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• Would anybody recommend learning J/K/APL?

  - by ozan

  I came across J/K/APL a few months ago while working my way through some project euler problems, and was intrigued, to say the least. For every elegant-looking 20 line python solution I produced, there'd be a gobsmacking 20 character J solution that ran in a tenth of the time. I've been keen to learn some basic J, and have made a few attempts at picking up the vocabulary, but have found the learning curve to be quite steep. To those who are familiar with these languages, would you recommend investing some time to learn one (I'm thinking J in particular)? I would do so more for the purpose of satisfying my curiosity than for career advancement or some such thing. Some personal circumstances to consider, if you care to: I love mathematics, and use it daily in my work (as a mathematician for a startup) but to be honest I don't really feel limited by the tools that I use (like python + NumPy) so I can't use that excuse. I have no particular desire to work in the finance industry, which seems to be the main port of call for K users at least. Plus I should really learn C# as a next language as it's the primary language where I work. So practically speaking, J almost definitely shouldn't be the next language I learn. I'm reasonably familiar with MATLAB so using an array-based programming language wouldn't constitute a tremendous paradigm shift. Any advice from those familiar with these languages would be much appreciated.

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• how to get Contact database schema.

  - by kamiomar

  Dear, is there any link that provide me the Contact Schema. when i store new phone number in mobile, the informaion store in the database. so i need schema to create my own table for back purpose. i have alreay get People table column by the follwoing code. boolean displayFlag = false; String str = ""; Uri CONTACT_URI = People.CONTENT_URI; Cursor cursor = mContext.getContentResolver().query(CONTACT_URI, null, null, null, null); String columnNames = ""; if (cursor != null) { try { cursor.getCount(); if (cursor.moveToFirst()) { String[] columns = cursor.getColumnNames(); for (int i = 0; i < columns.length; i++) { columnNames += "colName" + cursor.getColumnName(i) + " : " + cursor.getString(i) + "colValue"; } } } finally { cursor.close(); } } createImage(columnNames); if (displayFlag) { Toast.makeText(mContext, str, Toast.LENGTH_SHORT).show(); } } Thanks

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• Remotely connecting two non-local computers with sockets

  - by Velizar Hristov

  This question seems like something very obvious to ask, and yet I spent more than an hour trying to find an answer. First I host and wait for someone to connect. Then, from another instance of the application, I try to connect with a socket - for the constructor, I use InetAddress, port. The port is always right, and everything works if I use "localhost" for the address. However, if I type my IP, I get an IOException. I even sent the application to someone else, gave him my IP, and it didn't work. The aim of the application is to connect two computers. It's in Java. Here is the relevant code. Server: ServerSocket serverSocket = new ServerSocket(port); Socket clientSocket = serverSocket.accept(); Client: InetAddress a = InetAddress.getByName(ip); Socket s = new Socket(a, port); I don't get past that. Obviously, the values of int port and String ip are taken from text fields. Edit: the purpose of my application is to connect two non-local computers.

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• SpeechRecognizer causes ANR... I need help with Android speech API.

