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  • jQuery internals: Organization of the jQuery Object

    - by sonofdelphi
    I was going through the source code of jQuery. I'm having trouble understanding the wrapping strategy for the jQuery object. (function( window, undefined ) { // Define a local copy of jQuery var jQuery = function( selector, context ) { // The jQuery object is actually just the init constructor 'enhanced' return new jQuery.fn.init( selector, context ); }, .... .... .... // Expose jQuery to the global object window.jQuery = window.$ = jQuery; })(window); Specifically, what I'm not able to understand stems from the first line. What is the outermost unnamed container function? Why is it required? Why is the container function anonymous? What is the need for the outermost '(' parantheses ?

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  • Converting an AnsiString to a Unicode String

    - by jrodenhi
    I'm converting a D2006 program to D2010. I have a value stored in a single byte per character string in my database and I need to load it into a control that has a LoadFromStream, so my plan was to write the string to a stream and use that with LoadFromStream. But it did not work. In studying the problem, I see an issue that tells me that I don't really understand how conversion from AnsiString to Unicode string works. Here is some code I am puzzling over: oStringStream := TStringStream.Create(sBuffer); sUnicodeStream := oPayGrid.sStream; //explicit conversion to unicode string iSize1 := StringElementSize(oPaygrid.sStream); iSize2 := StringElementSize(sUnicodeStream); oStringStream.WriteString(sUnicodeStream); When I get to the last line, iSize1 does equal 1 and iSize2 does equal 2, so that part is what I understood from my reading. But, on the last line, after I write the string to the stream, and look at the Bytes Property of the string, it shows this (the string starts as '16,159'): (49 {$31}, 54 {$36}, 44 {$2C}, 49 {$31}, 53 {$35}, 57 {$39} ... I was expecting that it might look something like (49 {$31}, 00 {$00}, 54 {$36}, 00 {$00}, 44 {$2C}, 00 {$00}, 49 {$31}, 00 {$00}, 53 {$35}, 00 {$00}, 57 {$39}, 00 {$00} ... I'm not getting the right results out of the LoadFromStream because it is reading from the stream two bytes at a time, but the data it is receiving is not arranged that way. What is it that I should do to give the LoadFromStream a well formed stream of data based on a unicode string? Thank you for your help.

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  • Overriding constructors

    - by demas
    Here is sample code: class One def initialize(*args) case args.size when 0 puts "one initialize" when 1 puts "one initialize #{args[0]}" end end end class Two def initialize(*args) if args.size == 2 then puts "two initialize #{args[0]} and #{args[1]}" else super(args) end end end one = One.new one = One.new("thing") two = Two.new("some", "other") two = Two.new("some") Now I'm launching the code and getting the error message: [[email protected]][~/temp]% ruby test2.rb one initialize one initialize thing two initialize some and other test2.rb:17:in `initialize': wrong number of arguments(1 for 0) (ArgumentError) from test2.rb:17:in `initialize' from test2.rb:26:in `new' from test2.rb:26:in `<main>' How can I call parent's constructor from class Two ?

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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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  • Is Stream.Write thread-safe?

    - by Mike Spross
    I'm working on a client/server library for a legacy RPC implementation and was running into issues where the client would sometimes hang when waiting to a receive a response message to an RPC request message. It turns out the real problem was in my message framing code (I wasn't handling message boundaries correctly when reading data off the underlying NetworkStream), but it also made me suspicious of the code I was using to send data across the network, specifically in the case where the RPC server sends a large amount of data to a client as the result of a client RPC request. My send code uses a BinaryWriter to write a complete "message" to the underlying NetworkStream. The RPC protocol also implements a heartbeat algorithm, where the RPC server sends out PING messages every 15 seconds. The pings are sent out by a separate thread, so, at least in theory, a ping can be sent while the server is in the middle of streaming a large response back to a client. Suppose I have a Send method as follows, where stream is a NetworkStream: public void Send(Message message) { //Write the message to a temporary stream so we can send it all-at-once MemoryStream tempStream = new MemoryStream(); message.WriteToStream(tempStream); //Write the serialized message to the stream. //The BinaryWriter is a little redundant in this //simplified example, but here because //the production code uses it. byte[] data = tempStream.ToArray(); BinaryWriter bw = new BinaryWriter(stream); bw.Write(data, 0, data.Length); bw.Flush(); } So the question I have is, is the call to bw.Write (and by implication the call to the underlying Stream's Write method) atomic? That is, if a lengthy Write is still in progress on the sending thread, and the heartbeat thread kicks in and sends a PING message, will that thread block until the original Write call finishes, or do I have to add explicit synchronization to the Send method to prevent the two Send calls from clobbering the stream?

