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• Reserved Memory Addresses?

  - by Nate

  Is there a list of reserved memory addresses out there - a list of addresses that the memory of a user-space program could never be allocated to? I realize this is most likely per-OS or per-architecture, but I was hoping someone might know some of the more common OSes and Arches. I could only dig one up for a few versions of windows: for windows NT,2k and XP that would be: 0x00000000 - 0x0000ffff - lowest page is protected to simplify debugging 0x00001000 - 0x7ffeffff - memory area for your application 0x7fff0000 - 0x7fffffff - protected area to keep memory-functions from damaging the following part 0x80000000 - 0xffffffff - memory where the system including drivers and so on is located Anyone know about for Linux, or BSD (or anything else, for that matter)?

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• Java ServerSocketChannel SocketChannel (Callback)

  - by ikurtz

  I am trying to learn Java. I would like to implement a simple networked connect 4 game as well as a chat feature. I want my network logic to be non blocking so after much study I found that SocketChannel is what I am after regrading my needs. What has not made sense still is the lack of CallBack functions in SocketChannels.. Like one finds in C#. My query for this time is: How do I deliver the data received to the Chat or Game form (JFrame)? Some guidance is most welcome.

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• Using template specialization in C++

  - by user550413

  How can I write a function using template specialization that has 2 different input types and an output type: template <class input1, class input2, class output> and return the sum of the 2 numbers (integers/doubles). However, if I get 2 integers I want to return an integer type but for any other combinations of integer and double I'll always return double. I am trying to do that without using directly the '+' operator but having the next functions instead: double add_double_double(double a, double b) {return (a+b);} double add_int_double(int a, double b) {return ((double)(a)+b);} int add_int_int(int a, int b) {return (a+b);}

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• Composite pattern in C++ problem

  - by annouk

  Hello! I have to work with an application in C++ similar to a phone book: the class Agenda with an STL list of Contacts.Regarding the contacts hierarchy,there is a base-class named Contact(an abstract one),and the derived classes Friend and Acquaintance(the types of contact). These classes have,for instance, a virtual method called getName,which returns the name of the contact. Now I must implement the Composite pattern by adding another type of contact,Company(being derived from Contact),which also contains a collection of Contacts(an STL list as well),that can be either of the "leaf" type(Friends or Acquaintances),or they can be Companies as well. Therefore,Company is the Compound type. The question is: how and where can I implement an STL find_if to search the contact with a given name(via getName function or suggest me smth else) both among the "leaf"-type Contact and inside the Company collection? In other words,how do I traverse the tree in order to find possible matches there too,using an uniform function definition? I hope I was pretty clear...

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• Does the Internet make us less good programmers? [closed]

  - by stagas

  With all the information and code available nowadays on the Internet has that diminished our capability of remembering or learning stuff just because we know they're available somewhere out there, just a Google away or a StackOverflow question away? For example I find myself visiting php.net quite often to check the syntax of the same functions over and over again, not because my memory sucks, but I don't feel like keeping the information in me, since I know I'll find it again on the net. And about StackOverflow, isn't the process of figuring things out on your own supposed to improve your programming skills? If the answers are all just clicks away, do we actually learn something or just keep a pointer in our heads where to search for it again when we need it? Your thoughts are welcome. Hope it doesn't shut down as subjective or anything, the answers would be really interesting ;)

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• writing structs and classes to disk

  - by Phenom

  The following function writes a struct to a file. int btwrite(short rrn, BTPAGE *page_ptr) { long addr; addr = (long) rrn * (long) PAGESIZE + HEADERSIZE; lseek(btfd, addr, 0); return (write(btfd, page_ptr, PAGESIZE)); } The following is the struct. typedef struct { short keycount; /* number of keys in page */ int key[MAXKEYS]; /* the actual keys */ int value[MAXKEYS]; /* the actual values */ short child[MAXKEYS+1]; /* ptrs to rrns of descendants */ } BTPAGE; What would happen if I changed the struct to a class, would it still work the same? If I added class functions, would the size it takes up on disk increase?

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• OpenGL ES perspective projection

  - by TimeManx

  I'm having a hard time understanding how glFrustum & gluPerspective work. I understand the concept of perspective projection but the functions aren't behaving how I expect them to. For example, if I set the frustum this way glFrustumf(0, 10, 0, 10, 1, 100) and have a rectangle at points 0, 0, 1, 0, 10, 1, 10, 10, 1, 10, 0, 1 then the rectangle is drawn with its left edge at -5 & right edge at 5, so the left half of the rectangle isn't visible. And if x is translated, I'd expect y to be too. But that doesn't happen either. In whatever examples I've seen, the coordinates for the projection matrix are taken as glFrustumf(-10, 10, -10, 10, 1, 100) but either way, whatever part is shown should be dependent on the rectangle's coordinates, right?

