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• Do I assign different or the same class id to 32-bit and 64-bit versions of the same IFilter?

  - by sharptooth

  I've implemented my own Microsoft Search IFilter. I need two versions of it - 32-bit and 64-bit for deploying them on corresponding systems. In case of IFilters for any file extension I can only register one IFilter class id. Which means I can only use one version on any system. So having two class ids seems useless - it only makes the automatic installer more complex. Do I reuse the same COM class id for both or do I use different class ids?

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• malloc()/free() behavior differs between Debian and Redhat

  - by StasM

  I have a Linux app (written in C) that allocates large amount of memory (~60M) in small chunks through malloc() and then frees it (the app continues to run then). This memory is not returned to the OS but stays allocated to the process. Now, the interesting thing here is that this behavior happens only on RedHat Linux and clones (Fedora, Centos, etc.) while on Debian systems the memory is returned back to the OS after all freeing is done. Any ideas why there could be the difference between the two or which setting may control it, etc.?

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• Why can't I install psycopg2? (Python 2.6.4, PostgreSQL 8.4, OS X 10.6)

  - by cojadate

  After running python setup.py install I get the following: Warning: Unable to find 'pg_config' filebuilding 'psycopg2._psycopg' extension gcc-4.0 -arch ppc -arch i386 -fno-strict-aliasing -fno-common -dynamic -DNDEBUG -g -O3 - DPSYCOPG_DEFAULT_PYDATETIME=1 -DPSYCOPG_VERSION="2.2.1 (dt dec ext pq3)" -DPSYCOPG_EXTENSIONS=1 -DPSYCOPG_NEW_BOOLEAN=1 -DHAVE_PQFREEMEM=1 -DHAVE_PQPROTOCOL3=1 -I/Library/Frameworks/Python.framework/Versions/2.6/include/python2.6 -I. -c psycopg/psycopgmodule.c -o build/temp.macosx-10.3-fat-2.6/psycopg/psycopgmodule.o unable to execute gcc-4.0: No such file or directory error: command 'gcc-4.0' failed with exit status 1 There's probably something screamingly obvious there to anyone who knows the first thing about back-end web programming, but unfortunately it's all gobbledegook to me. The psycopg2 documentation was not helpful.

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• What makes COBOL such a hated language?

  - by cable

  I'm rather young and so I haven't experienced the times when COBOL was still in use and even going mainstream, maybe you can help me out. Everywhere I go and surf I: Am getting told about how horrible COBOL is See sites making fun of COBOL Hear that I should be happy that I don't have to use COBOL, from older programmers See others make anti-COBOL-ist jokes I don't know much about COBOL, except that it is still used everywhere as many old systems haven't got refactored and that it is even still developed and managed. I have also looked at some COBOL code examples but it seems like they are as rare and expensive as unicorn blood. If you close this question or give me sarcastic, irrelevant answers I'll have to learn COBOL to find it out the hard way. I'm serious.

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• Function Object in Java .

  - by Tony

  I wanna implement a javascript like method in java , is this possible ? Say , I have a Person class : public class Person { private String name ; private int age ; // constructor ,accessors are omitted } And a list with Person objects: Person p1 = new Person("Jenny",20); Person p2 = new Person("Kate",22); List<Person> pList = Arrays.asList(new Person[] {p1,p2}); I wanna implement a method like this: modList(pList,new Operation (Person p) { incrementAge(Person p) { p.setAge(p.getAge() + 1)}; }); modList receives two params , one is a list , the other is the "Function object", it loops the list ,and apply this function to every element in the list. In functional programming language,this is easy , I don't know how java do this? Maybe could be done through dynamic proxy, does that have a performance trade off?

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• How to use NSTableView's selectedRowIndexes?

  - by Jakub Lédl

  Hi guys, I'm just learning some basic programming in Objective C and Cocoa. I'm trying to get some data from NSTableView. Based on what I read in one tutorial, I wrote this: NSArray * items = [[itemsTableView selectedRowEnumerator] allObjects]; But then I learned that selectedRowEnumerator was deprecated already in 10.3 Panther and that I should use selectedRowIndexes. The problem is, I didn't find how to actually use the returned NSIndexSet to achieve the same result as with code written above. So, If anyone could give me a tip, I would be very grateful. Thanks.

