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• How to not persist NSManagedObjects retrieved from NSManagedObjectContext

  - by RickiG

  Hi I parse an xml file containing books, for each new node I go: Book *book = (Book*)[NSEntityDescription insertNewObjectForEntityForName:@"Book" inManagedObjectContext:managedObjectContext]; To obtain an NSManagedObject of my Core Data Book Entity, I then proceed to populate the managed Book object with data, add it to an array, rinse, repeat. When I am done, I present the list of books to the user. I have not yet executed the save: NSError *error; if (![managedObjectContext save:&error]) { NSLog(@"%@", [error domain]); } The user now selects one of the books, this one I would like to persist, but only this one, all the other books are of no interest to me any more. The Book Entity does not have/or is part of any relationships. It is just a "single" Entity. If I pull the "save lever" every Book object will be persisted and I will have to delete everything but my desired one. How would I get around this challenge, I can't really seem to find that particular use-case in the Core Data Programming Guide, which sort of also bugs me a bit, am I going against best practice here? Thanks for any help given.

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• Compiling cpp code in netbeans produce errors, how to solve it ?

  - by Rupertt Wind

  i use the netbeans with MinGW and MYSY make /debugger but when i compile a basic cpp code in it and run it it produces two erorrs this is the code runned and the output![alt text][1] box #include <iostream> void main() { cout << "Hello World!" << endl; cout << "Welcome to C++ Programming" << endl; } output is /usr/bin/make -f nbproject/Makefile-Debug.mk SUBPROJECTS= .build-conf make[1]: Entering directory `/d/Users/Home/Documents/NetBeansProjects/newApp' /usr/bin/make -f nbproject/Makefile-Debug.mk dist/Debug/MinGW-Windows/newapp.exe make[2]: Entering directory `/d/Users/Home/Documents/NetBeansProjects/newApp' mkdir -p dist/Debug/MinGW-Windows g++.exe -o dist/Debug/MinGW-Windows/newapp build/Debug/MinGW-Windows/newmain.o build/Debug/MinGW-Windows/newfile.o build/Debug/MinGW-Windows/main.o build/Debug/MinGW-Windows/newfile.o: In function `main': D:/Users/Home/Documents/NetBeansProjects/newApp/newfile.cpp:5: multiple definition of `main' build/Debug/MinGW-Windows/newmain.o:D:/Users/Home/Documents/NetBeansProjects/newApp/newmain.c:15: first defined here build/Debug/MinGW-Windows/main.o: In function `main': D:/Users/Home/Documents/NetBeansProjects/newApp/main.cpp:13: multiple definition of `main' build/Debug/MinGW-Windows/newmain.o:D:/Users/Home/Documents/NetBeansProjects/newApp/newmain.c:15: first defined here collect2: ld returned 1 exit status make[2]: *** [dist/Debug/MinGW-Windows/newapp.exe] Error 1 make[2]: Leaving directory `/d/Users/Home/Documents/NetBeansProjects/newApp' make[1]: *** [.build-conf] Error 2 make[1]: Leaving directory `/d/Users/Home/Documents/NetBeansProjects/newApp' make: *** [.build-impl] Error 2 BUILD FAILED (exit value 2, total time: 1s) how can i solve this ?

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• Python for a hobbyist programmer ( a few questions)

  - by Matt

  I'm a hobbyist programmer (only in TI-Basic before now), and after much, much, much debating with myself, I've decided to learn Python. I don't have a ton of free time to teach myself a hundred languages and all programming I do will be for personal use or for distributing to people who need them, so I decided that I needed one good, strong language to be good at. My questions: Is python powerful enough to handle most things that a typical programmer might do in his off-time? I have in mind things like complex stat generators based on user input for tabletop games, making small games, automate install processes, and build interactive websites, but probably a hundred things along those lines Does python handle networking tasks fairly well? Can python source be obscufated (mispelled I think), or is it going to be open-source by nature? The reason I ask this is because if I make something cool and distribute it, I don't want some idiot script kiddie to edit his own name in and say he wrote it And how popular is python, compared to other languages. Ideally, my language would be good and useful with help found online without extreme difficulty, but not so common that every idiot with computer knows python. I like the idea of knowing a slightly obscure language. Thanks a ton for any help you can provide.

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• Python: speed up removal of every n-th element from list.

