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• Using ARIMA to model and forecast stock prices using user-friendly stats program

  - by Brian

  Hi people, Can anyone please offer some insight into this for me? I'm coming from a functional magnetic resonance imaging research background where I analyzed a lot of time series data, and I'd like to analyze the time series of stock prices (or returns) by: 1) modeling a successful stock in a particular market sector and then cross-correlating the time series of this historically successful stock with that of other newer stocks to look for significant relationships; 2) model a stock's price time series and use forecasting (e.g., exponential smoothing) to predict future values of it. I'd like to use non-linear modeling methods (ARIMA and ARCH) to do this. Several questions: How often do ARIMA and ARCH modeling methods (given that the individual who implements them does so accurately) actually fit the stock time series data they target, and what is the optimal fit I can expect? Is the extent to which this model fits the data commensurate with the extent to which it predicts this stock time series' future values? Rather than randomly selecting stocks to compare or model, if profit is my goal, what is an efficient approach, if any, to selecting the stocks I'm going to analyze? Which stats program is the most user-friendly for this? Any thoughts on this would be great and would go a long way for me. Thanks, Brian

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• How to use DLL reference with an ActiveX <object> via JavaScript

  - by John Factorial

  My question: how can I set an ActiveX object's property via JavaScript to an enum value found in a non-ActiveX DLL? Problem description: I am instantiating an ActiveX object with the following object tag: <object classid="clsid:F338193D-2491-4D7B-80CE-03487041A278" id="VideoCapture1" width="500" height="500"></object> (This is the guid for the 3rd party ActiveX I'm using, "VisioForge_Video_Capture_4.VFVideoCapture4X") I have example C# code for using this ActiveX, which I am porting to JavaScript. Code like this works just fine: VideoCapture1.Debug_Mode = true; var devcount = VideoCapture1.Video_CaptureDevices_GetCount(); var devs = []; for (var i =0; i < devcount; ++i) { devs[devs.length] = VideoCapture1.Video_CaptureDevices_GetItem(i); } ... etc ... However, VideoCapture1 has some settings which refer to a DLL enum, like so (C# code): VideoCapture1.Mode = VisioForge_Video_Capture_4.TxVFMode.Mode_Video_Preview; I can see in Visual Web Developer that TxVFMode.Mode_Video_Preview is value 1 in the enum. However, the following JS does not appear to set the Mode properly: VideoCapture1.Mode = 1; Does anyone know how I can set VideoCapture1.Mode to the enum value found in the TxVFMode? PS: In Visual Web Developer, when I "Go to definition" on TxVFMode, I get the Guid for the enum. I thought I could create an with this Guid or instantiate a VisioForge_Video_Capture_4.TxVFMode in JS, but neither gives me a usable object.

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• Pass Variable to Java Method from an Ant Target

  - by user200317

  At the moment I have a .properties file to store settings related to the framework. Example: default.auth.url=http://someserver-at008:8080/ default.screenshots=false default.dumpHTML=false And I have written a class to extract those values and here is the method of that class. public static String getResourceAsStream(String defaultProp) { String defaultPropValue = null; //String keys = null; try { InputStream inputStream = SeleniumDefaultProperties.class.getClassLoader().getResourceAsStream(PROP_FILE); Properties properties = new Properties(); //load the input stream using properties. properties.load(inputStream); defaultPropValue = properties.getProperty(defaultProp); }catch (IOException e) { log.error("Something wrong with .properties file, check the location.", e); } return defaultPropValue; } Throughout the application I use method like follows to just exact property needed, public String getBrowserDefaultCommand() { String bcmd = SeleniumDefaultProperties.getResourceAsStream("default.browser.command"); if(bcmd.equals("")) handleMissingConfigProperties(SeleniumDefaultProperties.getResourceAsStream("default.browser.command")); return bcmd; } But I have not decided do a change to this and use ant and pass a parameter instead of using it from .properties file. I was wondering how could I pass a value to a Java Method using ANT. Non of these classes have Main methods and will not have any main. Due to this I was unable to use it as a java system properties. Thanks in advance.