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  • Compilation errors calling find_if using a functor

    - by Jim Wong
    We are having a bit of trouble using find_if to search a vector of pairs for an entry in which the first element of the pair matches a particular value. To make this work, we have defined a trivial functor whose operator() takes a pair as input and compares the first entry against a string. Unfortunately, when we actually add a call to find_if using an instance of our functor constructed using a temporary string value, the compiler produces a raft of error messages. Oddly (to me, anyway), if we replace the temporary with a string that we've created on the stack, things seem to work. Here's what the code (including both versions) looks like: typedef std::pair<std::string, std::string> MyPair; typedef std::vector<MyPair> MyVector; struct MyFunctor: std::unary_function <const MyPair&, bool> { explicit MyFunctor(const std::string& val) : m_val(val) {} bool operator() (const MyPair& p) { return p.first == m_val; } const std::string m_val; }; bool f(const char* s) { MyFunctor f(std::string(s)); // ERROR // std::string str(s); // MyFunctor f(str); // OK MyVector vec; MyVector::const_iterator i = std::find_if(vec.begin(), vec.end(), f); return i != vec.end(); } And here's what the most interesting error message looks like: /usr/include/c++/4.2.1/bits/stl_algo.h:260: error: conversion from ‘std::pair, std::allocator , std::basic_string, std::allocator ’ to non-scalar type ‘std::string’ requested Because we have a workaround, we're mostly curious as to why the first form causes problems. I'm sure we're missing something, but we haven't been able to figure out what it is.

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  • Panel is not displaying in JFrame