  - by ChristopheD

  I'm trying to solve this programming riddle and althought the solution (see code below) works correct, it is too slow for succesful submission. Any pointers as how to make this run faster? (removal of every n-th element from a list)? Or suggestions for a better algorithm to calculate the same; seems I can't think of anything else then brute-force for now... Basically the task at hand is: GIVEN: L = [2,3,4,5,6,7,8,9,10,11,........] 1. Take the first remaining item in list L (in the general case 'n'). Move it to the 'lucky number list'. Then drop every 'n-th' item from the list. 2. Repeat 1 TASK: Calculate the n-th number from the 'lucky number list' ( 1 <= n <= 3000) My current code (it calculates the 3000 first lucky numbers in about a second on my machine - but unfortunately too slow): """ SPOJ Problem Set (classical) 1798. Assistance Required URL: http://www.spoj.pl/problems/ASSIST/ """ sieve = range(3, 33900, 2) luckynumbers = [2] while True: wanted_n = input() if wanted_n == 0: break while len(luckynumbers) < wanted_n: item = sieve[0] luckynumbers.append(item) items_to_delete = set(sieve[::item]) sieve = filter(lambda x: x not in items_to_delete, sieve) print luckynumbers[wanted_n-1]

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• Java and tomcat vs ASP.NET and IIS

  - by Mark Cooper

  Until recently I'd considered myself to be a pretty good web programmer (coming up for 10yrs commercial experience on a variety of e-commerce, static and enterprise applications). I'm self taught and have always used the Microsoft product stack (ASP, ASP.NET)... My applications are always functional, relatively bug free, but have never been lightening quick. As a frequent web user I always found this to be the norm... how fast are the websites from the big tech players (eBay, Facebook, Microsoft, IBM, Dell, Telerik etc etc) - in truth none are particularly fast. I always attributed this to "the way things are with web apps"... ...then I cam across a product called Jira from atlasian and this has stopped me in my tracks... This application is fast, and I mean blindingly fast.. too fast to time the switches between pages, fully live content, lots of images and data and cross references etc etc... I run this on an intranet, with a large application DB, and this is running on a very normal server (single processor, SATA HDD, 8GB RAM). Am I missing something?? Are my programming techniques that bad?? I am wondering if this speed gain is down to it being written in Java and running on Tomcat. Does anyone have any benchmarks to compare JSP / ASP or Tomcat / IIS??? Thanks, Mark NOTE: this isn't a blatant plug for Jira. I don't work for them or have any affiliation to them... but I would like to be able to write applications like them :)

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• Visual Studio Conversion Suite

  - by KingPop

  I have this as my conversion program for the "Length", how can I do it the simpliest way instead of keeping the if, elseif, else too much, i do not have much experience and trying to improve my programming skills on visual studio 2008. Basically, I get annoyed with the formulas because I don't know if it is right, I use google but doesn't help because i don't know how to get it right when the program converts from type to type. Public Class Form2 Dim Metres As Integer Dim Centimetres As Integer Dim Inches As Integer Dim Feet As Integer Dim Total As Integer Private Sub Form2_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load ErrorMsg.Hide() End Sub Private Sub btnConvert_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnConvert.Click Metres = 1 Centimetres = 0.01 Inches = 0.0254 Feet = 0.3048 txtTo.Text = 0 If txtFrom.Text <> "" Then If IsNumeric(txtFrom.Text) And IsNumeric(txtTo.Text) Then If cbFrom.Text = "Metres" And cbTo.Text = "Centimetres" Then Total = txtFrom.Text * Metres txtTo.Text = Total ElseIf cbFrom.Text = "Metres" And cbTo.Text = "Inches" Then Total = txtFrom.Text * 100 txtTo.Text = Total ElseIf cbFrom.Text = "Metres" And cbTo.Text = "Feet" Then ElseIf cbFrom.Text = "Centimetres" And cbTo.Text = "Metres" Then ElseIf cbFrom.Text = "Centimetres" And cbTo.Text = "Inches" Then ElseIf cbFrom.Text = "Centimetres" And cbTo.Text = "Feet" Then ElseIf cbFrom.Text = "Inches" And cbTo.Text = "Metres" Then ElseIf cbFrom.Text = "Inches" And cbTo.Text = "Centimetres" Then ElseIf cbFrom.Text = "Inches" And cbTo.Text = "Feet" Then ElseIf cbFrom.Text = "Feet" And cbTo.Text = "Metres" Then ElseIf cbFrom.Text = "Feet" And cbTo.Text = "Centimetres" Then ElseIf cbFrom.Text = "Feet" And cbTo.Text = "Inches" Then End If End If End If End Sub End Class This is the source for what I have done at the moment.

