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  • are C functions declared in <c____> headers guaranteed to be in the global namespace as well as std?

    - by Evan Teran
    So this is something that I've always wondered but was never quite sure about. So it is strictly a matter of curiosity, not a real problem. As far as I understand, what you do something like #include <cstdlib> everything (except macros of course) are declared in the std:: namespace. Every implementation that I've ever seen does this by doing something like the following: #include <stdlib.h> namespace std { using ::abort; // etc.... } Which of course has the effect of things being in both the global namespace and std. Is this behavior guaranteed? Or is it possible that an implementation could put these things in std but not in the global namespace? The only way I can think of to do that would be to have your libstdc++ implement every c function itself placing them in std directly instead of just including the existing libc headers (because there is no mechanism to remove something from a namespace). Which is of course a lot of effort with little to no benefit. The essence of my question is, is the following program strictly conforming and guaranteed to work? #include <cstdio> int main() { ::printf("hello world\n"); } EDIT: The closest I've found is this (17.4.1.2p4): Except as noted in clauses 18 through 27, the contents of each header cname shall be the same as that of the corresponding header name.h, as specified in ISO/IEC 9899:1990 Programming Languages C (Clause 7), or ISO/IEC:1990 Programming Languages—C AMENDMENT 1: C Integrity, (Clause 7), as appropriate, as if by inclusion. In the C + + Standard Library, however, the declarations and definitions (except for names which are defined as macros in C) are within namespace scope (3.3.5) of the namespace std. which to be honest I could interpret either way. "the contents of each header cname shall be the same as that of the corresponding header name.h, as specified in ISO/IEC 9899:1990 Programming Languages C" tells me that they may be required in the global namespace, but "In the C + + Standard Library, however, the declarations and definitions (except for names which are defined as macros in C) are within namespace scope (3.3.5) of the namespace std." says they are in std (but doesn't specify any other scoped they are in).

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  • Why is it that I can include a header file in multiple cpp files that contains const int and not have a compiler error?

    - by tree
    Let's assume that I have files a.cpp b.cpp and file c.h. Both of the cpp files include the c.h file. The header file contains a bunch of const int definitions and when I compile them I get no errors and yet I can access those const as if they were global variables. So the question, why don't I get any compilation errors if I have multiple const definitions as well as these const int's having global-like scope?

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  • When are static class variables initialized during runtime?

    - by Jake
    Hi, I have the following: class Thing { static Thing PREDEFINED; type _private; Thing() { _private = initial_val; } } Thing Thing::PREDEFINED = redefined_val; in global scope, i have this Thing mything = Thing::PREDEFINED; but it does not have the desired effect. mything is still initial_value and there were no errors too. So, may I ask when is the static class variable initialized during runtime?

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  • What are nested/unnested package in Scala 2.8?

    - by retronym
    In Scala 2.7, I could write: package com.acme.bar class Bar . package com.acme.foo class Foo { new bar.Bar } This doesn't compile in Scala 2.8 -- however this does: package com.acme package bar class Bar . package com.acme package foo class Foo { new bar.Bar } What was the motivation for this? What is the precise meaning, with regards to scope and visibility? When should I use one form over the other?

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  • How to Highlight image based on selection in JSF

    - by Paul
    The images are displayed horizontally using . At first no images are selected if selected it has to be highlighted. If user changes the selection the old has to go normal and new has to be highlighted. while in edit mode we need to highlight the already selected image and they may change in this mode so highlight should change. Bean is in session scope. pls provide some solution.

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  • How do i free objects in C#

    - by assassin
    Hi, Can anyone please tell me how I can free objects in C#? For example, I have an object: Object obj1 = new Object(); //Some code using obj1 //Here I would like to free obj1, after it is no longer required and also more importantly its scope is the full run time of the program. Thanks for all your help

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  • How is it possible to legally write ::: in C++ and ??? in C#?

