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  • "Learning" Linux

    - by Strider
    I've been interested in computers for a long time and have fiddled with a lot of stuff which includes Linux. I started out with Red Hat when I was young (around 13) and lost all data, converting a FAT32 drive to something else. Later it was Knoppix which was really helpful in recovery and such. Then, it was Ubuntu. Also, I fiddled with Arch for some time, but, it breaks too often for my liking (maybe, I should have been more careful). Anyway, currently I use Ubuntu 9.04. I want to dig deeper into the Linux world now. I want to learn how things work and use the terminal more. I am a programmer as well, so, it will help a lot. So, the thing I wanted to ask were: Good books to learn and understand Linux Good habits to use Linux more efficiently. Good tools about which I should know. Amount of time you set aside to learn about new things each day. As a programmer, how do you setup and use Linux efficiently. Long list. I will be grateful to the answerers.

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  • Self hosted WCF ServiceHost/WebServiceHost Concurrency/Peformance Design Options (.NET 3.5)

    - by Kyle
    So I'll be providing a few functions via a self hosted (in a WindowsService) WebServiceHost (not sure how to process HTTP GET/POST with ServiceHost), one of which may be called a large amount of the time. This function will also rely on a connection in the appdomain (hosted by the WindowsService so it can stay alive over multiple requests). I have the following concerns and would be oh so thankful for any input/thoughts/comments: Concurrent access - how does the WebServiceHost handle a bunch of concurrent requests. Are they queued and processes sequentially or are new instances of the contracts automagically created? WebServiceHost - WindowsService communication - I need some form of communication from the WebServiceHost to the hosting WindowsService for things like requesting a new session if one does not exist. Perhaps implementing a class which extends the WebServiceHost with events which the WindowsService subscribes to... (unless there is another way I can set off an event in the WindowsService when a request is made...) Multiple WebServiceHosts or Contracts - Would it give any real performance gain to be running multiple WebServiceHost instances in different threads (one per endpoint perhaps?) - A better understanding of the first point would probably help here. WSDL - I'm not sure why (probably just need to do more reading), but I'm not sure how to get the WebServiceHost base endpoint to respond with a WDSL document describing the available contract. Not required as all the operations will be done via GET requests which will not likely change, but it would be nice to have... That's about it for the moment ;) I've been reading a lot on WCF and wish I'd gotten into it long ago, but definitely still learning.

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  • Metaprogramming - self explanatory code - tutorials, articles, books

    - by elena
    Hello everybody, I am looking into improving my programming skils (actually I try to do my best to suck less each year, as our Jeff Atwood put it), so I was thinking into reading stuff about metaprogramming and self explanatory code. I am looking for something like an idiot's guide to this (free books for download, online resources). Also I want more than your average wiki page and also something language agnostic or preferably with Java examples. Do you know of such resources that will allow to efficiently put all of it into practice (I know experience has a lot to say in all of this but i kind of want to build experience avoiding the flow bad decisions - experience - good decisions)? EDIT: Something of the likes of this example from the Pragmatic Programmer: ...implement a mini-language to control a simple drawing package... The language consists of single-letter commands. Some commands are followed by a single number. For example, the following input would draw a rectangle: P 2 # select pen 2 D # pen down W 2 # draw west 2cm N 1 # then north 1 E 2 # then east 2 S 1 # then back south U # pen up Thank you!

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  • SQLite self-join performance

    - by Derk
    What I essentially want, is to retreive all features and values of products which have a particular feature and value. For example: I want to know all available hard drive sizes of products that have an Intel processor. I have three tables: product_to_value (product_id, feature_id, value_id) features (id, value) // for example Processor family, Storage size, etc. values (id, value) // for example Intel, 60GB, etc The simplified query I have now: SELECT features.name, featurevalues.name, featurevalues.value FROM products, products as prod2, features, features as feat2, values, values as val2 WHERE products.feature = features.id AND products.value = values.id AND products.product = prod2.product AND prod2.feature_id = feat2.id AND prod2.value_id = val2.id AND features.id = ? AND feat2.id = ? All columns have an index. I am using SQLite. The problem is that it's very slow (70ms per query, without the self-join it's <1ms). Is there a smarter way to fetch data like this? Or is this too much to ask from SQLite? I personally think I am simply overlooking something, as I am quite new to SQLite.