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• DirectX Desktop

  - by Jonathan

  Hi. I'd like to make an animated desktop background for Windows 7 using DirectX. I'm using C#, SlimDX and a couple of P/Invoke imports of Windows API functions. I'm not brilliant with native Windows programming, but I've had a poke around online and I believe what I need to do is either: 1) Find the handle of the window containing the dekstop wallpaper, hook it up to a DirectX device and draw into it. 2) Make a new output window, and insert it above the desktop wallpaper but below the desktop icons. I've tried both these, but neither seems to work. If I navigate the Window heirarchy starting from the handle returned by GetDesktopWindow(), I can go Desktop - WorkerW - SHELLDLL_DefView - SysListView32. If I hook up a DirectX device to this handle, I can draw over the entire desktop, but it also covers the icons. If I create a Windows form, set its parent to SHELLDLL_DefView using SetParent() and then use SetWindowPos to play with its Z-order I can only seem to get it to go either behind the desktop wallpaper or in front of the desktop + icons. It looks as though the desktop wallpaper is background to the folder view containing the icons, and therefore what I am trying to do cannot work. The only solution then would be to not use the desktop for icons, or to find some alternative, e.g. overwriting the desktop then overlaying a transparent window containing a view of the contents of some folder. Does anyone have any idea of what I should be doing, or even whether what I want to do is possible? It seems you can draw to the desktop background using the GDI (as I believe the wxSnow program does), and I've seen something similar to what I want done by VLC Media Player under Windows XP with its DirectX wallpaper mode (interestingly, I can't seem to get this option enabled on my system). Thanks!

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• How to connect to a SOAP webServices with Android

  - by dom4

  Hi everyone,I'm programming an application who must send coordinate and request to a WebServices this is my code: private String SOAP_ACTION = "getAllPositions"; private String METHOD_NAME = "getAllPositions"; private String NAMESPACE = "http://session/"; private static final String URL ="http://192.41.218.56:8080/WSGeoEAR-WSGeoServer/NavFinderBean?WSDL"; /** Called when the activity is first created. */ @Override public void onCreate(Bundle icicle) { super.onCreate(icicle); setContentView(R.layout.main); SoapObject request = new SoapObject(NAMESPACE, METHOD_NAME); request.addProperty("idUtente",1); SoapSerializationEnvelope envelope = new SoapSerializationEnvelope(SoapEnvelope.VER11); envelope.dotNet = true; envelope.setOutputSoapObject(request); AndroidHttpTransport androidHttpTransport = new AndroidHttpTransport(URL); androidHttpTransport.setXmlVersionTag("<?xml version=\"1.0\" encoding=\"UTF-8\"?>"); androidHttpTransport.debug = true; try{ androidHttpTransport.call(SOAP_ACTION, envelope); SoapObject resultsRequestSOAP = (SoapObject) envelope.bodyIn; ArrayList<position> resultData = (ArrayList<position>)resultsRequestSOAP.getProperty("getAllPositionsResponse"); for(position p : resultData) { ((TextView)findViewById(R.id.lblStatus)).setText(p.getAllInformation()); } } catch(Exception E) { ((TextView)findViewById(R.id.lblStatus)).setText("ERROR:" + E.getClass().getName() + ": " + E.getMessage()); } } } I've also create a class position. It doesn't work,can someone help me?Thanks

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• Computer science textbooks

  - by Barrett Conrad

  I would like to try the book question a little bit differently. My goal is to know what the community thinks are the quintessential computer science textbooks. <beginsadstory>I lost all of my computer science and math books from college in Hurricane Katrina in 2005. I greatly miss having my familiar tomes to refer to when topics and problems come up, so I am looking to rebuild my library.<endsadstory> What are your recommendations for the best examples of academic caliber books for the field of computer science and its associated mathematics? I am looking for books on subjects like computational theory, programming languages, compilers, operating systems, algorithms and so on. Don't limit your suggestions to your textbooks only. If there is a book you have read that covers computer science or a related math in a formal way, but is not strictly a textbook, I would be love to hear about them as well. Finally, for the sake of creating a good reference for all of us, may I suggest posting one book per answer so they can be rated individually.

