the calls as long as I can easily build an interface for that in my GWT server side (e.g. HTTP requests to a servlet over SSL would be nice and trivial). The job manager does not need to have a very sophisticated queueing system. Running several processes either sequentially or in parallel should be fine. Determining how much compute time a process received during its lifetime would be nice (AFAIK, this might be challenging). I did not yet find any existing software that does this, including http://java-source.net/open-source/job-schedulers. I suspect I might have to build an RPC interface (with authentication etc, of course) around a job manager; maybe use something like Apache Commons Exec. In that case, I would prefer Java or Python for the job manager part. I would be happy to hear suggestions for either the former or latter scenario!

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• Algorithm for finding symmetries of a tree

  - by Paxinum

  I have n sectors, enumerated 0 to n-1 counterclockwise. The boundaries between these sectors are infinite branches (n of them). The sectors live in the complex plane, and for n even, sector 0 and n/2 are bisected by the real axis, and the sectors are evenly spaced. These branches meet at certain points, called junctions. Each junction is adjacent to a subset of the sectors (at least 3 of them). Specifying the junctions, (in pre-fix order, lets say, starting from junction adjacent to sector 0 and 1), and the distance between the junctions, uniquely describes the tree. Now, given such a representation, how can I see if it is symmetric wrt the real axis? For example, n=6, the tree (0,1,5)(1,2,4,5)(2,3,4) have three junctions on the real line, so it is symmetric wrt the real axis. If the distances between (015) and (1245) is equal to distance from (1245) to (234), this is also symmetric wrt the imaginary axis. The tree (0,1,5)(1,2,5)(2,4,5)(2,3,4) have 4 junctions, and this is never symmetric wrt either imaginary or real axis, but it has 180 degrees rotation symmetry if the distance between the first two and the last two junctions in the representation are equal. Edit: This is actually for my research. I have posted the question at mathoverflow as well, but my days in competition programming tells me that this is more like an IOI task. Code in mathematica would be excellent, but java, python, or any other language readable by a human suffices. Here are some examples (pretend the double edges are single and we have a tree) http://www2.math.su.se/~per/files.php?file=contr_ex_1.pdf http://www2.math.su.se/~per/files.php?file=contr_ex_2.pdf http://www2.math.su.se/~per/files.php?file=contr_ex_5.pdf Example 1 is described as (0,1,4)(1,2,4)(2,3,4)(0,4,5) with distances (2,1,3). Example 2 is described as (0,1,4)(1,2,4)(2,3,4)(0,4,5) with distances (2,1,1). Example 5 is described as (0,1,4,5)(1,2,3,4) with distances (2). So, given the description/representation, I want to find some algorithm to decide if it is symmetric wrt real, imaginary, and rotation 180 degrees. The last example have 180 degree symmetry. (These symmetries corresponds to special kinds of potential in the Schroedinger equation, which has nice properties in quantum mechanics.)

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• Escaping Code for Different Shells

  - by Jon Purdy

  Question: What characters do I need to escape in a user-entered string to securely pass it into shells on Windows and Unix? What shell differences and version differences should be taken into account? Can I use printf "%q" somehow, and is that reliable across shells? Backstory (a.k.a. Shameless Self-Promotion): I made a little DSL, the Vision Web Template Language, which allows the user to create templates for X(HT)ML documents and fragments, then automatically fill them in with content. It's designed to separate template logic from dynamic content generation, in the same way that CSS is used to separate markup from presentation. In order to generate dynamic content, a Vision script must defer to a program written in a language that can handle the generation logic, such as Perl or Python. (Aside: using PHP is also possible, but Vision is intended to solve some of the very problems that PHP perpetuates.) In order to do this, the script makes use of the @system directive, which executes a shell command and expands to its output. (Platform-specific generation can be handled using @unix or @windows, which only expand on the proper platform.) The problem is obvious, I should think: test.htm: <!-- ... --> <form action="login.vis" method="POST"> <input type="text" name="USERNAME"/> <input type="password" name="PASSWORD"/> </form> <!-- ... --> login.vis: #!/usr/bin/vision # Think USERNAME = ";rm -f;" @system './login.pl' { USERNAME; PASSWORD } One way to safeguard against this kind of attack is to set proper permissions on scripts and directories, but Web developers may not always set things up correctly, and the naive developer should get just as much security as the experienced one. The solution, logically, is to include a @quote directive that produces a properly escaped string for the current platform. @system './login.pl' { @quote : USERNAME; @quote : PASSWORD } But what should @quote actually do? It needs to be both cross-platform and secure, and I don't want to create terrible problems with a naive implementation. Any thoughts?

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