    - by mallikarjun
    I created a chat panel and added to Jframe but the panel is not displaying. But my sop in the chat panel are displaying in the console. Any one please let me know what could be the problem My Frame public class MyFrame extends JFrame { MyPanel chatClient; String input; public MyFrame() { input = (String)JOptionPane.showInputDialog(null, "Name:", "Connect to chat server", JOptionPane.QUESTION_MESSAGE, null,null, "Test"); input=input.trim(); chatClient = new MyPanel("localhost",input); setVisible(true); setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); add(chatClient); } public static void main(String...args){ new MyFrame(); } } MyPanel: public class MyPanel extends JPanel{ ChatClient chatClient; public MyPanel(String host, String uid) { chatClient= new ChatClient(host,uid); add(chatClient.getChatPanel()); this.setVisible(true); } } chat panel: public class ChatClient { Client client; String name; ChatPanel chatPanel; String hostid; public ChatClient(String host,String uid){ client = new Client(); client.start(); System.out.println("in constructor"); Network.register(client); client.addListener(new Listener(){ public void connected(Connection connection){ System.out.println("in client connected method"); Network.RegisterName registerName = new Network.RegisterName(); registerName.name=name; client.sendTCP(registerName); } public void received(Connection connection,Object object){ System.out.println("in client received method"); if (object instanceof Network.UpdateNames) { Network.UpdateNames updateNames = (Network.UpdateNames)object; //chatFrame.setNames(updateNames.names); System.out.println("got it message"); return; } if (object instanceof Network.ChatMessage) { Network.ChatMessage chatMessage = (Network.ChatMessage)object; //chatFrame.addMessage(chatMessage.text); System.out.println("send it message"); return; } } }); // end of listner name=uid.trim(); hostid=host.trim(); chatPanel = new ChatPanel(hostid,name); chatPanel.setSendListener(new Runnable(){ public void run(){ Network.ChatMessage chatMessage = new Network.ChatMessage(); chatMessage.chatMessage=chatPanel.getSendText(); client.sendTCP(chatMessage); } }); new Thread("connect"){ public void run(){ try{ client.connect(5000, hostid,Network.port); }catch(IOException e){ e.printStackTrace(); } } }.start(); }//end of constructor static public class ChatPanel extends JPanel{ CardLayout cardLayout; JList messageList,nameList; JTextField sendText; JButton sendButton; JPanel topPanel,bottomPanel,panel; public ChatPanel(String host,String user){ setSize(600, 200); this.setVisible(true); System.out.println("Chat panel "+host+"user: "+user); { panel = new JPanel(new BorderLayout()); { topPanel = new JPanel(new GridLayout(1,2)); panel.add(topPanel); { topPanel.add(new JScrollPane(messageList=new JList())); messageList.setModel(new DefaultListModel()); } { topPanel.add(new JScrollPane(nameList=new JList())); nameList.setModel(new DefaultListModel()); } DefaultListSelectionModel disableSelections = new DefaultListSelectionModel() { public void setSelectionInterval (int index0, int index1) { } }; messageList.setSelectionModel(disableSelections); nameList.setSelectionMode(ListSelectionModel.SINGLE_SELECTION); } { bottomPanel = new JPanel(new GridBagLayout()); panel.add(bottomPanel,BorderLayout.SOUTH); bottomPanel.add(sendText=new JTextField(),new GridBagConstraints(0,0,1,1,1,0,GridBagConstraints.CENTER,GridBagConstraints.BOTH,new Insets(0,0,0,0),0,0)); bottomPanel.add(sendButton=new JButton(),new GridBagConstraints(1,0,1,1,0,0,GridBagConstraints.CENTER,0,new Insets(0,0,0,0),0,0)); } } sendText.addActionListener(new ActionListener(){ public void actionPerformed(ActionEvent e){ sendButton.doClick(); } }); } public void setSendListener (final Runnable listener) { sendButton.addActionListener(new ActionListener() { public void actionPerformed (ActionEvent evt) { if (getSendText().length() == 0) return; listener.run(); sendText.setText(""); sendText.requestFocus(); } }); } public String getSendText () { return sendText.getText().trim(); } public void setNames (final String[] names) { EventQueue.invokeLater(new Runnable(){ public void run(){ DefaultListModel model = (DefaultListModel)nameList.getModel(); model.removeAllElements(); for(String name:names) model.addElement(name); } }); } public void addMessage (final String message) { EventQueue.invokeLater(new Runnable() { public void run () { DefaultListModel model = (DefaultListModel)messageList.getModel(); model.addElement(message); messageList.ensureIndexIsVisible(model.size() - 1); } }); } } public JPanel getChatPanel(){ return chatPanel; } }

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  • SoundPool.load() and FileDescriptor from file

    - by Hans
    I tried using the load function of the SoundPool that takes a FileDescriptor, because I wanted to be able to set the offset and length. The File is not stored in the Ressources but a file on the storage card. Even though neither the load nor the play function of the SoundPool throw any Exception or print anything to the console, the sound is not played. Using the same code, but use the file path string in the SoundPool constructor works perfectly. This is how I have tried the loading (start equals 0 and length is the length of the file in miliseconds): FileInputStream fileIS = new FileInputStream(new File(mFile)); mStreamID = mSoundPool.load(fileIS.getFD(), start, length, 0); mPlayingStreamID = mSoundPool.play(mStreamID, 1f, 1f, 1, 0, 1f); If I would use this, it works: mStreamID = mSoundPool.load(mFile, 0); mPlayingStreamID = mSoundPool.play(mStreamID, 1f, 1f, 1, 0, 1f); Any ideas anyone? Thanks

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  • Property in a Windows Forms form class only accessable after Load event

    - by Spooky2010
    I'm instantiating and calling Form B from Form A. FormB has some custom properties, to allow me to pass it things like sqlAdaptors and dataset instances. When i instantiate and show Form B from Form A as a dialog form with a Using statement, it all works fine, but i find the properties i pass are not available in Form B until after the form_load event has fired. I was under the impression the properties when passed to a instantiated class should be available from a constructor, but this is not the case. If it try to access the properties before the form load event i get a null reference exception. Is this correct behavior ?