  - by Dondo Chaka

  I'm trying to use Android's speech recognition package to record user speech and translate it to text. Unfortunately, when I attempt initiate listening, I get an ANR error that doesn't point to anything specific. As the SpeechRecognizer API indicates, a RuntimeException is thrown if you attempt to call it from the main thread. This would make me wonder if the processing was just too demanding... but I know that other applications use the Android API for this purpose and it is typically pretty snappy. java.lang.RuntimeException: SpeechRecognizer should be used only from the application's main thread Here is a (trimmed) sample of the code I'm trying to call from my service. Is this the proper approach? Thanks for taking the time to help. This has been a hurdle I haven't been able to get over yet. Intent intent = new Intent(RecognizerIntent.ACTION_RECOGNIZE_SPEECH); intent.putExtra(RecognizerIntent.EXTRA_LANGUAGE_MODEL, RecognizerIntent.LANGUAGE_MODEL_FREE_FORM); intent.putExtra(RecognizerIntent.EXTRA_CALLING_PACKAGE, "com.domain.app"); SpeechRecognizer recognizer = SpeechRecognizer .createSpeechRecognizer(this.getApplicationContext()); RecognitionListener listener = new RecognitionListener() { @Override public void onResults(Bundle results) { ArrayList<String> voiceResults = results .getStringArrayList(RecognizerIntent.EXTRA_RESULTS); if (voiceResults == null) { Log.e(getString(R.string.log_label), "No voice results"); } else { Log.d(getString(R.string.log_label), "Printing matches: "); for (String match : voiceResults) { Log.d(getString(R.string.log_label), match); } } } @Override public void onReadyForSpeech(Bundle params) { Log.d(getString(R.string.log_label), "Ready for speech"); } @Override public void onError(int error) { Log.d(getString(R.string.log_label), "Error listening for speech: " + error); } @Override public void onBeginningOfSpeech() { Log.d(getString(R.string.log_label), "Speech starting"); } }; recognizer.setRecognitionListener(listener); recognizer.startListening(intent);

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• What happens when we combine RAII and GOTO ?

  - by Robert Gould

  I'm wondering, for no other purpose than pure curiosity (because no one SHOULD EVER write code like this!) about how the behavior of RAII meshes with the use of Goto (lovely idea isn't it). class Two { public: ~Two() { printf("2,"); } }; class Ghost { public: ~Ghost() { printf(" BOO! "); } }; void foo() { { Two t; printf("1,"); goto JUMP; } Ghost g; JUMP: printf("3"); } int main() { foo(); } When running the following code in VS2005 I get the following output: 1,2,3 BOO! However I imagined, guessed, hoped that 'BOO!' wouldn't actually appear as the Ghost should have never been instantiated (IMHO, because I don't know the actual expected behavior of this code). Any Guru out there knows what's up? Just realized that if I instantiate an explicit constructor for Ghost the code doesn't compile... class Ghost { public: Ghost() { printf(" HAHAHA! "); } ~Ghost() { printf(" BOO! "); } }; Ah, the mystery ...

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• How do I mock a method with an open array parameter in PascalMock?

  - by Oliver Giesen

  I'm currently in the process of getting started with unit testing and mocking for good and I stumbled over the following method that I can't seem to fabricate a working mock implementation for: function GetInstance(const AIID: TGUID; out AInstance; const AArgs: array of const; const AContextID: TImplContextID = CID_DEFAULT): Boolean; (TImplContextID is just an alias for Integer) I thought it would have to look something like this: function TImplementationProviderMock.GetInstance( const AIID: TGUID; out AInstance; const AArgs: array of const; const AContextID: TImplContextID): Boolean; begin Result := AddCall('GetInstance') .WithParams([@AIID, AContextID]) .ReturnsOutParams([AInstance]) .ReturnValue; end; But the compiler complains about the .ReturnsOutParams([AInstance]) saying "Bad argument type in variable type array constructor.". Also I haven't found a way to specify the open array parameter AArgs at all. Also, is using the @-notation for the TGUID-typed parameter the right way to go? Is it possible to mock this method with the current version of PascalMock at all? Update: I now realize I got the purpose of ReturnsOutParams completely wrong: It's intended to be used for populating the values to be returned when defining the expectations rather than for mocking the call itself. I now think the correct syntax for mocking the out parameter would probably have to look more like this: function TImplementationProviderMock.GetInstance( const AIID: TGUID; out AInstance; const AArgs: array of const; const AContextID: TImplContextID): Boolean; var lCall: TMockMethod; begin lCall := AddCall('GetInstance').WithParams([@AIID, AContextID]); Pointer(AInstance) := lCall.OutParams[0]; Result := lCall.ReturnValue; end; The questions that remain are how to mock the open array parameter AArgs and whether passing the TGUID argument (i.e. a value type) by address will work out...