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  • wxPthon problems with Wrapping StaticText

    - by Scott B
    Hello. I am having an issue with wxPython. A simplified version of the code is posted below (white space, comments, etc removed to reduce size - but the general format to my program is kept roughly the same). When I run the script, the static text correctly wraps as it should, but the other items in the panel do not move down (they act as if the statictext is only one line and thus not everything is visible). If I manually resize the window/frame, even just a tiny amount, everything gets corrected and displays as it is should. I took screen shots to show this behavior, but I just created this account and thus don't have the required 10 reputation points to be allowed to post pictures. Why does it not display correctly to begin with? I've tried all sorts of combination's of GetParent().Refresh() or Update() and GetTopLevelParent().Update() or Refresh(). I've tried everything I can think of but cannot get it to display correctly without manually resizing the frame/window. Once re-sized, it works exactly as I want it to. Information: Windows XP Python 2.5.2 wxPython 2.8.11.0 (msw-unicode) Any suggestions? Thanks! Code: #! /usr/bin/python import wx class StaticWrapText(wx.PyControl): def __init__(self, parent, id=wx.ID_ANY, label='', pos=wx.DefaultPosition, size=wx.DefaultSize, style=wx.NO_BORDER, validator=wx.DefaultValidator, name='StaticWrapText'): wx.PyControl.__init__(self, parent, id, pos, size, style, validator, name) self.statictext = wx.StaticText(self, wx.ID_ANY, label, style=style) self.wraplabel = label #self.wrap() def wrap(self): self.Freeze() self.statictext.SetLabel(self.wraplabel) self.statictext.Wrap(self.GetSize().width) self.Thaw() def DoGetBestSize(self): self.wrap() #print self.statictext.GetSize() self.SetSize(self.statictext.GetSize()) return self.GetSize() class TestPanel(wx.Panel): def __init__(self, *args, **kwargs): # Init the base class wx.Panel.__init__(self, *args, **kwargs) self.createControls() def createControls(self): # --- Panel2 ------------------------------------------------------------- self.Panel2 = wx.Panel(self, -1) msg1 = 'Below is a List of Files to be Processed' staticBox = wx.StaticBox(self.Panel2, label=msg1) Panel2_box1_v1 = wx.StaticBoxSizer(staticBox, wx.VERTICAL) Panel2_box2_h1 = wx.BoxSizer(wx.HORIZONTAL) Panel2_box3_v1 = wx.BoxSizer(wx.VERTICAL) self.wxL_Inputs = wx.ListBox(self.Panel2, wx.ID_ANY, style=wx.LB_EXTENDED) sz = dict(size=(120,-1)) wxB_AddFile = wx.Button(self.Panel2, label='Add File', **sz) wxB_DeleteFile = wx.Button(self.Panel2, label='Delete Selected', **sz) wxB_ClearFiles = wx.Button(self.Panel2, label='Clear All', **sz) Panel2_box3_v1.Add(wxB_AddFile, 0, wx.TOP, 0) Panel2_box3_v1.Add(wxB_DeleteFile, 0, wx.TOP, 0) Panel2_box3_v1.Add(wxB_ClearFiles, 0, wx.TOP, 0) Panel2_box2_h1.Add(self.wxL_Inputs, 1, wx.ALL|wx.EXPAND, 2) Panel2_box2_h1.Add(Panel2_box3_v1, 0, wx.ALL|wx.EXPAND, 2) msg = 'This is a long line of text used to test the autowrapping ' msg += 'static text message. ' msg += 'This is a long line of text used to test the autowrapping ' msg += 'static text message. ' msg += 'This is a long line of text used to test the autowrapping ' msg += 'static text message. ' msg += 'This is a long line of text used to test the autowrapping ' msg += 'static text message. ' staticMsg = StaticWrapText(self.Panel2, label=msg) Panel2_box1_v1.Add(staticMsg, 0, wx.ALL|wx.EXPAND, 2) Panel2_box1_v1.Add(Panel2_box2_h1, 1, wx.ALL|wx.EXPAND, 0) self.Panel2.SetSizer(Panel2_box1_v1) # --- Combine Everything ------------------------------------------------- final_vbox = wx.BoxSizer(wx.VERTICAL) final_vbox.Add(self.Panel2, 1, wx.ALL|wx.EXPAND, 2) self.SetSizerAndFit(final_vbox) class TestFrame(wx.Frame): def __init__(self, *args, **kwargs): # Init the base class wx.Frame.__init__(self, *args, **kwargs) panel = TestPanel(self) self.SetClientSize(wx.Size(500,500)) self.Center() class wxFileCleanupApp(wx.App): def __init__(self, *args, **kwargs): # Init the base class wx.App.__init__(self, *args, **kwargs) def OnInit(self): # Create the frame, center it, and show it frame = TestFrame(None, title='Test Frame') frame.Show() return True if __name__ == '__main__': app = wxFileCleanupApp() app.MainLoop() EDIT: See my post below for a solution that works!