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  • Safe and polymorphic toEnum

    - by jetxee
    I'd like to write a safe version of toEnum: safeToEnum :: (Enum t, Bounded t) => Int -> Maybe t A naive implementation: safeToEnum :: (Enum t, Bounded t) => Int -> Maybe t safeToEnum i = if (i >= fromEnum (minBound :: t)) && (i <= fromEnum (maxBound :: t)) then Just . toEnum $ i else Nothing main = do print $ (safeToEnum 1 :: Maybe Bool) print $ (safeToEnum 2 :: Maybe Bool) And it doesn't work: safeToEnum.hs:3:21: Could not deduce (Bounded t1) from the context () arising from a use of `minBound' at safeToEnum.hs:3:21-28 Possible fix: add (Bounded t1) to the context of an expression type signature In the first argument of `fromEnum', namely `(minBound :: t)' In the second argument of `(>=)', namely `fromEnum (minBound :: t)' In the first argument of `(&&)', namely `(i >= fromEnum (minBound :: t))' safeToEnum.hs:3:56: Could not deduce (Bounded t1) from the context () arising from a use of `maxBound' at safeToEnum.hs:3:56-63 Possible fix: add (Bounded t1) to the context of an expression type signature In the first argument of `fromEnum', namely `(maxBound :: t)' In the second argument of `(<=)', namely `fromEnum (maxBound :: t)' In the second argument of `(&&)', namely `(i <= fromEnum (maxBound :: t))' As well as I understand the message, the compiler does not recognize that minBound and maxBound should produce exactly the same type as in the result type of safeToEnum inspite of the explicit type declaration (:: t). Any idea how to fix it?

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  • Usage of Assert.Inconclusive

    - by Johannes Rudolph
    Hi, Im wondering how someone should use Assert.Inconclusive(). I'm using it if my Unit test would be about to fail for a reason other than what it is for. E.g. i have a method on a class that calculates the sum of an array of ints. On the same class there is also a method to calculate the average of the element. It is implemented by calling sum and dividing it by the length of the array. Writing a Unit test for Sum() is simple. However, when i write a test for Average() and Sum() fails, Average() is likely to fail also. The failure of Average is not explicit about the reason it failed, it failed for a reason other than what it should test for. That's why i would check if Sum() returns the correct result, otherwise i Assert.Inconclusive(). Is this to be considered good practice? What is Assert.Inconclusive intended for? Or should i rather solve the previous example by means of an Isolation Framework?

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  • return by reference - which of the two is the correct one

    - by eriks
    i have the function: const A& f(...) {...} a. const A a1 = f(..); b. const A &a2 = f(...); which of the is the better one to use? in both cases, if i understand correctly, i prevent the possibility of modifying the returned object. in the first option, the copy constructor of A will be called - am i correct?

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  • Why can I call a non-const member function pointer from a const method?

    - by sdg
    A co-worker asked about some code like this that originally had templates in it. I have removed the templates, but the core question remains: why does this compile OK? #include <iostream> class X { public: void foo() { std::cout << "Here\n"; } }; typedef void (X::*XFUNC)() ; class CX { public: explicit CX(X& t, XFUNC xF) : object(t), F(xF) {} void execute() const { (object.*F)(); } private: X& object; XFUNC F; }; int main(int argc, char* argv[]) { X x; const CX cx(x,&X::foo); cx.execute(); return 0; } Given that CX is a const object, and its member function execute is const, therefore inside CX::execute the this pointer is const. But I am able to call a non-const member function through a member function pointer. Are member function pointers a documented hole in the const-ness of the world? What (presumably obvious to others) issue have we missed?

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  • Error in Python's os.walk?