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• NPTL Default Stack Size Problem

  - by eyazici

  Hello, I am developing a multithread modular application using C programming language and NPTL 2.6. For each plugin, a POSIX thread is created. The problem is each thread has its own stack area, since default stack size depends on user's choice, this may results in huge memory consumption in some cases. To prevent unnecessary memory usage I used something similar to this to change stack size before creating each thread: pthread_attr_t attr; pthread_attr_init (&attr); pthread_attr_getstacksize(&attr, &st1); if(pthread_attr_setstacksize (&attr, MODULE_THREAD_SIZE) != 0) perror("Stack ERR"); pthread_attr_getstacksize(&attr, &st2); printf("OLD:%d, NEW:%d - MIN: %d\n", st1, st2, PTHREAD_STACK_MIN); pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED); /* "this" is static data structure that stores plugin related data */ pthread_create(&this->runner, &attr, (void *)(void *)this->run, NULL); EDIT I: pthread_create() section added. This did not work work as I expected, the stack size reported by pthread_attr_getstacksize() is changed but total memory usage of the application (from ps/top/pmap output) did not changed: OLD:10485760, NEW:65536 - MIN: 16384 When I use ulimit -s MY_STACK_SIZE_LIMIT before starting application I achieve the expected result. My questions are: 1-) Is there any portable(between UNIX variants) way to change (default)thread stack size after starting application(before creating thread of course)? 2-) Is it possible to use same stack area for every thread? 3-) Is it possible completely disable stack for threads without much pain?

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• Make Python Socket Server More Efficient

  - by BenMills

  I have very little experience working with sockets and multithreaded programming so to learn more I decided to see if I could hack together a little python socket server to power a chat room. I ended up getting it working pretty well but then I noticed my server's CPU usage spiked up over 100% when I had it running in the background. Here is my code in full: http://gist.github.com/332132 I know this is a pretty open ended question so besides just helping with my code are there any good articles I could read that could help me learn more about this? My full code: import select import socket import sys import threading from daemon import Daemon class Server: def __init__(self): self.host = '' self.port = 9998 self.backlog = 5 self.size = 1024 self.server = None self.threads = [] self.send_count = 0 def open_socket(self): try: self.server = socket.socket(socket.AF_INET6, socket.SOCK_STREAM) self.server.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1) self.server.bind((self.host,self.port)) self.server.listen(5) print "Server Started..." except socket.error, (value,message): if self.server: self.server.close() print "Could not open socket: " + message sys.exit(1) def remove_thread(self, t): t.join() def send_to_children(self, msg): self.send_count = 0 for t in self.threads: t.send_msg(msg) print 'Sent to '+str(self.send_count)+" of "+str(len(self.threads)) def run(self): self.open_socket() input = [self.server,sys.stdin] running = 1 while running: inputready,outputready,exceptready = select.select(input,[],[]) for s in inputready: if s == self.server: # handle the server socket c = Client(self.server.accept(), self) c.start() self.threads.append(c) print "Num of clients: "+str(len(self.threads)) self.server.close() for c in self.threads: c.join() class Client(threading.Thread): def __init__(self,(client,address), server): threading.Thread.__init__(self) self.client = client self.address = address self.size = 1024 self.server = server self.running = True def send_msg(self, msg): if self.running: self.client.send(msg) self.server.send_count += 1 def run(self): while self.running: data = self.client.recv(self.size) if data: print data self.server.send_to_children(data) else: self.running = False self.server.threads.remove(self) self.client.close() """ Run Server """ class DaemonServer(Daemon): def run(self): s = Server() s.run() if __name__ == "__main__": d = DaemonServer('/var/servers/fserver.pid') if len(sys.argv) == 2: if 'start' == sys.argv[1]: d.start() elif 'stop' == sys.argv[1]: d.stop() elif 'restart' == sys.argv[1]: d.restart() else: print "Unknown command" sys.exit(2) sys.exit(0) else: print "usage: %s start|stop|restart" % sys.argv[0] sys.exit(2)

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• Why isn't the background image showing up on my webpage?