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  • Symfony Form render with Self Referenced Entity

    - by benarth
    I have an Entity containing Self-Referenced mapping. class Category { /** * @var integer * * @ORM\Column(name="id", type="integer") * @ORM\Id * @ORM\GeneratedValue(strategy="AUTO") */ private $id; /** * @var string * * @ORM\Column(name="name", type="string", length=100) */ private $name; /** * @ORM\OneToMany(targetEntity="Category", mappedBy="parent") */ private $children; /** * @ORM\ManyToOne(targetEntity="Category", inversedBy="children") * @ORM\JoinColumn(name="parent_id", referencedColumnName="id") */ private $parent; } In my CategoryType I have this : public function buildForm(FormBuilderInterface $builder, array $options) { $plan = $this->plan; $builder->add('name'); $builder->add('parent', 'entity', array( 'class' => 'xxxBundle:Category', 'property' => 'name', 'empty_value' => 'Choose a parent category', 'required' => false, 'query_builder' => function(EntityRepository $er) use ($plan) { return $er->createQueryBuilder('u') ->where('u.plan = :plan') ->setParameter('plan', $plan) ->orderBy('u.id', 'ASC'); }, )); } Actually, when I render the form field Category this is something like Cat1 Cat2 Cat3 Subcat1 Subcat2 Cat4 I would like to know if it's possible and how to display something more like, a kind of a simple tree representation : Cat1 Cat2 Cat3 -- Subcat1 -- Subcat2 Cat4 Regards.

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  • Oracle VM Blade Cluster Reference Configuration

    - by Ferhat Hatay
    Today we are happy to announce the availability of the Oracle VM blade cluster reference configuration for Sun Blade 6000 modular systems.  The new Oracle VM blade cluster reference configuration can help reduce the time to deploy virtual infrastructure by up to 98 percent when compared to multi-vendor configurations. Oracle's virtualization strategy is to simplify the deployment, management, and support of the enterprise stack from application to disk. The Oracle VM blade cluster reference configuration is a single-vendor solution that addresses every layer of the virtualization stack with Oracle hardware and software components. It enables quick and easy deployment of the virtualized infrastructure using components that have been tested together and are all supported together by one vendor — Oracle. All components listed in the reference configuration have been tested together by Oracle, reducing the need for customer testing and the time-consuming and complex effort of designing and deploying a stable configuration. Benefitting from pre-installed Oracle VM Server for x86 software on Oracle’s highly scalable and reliable Sun Blade servers with built-in networking and Oracle’s Sun ZFS Storage Appliance product line, the configuration provides high availability via the blade cluster as well as a documented best practice guide that helps reduce deployment time and cost for customers implementing highly virtualized applications or private cloud Infrastructure as a Service (IaaS) architectures. To further support easier, faster and lower-cost deployments, Oracle Linux, Oracle Solaris and Oracle VM are available for pre-install on select Sun x86 systems, and Oracle VM Templates are available for download for Oracle Applications, Oracle Fusion Middleware, Oracle Database, Oracle Real Application Clusters, and many other Oracle products. Key benefits of the Oracle VM blade cluster reference configuration include: Faster time to value – Begin deploying applications immediately because the optimized software stack is pre-configured for best practices and is ready-to-run on the recommended hardware platforms. Reduced deployment cost and risk – The entire hardware and software stack has been tested and is supported together by Oracle. Elastic scalability – As capacity needs grow, the system can be easily scaled in multiple dimensions with the ability to add compute, storage, and networking resources independently. For more information, see: Oracle white paper: Accelerating deployment of virtualized infrastructures with the Oracle VM blade cluster reference configuration Oracle technical white paper: Best Practices and Guidelines for Deploying the Oracle VM Blade Cluster Reference Configuration

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  • PyQt application architecture