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• Axis2 Webservice -> php

  - by Peter Hagström

  Hi! If I have understood Axis2 correct i can construct a WebService and then access it with any SOAP compatible client. I have a java class with a couple of methods that I have written in Eclipse, and then automatically constructed a service with the Axis2 plugin from WTP. This is the methods of my class. public int test(int i){ return i+2; } public Car CarTest(int speed){ return new Car("Biltest", speed); } public CarFactoryAdapter getCarFactory(){ carFact.getCars().add(new Car("Bmw", 250)); carFact.getCars().add(new Car("seat", 350)); carFact.getCars().add(new Car("saab", 150)); carFact.getCars().add(new Car("volv", 50)); return new CarFactoryAdapter(carFact); } The code seems to work when I try it with soapUI and the Axis2-web interface has recognized the methods of my service. But when Iam trying the methods that receives parameters with PHP´s built in soapClient i get a Unknown exception. The getCarFactory methods works at least as expected, but it seems kind of crippled if I can´t send parameters. Example of non working method invocation. ini_set('soap.wsdl_cache_ttl',0); $client = new SoapClient("http://192.168.128.162:8080/ComplexWebService/services/CarService?wsdl", array('soap_version' => SOAP_1_2, 'trace' => 1)); $ar['i'] = (int)100; print_r($client->__soapCall("test",$ar)); I need to make sure that the SOA framework i choose will be able to comunicate with many platforms, there will be clients in at least PHP and Java, but it would be good if it will work in for example .NET to.

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• Is there a good way to QuickCheck Happstack.State methods?

  - by Paul Kuliniewicz

  I have a set of Happstack.State MACID methods that I want to test using QuickCheck, but I'm having trouble figuring out the most elegant way to accomplish that. The problems I'm running into are: The only way to evaluate an Ev monad computation is in the IO monad via query or update. There's no way to create a purely in-memory MACID store; this is by design. Therefore, running things in the IO monad means there are temporary files to clean up after each test. There's no way to initialize a new MACID store except with the initialValue for the state; it can't be generated via Arbitrary unless I expose an access method that replaces the state wholesale. Working around all of the above means writing methods that only use features of MonadReader or MonadState (and running the test inside Reader or State instead of Ev. This means forgoing the use of getRandom or getEventClockTime and the like inside the method definitions. The only options I can see are: Run the methods in a throw-away on-disk MACID store, cleaning up after each test and settling for starting from initialValue each time. Write the methods to have most of the code run in a MonadReader or MonadState (which is more easily testable), and rely on a small amount of non-QuickCheck-able glue around it that calls getRandom or getEventClockTime as necessary. Is there a better solution that I'm overlooking?

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• How do you read a file line by line in your language of choice?

  - by Jon Ericson

  I got inspired to try out Haskell again based on a recent answer. My big block is that reading a file line by line (a task made simple in languages such as Perl) seems complicated in a functional language. How do you read a file line by line in your favorite language? So that we are comparing apples to other types of apples, please write a program that numbers the lines of the input file. So if your input is: Line the first. Next line. End of communication. The output would look like: 1 Line the first. 2 Next line. 3 End of communication. I will post my Haskell program as an example. Ken commented that this question does not specify how errors should be handled. I'm not overly concerned about it because: Most answers did the obvious thing and read from stdin and wrote to stdout. The nice thing is that it puts the onus on the user to redirect those streams the way they want. So if stdin is redirected from a non-existent file, the shell will take care of reporting the error, for instance. The question is more aimed at how a language does IO than how it handles exceptions. But if necessary error handling is missing in an answer, feel free to either edit the code to fix it or make a note in the comments.