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• Existing parsers in c# (BSD license or similar)

  - by Sylverdrag

  I am looking for parsers (in C#) for a bunch of formats. (PHP, ASP, some XML based formats, HTML,...pretty much anything I can get my hands on.) The purpose is to separate the text from the code and do some edits without messing up the code. I had a look at ANTLR, but while it seems like the "right tool", there is just too much prior knowledge assumed. I have an easier time writing a parser from scratch than understanding how to "easily" generate parsers from ANTLR. (I wrote a small parser for a specific type of RTF files within a couple days, so the task is probably within my reach, but as I have no formal knowledge of parsing/lexing, I am at loss with ANTLR) Then it occurred to me that there must existing parsers for many formats, so before I start writing yet another a brand new and potentially buggy version of the wheel, I figured I would check what parsers already exist and can be reused in a commercial product. I could use parsers for just about every format in existence, so this question would be a good place to make a list of all existing free parsers written in C#, if there are any. Thanks in advance for your suggestions

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• C++: is it safe to work with std::vectors as if they were arrays?

  - by peoro

  I need to have a fixed-size array of elements and to call on them functions that require to know about how they're placed in memory, in particular: functions like glVertexPointer, that needs to know where the vertices are, how distant they are one from the other and so on. In my case vertices would be members of the elements to store. to get the index of an element within this array, I'd prefer to avoid having an index field within my elements, but would rather play with pointers arithmetic (ie: index of Element *x will be x - & array[0]) -- btw, this sounds dirty to me: is it good practice or should I do something else? Is it safe to use std::vector for this? Something makes me think that an std::array would be more appropriate but: Constructor and destructor for my structure will be rarely called: I don't mind about such overhead. I'm going to set the std::vector capacity to size I need (the size that would use for an std::array, thus won't take any overhead due to sporadic reallocation. I don't mind a little space overhead for std::vector's internal structure. I could use the ability to resize the vector (or better: to have a size chosen during setup), and I think there's no way to do this with std::array, since its size is a template parameter (that's too bad: I could do that even with an old C-like array, just dynamically allocating it on the heap). If std::vector is fine for my purpose I'd like to know into details if it will have some runtime overhead with respect to std::array (or to a plain C array): I know that it'll call the default constructor for any element once I increase its size (but I guess this won't cost anything if my data has got an empty default constructor?), same for destructor. Anything else?

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• Is there a way to control how pytest-xdist runs tests in parallel?

  - by superselector

  I have the following directory layout: runner.py lib/ tests/ testsuite1/ testsuite1.py testsuite2/ testsuite2.py testsuite3/ testsuite3.py testsuite4/ testsuite4.py The format of testsuite*.py modules is as follows: import pytest class testsomething: def setup_class(self): ''' do some setup ''' # Do some setup stuff here def teardown_class(self): '''' do some teardown''' # Do some teardown stuff here def test1(self): # Do some test1 related stuff def test2(self): # Do some test2 related stuff .... .... .... def test40(self): # Do some test40 related stuff if __name__=='__main()__' pytest.main(args=[os.path.abspath(__file__)]) The problem I have is that I would like to execute the 'testsuites' in parallel i.e. I want testsuite1, testsuite2, testsuite3 and testsuite4 to start execution in parallel but individual tests within the testsuites need to be executed serially. When I use the 'xdist' plugin from py.test and kick off the tests using 'py.test -n 4', py.test is gathering all the tests and randomly load balancing the tests among 4 workers. This leads to the 'setup_class' method to be executed every time of each test within a 'testsuitex.py' module (which defeats my purpose. I want setup_class to be executed only once per class and tests executed serially there after). Essentially what I want the execution to look like is: worker1: executes all tests in testsuite1.py serially worker2: executes all tests in testsuite2.py serially worker3: executes all tests in testsuite3.py serially worker4: executes all tests in testsuite4.py serially while worker1, worker2, worker3 and worker4 are all executed in parallel. Is there a way to achieve this in 'pytest-xidst' framework? The only option that I can think of is to kick off different processes to execute each test suite individually within runner.py: def test_execute_func(testsuite_path): subprocess.process('py.test %s' % testsuite_path) if __name__=='__main__': #Gather all the testsuite names for each testsuite: multiprocessing.Process(test_execute_func,(testsuite_path,))