    - by L. De Leo
    I'm trying to give a sound structure to a PyQt application that implements a card game. So far I have the following classes: Ui_Game: this describes the ui of course and is responsible of reacting to the events emitted by my CardWidget instances MainController: this is responsible for managing the whole application: setup and all the subsequent states of the application (like starting a new hand, displaying the notification of state changes on the ui or ending the game) GameEngine: this is a set of classes that implement the whole game logic Now, the way I concretely coded this in Python is the following: class CardWidget(QtGui.QLabel): def __init__(self, filename, *args, **kwargs): QtGui.QLabel.__init__(self, *args, **kwargs) self.setPixmap(QtGui.QPixmap(':/res/res/' + filename)) def mouseReleaseEvent(self, ev): self.emit(QtCore.SIGNAL('card_clicked'), self) class Ui_Game(QtGui.QWidget): def __init__(self, window, *args, **kwargs): QtGui.QWidget.__init__(self, *args, **kwargs) self.setupUi(window) self.controller = None def place_card(self, card): cards_on_table = self.played_cards.count() + 1 print cards_on_table if cards_on_table <= 2: self.played_cards.addWidget(card) if cards_on_table == 2: self.controller.play_hand() class MainController(object): def __init__(self): self.app = QtGui.QApplication(sys.argv) self.window = QtGui.QMainWindow() self.ui = Ui_Game(self.window) self.ui.controller = self self.game_setup() Is there a better way other than injecting the controller into the Ui_Game class in the Ui_Game.controller? Or am I totally off-road?

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  • Verifying method with array passed by reference using Moq

    - by kaa
    Given the following interface public interface ISomething { void DoMany(string[] strs); void DoManyRef(ref string[] strs); } I would like to verify that the DoManyRef method is called, and passed any string array as the strs parameter. The following test fails: public void CanVerifyMethodsWithArrayRefParameter() { var a = new Mock<ISomething>().Object; var strs = new string[0]; a.DoManyRef(ref strs); var other = It.IsAny<string[]>(); Mock.Get(a).Verify(t => t.DoManyRef(ref other)); } While the following not requiring the array passed by reference passes: public void CanVerifyMethodsWithArrayParameter() { var a = new Mock<ISomething>().Object; a.DoMany(new[] { "a", "b" }); Mock.Get(a).Verify(t => t.DoMany(It.IsAny<string[]>())); } I am not able to change the interface to eliminate the by reference requirement.

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  • Pass-by-Reference Error

    - by TK
    I have a hook system setup... which is working on localhost... I put it live and get an error saying "Warning: Call-time pass-by-reference has been deprecated". Now, apparently the work around is to remove all "&" from your function calls, ie foo(&$me) to foo($me) and then in foo's function definition do "function foo(&$me)". However, I can not do this... because my hooks accept an array as arguments, I need a work around for this. Like I can use "run_hooks ( 'hook-name', $me );" or "run_hooks ( 'hook-name', array ( $me, $another_var, etc... ) )"; So this means I can not use "function run_hooks ( $hook_name, &$arguments )" because I'll get an error in php saying it can not pass "array()" as reference... Any ideas an a work around? Thanks.

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  • Fluent NHibernate Self Referencing Many To Many

