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• Python: Dynamic attribute name generation without exec() or eval()

  - by PyNewbie27

  Hi, I'm trying to dynamically create buttons at runtime with PyQT4.7 However, this being my first python program I'm not sure how to get the functionality I want. I would like to be able to substitute a text string for an attribute name: i.e. for each in xrange(4): myname = "tab1_button%s" % each #tab1_button0, tab1_button1, tab1_button2 #self.ui.tab1_button0 = QtGui.QPushButton(self.ui.tab) <--normal code to create a named button setattr(self.ui,myname,QtGui.QPushButton(self.ui.tab)) #rewrite of line above to dynamicly generate a button #here's where I get stuck. this code isn't valid, but it shows what i want to do self.ui.gridLayout.addWidget(self.ui.%s) % myname #I need to have %s be tab1_button1, tab1_button2, etc. I know the % is for string substituion but how can I substitute the dynamically generated attribute name into that statement? I assume there's a basica language construct I'm missing that allows this. Since it's my first program, please take it easy on me ;)

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• Google's OpenID identifier is different depending on the "consumer" domain name. How to avoid potent

  - by JohnnyO

  I'm currently testing an OpenID implementation, and I'm noticing that Google sends a different identifier for different consuming host name / domain name, even for the same user. For example, Google sends a different identifier when the requesting site is localhost, compared to the identifier they send when the requesting site is 127.0.0.1 for the same user. Note: I haven't actually tested this using public domain names, but I can't see why the behavior would be any different. My concern with Google's behavior is that if we ever choose to change our website domain name in the future, then users will no longer be able to log in to the website using Google's OpenId as the identity provider. This seems to be a big problem. Am I missing something, or are all OpenID consuming sites faced with this potential problem? I've also tested this with MyOpenId, but the identifier that MyOpenId creates is fixed, so this wouldn't be a problem with them. Thanks.

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• Preferred Method Of Application Purchase

  - by Chuck

  This is more of a "programmers" question, but felt that it was technical enough to belong on Stack Overflow instead. I'm launching an application soon that will follow the shareware model of purchase. I've thought about implementing this in a few ways: Limited access to the application until they purchase Full access to the application but expires after 30 day, requiring them to purchase to retain utility. Full access to the application indefinitely, but with a 10-15 second pop-up box on start-up asking them to register -- like mIRC does (or used to do). The method of authentication will be web-based. I'll provide them with an authentication key and they'll put it in the application. Whenever the application boots up, it'll check my web service and determine whether the application is genuine or not. This isn't my question. My question is: Is there a preferred method of implementation? I'd like to piss off the users as little as possible, but I'd also like to get paid for my work.

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• Mapping US zip code to time zone

  - by Doug Kavendek

  When users register with our app, we are able to infer their zip code when we validate them against a national database. What would be the best way to determine a good potential guess of their time zone from this zip code? We are trying to minimize the amount of data we explicitly have to ask them for. They will be able to manually set the time zone later if our best guess is wrong. I realize zip codes won't help with figuring out the time zone outside the US, but in that case we'd have to manually ask anyway, and we deal predominantly with the US regardless. I've found a lot of zip code databases, and so far only a few contain time zone information, but those that do are not free, such as this one. If it's absolutely necessary to pay a subscription to a service in order to do this, then it will not be worth it and we will just have to ask users explicitly. Although language isn't particularly relevant as I can probably convert things however needed, we're using PHP and MySQL.

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• Events raised by BackgroundWorker not executed on expected thread

  - by Topdown

  A winforms dialog is using BackgroundWorker to perform some asynchronous operations with significant success. On occasion, the async process being run by the background worker will need to raise events to the winforms app for user response (a message that asks the user if they wish to cancel), the response of which captured in an CancelEventArgs type of the event. Being an implementation of threading, I would have expected the RaiseEvent of the worker to fire, and then the worker would continue, hence requiring me to pause the worker until the response is received. Instead however, the worker is held to wait for the code executed by the raise event to complete. It seems like method I am calling via the event call is actually on the worker thread used by the background worker, and I am surprised, since I expected to see it on the Main Thread which is where the mainform is running. Also surprisingly, there are no cross thread exceptions thrown. Can somebody please explain why this is not as I expect?