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• Linux C debugging library to detect memory corruptions

  - by calandoa

  When working sometimes ago on an embedded system with a simple MMU, I used to program dynamically this MMU to detect memory corruptions. For instance, at some moment at runtime, the foo variable was overwritten with some unexpected data (probably by a dangling pointer or whatever). So I added the additional debugging code : at init, the memory used by foo was indicated as a forbidden region to the MMU; each time foo was accessed on purpose, access to the region was allowed just before then forbidden just after; a MMU irq handler was added to dump the master and the address responsible of the violation. This was actually some kind of watchpoint, but directly self-handled by the code itself. Now, I would like to reuse the same trick, but on a x86 platform. The problem is that I am very far from understanding how is working the MMU on this platform, and how it is used by Linux, but I wonder if any library/tool/system call already exist to deal with this problem. Note that I am aware that various tools exist like Valgrind or GDB to manage memory problems, but as far as I know, none of these tools car be dynamically reconfigured by the debugged code. I am mainly interested for user space under Linux, but any info on kernel mode or under Windows is also welcome!

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• ARM Assembly - Converting Endianness

  - by SoulBeaver

  Hello people! This is currently a homework project that me and my teammate are stuck on. We haven't been given much of an introduction into Assembly, and this is supposed to be our first homework exercise. The task is to create a program that converts 0xAABBCCDD into 0xDDCCBBAA. I'm not looking for an answer, as that would defeat the purpose, but we are getting severely frustrated over the difficulty of this stupid thing. We think we have a good start in creating a viable solution, but we just cannot come up with the rest of the program. First, we mask every single tupel (aa), (bb), (cc), (dd) into a different register: LDR R0, LittleEndian // 0xAABBCCDD AND R1, R0, #0xFF000000 // 0xAA AND R2, R0, #0x00FF0000 // 0xBB AND R3, R0, #0x0000FF00 // 0xCC AND R4, R0, #0x000000FF // 0xDD Then we try to re-align them into the R0 register, but hell if we could come up with a good solution... Our best effort came from: ORR R0, R1, LSL #24 ORR R0, R2, LSL #8 ORR R0, R3, LSR #8 ORR R0, R4, LSR #24 which produced 0xBBBBCCDD for some odd reason; we really don't know. Any hints would be greatly appreciated. Again, we are asking for help, but not for a solution. Cheers!

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• .NET Regular Expression to find actual words in text

  - by Mehdi Anis

  I am using VB .NET to write a program that will get the words from a suplied text file and count how many times each word appears. I am using this regular expression:- parser As New Regex("\w+") It gives me almost 100% correct words. Except when I have words like "Ms Word App file name is word.exe." or "is this a c# statment If(ab?1,0) ?" In such cases I get [word & exe] AND [If, a, b, 1 and 0] as seperate words. it would be nice (for my purpose) that I received word.exe and (If(ab?1,0) as words. I guess \w+ looks for white space, sentence terminating punctuation mark and other punctuation marks to determine a word. I want a similar regular Expression that will not break a word by a punctuation mark, if the punctuation mark is not the end of the word. I think end-of-word can be defined by a trailing WhiteSpace, Sentence terminating Punctuation (you may think of others). if you can suggest some regular expression 9for VB .NET) that will be great help. Thanks.

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• Automated Legal Processing

  - by Chris S

  Will it ever be possible to make legal systems quantifiable enough to process with computer algorithms? What technologies would have to be in place before this is possible? Are there any existing technologies that are already trying to accomplish this? Out of curiosity, I downloaded the text for laws in my local municipality, and tried applying some simple NLP tricks to extract rules from sentences. I had mixed results. Some sentences were very explicit (e.g. "Cars may not be left in the park overnight"), but other sentences seemed hopelessly vague (e.g. "The council's purpose is to ensure the well-being of the community"). I apologize if this is too open-ended a topic, but I've often wondered what society would look like if legal systems were based on less ambiguous language. Lawyers, and the legal process in general, are so expensive because they have to manually process a complex set of rules codified in ambiguous legal texts. If this system could be represented in software, this huge expense could potentially be eliminated, making the legal system more accessible for everyone.