    - by Mike Caron
    The os.walk documentation (http://docs.python.org/library/os.html? highlight=os.walk#os.walk), says I can skip traversing unwanted directories by removing them from the dir list. The explicit example from the docs: import os from os.path import join, getsize for root, dirs, files in os.walk('python/Lib/email'): print root, "consumes", print sum(getsize(join(root, name)) for name in files), print "bytes in", len(files), "non-directory files" if 'CVS' in dirs: dirs.remove('CVS') # don't visit CVS directories I see different behavior (using ActivePython 2.6.2). Namely for the code: >>> for root,dirs,files in os.walk(baseline): ... if root.endswith(baseline): ... for d in dirs: ... print "DIR: %s" % d ... if not d.startswith("keep_"): ... print "Removing %s\\%s" % (root,d) ... dirs.remove(d) ... ... print "ROOT: %s" % root ... I get the output: DIR: two Removing: two DIR: thr33 Removing: thr33 DIR: keep_me DIR: keep_me_too DIR: keep_all_of_us ROOT: \\mach\dirs ROOT: \\mach\dirs\ONE ROOT: \\mach\dirs\ONE\FurtherRubbish ROOT: \\mach\dirs\ONE\FurtherRubbish\blah ROOT: \\mach\dirs\ONE\FurtherRubbish\blah\Extracted ROOT: \\mach\dirs\ONE\FurtherRubbish\blah2\Extracted\Stuff_1 ... WTF? Why wasn't \\mach\dirs\ONE removed? It clearly doesn't start with "keep_".

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  • Postgres error with Sinatra/Haml/DataMapper on Heroku

    - by sevennineteen
    I'm trying to move a simple Sinatra app over to Heroku. Migration of the Ruby app code and existing MySQL database using Taps went smoothly, but I'm getting the following Postgres error: PostgresError - ERROR: operator does not exist: text = integer LINE 1: ...d_at", "post_id" FROM "comments" WHERE ("post_id" IN (4, 17,... ^ HINT: No operator matches the given name and argument type(s). You might need to add explicit type casts. It's evident that the problem is related to a type mismatch in the query, but this is being issued from a Haml template by the DataMapper ORM at a very high level of abstraction, so I'm not sure how I'd go about controlling this... Specifically, this seems to be throwing up on a call of p.comments from my Haml template, where p represents a given post. The Datamapper models are related as follows: class Post property :id, Serial ... has n, :comments end class Comment property :id, Serial ... belongs_to :post end This works fine on my local and current hosted environment using MySQL, but Postgres is clearly more strict. There must be hundreds of Datamapper & Haml apps running on Postgres DBs, and this model relationship is super-conventional, so hopefully someone has seen (and determined how to fix) this. Thanks!

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  • Interchange structured data between Haskell and C

    - by Eonil
    First, I'm a Haskell beginner. I'm planning integrating Haskell into C for realtime game. Haskell does logic, C does rendering. To do this, I have to pass huge complexly structured data (game state) from/to each other for each tick (at least 30 times per second). So the passing data should be lightweight. This state data may laid on sequential space on memory. Both of Haskell and C parts should access every area of the states freely. In best case, the cost of passing data can be copying a pointer to a memory. In worst case, copying whole data with conversion. I'm reading Haskell's FFI(http://www.haskell.org/haskellwiki/FFICookBook#Working_with_structs) The Haskell code look specifying memory layout explicitly. I have a few questions. Can Haskell specify memory layout explicitly? (to be matched exactly with C struct) Is this real memory layout? Or any kind of conversion required? (performance penalty) If Q#2 is true, Any performance penalty when the memory layout specified explicitly? What's the syntax #{alignment foo}? Where can I find the document about this? If I want to pass huge data with best performance, how should I do that? *PS Explicit memory layout feature which I said is just C#'s [StructLayout] attribute. Which is specifying in-memory position and size explicitly. http://www.developerfusion.com/article/84519/mastering-structs-in-c/ I'm not sure Haskell has matching linguistic construct matching with fields of C struct.