    - by Jeremy
    I have an entity called Books that can have a list of more books called RelatedBooks. The abbreviated Book entity looks something likes this: public class Book { public virtual long Id { get; private set; } public virtual IList<Book> RelatedBooks { get; set; } } Here is what the mapping looks like for this relationship HasManyToMany(x => x.RelatedBooks) .ParentKeyColumn("BookId") .ChildKeyColumn("RelatedBookId") .Table("RelatedBooks") .Cascade.SaveUpdate(); Here is a sample of the data that is then generated in the RelatedBooks table: BookId RelatedBookId 1 2 1 3 The problem happens when I Try to delete a book. If I delete the book that has an ID of 1, everything works ok and the RelatedBooks table has the two corresponding records removed. However if I try to delete the book with an ID of 3, I get the error "The DELETE statement conflicted with the REFERENCE constraint "FK5B54405174BAB605". The conflict occurred in database "Test", table "dbo.RelatedBooks", column 'RelatedBookId'". Basically what is happening is the Book cannot be deleted because the record in the RelatedBooks table that has a RelatedBookId of 3 is never deleted. How do I get that record to be deleted when I delete a book? EDIT After changing the Cascade from SaveUpdate() to All(), the same problem still exists if I try to delete the Book with an ID of 3. Also with Cascade set to All(), if delete the Book with and ID of 1, then all 3 books (ID's: 1, 2 and 3) are deleted so that won't work either. Looking at the SQL that is executed when the Book.Delete() method is called when I delete the Book with an ID of 3, it looks like the SELECT statement is looking at the wrong column (which I assume means that the SQL DELETE statment would make the same mistake, therefore never removing that record). Here is the SQL for the RelatedBook SELECT relatedboo0_.BookId as BookId3_ , relatedboo0_.RelatedBookId as RelatedB2_3_ , book1_.Id as Id14_0_ FROM RelatedBooks relatedboo0_ left outer join [Book] book1_ on relatedboo0_.RelatedBookId=book1_.Id WHERE relatedboo0_.BookId=3 The WHERE statment should look something like this for thie particular case: WHERE relatedboo0_.RelatedBookId = 3 SOLUTION Here is what I had to do to get it working for all cases Mapping: HasManyToMany(x => x.RelatedBooks) .ParentKeyColumn("BookId") .ChildKeyColumn("RelatedBookId") .Table("RelatedBooks"); Code: var book = currentSession.Get<Book>(bookId); if (book != null) { //Remove all of the Related Books book.RelatedBooks.Clear(); //Get all other books that have this book as a related book var booksWithRelated = currentSession.CreateCriteria<Book>() .CreateAlias("RelatedBooks", "br") .Add(Restrictions.Eq("br.Id", book.Id)) .List<Book>(); //Remove this book as a Related Book for all other Books foreach (var tempBook in booksWithRelated) { tempBook.RelatedBooks.Remove(book); tempBook.Save(); } //Delete the book book.Delete(); }

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  • WCF Self Host Service - Endpoints in C#

    - by Kyle
    My first few attempts at creating a self hosted service. Trying to make something up which will accept a query string and return some text but have have a few issues: All the documentation talks about endpoints being created automatically for each base address if they are not found in a config file. This doesn't seem to be the case for me, I get the "Service has zero application endpoints..." exception. Manually specifying a base endpoint as below seems to resolve this: using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.ServiceModel; using System.ServiceModel.Description; namespace TestService { [ServiceContract] public interface IHelloWorldService { [OperationContract] string SayHello(string name); } public class HelloWorldService : IHelloWorldService { public string SayHello(string name) { return string.Format("Hello, {0}", name); } } class Program { static void Main(string[] args) { string baseaddr = "http://localhost:8080/HelloWorldService/"; Uri baseAddress = new Uri(baseaddr); // Create the ServiceHost. using (ServiceHost host = new ServiceHost(typeof(HelloWorldService), baseAddress)) { // Enable metadata publishing. ServiceMetadataBehavior smb = new ServiceMetadataBehavior(); smb.HttpGetEnabled = true; smb.MetadataExporter.PolicyVersion = PolicyVersion.Policy15; host.Description.Behaviors.Add(smb); host.AddServiceEndpoint(typeof(IHelloWorldService), new BasicHttpBinding(), baseaddr + "SayHello"); //for some reason a default endpoint does not get created here host.Open(); Console.WriteLine("The service is ready at {0}", baseAddress); Console.WriteLine("Press to stop the service."); Console.ReadLine(); // Close the ServiceHost. host.Close(); } } } } I still think I'm doing something wrong as I don't get the normal "This is a web service...etc..." page when I load up the url How would I go about setting this up to return the value of name in SayHello(string name) when requested thusly: localhost:8080/HelloWorldService/SayHello?name=kyle Do I have to create an endpoing for the SayHello contract as well? I'm trying to walk before running, but this just seems like crawling...Service has zero application endpoints...

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  • Errors/warnings passing int/char arrays by reference

    - by Ankur Banerjee
    I'm working on a program where I try to pass parameters by reference. I'm trying to pass a 2D int array and a 1D char array by reference. Function prototype: void foo (int* (&a)[2][2], char* (&b)[4]) Function call: foo (a, b); However, when I compile the code with -ansi and -Wall flags on gcc, I get the following errors: foo.c: At top level: error: expected ‘)’ before ‘&’ token error: expected ‘;’, ‘,’ or ‘)’ before ‘char’ foo.c: In function ‘main’: error: too many arguments to function ‘foo’ I've stripped out the rest of the code of my program and concentrated on the bits which throw up the errors. I've searched around on StackOverflow and tried out different ways to pass the parameters, but none of them seem to work. (I took this way of passing parameters from the discussion on StackOverflow here.) Could you please tell me where I'm going wrong?