  - by William

  okay, so I'm trying to set up a webpage with a div wrapping two other divs, and the wrapper div has a background, and the other two are transparent. How come this isn't working? here is the CSS: .posttext{ float: left; width: 70%; text-align: left; padding: 5px; background-color: !important #transparent; } .postavi{ float: left; width: 100px; height: 100%; text-align: left; background-color: #transparent; padding: 5px; } .postwrapper{ background-image:url('images/post_bg.png'); background-position:left top; background-repeat:repeat-y; } and here is the HTML: <div class="postwrapper"> <div class="postavi"><img src="http://prime.programming-designs.com/test_forum/images/avatars/hacker.png" alt="hacker"/></div><div class="posttext"><p style="color: #ff0066">You will have bad luck today.</p>lol</div> </div>

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• ThreadAbortException (WebClient using DownloadFile to grab file from server)

  - by baron

  Hi Everyone, Referencing my Earlier Question, regarding downloading a file from a server and handling exceptions properly. I am positive that I had this solved, then in classic programming fashion, returned days later to frustratingly find it broken :-( Updated code: private static void GoGetIt(HttpContext context) { var directoryInfoOfWhereTheDirectoryFullOfFilesShouldBe = new FileInfo(......); var name = SomeBasicLogicToDecideName(); //if (!directoryInfoOfWhereTheDirectoryFullOfFilesShouldBe.RefreshExists()) //{ // throw new Exception(string.Format("Could not find {0}.", name)); //} var tempDirectory = ""; //Omitted - creates temporary directory try { directoryInfoOfWhereTheDirectoryFullOfFilesShouldBe.CopyAll(tempDirectory); var response = context.Response; response.ContentType = "binary/octet-stream"; response.AddHeader("Content-Disposition", string.Format("attachment;filename={0}.zip", name)); ZipHelper.ZipDirectoryToStream(tempDirectory, response.OutputStream); response.End(); } catch (Exception ex) { Debug.WriteLine(ex.ToString()); context.Response.StatusCode = 404; } finally { tempDirectory.DeleteWithPrejudice(); } } This was working fine, and returning the zip, otherwise if the file didn't exist returning 404. Then on the client side I could handle this: public bool Download() { try { using (var client = new WebClient()) { client.DownloadFile(name, tempFilePath); } } catch (Exception) { fileExists = false; } return fileExists; } But the problem now is two things. 1) I get System.Threading.ThreadAbortException: Thread was being aborted in the server side try-catch block. Usually this was just a file not found exception. I have no idea what or why that new exception is throwing? 2) Now that a different exception is throwing on the server side instead of the file not found, it would seem I can't use this set up for the application, because back on client side, any exception is assumed to be filenotfound. Any help, especially info on why this ThreadAbortException is throwing!?!? greatly appreciated. Cheers

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• Useful training courses that aren't specific to a single technology

  - by Dave Turvey

  I have possibly the best problem in the world. I have about £1600 left in a training budget and I need to find something to spend it on. I can spend it on anything that could be considered training. Books, courses, conferences, etc. I would like to find a course that would benifit a software developer but is not about learning a specific programming technology. I don't really want to spend it on a technical training course. These topics are usually best learned with a good book and some trial and error. I have also already been on a general business/management training course and a PRINCE2 project management course. I am currently working on a project on my own so am responsible for communicating with the client, requirements gathering, project management, etc., as well as the coding. What training have you found useful outside the usual technical stuff? Has anyone done any business analysis courses? What were they like? Are there any courses on some of the practicalities of working with software, e.g. automated test and deployment strategies, handling technical support? I would prefer a course in the UK but I can travel if necessary.

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• Front End Developer v/s PHP-MySQL Engineer

  - by user301943

  Hello, I want to decide which of this would be a more viable career option? I am ready to quit my current job and hence I am looking for new opportunity. Current job is maintainence and no more active development. My current role is of a PHP/MySQL Developer. I very well understand web-programming and am comfortable with RoR/Sinatra/Zend MVC/JQuery/JSON manipulation, etc. I understand MySQL InnoDB/MyISAM engine and how one differs from the other, etc. Basically, I could very well manage the deployment of a web-application end-to-end including configuration of Apache/Nginx servers, memcache,etc On the other hand, I am being offered a Sr.Front End Web developer that would require me to extensively write HTML/CSS crossbrowser/crossplatform compliant code. I very well understand XHTML/CSS/Box model etc. I would be working on Drupal for the management of websites. While I understand continuing to work on server-side technologies would always be a good career path, how would the role of Core front-end developer turn out to be? If I take this opportunity, will I eventually get a chance to focus onto UCD, HCI, Information Architect,etc. So are these kinda roles possible if I focus on front end development? No offenses to the Front end developers, just want to understand if this is something I want to gain a mastery over. I have 2 yrs of industry experience after graduating with a MS-Computer Science. Although, I have a CS degree, if I were to take uip serious front-end role; I could probably go back and take up some design/HCI/UI courses. Please advise.