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• Using Python tuples as vectors

  - by Etaoin

  I need to represent immutable vectors in Python ("vectors" as in linear algebra, not as in programming). The tuple seems like an obvious choice. The trouble is when I need to implement things like addition and scalar multiplication. If a and b are vectors, and c is a number, the best I can think of is this: tuple(map(lambda x,y: x + y, a, b)) # add vectors 'a' and 'b' tuple(map(lambda x: x * c, a)) # multiply vector 'a' by scalar 'c' which seems inelegant; there should be a clearer, simpler way to get this done -- not to mention avoiding the call to tuple, since map returns a list. Is there a better option?

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• Why the "mutable default argument fix" syntax is so ugly, asks python newbie

  - by Cawas

  Now following my series of "python newbie questions" and based on another question. Go to http://python.net/~goodger/projects/pycon/2007/idiomatic/handout.html#other-languages-have-variables and scroll down to "Default Parameter Values". There you can find the following: def bad_append(new_item, a_list=[]): a_list.append(new_item) return a_list def good_append(new_item, a_list=None): if a_list is None: a_list = [] a_list.append(new_item) return a_list So, question here is: why is the "good" syntax over a known issue ugly like that in a programming language that promotes "elegant syntax" and "easy-to-use"? Why not just something in the definition itself, that the "argument" name is attached to a "localized" mutable object like: def better_append(new_item, a_list=[].local): a_list.append(new_item) return a_list I'm sure there would be a better way to do this syntax, but I'm also almost positive there's a good reason to why it hasn't been done. So, anyone happens to know why?

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• What should be done first: Code reviews or Unit tests?

  - by goldenmean

  Hello, If a developer implements code for some module and wants to get it reviewed. What should be the order : *First unit test the module after designing test cases for the module, debugging and fixing the bugs and then give the modified code for peer code review (Pros- Code to be reviewed is 'clean' to a good extent. Reduces some avoidable review comments and rework. Cons- Developer might spend large time debugging/fixing a bug which could have pointed/anticipated in peer code reviews) Or *First do the code review with peers and then go for unit testing. What are your thoughts/experience on this? I believe this approach for unit testing, code reviewing should be programming language agnostic, but it would be interesting to know otherwise(if applicable) with specific examples. -AD

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• capistrano put() and upload() both failing

  - by Kyle

  With capistrano, I am deploying a Rails application from Mac OS X 10.5 to CentOS 5.2 Note that deploy.rb and the server environment have not changed in over a year. There is a task within our deploy.rb file called upload: put(File.read( file ),"#{shared_path}/#{filename}", :via => :scp) This fails each and every time with the following exception: No such file or directory - /srv/ourapp/releases/20100104194410/config/database.yml My local copy of config/database.yml is failing to upload properly. I've verified it's not our internet connection, as this happens on three different connections and two different systems. I've also tried to swap out put() for upload() but get the same result; also, dropping :via = :scp, and/or trying to force :sftp instead similarly fails. Relevant info: $ cap -V Capistrano v2.5.10 $ ruby -v ruby 1.8.7 (2008-08-11 patchlevel 72) [i686-darwin9.6.0]

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• How do I draw an ellipse with arbitrary orientation pixel by pixel?

  - by amc

  Hi, I have to draw an ellipse of arbitrary size and orientation pixel by pixel. It seems pretty easy to draw an ellipse whose major and minor axes align with the x and y axes, but rotating the ellipse by an arbitrary angle seems trickier. Initially I though it might work to draw the unrotated ellipse and apply a rotation matrix to each point, but it seems as though that could cause errors do to rounding, and I need rather high precision. Is my suspicion about this method correct? How could I accomplish this task more precisely? I'm programming in C++ (although that shouldn't really matter since this is a more algorithm-oriented question).

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• NoSQL and meteorological data

  - by christian studer

  So there's this new cool thing, these NoSQL-databases. And so there's my data: Rows of rows of rows of meteorological data: Values, representing certain measurements at a certain station (Identified by a WMO number, not coordinates), at a certain time. Not every station measures every parameter, not every parameter is measured all the time. I store this data (30 years worth of hourly values, resulting in ~1 billion values) currently in MySQL. The continous growth and the forseeable addition of even more data give me a little headache. Reading about the document based NoSQL systems which seem to scale rather easily, I was wondering if NoSQL is a viable data storage concept for meteorological data too. Do you have any experience with this?