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• How best to calculate derived currency rate conversions using C#/LINQ?

  - by chillitom

  class FxRate { string Base { get; set; } string Target { get; set; } double Rate { get; set; } } private IList<FxRate> rates = new List<FxRate> { new FxRate {Base = "EUR", Target = "USD", Rate = 1.3668}, new FxRate {Base = "GBP", Target = "USD", Rate = 1.5039}, new FxRate {Base = "USD", Target = "CHF", Rate = 1.0694}, new FxRate {Base = "CHF", Target = "SEK", Rate = 8.12} // ... }; Given a large yet incomplete list of exchange rates where all currencies appear at least once (either as a target or base currency): What algorithm would I use to be able to derive rates for exchanges that aren't directly listed? I'm looking for a general purpose algorithm of the form: public double Rate(string baseCode, string targetCode, double currency) { return ... } In the example above a derived rate would be GBP-CHF or EUR-SEK (which would require using the conversions for EUR-USD, USD-CHF, CHF-SEK) Whilst I know how to do the conversions by hand I'm looking for a tidy way (perhaps using LINQ) to perform these derived conversions perhaps involving multiple currency hops, what's the nicest way to go about this?

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• How to hide the console of batch scripts without losing std err/out streams

  - by cooper.thompson

  My question is similar to Running a CMD or BAT in silent mode, but with one additional constraint. If you use WshScript.Run in vbscript, you lose access to the standard in/error/out streams of the process. WshScript.Exec gives you access to the standard streams, but you can't hide your windows. How can you have your cake (hide the windows) and eat it too (have direct access to the console streams)? I'm currently thinking about a C++ executable which creates a new Windows Station and Desktop, (see MSDN) and runs a specified script within that new Desktop (I'm not yet an expert on Window Stations and Desktops, so this idea may be retarded). This idea is based loosely on Condor's USE_VISIBLE_DESKTOP feature, which, if disabled, runs Condor jobs in a non-visible Desktop. I haven't quite figured out if this requires elevated priveledge. The tradeoff of this approach is that your script can disappear into limbo if it blocks on user input. Does anyone have any additional ideas? Or feedback on the approach outlined above? Edit: Also, the purpose of our script is to set up the user environment, so running as another user, or as a system scheduled task isn't really an option (unless there are clever tricks I don't know about).

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• .NET consumer of ActiveX throwing TargetParameterCountException

  - by DevSolo

  I have a .NET (3.5 w/ Dev Studio 2008) app that hosts a visual Active X (written in C++ w/ Dev Studio 2003). Have access to all sources, but can't easily move the Active X control up to 2008. This as worked fine in the past. Made some changes to the Active X control and now, when calling one method on the Active X, I'm getting a TargetParameterCountException 100% of the time. The signature of the Active X method is: LONG CMyActive::License(LPCTSTR string1, LPCTSTR string2, LONG long1, LPCTSTR string3, LPCTSTR string4); When viewing the method in object browser of reflector, .NET sees it as: public virtual int License(string string1, string string2, int long1, string string3, string string4) I renamed the parameters for demonstration purpose (boss gets twitchy about any code). I left the method name, as it could be relevant. There are method calls prior that work. I just can't seen to figure out why I'm all of a sudden getting this exception. The HRESULT is 0x8002000e and a quick search seems to indicate that's a general one. Thanks to all for reading.

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• Parsing data with Clojure, interval problem.