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• multi thread apps crashes in release mode

  - by etzarfat

  Hello, I'm using Visual Studio 2008 (programming in c). I've a weird problem I worte a program that has 2 threads that runs simultaneously, a recording thread (using audio card to record into memory) and a translation thread (using a speech engine to recognize the words). when I run my program in debug mode (aka setting a breakpoint in the code) it runs great, however when I run in debug mode or release mode (outside the visual studio enviroment) it crashes and give me the following exception: "Unhandled exception at 0x7c911129 in LowLevel.exe: 0xC0000005: Access violation reading location 0x014c7245." My stack looks: LowLevel.exe!__set_flsgetvalue() Line 256 + 0xc bytes C LowLevel.exe!_isleadbyte_l(int c=4359676, localeinfo_struct * plocinfo=0x00000001) Line 57 C++ 014b00d8() LowLevel.exe!PlayDateOfExam(int option=1) Line 2240 + 0x7 bytes C++ LowLevel.exe!NSCThread(void * arg=0x00000000) Line 1585 + 0xb bytes C++ kernel32.dll!7c80b729() winmm.dll!76b5b294() I uses the following file in my project "nsc.lib" and WinMM.lib" I'm not really familiar with threads I used a sample (which works great) and built on it. I saw a similiar question year on the forum but I didn't really understand the answers since I'm not familiar with with threads. Can someone help me? Thanks

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• New at Python: GLPK not building properly / Python ImportError

  - by Merjit

  This is a beginner question, and a follow-up to this one, where I was pointed to GLPK. I'm trying to get PyGLPK, a Python binding for the GNU Linear Programming Kit up and running, but no matter what I do, I can't seem to build and install GLPK so that Python finds it correctly. This comes after running ./configure, make, and sudo make install on the GLPK libraries, and following the instructions for PyGLPK. Specifically, here is the error I get: >>> import glpk Traceback (most recent call last): File "<stdin>", line 1, in <module> ImportError: dlopen(/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/site- packages/glpk.so, 2): Symbol not found: __glp_lpx_print_ips Referenced from: /Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/site-packages/glpk.so Expected in: dynamic lookup I assume that something isn't linking to somewhere else, and that it probably has something to do with paths and environment variables. However, here's where my abilities in the shell fail, and I'm at a loss over what to do next. Again, there is probably a simple answer to this, but I haven't had any luck with Google using the terminology I know.

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• Maths Question: number of different permutations

  - by KingCong

  This is more of a maths question than programming but I figure a lot of people here are pretty good at maths! :) My question is: Given a 9 x 9 grid (81 cells) that must contain the numbers 1 to 9 each exactly 9 times, how many different grids can be produced. The order of the numbers doesn't matter, for example the first row could contain nine 1's etc. This is related to Sudoku and we know the number of valid Sudoku grids is 6.67×10^21, so since my problem isn't constrained like Sudoku by having to have each of the 9 numbers in each row, column and box then the answer should be greater than 6.67×10^21. My first thought was that the answer is 81! however on further reflection this assume that the 81 number possible for each cell are different, distinct number. They are not, there are 81 possible numbers for each cell but only 9 possible different numbers. My next thought was then that each of the cells in the first row can be any number between 1 and 9. If by chance the first row happened to be all the same number, say all 1s, then each cell in the second row could only have 8 possibilites, 2-9. If this continued down until the last row then number of different permutations could be calculated by 9^2 * 8^2 * 7^2 ..... * 1^2. However this doesn't work if each row doesn't contain 9 of the same number. It's been quite a while since I studied this stuff and I can't think of a way to work it out, I'd appreciate any help anyone can offer.