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• Two divs with wrapping text sharing the same line

  - by Jerad Rose

  Simple problem - How do I get these two divs to share the same line: <div style="width: 200px; padding: 0; background-color: #f00; float: left; display: inline; ">Lorem ipsum dolor sit</div> <div style="margin-left: 200px; padding: 0; background-color: #0f0; float: right; display: inline; ">Cum sociis natoque penatibus et magnis dis parturient montes, nascetur ridiculus mus. Duis interdum leo nec purus eleifend ut laoreet metus varius. Praesent lobortis risus sem. Duis gravida risus convallis purus dapibus fermentum. Nulla nec arcu pellentesque justo hendrerit pulvinar id ac velit. Nulla cursus volutpat risus, id volutpat metus tempus eget. Morbi rhoncus, diam sed vestibulum elementum, odio nulla faucibus ligula, ut dapibus lorem nunc vitae purus. Nam commodo iaculis ultricies. Etiam in velit dolor, vel convallis tellus. Aliquam tincidunt, erat ac dictum varius, sapien mi faucibus est, sit amet venenatis nisl massa non turpis. Donec eget libero mauris. Cras ac magna est, id hendrerit est.</div> Thanks in advance.

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• GUI toolkit for Unicode text app?

  - by wrp

  In developing a tool for processing text in exotic scripts, I'm having trouble choosing a GUI toolkit. The main part of the interface is to be a text editor, not much more elaborate than Notepad, but with its own input method editor. It is to be extensible in a scripting language so that non-programmers can develop their own input methods and display routines. It will be assumed that all files are UTF-8. More elaborate support like regexes is not needed. The main sticking points are: characters beyond the Basic Multilingual Plane right-to-left and bi-directional text extension in a scripting language cross-platform Linux/Windows/OS X My first choice was Tcl/Tk, but it lacks bidi and going beyond the BMP seems dodgy. At the other extreme, I've considered Qt with embedded ECMAScript, but that might be heavier and less malleable than I would like. I'm even thinking about making it browser based, but I'm concerned that the IM for large scripts would be too heavy for client-side processing. I've also looked at a few similar projects in Java, but the quality of the font rendering in SWING has been unacceptable. What are your experiences in handling Unicode with various toolkits? Are there other serious issues I haven't considered? What would you recommend for doing this in the lightest way?

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• What's wrong with debugging in Eclipse on Android?

  - by Sebastian Dwornik

  I've obviously been spoiled by Visual Studio, because although I'm just learning Android and the Eclipse environment, debugging apps in Eclipse is becoming a serious detriment to further development. For example, Eclipse will compile this divide by zero just fine: public class Lesson2Main extends Activity { /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate (savedInstanceState); int i = 1 / 0; TextView tv = new TextView (this); tv.setText ("Hello, Android!"); setContentView (tv); } } And then, when it executes it under the debugger, I will get a full screen of useless debug info, non of which actually points me to the specific line containing the error. The stackTrace is null within the exception ('e') info tree, and it simply states a message stating 'ArithmeticException'. (that's nice, how about you point me in the direction of where you found it!?) I've looked all over the screen and am baffled that this IDE can't get this right. Does developing with Eclipse resort everyone back to 1991 with printf() like logging at every interval then to track down bugs? Seriously. Is there a configuration or plug-in that I'm missing to help with this? I haven't tested this case with XCode, but if the iPhone dev. IDE handles this more like Visual Studio, then no wonder the Android marketplace has so few apps. I'm excited about Android, but it seems that Eclipse is getting in the way.