    - by daveny
    These questions are a kind of game, and I did not find the solution for them. It is possible to write ::: in C++ without using quotes or anything like this and the compiler will accept it (macros are prohibited too). And the same is true for C# too, but in C#, you have to write ???. I think C++ will use the :: scope operator and C# will use ? : , but I do not know the answers to them. Any idea?

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  • Static variables in C and C++

    - by Naveen
    Is there any difference between a variable declared as static outside any function between C and C++. I read that static means file scope and the variables will not be accessible outside the file. I also read that in C, global variables are static . So does that mean that global variables in C can not be accessed in another file?

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  • OGNL thread safety

    - by Dewfy
    I'm going to reuse OGNL library out of Struts2 scope. I have rather large set of formulas, that is why I would like to precompile all of them: Ognl.parseExpression(expressionString); But I'm not sure if precompiled expression can be used in multi-thread environment. Does anybody knows if it can be used?

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  • Objective-C memory management issue

    - by Toby Wilson
    I've created a graphing application that calls a web service. The user can zoom & move around the graph, and the program occasionally makes a decision to call the web service for more data accordingly. This is achieved by the following process: The graph has a render loop which constantly renders the graph, and some decision logic which adds web service call information to a stack. A seperate thread takes the most recent web service call information from the stack, and uses it to make the web service call. The other objects on the stack get binned. The idea of this is to reduce the number of web service calls to only those appropriate, and only one at a time. Right, with the long story out of the way (for which I apologise), here is my memory management problem: The graph has persistant (and suitably locked) NSDate* objects for the currently displayed start & end times of the graph. These are passed into the initialisers for my web service request objects. The web service call objects then retain the dates. After the web service calls have been made (or binned if they were out of date), they release the NSDate*. The graph itself releases and reallocates new NSDates* on the 'touches ended' event. If there is only one web service call object on the stack when removeAllObjects is called, EXC_BAD_ACCESS occurs in the web service call object's deallocation method when it attempts to release the date objects (even though they appear to exist and are in scope in the debugger). If, however, I comment out the release messages from the destructor, no memory leak occurs for one object on the stack being released, but memory leaks occur if there are more than one object on the stack. I have absolutely no idea what is going wrong. It doesn't make a difference what storage symantics I use for the web service call objects dates as they are assigned in the initialiser and then only read (so for correctness' sake are set to readonly). It also doesn't seem to make a difference if I retain or copy the dates in the initialiser (though anything else obviously falls out of scope or is unwantedly released elsewhere and causes a crash). I'm sorry this explanation is long winded, I hope it's sufficiently clear but I'm not gambling on that either I'm afraid. Major big thanks to anyone that can help, even suggest anything I may have missed?

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  • Determine application version

    - by rayman
    Hi, I wanna know if there is anyway to determine not through the packages, but through applications the version of an application which isnt the current application. let's say right now i am in the scope of app A. and i wanna run an activity from app B. i wanna check before the version code of app B. thanks, ray.

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  • Strategy to rename the require_once function?

    - by openfrog
    Rather than just writing a new function called import() i'd like to know if there's a better solution. Otherwise require_once would be included in the scope of import() only, which is bad for any "global" variable there. My import() function would work differently than require_once, but serves the same purpose (enhanced usability).

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  • Overlapping and Stacking in CSS