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  • alternative to #include within namespace { } block

    - by Jeff
    Edit: I know that method 1 is essentially invalid and will probably use method 2, but I'm looking for the best hack or a better solution to mitigate rampant, mutable namespace proliferation. I have multiple class or method definitions in one namespace that have different dependencies, and would like to use the fewest namespace blocks or explicit scopings possible but while grouping #include directives with the definitions that require them as best as possible. I've never seen any indication that any preprocessor could be told to exclude namespace {} scoping from #include contents, but I'm here to ask if something similar to this is possible: (see bottom for explanation of why I want something dead simple) // NOTE: apple.h, etc., contents are *NOT* intended to be in namespace Foo! // would prefer something most this: namespace Foo { #include "apple.h" B *A::blah(B const *x) { /* ... */ } #include "banana.h" int B::whatever(C const &var) { /* ... */ } #include "blueberry.h" void B::something() { /* ... */ } } // namespace Foo ... // over this: #include "apple.h" #include "banana.h" #include "blueberry.h" namespace Foo { B *A::blah(B const *x) { /* ... */ } int B::whatever(C const &var) { /* ... */ } void B::something() { /* ... */ } } // namespace Foo ... // or over this: #include "apple.h" namespace Foo { B *A::blah(B const *x) { /* ... */ } } // namespace Foo #include "banana.h" namespace Foo { int B::whatever(C const &var) { /* ... */ } } // namespace Foo #include "blueberry.h" namespace Foo { void B::something() { /* ... */ } } // namespace Foo My real problem is that I have projects where a module may need to be branched but have coexisting components from the branches in the same program. I have classes like FooA, etc., that I've called Foo::A in the hopes being able to branch less painfully as Foo::v1_2::A, where some program may need both a Foo::A and a Foo::v1_2::A. I'd like "Foo" or "Foo::v1_2" to show up only really once per file, as a single namespace block, if possible. Moreover, I tend to prefer to locate blocks of #include directives immediately above the first definition in the file that requires them. What's my best choice, or alternatively, what should I be doing instead of hijacking the namespaces?

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  • Where to maintain common information, that could be accessed by all forms

    - by The King
    Hi All, This is my first winform app in .NET... I have made a couple of ASP.NET app... In this app, I have some common variables, like current user name, his selected process etc.. etc.. This should be made accessible from all forms in the app at any time... How could I do this... Is there any place like "Session" in ASP.NET here... Further How do coders generally pass information from one form to another... Here I want to pass on the info I acquired in the first form to the subsequent forms... I use constructor overloading and pass the values as parameters... I'm pretty sure there has to be a better way to do it... Thanks for your time...

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  • Building a control-flow graph from an AST with a visitor pattern using Java

    - by omegatai
    Hi guys, I'm trying to figure out how to implement my LEParserCfgVisitor class as to build a control-flow graph from an Abstract-Syntax-Tree already generated with JavaCC. I know there are tools that already exist, but I'm trying to do it in preparation for my Compilers final. I know I need to have a data structure that keeps the graph in memory, and I want to be able to keep attributes like IN, OUT, GEN, KILL in each node as to be able to do a control-flow analysis later on. My main problem is that I haven't figured out how to connect the different blocks together, as to have the right edge between each blocks depending on their nature: branch, loops, etc. In other words, I haven't found an explicit algorithm that could help me build my visitor. Here is my empty Visitor. You can see it works on basic langage expressions, like if, while and basic operations (+,-,x,^,...) public class LEParserCfgVisitor implements LEParserVisitor { public Object visit(SimpleNode node, Object data) { return data; } public Object visit(ASTProgram node, Object data) { data = node.childrenAccept(this, data); return data; } public Object visit(ASTBlock node, Object data) { } public Object visit(ASTStmt node, Object data) { } public Object visit(ASTAssignStmt node, Object data) { } public Object visit(ASTIOStmt node, Object data) { } public Object visit(ASTIfStmt node, Object data) { } public Object visit(ASTWhileStmt node, Object data) { } public Object visit(ASTExpr node, Object data) { } public Object visit(ASTAddExpr node, Object data) { } public Object visit(ASTFactExpr node, Object data) { } public Object visit(ASTMultExpr node, Object data) { } public Object visit(ASTPowerExpr node, Object data) { } public Object visit(ASTUnaryExpr node, Object data) { } public Object visit(ASTBasicExpr node, Object data) { } public Object visit(ASTFctExpr node, Object data) { } public Object visit(ASTRealValue node, Object data) { } public Object visit(ASTIntValue node, Object data) { } public Object visit(ASTIdentifier node, Object data) { } } Can anyone give me a hand? Thanks!