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• Java generics: Illegal forward reference

  - by Arian

  Given a generic interface interface Foo<A, B> { } I want to write an implementation that requires A to be a subclass of B. So I want to do class Bar<A, B super A> implements Foo<A, B> { } // --> Syntax error or class Bar<A extends B, B> implements Foo<A, B> { } // --> illegal forward reference But the only solution that seems to work is this: class Bar<B, A extends B> implements Foo<A, B> { } which is kind of ugly, because it reverses the order of the generic parameters. Are there any solutions or workarounds to this problem?

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• Force CL-Lex to read whole word

  - by Flávio Cruz

  I'm using CL-Lex to implement a lexer (as input for CL-YACC) and my language has several keywords such as "let" and "in". However, while the lexer recognizes such keywords, it does too much. When it finds words such as "init", it returns the first token as IN, while it should return a "CONST" token for the "init" word. This is a simple version of the lexer: (define-string-lexer lexer (...) ("in" (return (values :in $@))) ("[a-z]([a-z]|[A-Z]|\_)" (return (values :const $@)))) How do I force the lexer to fully read the whole word until some whitespace appears?

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• database vs flat file, which is a faster structure for "regex" matching with many simultaneous reque

  - by Jamex

  Hi, which structure returns faster result and/or less taxing on the host server, flat file or database (mysql)? Assume many users (100 users) are simultaneously query the file/db. Searches involve pattern matching against a static file/db. File has 50,000 unique lines (same data type). There could be many matches. There is no writing to the file/db, just read. Is it possible to have a duplicate the file/db and write a logic switch to use the backup file/db if the main file is in use? Which language is best for the type of structure? Perl for flat and PHP for db? Addition info: If I want to find all the cities have the pattern "cis" in their names. Which is better/faster, using regex or string functions? Please recommend a strategy TIA

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• database vs flat file, which is a faster structure for regex matching with many simultaneous request

  - by Jamex

  Hi, which structure returns faster result and/or less taxing on the host server, flat file or database (mysql)? Assume many users (100 users) are simultaneously query the file/db. Searches involve pattern matching using regex against a static file/db. File has 50,000 unique lines (same data type). There could be many matches. There is no writing to the file/db, just read. Is it possible to have a duplicate the file/db and write a logic switch to use the backup file/db if the main file is in use? Which language is best for the type of structure? Perl for flat and PHP for db? TIA

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• Java interface and abstract class issue

  - by George2

  Hello everyone, I am reading the book -- Hadoop: The Definitive Guide, http://www.amazon.com/Hadoop-Definitive-Guide-Tom-White/dp/0596521979/ref=sr_1_1?ie=UTF8&s=books&qid=1273932107&sr=8-1 In chapter 2 (Page 25), it is mentioned "The new API favors abstract class over interfaces, since these are easier to evolve. For example, you can add a method (with a default implementation) to an abstract class without breaking old implementations of the class". What does it mean (especially what means "breaking old implementations of the class")? Appreciate if anyone could show me a sample why from this perspective abstract class is better than interface? thanks in advance, George

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• How to instantly termainate an un-supervised script on demand?

  - by errr

  I have a GUI which resembles an interpreter. It allows the user to write a script in Jython (implementation of Python in Java) and run it whenever he wants. Apart from that, I also wish to allow the user to instantly terminate the run whenever he wants. Thing is, I don't really know how to do it. The script is being run on a different Thread, but I don't know of any secure way to stop/interrupt/terminate a thread in the middle of its run, let alone not knowing what is being run by the thread/script (it could be a simple task or maybe some sort of a heavy SQL query against a DB, and a DB is something which requires careful resource handling). How can I instantly terminate such run on demand?

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• Types in Bytecode

  - by HH

  Hey everyone, I've been working for some time on (Java) Bytecode, however, it had never occurred to me to ask why are some instructions typed? I understand that in an ADD operation, we need to distinguish between an integer addition and a FP addition (that's why we have IADD and FADD). However, why do we need to distinguish between ISTORE and FSTORE? They both involve the exact same operation, which is moving 32 bits from the stack to a local variable position? The only answer I can think of is for type-safety, to prevent this: (ILOAD, ILOAD, FADD). However, I believe that type-safety is already enforced at the Java language level. OK, the Class file format is not directly coupled with Java, so is this a way to enforce type-safety for languages that do not support it? Any thought? Thank you.