    - by ApacheCode
    Hello, I'm a programmer and learning new techniques in web development. I've ran into a problem if you could look at the link below. http://bailesslaw.com/Bailess_003/bailesHeader/header.html This example I made isnt fixed and it needs to be, which is becoming difficult. This looks fine on here, but when I put those layers on main website, index.html, place this code as the header, the banner moves in the documents position 0,0 . I need these boxes fixed, center page and I cannot get them to do that without messing up the layers order and content. Layer1-rotating images, js causes the rotation Layer2-blue triangle with backdrop effect overlapping layer 1, Layer 3-is a static image with a high z-index Below I including some code, the important part that needs 3 overlapped layers exactly matching in width and height, except it has to be fixed in center 780px wide. Code: <style rel="stylesheet" type="text/css"> div#layer1 { border: 1px solid #000; height: 200px; left: 0px; position: fixed; top: 0px; width: 780px; z-index: 1; } div#layer2 { border: 1px solid #000; height: 200px; left: 0px; position: absolute; top: 0px; width: 780px; z-index: 2; } div#layer3 { border: 1px solid #000000; height: 200px; left: 0px; position: absolute; top: 0px; width: 780px; z-index: 3; } </style> </head> <body class="oneColFixCtr"> <div id="container"> <div id="mainContent"> <div id="layer1"> </div> <div id="layer2"> <div class="slideshow"> <span id="rotating1"> <p class="rotating"> </p> </span> <span id="rotating2"> <p class="rotating"> </p> </span> <span id="rotating3"> <p class="rotating"> </p> </span> <span id="rotating4"> <p class="rotating"> </p> </span> </div> </div> <div id="layer3"> <table width="385" border="0"> <tr> <th width="81" scope="col"> &nbsp; </th> <th width="278" scope="col"> &nbsp; </th> <th width="12" scope="col"> &nbsp; </th> </tr> <tr> <td> &nbsp; </td> <td> </td> <td> &nbsp; </td> </tr> <tr> <td> &nbsp; </td> <td> &nbsp; </td> <td> &nbsp; </td> </tr> </table> </div> </div> <!-- end #container --> </div> </body> </body> </html> CSS: @charset "utf-8"; CSS code: #rotating1 { height: 200px; width: 780px; } #rotating2 { height: 200px; width: 780px; } #rotating3 { height: 200px; width: 780px; } #main { background-repeat: no-repeat; height: 200px; width: 780px; z-index: 100; } #test { width: 780px; z-index: 2; } #indexContent { background-color: #12204d; background-repeat: no-repeat; height: 200px; width: 780px; z-index: 1; } #indexContent p { padding: .5em 2em .5em 2em; text-align: justify; text-indent: 2em; } .rotating { float: right; margin-top: 227px; text-indent: 0px !important; } .clearfix:after { clear: both; content: " "; display: block; font-size: 0; height: 0; visibility: hidden; } .clearfix { display: inline-block; } * html .clearfix { height: 1%; } .clearfix { display: block; }

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  • Question regarding the method local innerclasses accesing the local variables of the method

    - by flash
    Hi I was going through the SCJP book about the innerclasses, and found this statement, it goes something like this. "A method local class can only refer to the local variables which are marked final" and in the explanation the reason specified is about the scope and lifetime of the local class object and the local variables on the heap, But I am unable to understand that.am I missing anything here about 'final'??

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  • How to approach copying objects with smart pointers as class attributes?

    - by tomislav-maric
    From the boost library documentation I read this: Conceptually, smart pointers are seen as owning the object pointed to, and thus responsible for deletion of the object when it is no longer needed. I have a very simple problem: I want to use RAII for pointer attributes of a class that is Copyable and Assignable. The copy and assignment operations should be deep: every object should have its own copy of the actual data. Also, RTTI needs to be available for the attributes (their type may also be determined at runtime). Should I be searching for an implementation of a Copyable smart pointer (the data are small, so I don't need Copy on Write pointers), or do I delegate the copy operation to the copy constructors of my objects as shown in this answer? Which smart pointer do I choose for simple RAII of a class that is copyable and assignable? (I'm thinking that the unique_ptr with delegated copy/assignment operations to the class copy constructor and assignment operator would make a proper choice, but I am not sure) Here's a pseudocode for the problem using raw pointers, it's just a problem description, not a running C++ code: // Operation interface class ModelOperation { public: virtual void operate = (); }; // Implementation of an operation called Special class SpecialModelOperation : public ModelOperation { private: // Private attributes are present here in a real implementation. public: // Implement operation void operate () {}; }; // All operations conform to ModelOperation interface // These are possible operation names: // class MoreSpecialOperation; // class DifferentOperation; // Concrete model with different operations class MyModel { private: ModelOperation* firstOperation_; ModelOperation* secondOperation_; public: MyModel() : firstOperation_(0), secondOperation_(0) { // Forgetting about run-time type definition from input files here. firstOperation_ = new MoreSpecialOperation(); secondOperation_ = new DifferentOperation(); } void operate() { firstOperation_->operate(); secondOperation_->operate(); } ~MyModel() { delete firstOperation_; firstOperation_ = 0; delete secondOperation_; secondOperation_ = 0; } }; int main() { MyModel modelOne; // Some internal scope { // I want modelTwo to have its own set of copied, not referenced // operations, and at the same time I need RAII to work for it, // as soon as it goes out of scope. MyModel modelTwo (modelOne); } return 0; }