  - by Andrea Di Persio

  Hello! I'm writing a little parser in clojure for learning purpose. basically is a TSV file parser that need to be put in a database, but I added a complication. The complication itself is that in the same file there are more intervals. The file look like this: ###andreadipersio 2010-03-19 16:10:00### USER COMM PID PPID %CPU %MEM TIME root launchd 1 0 0.0 0.0 2:46.97 root DirectoryService 11 1 0.0 0.2 0:34.59 root notifyd 12 1 0.0 0.0 0:20.83 root diskarbitrationd 13 1 0.0 0.0 0:02.84` .... ###andreadipersio 2010-03-19 16:20:00### USER COMM PID PPID %CPU %MEM TIME root launchd 1 0 0.0 0.0 2:46.97 root DirectoryService 11 1 0.0 0.2 0:34.59 root notifyd 12 1 0.0 0.0 0:20.83 root diskarbitrationd 13 1 0.0 0.0 0:02.84 I ended up with this code: (defn is-header? "Return true if a line is header" [line] (> (count (re-find #"^\#{3}" line)) 0)) (defn extract-fields "Return regex matches" [line pattern] (rest (re-find pattern line))) (defn process-lines [lines] (map process-line lines)) (defn process-line [line] (if (is-header? line) (extract-fields line header-pattern)) (extract-fields line data-pattern)) My idea is that in 'process-line' interval need to be merged with data so I have something like this: ('andreadipersio', '2010-03-19', '16:10:00', 'root', 'launchd', 1, 0, 0.0, 0.0, '2:46.97') for every row till the next interval, but I can't figure how to make this happen. I tried with something like this: (def process-line [line] (if is-header? line) (def header-data (extract-fields line header-pattern))) (cons header-data (extract-fields line data-pattern))) But this doesn't work as excepted. Any hints? Thanks!

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• Exception calling remote SOAP call from thread

  - by Duncan

  This is an extension / next step of this question I asked a few minutes ago. I've a Delphi application with a main form and a thread. Every X seconds the thread makes a web services request for a remote object. It then posts back to the main form which handles updating the UI with the new information. I was previously using a TTimer object in my thread, and when the TTimer callback function ran, it ran in the context of the main thread (but the remote web services request did work). This rather defeated the purpose of the separate thread, and so I now have a simple loop and sleep routine in my thread's Execute function. The problem is, an exception is thrown when returning from GetIMySOAPService(). procedure TPollingThread.Execute; var SystemStatus : TCWRSystemStatus; begin while not Terminated do begin sleep(5000); try SystemStatus := GetIMySOAPService().GetSystemStatus; PostMessage( ParentHandle, Integer(apiSystemStatus), Integer(SystemStatus), 0 ); SystemStatus.DataContext := nil; LParam(SystemStatus) := 0; except end; end; end; Can anyone advise as to why this exception is being thrown when calling this function from the thread? I'm sure I'm overlooking something fundamental and simple. Thanks, Duncan

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• At which line in the following code should I commit my unit of work?

  - by Pure.Krome

  I have the following code which is in a transaction. I'm not sure where/when I should be commiting my unit of work. On purpose, I've not mentioned what type of Respoistory i'm using - eg. Linq-To-Sql, Entity Framework 4, NHibernate, etc. If someone knows where, can they please explain WHY they have said, where? (i'm trying to understand the pattern through example(s), as opposed to just getting my code to work). Here's what i've got :- using ( TransactionScope transactionScope = new TransactionScope ( TransactionScopeOption.RequiresNew, new TransactionOptions { IsolationLevel = IsolationLevel.ReadUncommitted } ) ) { _logEntryRepository.InsertOrUpdate(logEntry); //_unitOfWork.Commit(); // Here, commit #1 ? // Now, if this log entry was a NewConnection or an LostConnection, // then we need to make sure we update the ConnectedClients. if (logEntry.EventType == EventType.NewConnection) { _connectedClientRepository.Insert( new ConnectedClient { LogEntryId = logEntry.LogEntryId }); //_unitOfWork.Commit(); // Here, commit #2 ? } // A (PB) BanKick does _NOT_ register a lost connection, // so we need to make sure we handle those scenario's as a LostConnection. if (logEntry.EventType == EventType.LostConnection || logEntry.EventType == EventType.BanKick) { _connectedClientRepository.Delete( logEntry.ClientName, logEntry.ClientIpAndPort); //_unitOfWork.Commit(); // Here, commit #3 ? } _unitOfWork.Commit(); // Here, commit #4 ? transactionScope.Complete(); }

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• How can I make a family of singletons?