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• KeyUp processed for wrong control

  - by Mikael

  I have made a simple test application for the issue, two winforms each containing a button. The button on the first form opens the other form when clicked. It also subscribes to keyup events. The second form has its button set as "AcceptButton" and in the Clicked event we sleep for 1s and then set DialogResult to true (the sleep is to simulate some processing done) When enter is used to close this second form the KeyUp event of the button on the first form is triggered, even though the key was released well before the second had passed so the second form was still shown and focused. If any key other then enter is pressed in the second form the event is not triggered for the button on the first form. First form: public Form1() { InitializeComponent(); buttonForm2.KeyUp += new KeyEventHandler(cntKeyUp); } void cntKeyUp(object sender, KeyEventArgs e) { MessageBox.Show(e.KeyCode.ToString()); } private void buttonForm2_Click(object sender, EventArgs e) { using (Form2 f = new Form2()) { f.ShowDialog(); } } Second form: private void button1_Click(object sender, EventArgs e) { Thread.Sleep(1000); this.DialogResult = DialogResult.OK; } Does anyone know why the event is triggered for the button on the non active form and what can be done to stop this from happening?

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• I Need a Human Readable, Yet Parse-able Document Format

  - by macinjosh

  I'm working on one of those projects where there are a million better ways to accomplish what I need but I have no choice and I have to do it this way. Here it is: There is a web form, when the user fills it out and hits a submit a human readable text file is created using the form data. It looks like this: field_1: value for field one field_2: value for field two more data for field two (field two has a newline in it!) field3: some more data My problem is this: I need to parse this text file back into the web form so that the user can edit it. How could I, in a foolproof way, accomplish this? A database is not an option, I have to use these text files. My Questions: Is there a foolproof way to do this using the format in the example above? What human readable format would work better (in other words I can change the format) Human readable means that a non programmer could read it and know what is what. This project uses PHP.

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• Auto-resolving a hostname in WCF Metadata Publishing

  - by Mike C

  I am running a self-hosted WCF service. In the service configuration, I am using localhost in my BaseAddresses that I hook my endpoints to. When trying to connect to an endpoint using the WCF test client, I have no problem connecting to the endpoint and getting the metadata using the machine's name. The problem that I run into is that the client that is generated from metadata uses localhost in the endpoint URLs it wants to connect to. I'm assuming that this is because localhost is the endpoint URL published by metadata. As a result, any calls to the methods on the service will fail since localhost on the calling machine isn't running the service. What I would like to figure out is if it is possible for the service metadata to publish the proper URL to a client depending on the client who is calling it. For example, if I was requesting the service metadata from a machine on the same network as the server the endpoint should be net.tcp://MYSERVER:1234/MyEndpoint. If I was requesting it from a machine outside the network, the URL should be net.tcp://MYSERVER.mydomain.com:1234/MyEndpoint. And obviously if the client was on the same machine, THEN the URL could be net.tcp://localhost:1234/MyEndpoint. Is this just a flaw in the default IMetadataExchange contract? Is there some reason the metadata needs to publish the information in a non-contextual way? Is there another way I should be configuring my BaseAddresses in order to get the functionality I want? Thanks, Mike

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• can't increment Glib::ustring::iterator (getting "invalid lvalue in increment" compiler error)

  - by davka

  in the following code: int utf8len(char* s, int len) { Glib::ustring::iterator p( string::iterator(s) ); Glib::ustring::iterator e ( string::iterator(s+len) ); int i=0; for (; p != e; p++) // ERROR HERE! i++; return i; } I get the compiler error on the for line, which is sometimes "invalid lvalue in increment", and sometimes "ISO C++ forbids incrementing a pointer of type etc... ". Yet, the follwing code: int utf8len(char* s) { Glib::ustring us(s); int i=0; for (Glib::ustring::iterator p = us.begin(); p != us.end(); p++) i++; return i; } compiles and works fine. according the Glib::ustring documentation and the include file, ustring iterator can be constructed from std::string iterator, and has operator++() defined. Weird? BONUS QUESTION :) Is there a difference in C++ between the 2 ways of defining a variable: classname ob1( initval ); classname ob1 = initval; I believed that they are synonymous; yet, if I change Glib::ustring::iterator p( string::iterator(s) ); to Glib::ustring::iterator p = string::iterator(s); I get a compiler error (gcc 4.1.2) conversion from ‘__gnu_cxx::__normal_iterator, std::allocator ’ to non-scalar type ‘Glib::ustring_Iterator<__gnu_cxx::__normal_iterator, std::allocator ’ requesed thanks a lot!