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  • Multiple Context menus in PyQt based on mouse location

    - by Nader
    I have a window with multiple tables using QTableWidget (PyQt). I created a popup menu using the right click mouse and it works fine. However, I need to create different popup menu based on which table the mouse is hovering over at the time the right mouse is clicked. How can I get the mouse to tell me which table it is hovering over? or, put in another way, how to implement a method so as to have a specific context menu based on mouse location? I am using Python and PyQt. My popup menu is developed similar to this code (PedroMorgan answer from Qt and context menu): class Foo( QtGui.QWidget ): def __init__(self): QtGui.QWidget.__init__(self, None) # Toolbar toolbar = QtGui.QToolBar() # Actions self.actionAdd = toolbar.addAction("New", self.on_action_add) self.actionEdit = toolbar.addAction("Edit", self.on_action_edit) self.actionDelete = toolbar.addAction("Delete", self.on_action_delete) # Tree self.tree = QtGui.QTreeView() self.tree.setContextMenuPolicy( Qt.CustomContextMenu ) self.connect(self.tree, QtCore.SIGNAL('customContextMenuRequested(const QPoint&)'), self.on_context_menu) # Popup Menu self.popMenu = QtGui.QMenu( self ) self.popMenu.addAction( self.actionEdit ) self.popMenu.addAction( self.actionDelete ) self.popMenu.addSeparator() self.popMenu.addAction( self.actionAdd ) def on_context_menu(self, point): self.popMenu.exec_( self.tree.mapToGlobal(point) )

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  • make reference to an empty query in flex

    - by Adam
    a bit of a dumb questions I'm sure I'm trying to allow user to set an item to be default. I've got a function that run a query to first find the current default item. Then runs a second query that unsets the current default item. Then a third query runs to set the new user selected item to be the default. This seem to work fine when a default item has been perviously selected, but when I try to set the default item initially I get the good old "Cannot access a property or method of a null object reference." error. This is because the first query that runs returns no items I'm sure. So I need to write an if statement that if the first query returns nothing to skip the second and go right to the third. The only problem is I can't make a reference to a null object. So how do I go about writing this statement. Thanks

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  • compile time if && return string reference optimization

    - by Truncheon
    Hi. I'm writing a series classes that inherit from a base class using virtual. They are INT, FLOAT and STRING objects that I want to use in a scripting language. I'm trying to implement weak typing, but I don't want STRING objects to return copies of themselves when used in the following way (instead I would prefer to have a reference returned which can be used in copying): a = "hello "; b = "world"; c = a + b; I have written the following code as a mock example: #include <iostream> #include <string> #include <cstdio> #include <cstdlib> std::string dummy("<int object cannot return string reference>"); struct BaseImpl { virtual bool is_string() = 0; virtual int get_int() = 0; virtual std::string get_string_copy() = 0; virtual std::string const& get_string_ref() = 0; }; struct INT : BaseImpl { int value; INT(int i = 0) : value(i) { std::cout << "constructor called\n"; } INT(BaseImpl& that) : value(that.get_int()) { std::cout << "copy constructor called\n"; } bool is_string() { return false; } int get_int() { return value; } std::string get_string_copy() { char buf[33]; sprintf(buf, "%i", value); return buf; } std::string const& get_string_ref() { return dummy; } }; struct STRING : BaseImpl { std::string value; STRING(std::string s = "") : value(s) { std::cout << "constructor called\n"; } STRING(BaseImpl& that) { if (that.is_string()) value = that.get_string_ref(); else value = that.get_string_copy(); std::cout << "copy constructor called\n"; } bool is_string() { return true; } int get_int() { return atoi(value.c_str()); } std::string get_string_copy() { return value; } std::string const& get_string_ref() { return value; } }; struct Base { BaseImpl* impl; Base(BaseImpl* p = 0) : impl(p) {} ~Base() { delete impl; } }; int main() { Base b1(new INT(1)); Base b2(new STRING("Hello world")); Base b3(new INT(*b1.impl)); Base b4(new STRING(*b2.impl)); std::cout << "\n"; std::cout << b1.impl->get_int() << "\n"; std::cout << b2.impl->get_int() << "\n"; std::cout << b3.impl->get_int() << "\n"; std::cout << b4.impl->get_int() << "\n"; std::cout << "\n"; std::cout << b1.impl->get_string_ref() << "\n"; std::cout << b2.impl->get_string_ref() << "\n"; std::cout << b3.impl->get_string_ref() << "\n"; std::cout << b4.impl->get_string_ref() << "\n"; std::cout << "\n"; std::cout << b1.impl->get_string_copy() << "\n"; std::cout << b2.impl->get_string_copy() << "\n"; std::cout << b3.impl->get_string_copy() << "\n"; std::cout << b4.impl->get_string_copy() << "\n"; return 0; } It was necessary to add an if check in the STRING class to determine whether its safe to request a reference instead of a copy: Script code: a = "test"; b = a; c = 1; d = "" + c; /* not safe to request reference by standard */ C++ code: STRING(BaseImpl& that) { if (that.is_string()) value = that.get_string_ref(); else value = that.get_string_copy(); std::cout << "copy constructor called\n"; } If was hoping there's a way of moving that if check into compile time, rather than run time.

