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  • variable being weirdly deleted

    - by calccrypto
    im having a weird problem with one variable: its not being recognized but its still printing. i would post my code, but it is massive. the basic idea is: # pseudocode def function(stuff): <do stuff> # These are the only 2 conditions if tag == 3: pka = <a string> if tag == 4: pka = <a string> print pka # (1) print pka # (2) <do stuff not modifying pka> print pka # (3) if pka == 'RSA': <do stuff> elif pka == 'DSA': <do stuff> my code will error at (2). however, it will print out (1), (2), and (3), all of which are the same. is there any general explanation of why this is happening? if my code is really needed, i will post it, but otherwise, i would rather not due to its size update: now the code will error at the if statement after (3), saying UnboundLocalError: local variable 'pka' referenced before assignment even though (1),(2),(3) just printed

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  • Can the lock function be used to implement thread-safe enumeration?

    - by Daniel
    I'm working on a thread-safe collection that uses Dictionary as a backing store. In C# you can do the following: private IEnumerable<KeyValuePair<K, V>> Enumerate() { if (_synchronize) { lock (_locker) { foreach (var entry in _dict) yield return entry; } } else { foreach (var entry in _dict) yield return entry; } } The only way I've found to do this in F# is using Monitor, e.g.: let enumerate() = if synchronize then seq { System.Threading.Monitor.Enter(locker) try for entry in dict -> entry finally System.Threading.Monitor.Exit(locker) } else seq { for entry in dict -> entry } Can this be done using the lock function? Or, is there a better way to do this in general? I don't think returning a copy of the collection for iteration will work because I need absolute synchronization.

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  • Can functions like sin() be redefined, in Fortran, C or Java?

    - by EOL
    Can a mathematical function like sin() be redefined, in Fortran, C or Java code, while preserving the default behavior of other mathematical functions like cos()? Or can another function named sin() but that accepts different argument types be defined in addition to the built-in sin()? I am interested in general features of these languages (I am thinking of applications like the implementation of non-usual number algebras). I tried to define a sin() function in a Fortran 95 program, but the intrinsic sin() function was called instead… Is there a way around this? what about C and Java?

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  • Binding to object properties in C++

    - by Rich.Carpenter
    I've seen in WPF where you can bind control values to properties of other controls. How is that binding accomplished in C++? For example, if I have a class called Car and a guage control called RPM, how do I tie the value of RPM to the member variable Car.RPM, so that when Car.RPM changes, it is automatically (as in without a specific update call coded by me) reflected by the RPM control? General answers or directions to pertinent resources would be fine also, as I'm just beginning to dabble in C++ and haven't had much Google luck with this particular question.

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  • C++ Header Guard issues

    - by JP
    I am making a small C++ framework, which contains many .h and .cpp. I have created a general include which include all my .h file such as: framework.h #include "A.h" #include "B.h" #include "C.h" each .h header are protected with include guard such as #ifndef A_HEADER #define A_HEADER ... #endif The issues is, I would like to be able to include "framework.h" inside all the sub .h such as, but it cause lots of compiler error: #ifndef A_HEADER #define A_HEADER #include "framework.h" ... #endif If instead I use the real header file for each sub header, and the framework.h for what ever use my framework it works fine.. I would just like to include the main header inside all my sub .h so I dont need to include all the dependency everytime. Thanks :)

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  • C++ Multiple Inheritance Question

    - by John
    The scenario generating this is quite complex so I'll strip out a few pieces and give an accurate representation of the classes involved. /* This is inherited using SI by many classes, as normal */ class IBase { virtual string toString()=0; }; /* Base2 can't inherit IBase due to other methods on IBase which aren't appropriate */ class Base2 { string toString() { ... } }; /* a special class, is this valid? */ class Class1 : public IBase, public Base2 { }; So, is this valid? Will there be conflicts on the toString? Or can Class1 use Base2::toString to satisfy IBase? Like I say there are lots of other things not shown, so suggestions for major design changes on this example are probably not that helpful... though any general suggestions/advice are welcome.