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  • No clock with FTDIchip FT2232 MPSSE mode

    - by Simi
    Hello, I'm trying to write/read to an extern device connected to a FTDIchip FT2232 MPSSE mode using SPI. I'm using the SPI function given by FTDI for Labview. I'm doing this: Open_Device - Init_Device - Write/Read - Close_Device The problem is that I don't have a clock signal on the scope when I try to read/write. Do you have a solution? Thanks

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  • lisp, differences in assignment functions

    - by johnc
    I'm pretty new to lisp, so apologies for what may be a simple question, Whilst I understand the difference between DEFVAR and DEFPARAMETER (defvar only sets undefined variables), and the LET is for local scope only, what is the is the use of SETF as opposed to the other, previously mentioned assignment functions?

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  • Force deletion of slot in boost::signals2

    - by villintehaspam
    Hi! I have found that boost::signals2 uses sort of a lazy deletion of connected slots, which makes it difficult to use connections as something that manages lifetimes of objects. I am looking for a way to force slots to be deleted directly when disconnected. Any ideas on how to work around the problem by designing my code differently are also appreciated! This is my scenario: I have a Command class responsible for doing something that takes time asynchronously, looking something like this (simplified): class ActualWorker { public: boost::signals2<void ()> OnWorkComplete; }; class Command : boost::enable_shared_from_this<Command> { public: ... void Execute() { m_WorkerConnection = m_MyWorker.OnWorkDone.connect(boost::bind(&Command::Handle_OnWorkComplete, shared_from_this()); // launch asynchronous work here and return } boost::signals2<void ()> OnComplete; private: void Handle_OnWorkComplete() { // get a shared_ptr to ourselves to make sure that we live through // this function but don't keep ourselves alive if an exception occurs. shared_ptr<Command> me = shared_from_this(); // Disconnect from the signal, ideally deleting the slot object m_WorkerConnection.disconnect(); OnComplete(); // the shared_ptr now goes out of scope, ideally deleting this } ActualWorker m_MyWorker; boost::signals2::connection m_WorkerConnection; }; The class is invoked about like this: ... boost::shared_ptr<Command> cmd(new Command); cmd->OnComplete.connect( foo ); cmd->Execute(); // now go do something else, forget all about the cmd variable etcetera. the Command class keeps itself alive by getting a shared_ptr to itself which is bound to the ActualWorker signal using boost::bind. When the worker completes, the handler in Command is invoked. Now, since I would like the Command object to be destroyed, I disconnect from the signal as can be seen in the code above. The problem is that the actual slot object is not deleted when disconnected, it is only marked as invalid and then deleted at a later time. This in turn appears to depend on the signal to fire again, which it doesn't do in my case, leading to the slot never expiring. The boost::bind object thus never goes out of scope, holding a shared_ptr to my object that will never get deleted. I can work around this by binding using the this pointer instead of a shared_ptr and then keeping my object alive using a member shared_ptr which I then release in the handler function, but it kind of makes the design feel a bit overcomplicated. Is there a way to force signals2 to delete the slot when disconnecting? Or is there something else I could do to simplify the design? Any comments are appreciated!

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