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  • Python: Why Does a Method Behave Differently with an Added Parameter?

    - by SteveStifler
    I have a method in a Pygame Sprite subclass, defined as such: def walk(self): """move across screen""" displacement = self.rect.move((self.move, 0)) if self.rect.left < self.area.left or self.rect.right > self.area.right: self.move = -self.move displacement = self.rect.move((self.move, 0)) self.rect = displacement I modified it, adding a parameter speed_x, and now the program is broken. def walk(self, speed_x): """move across screen""" displacement = self.rect.move((speed_x, 0)) if self.rect.left < self.area.left or self.rect.right > self.area.right: speed_x = -speed_x displacement = self.rect.move((speed_x, 0)) self.rect = displacement Before I called the method like this: def update(self): self.walk() Now I do: def update(self): self.walk(self.move) Why doesn't this work?

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  • [Tkinter/Python] Different line widths with canvas.create_line?

    - by Sam
    Does anyone have any idea why I get different line widths on the canvas in the following example? from Tkinter import * bigBoxSize = 150 class cFrame(Frame): def __init__(self, master, cwidth=450, cheight=450): Frame.__init__(self, master, relief=RAISED, height=550, width=600, bg = "grey") self.canvasWidth = cwidth self.canvasHeight = cheight self.canvas = Canvas(self, bg="white", width=cwidth, height=cheight, border =0) self.drawGridLines() self.canvas.pack(side=TOP, pady=20, padx=20) def drawGridLines(self, linewidth = 10): self.canvas.create_line(0, 0, self.canvasWidth, 0, width= linewidth ) self.canvas.create_line(0, 0, 0, self.canvasHeight, width= linewidth ) self.canvas.create_line(0, self.canvasHeight, self.canvasWidth + 2, self.canvasHeight, width= linewidth ) self.canvas.create_line(self.canvasWidth, self.canvasHeight, self.canvasWidth, 1, width= linewidth ) self.canvas.create_line(0, bigBoxSize, self.canvasWidth, bigBoxSize, width= linewidth ) self.canvas.create_line(0, bigBoxSize * 2, self.canvasWidth, bigBoxSize * 2, width= linewidth) root = Tk() C = cFrame(root) C.pack() root.mainloop() It's really frustrating me as I have no idea what's happening. If anyone can help me out then that'd be fantastic. Thanks!

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  • Problem passing a reference as a named parameter to a variadic function

    - by Michael Mrozek
    I'm having problems in Visual Studio 2003 with the following: void foo(const char*& str, ...) { va_list args; va_start(args, str); const char* foo; while((foo = va_arg(args, const char*)) != NULL) { printf("%s\n", foo); } } When I call it: const char* one = "one"; foo(one, "two", "three", NULL); I get: Access violation reading location 0xcccccccc on the printf() line -- va_arg() returned 0xcccccccc. I finally discovered it's the first parameter being a reference that breaks it -- if I make it a normal char* everything is fine. It doesn't seem to matter what the type is; being a reference causes it to fail at runtime. Is this a known problem with VS2003, or is there some way in which that's legal behavior? It doesn't happen in GCC; I haven't tested with newer Visual Studios to see if the behavior goes away

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  • WCF service reference stopped generating code for one project