  - by Jay

  I want to create a set of classes that share a lot of common behavior. Of course in OOP when you think that you automatically think "abstract class with subclasses". But among the things I want these classes to do is to each have a static list of instances of the class. The list should function as sort of a singleton within the class. I mean each of the sub-classes has a singleton, not that they share one. "Singleton" to that subclass, not a true singleton. But if it's a static, how can I inherit it? Of course code like this won't work: public abstract A { static List<A> myList; public static List getList() { if (myList==null) myList=new ArrayList<A>(10); return myList; } public static A getSomethingFromList() { List listInstance=getList(); ... do stuff with list ... } public int getSomethingFromA() { ... regular code acting against current instance ... } } public class A1 extends A { ... } public class A2 extends A { ... } A1 somethingfromA1List=(A1) A1.getSomethingFromList(); A2 somethingfromA2List=(A2) A2.getSomethingFromList(); The contents of the list for each subclass would be different, but all the code to work on the lists would be the same. The problem with the above code is that I'd only have one list for all the subclasses, and I want one for each. Yes, I could replicate the code to declare the static list in each of the subclasses, but then I'd also have to replicate all the code that adds to the lists and searches the list, etc, which rather defeats the purpose of subclassing. Any ideas on how to do this without replicating code?

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• When NOT TO USE 'this' keyword?

  - by LifeH2O

  Sorry for asking it again, there are already 3 questions about this keyword. But all of them tell the purpose of 'this'. My question is when not to use 'this' keyword . OR Is it all right to use this keyword always in situation like the code class RssReader { private XmlTextReader _rssReader; private XmlDocument _rssDoc; private XmlNodeList _xn; protected XmlNodeList Item { get { return _xn; } } public int Count { get { return _count; } } public bool FetchFeed(String url) { this._rssReader = new XmlTextReader(url); this._rssDoc = new XmlDocument(); _rssDoc.Load(_rssReader); _xn = _rssDoc.SelectNodes("/rss/channel/item"); _count = _xn.Count; return true; } } here i have not used 'this' with "_xn" and "_count" also not with "_rssDoc.Load(_rssReader);" is it fine? Should i use "this" with all occurrences of class variables within the class?

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• Fastest inline-assembly spinlock

  - by sigvardsen

  I'm writing a multithreaded application in c++, where performance is critical. I need to use a lot of locking while copying small structures between threads, for this I have chosen to use spinlocks. I have done some research and speed testing on this and I found that most implementations are roughly equally fast: Microsofts CRITICAL_SECTION, with SpinCount set to 1000, scores about 140 time units Implementing this algorithm with Microsofts InterlockedCompareExchange scores about 95 time units Ive also tried to use some inline assembly with __asm {} using something like this code and it scores about 70 time units, but I am not sure that a proper memory barrier has been created. Edit: The times given here are the time it takes for 2 threads to lock and unlock the spinlock 1,000,000 times. I know this isn't a lot of difference but as a spinlock is a heavily used object, one would think that programmers would have agreed on the fastest possible way to make a spinlock. Googling it leads to many different approaches however. I would think this aforementioned method would be the fastest if implemented using inline assembly and using the instruction CMPXCHG8B instead of comparing 32bit registers. Furthermore memory barriers must be taken into account, this could be done by LOCK CMPXHG8B (I think?), which guarantees "exclusive rights" to the shared memory between cores. At last [some suggests] that for busy waits should be accompanied by NOP:REP that would enable Hyper-threading processors to switch to another thread, but I am not sure whether this is true or not? From my performance-test of different spinlocks, it is seen that there is not much difference, but for purely academic purpose I would like to know which one is fastest. However as I have extremely limited experience in the assembly-language and with memory barriers, I would be happy if someone could write the assembly code for the last example I provided with LOCK CMPXCHG8B and proper memory barriers in the following template: __asm { spin_lock: ;locking code. spin_unlock: ;unlocking code. }