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  • Why wasn't C# designed with 'const' for variables and methods?

    - by spoulson
    I suspect const was simplified for the C# spec for general language simplicity. Was there a specific reason we can't declare variable references or methods as const like we can with C++? e.g.: const MyObject o = new MyObject(); // Want const cast referenece of MyObject o.SomeMethod(); // Theoretically legal because SomeMethod is const o.ChangeStuff(); // Theoretically illegal because ChangeStuff is not const class MyObject { public int val = 0; public void SomeMethod() const { // Do stuff, but can't mutate due to const declaration. } public void ChangeStuff() { // Code mutates this instance. Can't call with const reference. val++; } }

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  • Getting a "summary" of a webpage

    - by MattiasK
    I have something of a a hairy problem, I'd like to generate a couple of paragraphs of "description" of a given url, normally the start of an article. The Meta description field is one way to go but it isn't always good or set properly. It's fair to say it's a bit problematic to accomplish this from the screenscraped HTML. I had a general idea that perhaps one could scan the HTML for the first "appropriate" segment but it's hard to say what that is, perhaps something like the first paragraph containing a certain amount of text... Anyone have any good ideas? :) It doesn't have to be foolproof

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  • Why Do Programmers Get So Invested in their Favorite Technologies?

    - by Pierreten
    I've noticed this culture surrounding Ruby where developers truly believe that they are somehow more gifted than developers of other languages, regardless of experience and talent (even when that isn't the case, I've met some extremely junior Ruby developers come up with some pretty basic constructs, and pass them off as some sort of revolutionary idea). The derision of strongly typed languages seems to be a common theme as well; regardless of its merits. Is there something particular to the Ruby syntax in general that is to account for this? Is there a sociological component to it?

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  • Commercial CMS on Google App Engine, violation of terms?

    - by Yaggo
    I'm developing commercial CMS running on Google App Engine. I'm thinking of selling it in two ways: 1) Software as a service (SaS). The CMS running in my App Engine account (as single app), hosting the sites of all customers. A turn-key solution for "end user" customers. 2) Licence for running the CMS in customer's own App Engine account. Targeted for digital agencies for reselling as SaS. Being not a lawyer myself, I don't trust my abilities to read between the lines of TOS jargon. Counting on the general knowledge of SO community, my question is: do the above scenarios violate the App Engine Terms of Service?

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  • SQL Server JOIN with optional NULL values

    - by Paul McLoughlin
    Imagine that we have two tables as follows: Trades ( TradeRef INT NOT NULL, TradeStatus INT NOT NULL, Broker INT NOT NULL, Country VARCHAR(3) NOT NULL ) CTMBroker ( Broker INT NOT NULL, Country VARCHAR(3) NULL ) (These have been simplified for the purpose of this example). Now, if we wish to join these two tables on the Broker column, and if a country exists in the CTMBroker table on the Country, we have the following two choices: SELECT T.TradeRef,T.TradeStatus FROM Trades AS T JOIN CTMBroker AS B ON B.Broker=T.Broker AND ISNULL(B.Country, T.Country) = T.Country or SELECT T.TradeRef,T.TradeStatus FROM Trades AS T JOIN CTMBroker AS B ON B.Broker=T.Broker AND (B.COUNTRY=T.Country OR B.Country IS NULL) These are both logically equivalent, however in this specific circumstance for our database (SQL Server 2008, SP1) two different execution plans are produced for these two queries with the second version significantly outperforming the first version in terms of both time and logical reads. My question really is as follows: as a general rule would (2) be preferred to (1), or does this just happen to be exploiting some particular idiosyncracy of the optimiser in 2008 SP1 (that could therefore change with future versions of SQL Server).

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  • Web.xml ExceptionType

    - by andrew007
    Hi, is it possible to define two sections in the web.xml in order to catch two different exception types: <!-- general exception --> <error-page> <exception-type>**java.lang.Exception**</exception-type> <location>/generalError.jsp</location> </error-page> <!-- specific exception --> <error-page> <exception-type>org.myapp.myException</exception-type> <location>/sessionTimeout.jsp</location> </error-page> Does it has any conflict? THANKS!