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• Analysis and Design for Functional Programming

  - by edalorzo

  How do you deal with analysis and design phases when you plan to develop a system using a functional programming language like Haskell? My background is in imperative/object-oriented programming languages, and therefore, I am used to use case analysis and the use of UML to document the design of program. But the thing is that UML is inherently related to the object-oriented way of doing software. And I am intrigued about what would be the best way to develop documentation and define software designs for a system that is going to be developed using functional programming. Would you still use use case analysis or perhaps structured analysis and design instead? How do software architects define the high-level design of the system so that developers follow it? What do you show to you clients or to new developers when you are supposed to present a design of the solution? How do you document a picture of the whole thing without having first to write it all? Is there anything comparable to UML in the functional world?

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• EXC_BAD_ACCESS when trying to release an ABRecordRef

  - by synic

  I've got the following class that is a wrapper around an ABPerson (ABRecordRef): @interface Recipient : NSObject { ABRecordRef person; } - (id)initWithPerson:(ABRecordRef)person; @end @implementation - (id)initWithPerson:(ABRecordRef)_person { if(self = [super init]) person = CFRetain(_person); return self; } - (void)dealloc { if(person) CFRelease(person); [super dealloc]; } @end I've left some of the methods out, but they aren't relevant to this question. Everything works fine, except I get an EXC_BAD_ACCESS on the if(person) CFRelease(person); line. Why does this happen? I'm not calling CFRelease or CFRetain at all anywhere else in my app.

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• Most efficient approach for multilingual PHP website

  - by alexteg

  I am working on a large multilingual website and I am considering different approaches for making it multilingual. The possible alternatives I can think of are: The Gettext functions with generation of .po files One MySQL table with the translations and a unique string ID for each text PHP-files with arrays containing the different translations with unique string IDs As far as I have understood the Gettext functions should be most efficient, but my requirement is that it should be possible to change a text string in the original reference language (English) without the other translations of that string automatically reverting back to English just because a couple of words changed. Is this possible with Gettext? What is the least resource demanding solution? Is using the Gettext functions or PHP files with arrays more or less equally resource demanding? Any other suggestions for more efficient solutions?

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• Java's ThreadPoolExecutor equivalent for C#?

  - by chillitom

  Hi Guys, I used to make good use of Java's ThreadPoolExecutor class and have yet to find a good equivalent in C#. I know of ThreadPool.QueueUserWorkItem which is useful in many cases but no good if you want to control the number of threads assigned to a task or have multiple individual queues for different task types. For example I liked to use a ThreadPoolExecutor with a single thread to guarantee sequential execution of asynchronous calls.. Is there an easy way to do this in C#? Is there a non-static thread pool implementation? Thanks, T.

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• Using read() directly into a C++ std:vector

  - by Joe

  I'm wrapping up user space linux socket functionality in some C++ for an embedded system (yes, this is probably reinventing the wheel again). I want to offer a read and write implementation using a vector. Doing the write is pretty easy, I can just pass &myvec[0] and avoid unnecessary copying. I'd like to do the same and read directly into a vector, rather than reading into a char buffer then copying all that into a newly created vector. Now, I know how much data I want to read, and I can allocate appropriately (vec.reserve). I can also read into &myvec[0], though this is probably a VERY BAD IDEA. Obviously doing this doesn't allow myvec.size to return anything sensible. Is there any way of doing this that 1) Doesn't completely feel yucky from a safety/C++ perspective and 2) Doesn't involve two copies of the data block - once from kernel to user space and once from a C char * style buffer into a C++ vector. Any thoughts collective?

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• Use delegate for Projection in Linq to SQL

  - by Redeemed1

  I have code something like this in an IRepository implementation in Linq to Sql: var newlist = from h in list where h.StringProp1 == "1" select new MyBusinessBO{ firstProp = h.StringProp1, secondProp = h.StringProp2 }; The projection into MyBusinessBO is not difificult but when the Business Object has many properties the projection code becomes very lengthy. Also, as the projection can occur in several places in the Repository we break the DRY principle. Is there any way to abstract out the projection or replace it with a delegate? I.e. replace the code firstProp = h.StringProp1, secondProp = h.StringProp2 with something reusable?