    - by Mike Pateras
    I have references to two different WCF services in a project. I updated the reference for one of the services, and now no code is generated for it. The references.cs file just has the "this is genrated code" comment at the top. Updating that same service in other projects and updating the other service both work fine. It's only that one service reference in this one project that's causing the problem, and I'm getting no information from Visual Studio (it just says it failed to generate code and I should look at the other errors, which provide no information). If I uncheck the "reuse types in referenced assemblies", code is generated, but I don't want to have this one project be different from the others. I'd like to solve the problem. Re-checking the reuse type option produces an empty references.cs file, again. The collection type doesn't seem to matter, either. How can I diagnose and solve this problem?

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  • wxpython PyGridTableBase

    - by nozkan
    Hi, I want to use editable choice editor with PyGridTableBase. When I edit a cell it is crashing What is error in my code? My python code: import wx import wx.grid as gridlib class MyTableBase(gridlib.PyGridTableBase): def __init__(self): gridlib.PyGridTableBase.__init__(self) self.data = {0:["value 1", "value 2"], 1:["value 3", "value 4", "value 5"]} self.column_labels = [unicode(u"Label 1"), unicode(u"Label 2"), unicode(u"Label 3")] self._rows = self.GetNumberRows() self._cols = self.GetNumberCols() def GetColLabelValue(self, col): return self.column_labels[col] def GetNumberRows(self): return len(self.data.keys()) def GetNumberCols(self): return len(self.column_labels) def GetValue(self, row, col): try: if col > self.GetNumberCols(): raise IndexError return self.data[row][col] except IndexError: return None def IsEmptyCell(self, row, col): if self.data[row][col] is not None: return True else: return False def GetAttr(self, row, col, kind): attr = gridlib.GridCellAttr() editor = gridlib.GridCellChoiceEditor(["xxx", "yyy", "zzz"], allowOthers = True) attr.SetEditor(editor) attr.IncRef() return attr class MyDataGrid(gridlib.Grid): def __init__(self, parent): gridlib.Grid.__init__(self, parent, wx.NewId()) self.base_table = MyTableBase() self.SetTable(self.base_table) if __name__ == '__main__': app = wx.App(redirect = False) frame = wx.Frame(None, wx.NewId(), title = u"Test") grid_ = MyDataGrid(frame) frame.Show() app.MainLoop()

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  • Specializating a template function that takes a universal reference parameter

    - by David Stone
    How do I specialize a template function that takes a universal reference parameter? foo.hpp: template<typename T> void foo(T && t) // universal reference parameter foo.cpp template<> void foo<Class>(Class && class) { // do something complicated } Here, Class is no longer a deduced type and thus is Class exactly; it cannot possibly be Class &, so reference collapsing rules will not help me here. I could perhaps create another specialization that takes a Class & parameter (I'm not sure), but that implies duplicating all of the code contained within foo for every possible combination of rvalue / lvalue references for all parameters, which is what universal references are supposed to avoid. Is there some way to accomplish this? To be more specific about my problem in case there is a better way to solve it: I have a program that can connect to multiple game servers, and each server, for the most part, calls everything by the same name. However, they have slightly different versions for a few things. There are a few different categories that these things can be: a move, an item, etc. I have written a generic sort of "move string to move enum" set of functions for internal code to call, and my server interface code has similar functions. However, some servers have their own internal ID that they communicate with, some use strings, and some use both in different situations. Now what I want to do is make this a little more generic. I want to be able to call something like ServerNamespace::server_cast<Destination>(source). This would allow me to cast from a Move to a std::string or ServerMoveID. Internally, I may need to make a copy (or move from) because some servers require that I keep a history of messages sent. Universal references seem to be the obvious solution to this problem. The header file I'm thinking of right now would expose simply this: namespace ServerNamespace { template<typename Destination, typename Source> Destination server_cast(Source && source); } And the implementation file would define all legal conversions as template specializations.

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  • How can I consume A web-service reference like a dll

    - by Sergiu
    I have a small question: Can we consume a web-service reference like a sample dll? I mean something like following: 1. Add reference to assembly in the references 2. add namespace to using (using mywebservice) 3. use it in code like: var service = new mywebservice.Service1(); var result = service.GetSomething()? Why I'm asking? It's because of I tried but I get a "strange" error: Cannot load assembly "MyService.dll version, and so on". Thanks in advance!

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