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  • Strict pointer aliasing: any solution for a specific problem?

    - by doublep
    I have a problem caused by breaking strict pointer aliasing rule. I have a type T that comes from a template and some integral type Int of the same size (as with sizeof). My code essentially does the following: T x = some_other_t; if (*reinterpret_cast <Int*> (&x) == 0) ... Because T is some arbitary (other than the size restriction) type that could have a constructor, I cannot make a union of T and Int. (This is allowed only in C++0x only and isn't even supported by GCC yet). Is there any way I could rewrite the above pseudocode to preserve functionality and avoid breaking strict aliasing rule? Note that this is a template, I cannot control T or value of some_other_t; the assignment and subsequent comparison do happen inside the templated code. (For the record, the above code started breaking on GCC 4.5 if T contains any bit fields.)

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  • Output is different for R-value and L-value. Why?

    - by Leonid Volnitsky
    Can someone explain to me why output for R-value is different from L-value? #include <iostream> #include <vector> using namespace std; template<typename Ct> struct ct_wrapper { Ct&& ct; // R or L ref explicit ct_wrapper(Ct&& ct) : ct(std::forward<Ct>(ct)) { std::cout << this->ct[1];}; }; int main() { // L-val vector<int> v{1,2,3}; ct_wrapper<vector<int>&> lv(v); cout << endl << lv.ct[0] << lv.ct[1] << lv.ct[2] << endl; // R-val ct_wrapper<vector<int>&&> rv(vector<int>{1,2,3}); cout << endl << rv.ct[0] << rv.ct[1] << rv.ct[2] << endl; } Output (same for gcc48 and clang32): 2 123 2 003

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  • Multithread Communication

    - by Robert
    I'm creating a WPF application that uses a custom object to populate all the controls. The constructor of that object is initiated by an EventHandler that waits for an API. The problem I'm having is when I try to access any information from that object using a button for example, it returns an error saying "The calling thread cannot access this object because a different thread owns it". I'm assuming this is because the EventHandler creates a new thread which doesn't allow the MainThread to have access to it. Any ideas on how to get around this?

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  • Why is partial specialziation of a nested class template allowed, while complete isn't?

    - by drhirsch
    template<int x> struct A { template<int y> struct B {};. template<int y, int unused> struct C {}; }; template<int x> template<> struct A<x>::B<x> {}; // error: enclosing class templates are not explicitly specialized template<int x> template<int unused> struct A<x>::C<x, unused> {}; // ok So why is the explicit specialization of a inner, nested class (or function) not allowed, if the outer class isn't specialiced too? Strange enough, I can work around this behaviour if I only partially specialize the inner class with simply adding a dummy template parameter. Makes things uglier and more complex, but it works. Note: I need this feature for recursive templates of the inner class for a set of the outer class. To make things even more complicate, in reality I only need a template function instead of the inner class. But partial specialization of functions is generally disallowed somewhere else in the standard ^^

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  • page redirection problem via Bean in Js1.1

    - by johnbritto
    I have a requested scoped managed bean, called AuthenticationBean. I am developing a smal application with a login module, user activation and deactivation. When I click on the activate or deactivate link, then the action is processed in AuthenticationBean. I want thereafter redirect to some page depending on the activate or deactivate link. I have tried the following in the bean constructor: FacesContext.getCurrentInstance().getExternalContext().redirect("/user/activate.jsp"); But this code is not working. Please help me.

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  • Lua metatable Objects cannot be purge from memory?