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• If you could unlearn everything you know, and start again

  - by Rob Conery

  I'm giving a presentation at NDC 2010 and in one of the talks I'm going to focus on education and its power over your career (and you personally). There are people who mercilessly educate themselves, and there are others who are a bit ho-hum about it, feeling a bit of apathy. If you remove all of the risk associated surrounding a "refocus" of your career - what choices would you make? What things would you learn and what would you do with it? Think of it as a reroll, Ground Hog day, starting over from scratch today. What platform and language choices would you make and why? Most important to me are those who are completely happy where they are - would love to hear more about what it is that keeps you where you're at. Please do let me know what platform and tools you work with - it would help tremendously! Thanks in advance.

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• How do you implement syntax highlighting?

  - by ML

  I am embarking on some learning and I want to write my own syntax highlighting for files in C++. Can anyone give me ideas on how to go about doing this? To me it seems that when a file is opened: It would need to be parsed and decided what type of source file it is. Trusting the extension might not be fool-proof A way to know what keywords/commands apply to what language A way to decide what color each keyword/command gets I want to do this on OS X, using C++ or Objective-C. Can anyone provide pointers on how I might get started with this?

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• What's a good unit test framework for Common Lisp projects?

  - by Lorenzo V.

  I need to write a unit test suite for a project I am developing in my spare time. Being a CL newbie I was overwhelmed by the amount of choices for a CL implementation, I spent quite some time to choose one. Now I am facing exactly the same thing with unit test frameworks. A quick glance at http://www.cliki.net/test%20framework shows 20 unit test frameworks! Choice is good but for a novice like me this can be a bit confusing and given the number of frameworks it would be painful to try them all. I would like to use a framework which: Is reasonably well maintained Easy to use but with some degree of flexibility Offers some sort of integration with Emacs (or it is possible to easily integrate it with Emacs) Integration with git post-commit hooks Integration with a continous integration system (such as buildbot) What are your experiences in this field?

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• Help Me Understand C++ Header files and Classes

  - by JamesW

  OK, So I am trying to transition from intermediate Delphi to C++ Object Oriented programing. I have read Ivar Horton's book on visual C++ 2010. I can pull off the simple console applications no problem. I get the language itself (kinda). Where I am struggling is with headers and classes. I also understand what header files and classes do in general. What I am not getting is the implementation when do I use a header or a class? Do I need to create classes for everything I do? Do my actual work functions need to be in header files or in CPP files? I'm lost on the proper uses of these and could use some real world guidance from more experienced programmers. I am trying to transition to windows applications using the MFC if that is helpful.

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• Garbage collection when compiling to C

  - by Jules

  What are the techniques of garbage collection when compiling a garbage collected language to C? I know of two: maintain a shadow stack that saves all roots explicitly in a data structure use a conservative garbage collector like Boehm's The first technique is slow, because you have to maintain the shadow stack. Potentially every time a function is called, you need to save the local variables in a data structure. The second technique is also slow, and inherently does not reclaim all garbage because of using a conservative garbage collector. My question is: what is the state of the art of garbage collection when compiling to C. Note that I do not mean a convenient way to do garbage collection when programming in C (this is the goal of Boehm's garbage collector), just a way to do garbage collection when compiling to C.

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• What parallel programming model do you recommend today to take advantage of the manycore processors

  - by Doctor J

  If you were writing a new application from scratch today, and wanted it to scale to all the cores you could throw at it tomorrow, what parallel programming model/system/language/library would you choose? Why? I am particularly interested in answers along these axes: Programmer productivity / ease of use (can mortals successfully use it?) Target application domain (what problems is it (not) good at?) Concurrency style (does it support tasks, pipelines, data parallelism, messages...?) Maintainability / future-proofing (will anybody still be using it in 20 years?) Performance (how does it scale on what kinds of hardware?) I am being deliberately vauge on the nature of the application in anticipation of getting good general answers useful for a variety of applications.

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• Erlang on a JVM/CLR

  - by Fortyrunner

  I've just started reading Joe Armstrongs book on Erlang and listened to his excellent talk on Software Engineering Radio. Its an interesting language/system and one whose time seems to have come around with the advent of multi-core machines. My question is: what is there to stop it being ported to the JVM or CLR? I realise that both virtual machines aren't setup to run the lightweight processes that Erlang calls for - but couldn't these be simulated by threads? Could we see a lightweight or cutdown version of Erlang on a non Erlang VM?

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