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• Calling AddEventListener in a loop with a variable element name

  - by user302209

  Hi, I'm trying to do the following: I have a set of images and select (dropdown) HTML elements, 30 of each one. I'm trying to use AddEventListener on a loop from 1 to 30 so that when I change the value of the select, the image src is updated (and the image changes). The AddEventListener function is this one: function AddEventListener(element, eventType, handler, capture) { if (element.addEventListener) element.addEventListener(eventType, handler, capture); else if (element.attachEvent) element.attachEvent("on" + eventType, handler); } I tried this and it worked: var urlfolderanimalimages = "http://localhost/animalimages/"; var testselect = "sel15"; var testimg = "i15"; AddEventListener(document.getElementById(testselect), "change", function(e) { document.getElementById(testimg).src = urlfolderanimalimages + document.getElementById(testselect).value; document.getElementById(testimg).style.display = 'inline'; if (e.preventDefault) e.preventDefault(); else e.returnResult = false; if (e.stopPropagation) e.stopPropagation(); else e.cancelBubble = true; }, false); But then I tried to call it in a loop and it doesn't work. The event is added, but when I change any select, it will update the last one (the image with id i30). var urlfolderanimalimages = "http://localhost/animalimages/"; for (k=1;k<=30;k++) { var idselect = "sel" + k; var idimage = "i" + k; AddEventListener(document.getElementById(idselect), "change", function(e) { document.getElementById(idimage).src = urlfolderanimalimages + document.getElementById(idselect).value; document.getElementById(idimage).style.display = 'inline'; if (e.preventDefault) e.preventDefault(); else e.returnResult = false; if (e.stopPropagation) e.stopPropagation(); else e.cancelBubble = true; }, false); } What am I doing wrong? I'm new to JavaScript (and programming in general), so sorry for the vomit-inducing code :(

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• Always can't separate these guys: ascending and descending! Are there good examples?

  - by mystify

  As a non-english dude, I have trouble differentiating this. When I try to translate this into my language, I get something weird like "go up" for ascending. So lets say I want to sort the names of all my pets alphabetically. I want that A comes first, then B, then C... and so on. So since the alphabet is not a number for me, my brain refuses to grok what's "going up". A = 0? B = 1? C = 2? If yes, then ascending would be what I'm most of the time looking for. Table would start showing A, then B, then C... Or is that the other way around? Must I look from the bottom of the table, up? And with numbers: If it's an ascending order, the smallest comes first? (would seem logical...) Can someone post a short but good example for what is an ascending sort order, and what is an descending sort order? And does that apply to whatever platform, programming language, API, etc.?

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• An alternative to reading input from Java's System.in

  - by dvanaria

  I’m working on the UVa Online Judge problem set archive as a way to practice Java, and as a way to practice data structures and algorithms in general. They give an example input file to submit to the online judge to use as a starting point (it’s the solution to problem 100). Input from the standard input stream (java.lang.System.in) is required as part of any solution on this site, but I can’t understand the implementation of reading from System.in they give in their example solution. It’s true that the input file could consist of any variation of integers, strings, etc, but every solution program requires reading basic lines of text input from System.in, one line at a time. There has to be a better (simpler and more robust) method of gathering data from the standard input stream in Java than this: public static String readLn(int maxLg) { byte lin[] = new byte[maxLg]; int lg = 0, car = -1; String line = “”; try { while (lg < maxLg) { car = System.in.read(); if ((car < 0) || (car == ‘\n’)) { break; } lin[lg++] += car; } } catch (java.io.IOException e) { return (null); } if ((car < 0) && (lg == 0)) { return (null); // eof } return (new String(lin, 0, lg)); } I’m really surprised by this. It looks like something pulled directly from K&R’s “C Programming Language” (a great book regardless), minus the access level modifer and exception handling, etc. Even though I understand the implementation, it just seems like it was written by a C programmer and bypasses most of Java’s object oriented nature. Isn’t there a better way to do this, using the StringTokenizer class or maybe using the split method of String or the java.util.regex package instead?

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• Beginner video capture and processing/Camera selection

  - by mattbauch

  I'll soon be undertaking a research project in real-time event recognition but have no experience with the programming aspect of video capture (I'm an upperclassman undergraduate in computer engineering). I want to start off on the right foot so advice from anyone with experience would be great. The ultimate goal is to track events such as a person standing up/sitting down, entering/leaving a room, possibly even shrugging/slumping in posture, etc. from a security camera-like vantage point. First of all, which cameras/companies would you recommend? I'm looking to spend ~$100, more if necessary but not much. Great resolution isn't a must, but is desirable if affordable. What about IP network cameras vs. a USB type webcam? Webcams are less expensive, but IP cameras seem like they'd be much less work to deal with in software. What features should I look for in the camera? Once I've selected a camera, what does converting its output to a series of RGB bitmaps entail? I've never dealt with video encoding/decoding so a starting point or a tutorial that will guide me up to this point would be great if anyone has suggestions. Finally, what is the best (least complicated/most efficient) way to display video from the camera plus my own superimposed images (boxes around events in progress, for instance) in a GUI application? I can work on any operating system in any language. I have some experience with win32 GUIs and Java GUIs. The focus of the project is on the algorithm and so I'm trying to get the video capture/display portion of the app done cleanly and quickly. Thanks for any responses!!