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• In App Purchase Unique Identifying Data

  - by dageshi

  O.K so I'm writing a iPhone travel guide, you purchase a subscription to a travel guide for 3 months, it downloads a fairly hefty database and for 3 months that database gets updated weekly with new stuff. Now what I'd like to do is make the user enter their email address as a one off action before they purchase their first guide, for China say. The purpose for doing this is 1) To allow me to contact the user by email when they add a note/tip for a particular place (the app will allow them to send notes & information to me) 2) To Uniquely identify who has purchased the subscription so that if they wipe their device and reinstall the app they can plug the email address in and pickup their subscriptions again. Or so they can use the same subscription on another device they own. My concerns are 1) Will Apple allow the email method of restoring functionality to a second or restored device? 2) As long as I tell the user what I'm using their email address for (aka I won't sell it to anyone else and use it for X purposes) will it be o.k to ask for said email address? And as a side note, can I tack the devices unique id onto my server comms to track devices or is apple going to through a hissy fit about that as well?

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• __toString magic and type coercion

  - by TomcatExodus

  I've created a Template class for managing views and their associated data. It implements Iterator and ArrayAccess, and permits "sub-templates" for easy usage like so: <p><?php echo $template['foo']; ?></p> <?php foreach($template->post as $post): ?> <p><?php echo $post['bar']; ?></p> <?php endforeach; ?> Anyways, rather than using inline core functions, such as hash() or date(), I figured it would be useful to create a class called TemplateData, which would act as a wrapper for any data stored in the templates. This way, I can add a list of common methods for formatting, for example: echo $template['foo']->asCase('upper'); echo $template['bar']->asDate('H:i:s'); //etc.. When a value is set via $template['foo'] = 'bar'; in the controllers, the value of 'bar' is stored in it's own TemplateData object. I've used the magic __toString() so when you echo a TemplateData object, it casts to (string) and dumps it's value. However, despite the mantra controllers and views should not modify data, whenever I do something like this: $template['foo'] = 1; echo $template['foo'] + 1; //exception It dies on a Object of class TemplateData could not be converted to int; Unless I recast $template['foo'] to a string: echo ((string) $template['foo']) + 1; //outputs 2 Sort of defeats the purpose having to jump through that hoop. Are there any workarounds for this sort of behavior that exist, or should I just take this as it is, an incidental prevention of data modification in views?

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• Controller changes format on variables when publishing

  - by Christoffer

  I am a newbie to ROR but catching on quickly. I have been working on this problem for a couple of hours now and it seems like a bug. I does not make any sense. I have a database with the following migration: class CreateWebsites < ActiveRecord::Migration def self.up create_table :websites do |t| t.string :name t.integer :estimated_value t.string :webhost t.string :purpose t.string :description t.string :tagline t.string :url t.integer :adsense t.integer :tradedoubler t.integer :affiliator t.integer :adsense_cpm t.boolean :released t.string :empire_type t.string :oldid t.string :old_outlink_policy t.string :old_inlink_policy t.string :old_priority t.string :old_profitability t.integer :priority_id t.integer :project_id t.integer :outlink_policy_id t.integer :inlink_policy_id t.timestamps end end def self.down drop_table :websites end end I have verified that what is created in the database also is integers, strings etc according to this migration. I have not touched the controller after generating it through scaffold, i.e. it is the standard controller with show, index etc. Now. When I enter data into the database, either through the web form, in rails console or directly in the database - such as www.domain.com for url or 500 for adsense - it will be created in the db without problem. However, when it is being published on the website the variables go completely nuts. Adsense (integer) turns into date, url (string) turns into a float, and so on. This only happens to a few of the variables. This will also create a problem with "argument out of range" since I input 500 and Rails will try to output it as date = crash and "argument out of range". So, how do I fix/trouble shoot this? Why do the formats change? Could it be because of the respond_to in the controller? Cheers, Christoffer

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