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• how to create a particle system on iphone and retain the created particles?

  - by lukya

  Hi all, I need to create a particle system and retain the created particles. I need to shake / move the created particles with the iphone accelerometer. Also, the number of particles needs to be very high (I need to show sand!). I do not have any OpenGLES programming experience. After initial search, I found Cocos2D can be used for particle generation. But there is no way of retaining the particles in the CCParticle system. As a work around, I tried creating many sprites at the end of particle generation and shown them as particles. But moving few number of sprites with accelerometer drops the frame rate considerably. Please suggest how this can be achieved and whether I should look for some other framework or if some kind of similar demo code is available. Thanks, Swapnil

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• iphone using 2 tableview

  - by Anonymous

  Hi, I 'm a iphone programming newbie. I m trying to implement an app with multi-level tableviews. The idea is if someone selects something on the first screen say then a new view opens(tableview) car make> list of models Honda > Acura, S2000,accord ... My challenge is to show the list of models in a new tableview & secondly change the size of hte list depending on the car selected. I have programmed so that when i select 'Honda' a new tableview opens. How do i populate data for the second table?? Any suggestions on how to proceed? thanks

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• Importing ctype; embedding python in C++ application

  - by Drew

  I'm trying to embed python within a C++ based programming language (CCL: The compuatational control language, not that any of you have heard of it). Thus, I don't really have a "main" function to make calls from. I have made a test .cc program with a main, and when I compile it and run it, I am able to import my own python modules and system modules for use. When I embed my code in my CCL-based program and compile it (with g++), it seems I have most functionality, but I get the import error: ImportError: /usr/lib/python2.6/lib-dynload/_ctypes.so: undefined symbol: PyType_GenericNew Can someone explain this to me and how to go about solving it? It seems like I've linked the objects correctly. Thanks.

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• Algorithm for Source Control System?

  - by Michael Stum

  I need to write a simple source control system and wonder what algorithm I would use for file differences? I don't want to look into existing source code due to license concerns. I need to have it licensed under MPL so I can't look at any of the existing systems like CVS or Mercurial as they are all GPL licensed. Just to give some background, I just need some really simple functions - binary files in a folder. no subfolders and every file behaves like it's own repository. No Metadata except for some permissions. Overall really simple stuff, my single concern really is how to store only the differences of a file from revision to revision without wasting too much space but also without being too inefficient (Maybe store a full version every X changes, a bit like Keyframes in Videos?)

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• Editting ForeignKey from "child" table

  - by profuel

  I'm programming on py with django. I have models: class Product(mymodels.Base): title = models.CharField() price = models.ForeignKey(Price) promoPrice = models.ForeignKey(Price, related_name="promo_price") class Price(mymodels.Base): value = models.DecimalField(max_digits=10, decimal_places=3) taxValue = models.DecimalField("Tax Value", max_digits=10, decimal_places=3) valueWithTax = models.DecimalField("Value with Tax", max_digits=10, decimal_places=3) I want to see INPUTs for both prices when editing product, but cannot find any possibility to do that. inlines = [...] works only from Price to Product, which is stupid in this case. Thanx for adnvance.

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• 3 hash functions to best hash sliding window strings for a bloom filter with minimum collisions

  - by Duaa

  Hi all: I need 3 hash functions to hash strings of a sliding window moving over a text, to be used later to search within a bloom vector. I'm using C# in my programming I read something about rolling hash functions and cyclic polynomials, they are used for sliding window applications. But really, I did not find any codes, they are just descriptions So please, if anyone have any idea about 3 best C# hash functions to use with sliding window strings of fixed size (5-char), that consume less time and have minimum number of collisions, either they are rolling hash functions or others, please help me with some C# codes or links to hash functions names Duaa

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• Give me a practical use-case of Multi-set

  - by Calm Storm

  I would like to know a few practical use-cases (if they are not related/tied to any programming language it will be better).I can associate Sets, Lists and Maps to practical use cases. For example if you wanted a glossary of a book where terms that you want are listed alphabetically and a location/page number is the value, you would use the collection TreeMap(OrderedMap which is a Map) Somehow, I can't associate MultiSets with any "practical" usecase. Does someone know of any uses? http://en.wikipedia.org/wiki/Multiset does not tell me enough :) PS: If you guys think this should be community-wiki'ed it is okay. The only reason I did not do it was "There is a clear objective way to answer this question".