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  • sql insert statement with a lot of same where clause and one different where cluase

    - by william
    I m sry if the title is not clear. Here's my proble. I created a new table which will show total, average and maximum values. I have to insert the results into that table. That table will have only 4 rows. No Appointment, Appointment Early, Appointment Late and Appointment Punctual. So.. I have sth like.. insert into newTable select 'No Appointment' as 'Col1', avg statement, total statement, max statement from orgTable where (general conditions) and (unique condition to check NO APPOINTMENT); I have to do that same thing for another 3 rows.. where only the unique condition is different to check early, punctual or late.. So..the statement is super long. I wanna reduce the size.. How can I achieve that?

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  • Sphinx: change column set for searching in runtime

    - by Fedyashev Nikita
    I use Ultrasphinx gem plugin as a wrapper for accessing Sphinx search daemon. My model declaration: class Foo < ActiveRecord::Base is_indexed :fields => ['content', 'private_notes', 'user_id'] Client code: filters = {} if type == "private" # search only in `content` column filters['user_id'] = current_user.id else # search in `content` and `private_notes` columns end results = Ultrasphinx::Search.new(:query => params[:query], :per_page => 20, :page => params[:page] || 1, :filters => filters) The problem I have now with Ultrasphinx gem(or Sphinx, in general?) is that it does not allow me to change set of fields where to look for matches IN RUNTIME How can I solve this problem?

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  • c++11 atomic ordering: extended total order memory_order_seq_cst for locks

    - by itaj
    There's this note in c++11 29.3-p3: [ Note: Although it is not explicitly required that S include locks, it can always be extended to an order that does include lock and unlock operations, since the ordering between those is already included in the "happens before" ordering. - end note ] What does it mean by "always"? I can understand that any certain implementation can be designed to support such an extended S. But in some general implementation that wasn't designed for it, I don't see that S can be extended so. I had sent this question to comp.std.c++ but got no answers there. http://groups.google.com/group/comp.std.c++/browse_frm/thread/5242fa70d0594d1b#

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  • How do open source projects obtain license for commercial software without spending a lot of money?

    - by Ikaso
    I just joined an open source project on codeplex. The project is based on the .NET compact framework. So the development tool is Visual Studio. Currently I am using some trial version of Visual Studio which is going to end and I wondered how can I obtain a valid license to work on the project without spending a lot of money. Please pay attention that the Express edition does not help me since my application is running on Windows Mobile 6.5 which is not supported on the Express edition (and the 2010 Express edition supports only Windows Mobile Phone 7 series development). In the general sense, are there some organizations that donate software licenses for open source projects?

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  • Why Are Ruby Programmers So Full of Themselves? [closed]

    - by Pierreten
    I've noticed this culture surrounding Ruby where developers truly believe that they are somehow more gifted than developers of other languages, regardless of experience and talent (even when that isn't the case, I've met some extremely junior Ruby developers come up with some pretty basic constructs, and pass them off as some sort of revolutionary idea). The derision of strongly typed languages seems to be a common theme as well; regardless of its merits. Is there something particular to the Ruby syntax in general that is to account for this? Is there a socialogical component to it?

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  • Future of web services

    - by Landon Ashes
    I want to know what are the possible Future research areas Regarding "Web Services" and in what direction "Web Services" are moving. I am not talking about "Microsoft Web Services". I am talking about "Web Services" in general. I did google but what ever i found was like couple of years old and obsolete. couldnt get any direction from IEEE too. Plz some expert of this line should guide me. I will be obliged like anything. Thanks in Advance.

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  • As a programmer what single discovery has given you the greatest boost in productivity?

    - by ChrisInCambo
    This question has been inspired by my recent discovery/adoption of distributed version control. I started using it (mercurial) just because I liked the idea of still being able to make commits at times when I couldn't connect to the central server. I never expected it would give me a large boost in general productivity, but a pleasant side effect I discovered was that making a new clone every time I started a new task and giving that clone a descriptive folder name is extremely effective at keeping me on task resulting is a noticeable productivity increase. So as a programmer what single discovery has given you the greatest boost in productivity? Extra respect for answers which involve tools or practices that aren't so obvious from the outside!