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• How to create a fully lazy singleton for generics

  - by Brendan Vogt

  I have the following code implementation of my generic singleton provider: public sealed class Singleton<T> where T : class, new() { Singleton() { } public static T Instance { get { return SingletonCreator.instance; } } class SingletonCreator { static SingletonCreator() { } internal static readonly T instance = new T(); } } This sample was taken from 2 articles and I merged the code to get me what I wanted: http://www.yoda.arachsys.com/csharp/singleton.html and http://www.codeproject.com/Articles/11111/Generic-Singleton-Provider. This is how I tried to use the code above: public class MyClass { public static IMyInterface Initialize() { if (Singleton<IMyInterface>.Instance == null // Error 1 { Singleton<IMyInterface>.Instance = CreateEngineInstance(); // Error 2 Singleton<IMyInterface>.Instance.Initialize(); } return Singleton<IMyInterface>.Instance; } } And the interface: public interface IMyInterface { } The error at Error 1 is: 'MyProject.IMyInterace' must be a non-abstract type with a public parameterless constructor in order to use it as parameter 'T' in the generic type or method 'MyProject.Singleton<T>' The error at Error 2 is: Property or indexer 'MyProject.Singleton<MyProject.IMyInterface>.Instance' cannot be assigned to -- it is read only How can I fix this so that it is in line with the 2 articles mentioned above? Any other ideas or suggestions are appreciated.

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• Module based web project directory layout with git and symlinks

  - by karlthorwald

  I am planning my directory structure for a linux/apache/php web project like this: Only www.example.com/webroot/ will be exposed in apache www.example.com/ webroot/ index.php module1/ module2/ modules/ module1/ module1.class.php module1.js module2/ module2.class.php module2.css lib/ lib1/ lib1.class.php the modules/ and lib/ directory will only be in the php path. To make the css and js files visible in the webroot directory I am planning to use symlinks. webroot/ index.php module1/ module1.js (symlinked) module2/ module2.css (symlinked) I tried following these principles: layout by modules and libraries, not by file type and not by "public' or 'non public', index.php is an exception. This is for easier development. symlinking files that need to be public for the modules and libs to a public location, but still mirroring the layout. So the module structure is also visible in the resulting html code in the links, which might help development. How will git handle the symlinking of the single files correctly, is there something to consider? When it comes to images I will need to link directories, how to handle that with git? modules/ module3/ module3.class.php img/ img1.jpg img2.jpg img3.jpg They should be linked here: webroot/ module3/ img/ (symlinked ?) So this is a git and symlink question. But I would be interested to hear comments about the php layout, maybe you want to use the comment function for this.

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• archiving strategies and limitations of data in a table

  - by Samuel

  Environment: Jboss, Mysql, JPA, Hibernate Our web application will be catering to a large amount of users (~ 1,000,000) and there are a lots of child table where user specific data are stored (e.g. personal, health, forum contributions ...). What would be the best practice to archive user & user specific information. [a] Would it be wise to move the archived user & user specific information to their respective tables within the same database (e.g. user_archive, user_forum_comments_archive ...) OR [b] Would you just mark the database entries with a flag in the original table(s) and just query only non archived entries. We have a unique constraint on User.loginid, how do you handle this requirement if the users are archived via 1-[a] (i.e if a user with loginid 'samuel' gets moved into the archive table and if a new user gets added with the same name in the original table, how would you prevent this. What would be the best strategy to address the unique key constraints. We have a requirement to selectively archive records and bring it back if necessary, will you rely on database tools are would you handle this via your persistence APIs exposed by the JPA entity model.