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• Cocoa NSStream TCP connection to FTP

  - by Chuck

  Hi, I'm new to Cocoa, but not to programming. Recently I decided I wanted to write a FTP client for Mac, and so I first made it in the language I'm most comfortable in (on Windows), and then moved on to Cocoa when I had the workings of FTP communications down. My question is (apparently) a bit controversial: How do I establish a read/writeable connection to (a ftp server)? What I have so far (non working obviously): NSInputStream *iStream; NSOutputStream *oStream; NSHost *host = [NSHost hostWithAddress:@"127.0.0.1"]; [NSStream getStreamsToHost:host port:3333 inputStream:&iStream outputStream:&oStream]; // ftp port: 3333 [iStream retain]; [oStream retain]; [iStream scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode]; [oStream scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode]; [iStream setDelegate:self]; [oStream setDelegate:self]; // which is not implemented apparently [iStream open]; [oStream open]; // .... [iStream write: (const uint8_t *)buf maxLength:8]; Which is partially based on http://developer.apple.com/mac/library/documentation/cocoa/Conceptual/Streams/Articles/NetworkStreams.html Now, why have I chosen NSStream? Because while this question is merely about how to connect to a FTP stream, my whole project will also include SSL and as far as I've been able to search here and on google, NSStream is capable of "switching" to a SSL connection. I've not been able to see the connection being made (which I'm usually able to do), but I also heard something about having to write to the stream before the stream will open? Any pointers are greatly appreciated, and sorry if my question is annoying - I'm new to Cocoa :)

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• Highlighting a Table Correctly Despite rowspan and colspan attributes - WITHOUT jQuery

  - by ScottSEA

  Thanks to some !#$#@ in another department who wrote some crap code, I am unable to use the jQuery library - despite my fervent desire to do so. Their software has already been released into the world, and I have to be compatible. ============================================ I am trying to highlight a table. Desired behavior: Clicking on a cell in the body highlights the row. Clicking on a cell in the head highlights the column. If a column and row are both highlighted, the intersection is highlighted a different color (super-highlight). Clicking on a previously super-highlighted cell turns off the highlights. This behavior is simple enough to do with a basic table, but when rowspans and colspans start rearing their ugly heads, things start to get a little wonky... highlighting cell[5], for instance, no longer works reliably. My thought, in order to speed execution time of the highlighting itself (by changing a class name), is to pre-calculate the 'offsets' of all cells - with a 'colStart' and 'colEnd', 'rowStart' and 'rowEnd' when the page loads and store that in an array somehow. The question: How would YOU implement this functionality? I am fairly rusty at my JavaScript, awfully rudimentary in my programming skills and would benefit greatly from some guidance. Thanks, Scott.

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• Is it a good practice to suppress warnings?

  - by Chris Cooper

  Sometimes while writing Java in Eclipse, I write code that generates warnings. A common one is this, which I get when extending the Exception class: public class NumberDivideException extends Exception { public NumberDivideException() { super("Illegal complex number operation!"); } public NumberDivideException(String s) { super(s); } } // end NumberDivideException The warning: The serializable class NumberDivideException does not declare a static final serialVersionUID field of type long. I know this warning is caused by my failure to... well, it says right above. I could solve it by including the serialVersionUID, but this is a one hour tiny assignment for school; I don't plan on serializing it anytime soon... The other option, of course, is to let Eclipse add @SuppressWarnings("serial"). But every time my mouse hovers over the Suppress option, I feel a little guilty. For programming in general, is it a good habit to suppress warnings? (Also, as a side question, is adding a "generated" serialVersionUID like serialVersionUID = -1049317663306637382L; the proper way to add a serialVersionUID, or do I have to determine the number some other way?)

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