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  • Python editor/IDE for OS X

    - by TheJuice
    As a (reasonably) new Python programmer, what IDEs or editors would you recommend for Python programming on OS X and why (i.e. what features/capabilities/workflow techniques really help)? I've used Xcode and played a bit with TextMate but I can't really say that either have really hit the spot for me (although TextMate's code completion is pretty neat, I think i've been spoilt with code-completion facilities provided by editors for statically-typed languages so maybe i'm subconsciously comparing apples and oranges) I'm looking to increase my efficacy with Python and any tips would be appreciated. I know people have asked similar questions for Python IDEs in general but I am specifically concentrating on OS X and the 'Mac way'. If Xcode or TextMate are thought highly of, perhaps some suggestions as to how I could get the most benefit from the tools would help.

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  • Dynamic binding in C++

    - by chmike
    I'm implementing a CORBA like server. Each class has remotely callable methods and a dispatch method with two possible input, a string identifying the method or an integer which would be the index of the method in a table. A mapping of the string to the corresponding integer would be implemented by a map. The caller would send the string on the first call and get back the integer with the response so that it simply has to send the integer on subsequent calls. It is just a small optimization. The integer may be assigned dynamically on demand by the server object. The server class may be derived from another class with overridden virtual methods. What could be a simple and general way to define the method binding and the dispatch method ?

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  • MVC design pattern - who loads view initially

    - by enableDeepak
    This query is about MVC design pattern in general and not ASP.net MVC framework I understand in MVC (desktop application): 1. User clicks something in view 2. this is passed on to controller to manage 3. controller makes some changes in Model 4. Model calls method on view which has the logic to refresh UI Questions around these: Q1) Can controller also modify View or Model only updates View? Q2) When screen loads for the first time, there is no Model change. Then, who fetches data from model and populates view? View directly calls Model and populates itself OR controller gets data and passes to view method OR some dummy event is raised at Model which updates View?

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  • Do I have to store a TcpClient even though I only care about its stream?

    - by mafutrct
    A new instance of a TcpClient connects to a remote host. Its NetworkStream is retrieved and stored. Do I have to store the TcpClient itself as well to make sure it is not garbage collected? In case you're going to answer "You have to store it to be able to dispose it": In my specific case, the TcpClient is usually living for a long time (app lifetime), so disposing it is not really a must. However, I agree that, in general, it has to be stored just to be able to call Dispose.

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  • Isolated storage

    - by Costa
    Hi I am not sure that I understand Isolated storage. I read the article http://msdn.microsoft.com/en-us/library/3ak841sy%28VS.80%29.aspx 1) Why I don't just use App data folder? 2) In the link above : "With isolated storage, data is always isolated by user and by assembly. Credentials such as the origin or the strong name of the assembly determine assembly identity. Data can also be isolated by application domain, using similar credentials." I can't think about a scenario that makes this future important. In general I don't understand the philosophy and the need of "isolated storage" which inspire MS to create such a thing. Thanks

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  • "Socket operation on non-socket" error due to strange sytax

    - by Robert S. Barnes
    I ran across the error Socket operation on non-socket in some of my networking code when calling connect and spent a lot of time trying to figure out what was causing it. I finally figured out that the following line of code was causing the problem: if ((sockfd = socket( ai->ai_family, ai->ai_socktype, ai->ai_protocol) < 0)) { See the problem? Here's what the line should look like: if ((sockfd = socket( ai->ai_family, ai->ai_socktype, ai->ai_protocol)) < 0) { What I don't understand is why the first, incorrect line doesn't produce a warning. To put it another way, shouldn't the general form: if ( foo = bar() < baz ) do_somthing(); look odd to the compiler, especially running with g++ -Wall -Wextra? If not, shouldn't it at least show up as "bad style" to cppcheck, which I'm also running as part of my compile?

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