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• casting Collection<SomeClass> to Collection<SomeSuperClass>

  - by skrebbel

  Hi all, I'm sure this has been answered before, but I really cannot find it. I have a java class SomeClass and an abstract class SomeSuperClass. SomeClass extends SomeSuperClass. Another abstract method has a method that returns a Collection<SomeSuperClass>. In an implementation class, I have a Collection<SomeClass> myCollection I understand that I cannot just return myCollection, because Collection<SomeClass> does not inherit from Collection<SomeSuperClass>. Nevertheless, I know that everything in myCollection is a SomeSuperClass because after all, they're SomeClass objects which extend SomeSuperClass. How can I make this work? I.e. I want public class A { private Collection<SomeClass> myCollection; public Collection<SomeSuperClass> getCollection() { return myCollection; //compile error! } } The only way I've found is casting via a non-generic type and getting unchecked warnings and whatnot. There must be a more elegant way, though? I feel that also using Collections.checkedSet() and friends are not needed, since it is statically certain that the returned collection only contains SomeClass objects (this would not be the case when downcasting instead of upcasting, but that's not what I'm doing). What am I missing? Thanks!

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• My Thread Programs Block

  - by user315378

  I wrote a program that worked as a server. Knowing that "accept" was blocking the program. I wanted to launch a thread with this statement to prevent precisely that the program crashes, but this still happens. Can anybody help? Post code Thanks -(IBAction)Connetti{ if(switchConnessione.on){ int port = [fieldPort.text intValue]; labelStatus.text = [[NSString alloc] initWithFormat:@"Il Server è attivo"]; server_len = sizeof(server); server.sin_family = AF_INET; server.sin_port = htons((u_short)port); server.sin_addr.s_addr = INADDR_ANY; sd = socket (AF_INET, SOCK_STREAM, 0); bind(sd, (struct sockaddr*)&server, sizeof(server)); listen(sd, 1); [NSThread detachNewThreadSelector:@selector(startThreadAccept) toTarget:self withObject:nil]; } else { labelStatus.text = [[NSString alloc] initWithFormat:@"Server non attivo"]; switchChat.on = FALSE; switchChat.enabled = FALSE; } } -(void)startThreadAccept{ NSAutoreleasePool *pool = [[NSAutoreleasePool alloc]init]; [self performSelectorOnMainThread:@selector(acceptConnection) withObject:nil waitUntilDone:NO]; [pool release]; } -(void)acceptConnection{ new_sd = accept(sd, (struct sockaddr*)&server, &server_len); labelStatus.text = [[NSString alloc] initWithFormat:@"Ho accettato una connessione:%d", new_sd]; switchChat.enabled = TRUE; }

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• How to parse rss from a php page, using jQuery/jFeed?

  - by ricebowl

  I'm trying to fumble my way through parsing rss sensibly, using jQuery and jFeed. Because of the same origin policy I'm pulling the BBC's health news feed into a local page (http://www.davidrhysthomas.co.uk/play/proxy.php). Originally this was just the same proxy.php script as available in the jFeed download package, but due to my host's disabling allow_url_fopen() I've amended the php to the following: $url = "http://newsrss.bbc.co.uk/rss/newsonline_uk_edition/health/rss.xml"; $ch = curl_init(); curl_setopt($ch, CURLOPT_URL, $url); curl_setopt($ch, CURLOPT_HEADER, 0); curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1); $data = curl_exec($ch); echo "$data"; curl_close($ch); Which seems to generate the same/comparable contents as the original fopen on my local machine. Now that seems to be working, I'm looking at setting the jFeed script up to work with the page and, to my embarrassment, don't see how. I understand that, at the least, this should work: jQuery.getFeed({ url: 'http://www.davidrhysthomas.co.uk/play/proxy.php', success: function(feed) { alert(feed.title); } }); ...but, as I'm sure you anticipate, it doesn't. What non-output there is, is available for your perusal here: http://www.davidrhysthomas.co.uk/play/exampleTest.html. And I honestly don't have a clue what to do about it. If anyone could offer some pointers, tips, hints, or, at a pinch, a quick slap around the cheeks and a 'pull yourself together!' it'd be much appreciated... Thanks in advance =)

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• How large a role does subjectiveness play in programming?