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• Pros and Cons of Java HTML to XML cleaners

  - by cjavapro

  I am looking to allow HTML emails (and other HTML uploads) without letting in scripts and stuff. I plan to have a white list of safe tags and attributes as well as a whitelist of CSS tags and value regexes (to prevent automatic return receipt). I asked a question: Parse a badly formatted XML document (like an HTML file) I found there are many many ways to do this. Some systems have built in sanitizers (which I don't care so much about). I will post some answers and say Community Wiki. Please post any other options you like and say Community Wiki so they can be voted on. Also any comments or wiki edits on what part of a certain product is better and what is not would be greatly appreciated. This page is a very nice listing page but I get kinda lost http://java-source.net/open-source/html-parsers

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• COM port - how to identify a device (.net/c#)

  - by argh

  Hi, I'm programming for Windows CE and I need to connect to a scanner. There is no problem - I know that it is on port COM0, but if I plug in another device earlier it gets another COM port... to get all com ports the easy way is: SerialPort.GetPortNames() But I don't know how to identify a device? Is there any standard way? I can't 'ping' it since there is one device that only sends data... it spams data all the time... and I don't know how to 'ping' a device...

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• What to know - for building a form with PHP and MySQL

  - by Tal Galili

  Hello all, I have three weeks to perform the following basic task. I wish to create an online form in PHP that will get 5 numbers and with them: save the numbers to a MySQL DB do a simple computation on the numbers and return them as an output to the visitor I already have a domain, hosting and a MySQL database+user. I don't know PHP, or SQL or databases. I do have prior knowledge in C and R (which means I have some of the basics of programming, and I am not intimidated of a new languages). My question are: Am I missing something? is there some other skill I should have for this task that I don't know of? What is a good way to learn the skills needed for the task I described? Hope the question isn't too basic/general. Thanks!

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• kill -9 and production application

  - by valodzka

  Which problem can cause kill -9 in production application (in linux to be exact)? I have application which do some periodical work, stopping these takes long time, and I don't care if some jobs will be aborted - work can be finished by new processes. So can I use kill -9 just to stop it immediately or this can cause serious OS problems? For example, Unicorn, uses it as normal working procedure: When your application goes awry, a BOFH can just "kill -9" the runaway worker process without worrying about tearing all clients down, just one. But this article claims: The -9 (or KILL) argument to kill(1) should never be used on Unix systems

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• Ethics of assisting other programmers, where do we draw the line?

  - by Chris

  In general, not just in relation to stackoverflow, sometimes I'm asked a programming question for which the answer will probably be used for good purposes, but there is a chance that it could not be. Two recent examples which reminded me of some real world questions I've been asked are: Send email to many users, and keep a formless application from closing for a keyboard hook Though I don't believe the intent of the authors of those questions is in any way nefarious, occasionally someone does ask such a question for purposes of aiding a spamming effort, or creating a keylogger. Even though the questioner and answerers had good intent, a 3rd party could pervert those answers to create a piece of malware or a spam utility. Should we always trust the questioner to use the answer for good? Should we feel obligated to ask the purpose of a question, and how the answer will be used? And how can we prevent answers from being overheard (when asked verbally) or being referenced (when posted publicly online) and then used for unsavory purposes?

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• Could Grand Central Dispatch (`libdispatch`) ever be made available on Windows?

  - by elliottcable

  I’m looking into multithreading, and GCD seems like a much better option than manually writing a solution using pthread.h and pthreads-win32. However, although it looks like libdispatch is either working on, or soon going to be working on, most newer POSIX-compatible systems… I have to ask, what about Windows? What are the chances of libdispatch being ported to Windows? What are the barriers preventing that from happening? If it came down to it, what would I need to do to preform that portage? Edit: Some things I already know, to get the discussion started: We need a blocks-compatible compiler that will compile on Windows, no? Will PLBlocks handle that? Can we use the LLVM blocks runtime? Can’t we replace all the pthread.h dependencies in userspace libdispatch with APR calls, for portability? Or, alternatively, use pthreads-win32 I suppose…

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