    - by Prometheus3k
    Hi there, I'm using a proprietary platform that reported memory usage in realtime on screen. I decided to use a Class.lua I found on http://lua-users.org/wiki/SimpleLuaClasses However, I noticed memory issues when purging object created by this using a simple Account class. Specifically, I would start with say 146k of memory used, create 1000 objects of a class that just holds an integer instance variable and store each object into a table. The memory used is now 300k I would then exit, iterating through the table and setting each element in the table to nil. But would never get back the 146k, usually after this I am left using 210k or something similar. If I run the load sequence again during the same session, it does not exceed 300k so it is not a memory leak. I have tried creating 1000 integers in a table and setting these to nil, which does give me back 146k. In addition I've tried a simpler class file (Account2.lua) that doesn't rely on a class.lua. This still incurs memory fragmentation but not as much as the one that uses Class.lua Can anybody explain what is going on here? How can I purge these objects and get back the memory? here is the code --------Class.lua------ -- class.lua -- Compatible with Lua 5.1 (not 5.0). --http://lua-users.org/wiki/SimpleLuaClasses function class(base,ctor) local c = {} -- a new class instance if not ctor and type(base) == 'function' then ctor = base base = nil elseif type(base) == 'table' then -- our new class is a shallow copy of the base class! for i,v in pairs(base) do c[i] = v end c._base = base end -- the class will be the metatable for all its objects, -- and they will look up their methods in it. c.__index = c -- expose a ctor which can be called by () local mt = {} mt.__call = function(class_tbl,...) local obj = {} setmetatable(obj,c) if ctor then ctor(obj,...) else -- make sure that any stuff from the base class is initialized! if base and base.init then base.init(obj,...) end end return obj end c.init = ctor c.instanceOf = function(self,klass) local m = getmetatable(self) while m do if m == klass then return true end m = m._base end return false end setmetatable(c,mt) return c end --------Account.lua------ --Import Class template require 'class' local classname = "Account" --Declare class Constructor Account = class(function(acc,balance) --Instance variables declared here. if(balance ~= nil)then acc.balance = balance else --default value acc.balance = 2097 end acc.classname = classname end) --------Account2.lua------ local account2 = {} account2.classname = "unnamed" account2.balance = 2097 -----------Constructor 1 do local metatable = { __index = account2; } function Account2() return setmetatable({}, metatable); end end --------Main.lua------ require 'Account' require 'Account2' MAX_OBJ = 5000; test_value = 1000; Obj_Table = {}; MODE_ACC0 = 0 --integers MODE_ACC1 = 1 --Account MODE_ACC2 = 2 --Account2 TEST_MODE = MODE_ACC0; Lua_mem = ""; print("##1) collectgarbage('count'): " .. collectgarbage('count')); function Load() for i=1, MAX_OBJ do if(TEST_MODE == MODE_ACC0 )then table.insert(Obj_Table, test_value); elseif(TEST_MODE == MODE_ACC1 )then table.insert(Obj_Table, Account(test_value)); --Account.lua elseif(TEST_MODE == MODE_ACC2 )then table.insert(Obj_Table, Account2()); --Account2.lua Obj_Table[i].balance = test_value; end end print("##2) collectgarbage('count'): " .. collectgarbage('count')); end function Purge() --metatable purge if(TEST_MODE ~= MODE_ACC0)then --purge stage 0: print("set each elements metatable to nil") for i=1, MAX_OBJ do setmetatable(Obj_Table[i], nil); end end --purge stage 1: print("set table element to nil") for i=1, MAX_OBJ do Obj_Table[i] = nil; end --purge stage 2: print("start table.remove..."); for i=1, MAX_OBJ do table.remove(Obj_Table, i); end print("...end table.remove"); --purge stage 3: print("create new object_table {}"); Obj_Table= {}; --purge stage 4: print("collectgarbage('collect')"); collectgarbage('collect'); print("##3) collectgarbage('count'): " .. collectgarbage('count')); end --Loop callback function OnUpdate() collectgarbage('collect'); Lua_mem = collectgarbage('count'); end ------------------- --NOTE: --On start of game runs Load(), another runs Purge() --Update I've updated the code with suggestions from comments below, and will post my findings later today.

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