  - by Bob

  I often read about the importance of readability and maintainability. Or, I read very strong opinions about which syntax features are bad or good. Or discussions about the values of certain paradigms, like OOP. Aside from that, this same question floats about in my mind whenever I read debates on SO or Meta about subjective questions. Or read questions about best practices and sometimes find myself or others disagreeing. What role does subjectiveness play within the programming realm? Sometimes I think it plays a large role. Software developers are engineers in a way, but also people. A large part of programming is dealing with code that's human readable. This is very different from Math or Physics or other disciplines with very exact and structured rules. Here the exact structure and rules are largely up in the air, changeable on a whim, and hence the amount of languages in existence. And one person may find one language very readable, and another person may find their own language the most comforting. The same with practices. One person may not like certain accepted practices. I myself find splitting classes into different files very unreadable, for instance. But, I can't say rules haven't helped in general. Certain practices have and do make life easier. And new languages have given rise to syntax and structure that make life easier. There's certainly been a progression towards code that is easier to read and maintain even given a largely diverse group of people. So maybe these things aren't as subjective as I thought. It reminds me, in a way, of UI design. Certainly it's subjective, but then there's an entire discipline involved in crafting good UI and it tends to work. Is there something non-subjective about the ideas behind maintainability, readability, and other best practices? Is there something tangible to grasp when one develops a new language or thinks of new practices?

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• Why boost property tree write_json saves everything as string? Is it possible to change that?

  - by pprzemek

  I'm trying to serialize using boost property tree write_json, it saves everything as strings, it's not that data are wrong, but I need to cast them explicitly every time and I want to use them somewhere else. (like in python or other C++ json (non boost) library) here is some sample code and what I get depending on locale: boost::property_tree::ptree root, arr, elem1, elem2; elem1.put<int>("key0", 0); elem1.put<bool>("key1", true); elem2.put<float>("key2", 2.2f); elem2.put<double>("key3", 3.3); arr.push_back( std::make_pair("", elem1) ); arr.push_back( std::make_pair("", elem2) ); root.put_child("path1.path2", arr); std::stringstream ss; write_json(ss, root); std::string my_string_to_send_somewhare_else = ss.str(); and my_string_to_send_somewhere_else is sth. like this: { "path1" : { "path2" : [ { "key0" : "0", "key1" : "true" }, { "key2" : "2.2", "key3" : "3.3" } ] } } Is there anyway to save them as the values, like: "key1" : true or "key2" : 2.2 ?

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• Performance question: Inverting an array of pointers in-place vs array of values

  - by Anders

  The background for asking this question is that I am solving a linearized equation system (Ax=b), where A is a matrix (typically of dimension less than 100x100) and x and b are vectors. I am using a direct method, meaning that I first invert A, then find the solution by x=A^(-1)b. This step is repated in an iterative process until convergence. The way I'm doing it now, using a matrix library (MTL4): For every iteration I copy all coeffiecients of A (values) in to the matrix object, then invert. This the easiest and safest option. Using an array of pointers instead: For my particular case, the coefficients of A happen to be updated between each iteration. These coefficients are stored in different variables (some are arrays, some are not). Would there be a potential for performance gain if I set up A as an array containing pointers to these coefficient variables, then inverting A in-place? The nice thing about the last option is that once I have set up the pointers in A before the first iteration, I would not need to copy any values between successive iterations. The values which are pointed to in A would automatically be updated between iterations. So the performance question boils down to this, as I see it: - The matrix inversion process takes roughly the same amount of time, assuming de-referencing of pointers is non-expensive. - The array of pointers does not need the extra memory for matrix A containing values. - The array of pointers option does not have to copy all NxN values of A between each iteration. - The values that are pointed to the array of pointers option are generally NOT ordered in memory. Hopefully, all values lie relatively close in memory, but *A[0][1] is generally not next to *A[0][0] etc. Any comments to this? Will the last remark affect performance negatively, thus weighing up for the positive performance effects?

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• unistd.h related problem when compiling bison & flex program under vc++

  - by Eric

  I'm using bison & flex (downloaded via cygwin) with vc++. When I compile the program I got an error: ...: fatal error C1083: Cannot open include file: 'unistd.h': No such file or directory The corresponding code in the flex-generated file is: #ifndef YY_NO_UNISTD_H /* Special case for "unistd.h", since it is non-ANSI. We include it way * down here because we want the user's section 1 to have been scanned first. * The user has a chance to override it with an option. */ /* %if-c-only */ #include <unistd.h> /* %endif */ /* %if-c++-only */ /* %endif */ #endif If I define YY_NO_UNISTD_H in the flex file(.l) this error will disappear, but I get several other errors: ...: error C2447: '{' : missing function header (old-style formal list?) ...: warning C4018: '<' : signed/unsigned mismatch ...: error C3861: 'isatty': identifier not found How can I fix this problem? All these errors occur in the flex-generated scanner. I know it's because unistd.h doesn't exist in windows. Do I have to write my own unistd.h? If so how to write it in order to eliminate those errors?

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• How to use reflection to call a method and pass parameters whose types are unknown at compile time?

  - by MandoMando

  I'd like to call methods of a class dynamically with parameter values that are "parsed" from a string input. For example: I'd like to call the following program with these commands: c:myprog.exe MethodA System.Int32 777 c:myprog.exe MethodA System.float 23.17 c:myprog.exe MethodB System.Int32& 777 c:myprog.exe MethodC System.Int32 777 System.String ThisCanBeDone static void Main(string[] args) { ClassA aa = new ClassA(); System.Type[] types = new Type[args.Length / 2]; object[] ParamArray = new object[types.Length]; for (int i=0; i < types.Length; i++) { types[i] = System.Type.GetType(args[i*2 + 1]); // LINE_X: this will obviously cause runtime error invalid type/casting ParamArray[i] = args[i*2 + 2]; MethodInfo callInfo = aa.GetType().GetMethod(args[0],types); callInfo.Invoke(aa, ParamArray); } // In a non-changeable classlib: public class ClassA { public void MethodA(int i) { Console.Write(i.ToString()); } public void MethodA(float f) { Console.Write(f.ToString()); } public void MethodB(ref int i) { Console.Write(i.ToString()); i++; } public void MethodC(int i, string s) { Console.Write(s + i.ToString()); } public void MethodA(object o) { Console.Write("Argg! Type Trapped!"); } } "LINE_X" in the above code is the sticky part. For one, I have no idea how to assign value to a int or a ref int parameter even after I create it using Activator.CreatInstance or something else. The typeConverter does come to mind, but then that requires an explicit compile type casting as well. Am I looking at CLR with JavaScript glasses or there is way to do this?

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• Business entity: private instance VS single instance

  - by taoufik

  Suppose my WinForms application has a business entity Order, the entity is used in multiple views, each view handles a different domain or use-case in the application. As an example, one managing orders, the other one digging into one order and displaying additional data. If I'd use nHibernate (or any other ORM) and use one session/dataContext per view (or per db action), I'd end up getting two different instances for the same Order (let's say orderId = 1). Although functionally the same entity, they are technically two different instances. Yes, I could implement Equals/GetHashcode to make them "seem" the same. Why would you go for a single instance per entity vs private instances per view or per use-case? Having single instances has the advantage of sharing INotifyPropertyChanged events, and sharing additional (non-persistent) data. Having a private instance in each view would give you the flexibility of the undo functionality on a view level. In the example above, I'd allow the user to change order details, and give them the flexibility to not save the change. Here, synchronisation between the view/use-case happens on a data persistence level. What would your argument be?

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