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• Calling a Sub or Function contained in a module using "CallByName" in VB/VBA

  - by Kratz

  It is easy to call a function inside a classModule using CallByName How about functions inside standard module? 'inside class module 'classModule name: clsExample Function classFunc1() MsgBox "I'm class module 1" End Function ' 'inside standard module 'Module name: module1 Function Func1() MsgBox "I'm standard module 1" End Function ' ' The main sub Sub Main() ' to call function inside class module dim clsObj as New clsExample Call CallByName(clsObj,"ClassFunc1") ' here's the question... how to call a function inside a standard module ' how to declare the object "stdObj" in reference to module1? Call CallByName(stdObj,"Func1") ' is this correct? End Sub

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• Order of execution and style of coding in Python

  - by Jason

  Hi guys. I am new to Python so please don't flame me if the question is too basic :) I have read that Python is executed from top - to - bottom. If this is the case, why do programs go like this: def func2(): def func1(): #call func2() def func() #call func1() if __name__ == '__main__': call func() So from what I have seen, the main function goes at last and the other functions are stacked on top of it. Am I wrong in saying this? If no, why isn't the main function or the function definitions written from top to bottom?

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• Sleeping a thread blocking stdin

  - by Sid

  Hey, I'm running a function which evaluates commands passed in using stdin and another function which runs a bunch of jobs. I need to make the latter function sleep at regular intervals but that seems to be blocking the stdin. Any advice on how to resolve this would be appreciated. The source code for the functions is def runJobs(comps, jobQueue, numRunning, limit, lock): while len(jobQueue) >= 0: print(len(jobQueue)); if len(jobQueue) > 0: comp, tasks = find_computer(comps, 0); #do something time.sleep(5); def manageStdin(): print "Global Stdin Begins Now" for line in fileinput.input(): try: print(eval(line)); except Exception, e: print e; --Thanks

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• Anyway to improve my gzip PHP method?

  - by Joe

  I Gzip my pages currently like so: <?php ob_start("ob_gzhandler"); //my page content ob_flush(); ?> However, I read a comment somewhere, earlier on, that this method uses a lot of memory, and I know that my website has been using a lot of memory on my virtual private server, so I thought it would be nice if I knew a way to reduce memory usage. I tested my site with an online gzip tester which says my websites are sending gzipped pages, so my gzip method works, but the main obviously I'm looking for a less memory intensive option, if any. I appreciate all suggestions. :) Oh and merry christmas ;P

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• Can I replace a method on a jQuery UI object? How?

  - by Cheeso

  If I want to tweak some of the capability of a jQuery UI object, by replacing one of the functions, how would I go about doing that? Example: suppose I wanted to modify the way the jQuery autocomplete widget rendered the suggestions. There's a method on the autocomplete object that looks like this: _renderItem: function( ul, item) { return $( "<li></li>" ) .data( "item.autocomplete", item ) .append( "<a>" + item.label + "</a>" ) .appendTo( ul ); }, Could I replace this? How? What syntax would I use?

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• How to keep the first result of a function from Prolog?

  - by zuhakasa

  I need to write a customized function that will be called many times by other fixed functions. In this function, at the first called time, it will return the total number of lines of a file. The second called time of this function, forward, will return the number of lines in small sections of this file. My question is how I keep the first returned result(total number of lines of a file) and use it for the next called times of my function. I need to write or declare any thing only in this function(not in the caller). Something like this: myFunction(Input, MyResult, FirstResult) :- calculateInputFunction(Input, Result), !, MyResult is Result, ... . The problem is, every time myFunction is called, it receives different Input and returns different MyResult. But I would like to keep the first MyResult to use for next called times of myFunction. How can I do that? Thanks very much for your answer in advance.

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• Is PThread a good choice for multi-platorm C/C++ multi-threading program?

  - by RogerV

  Been doing mostly Java and smattering of .NET for last five years and haven't written any significant C or C++ during that time. So have been away from that scene for a while. If I want to write a C or C++ program today that does some multi-threading and is source code portable across Windows, Mac OS X, and Linux/Unix - is PThread a good choice? The C or C++ code won't be doing any GUI, so won't need to worry with any of that. For the Windows platform, I don't want to bring a lot of Unix baggage, though, in terms of unix emulation runtime libraries. Would prefer a PThread API for Windows that is a thin-as-possible wrapper over existing Windows threading APIs. ADDENDUM EDIT: Am leaning toward going with boost:thread - I also want to be able to use C++ try/catch exception handling too. And even though my program will be rather minimal and not particularly OOPish, I like to encapsulate using class and namespace - as opposed to C disembodied functions.

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• How to access constant defined in child class?

  - by kavoir.com

  I saw this example from php.net: <?php class MyClass { const MY_CONST = "yonder"; public function __construct() { $c = get_class( $this ); echo $c::MY_CONST; } } class ChildClass extends MyClass { const MY_CONST = "bar"; } $x = new ChildClass(); // prints 'bar' $y = new MyClass(); // prints 'yonder' ?> But $c::MY_CONST is only recognized in version 5.3.0 or later. The class I'm writing may be distributed a lot. Basically, I have defined a constant in ChildClass and one of the functions in MyClass (father class) needs to use the constant. Any idea?

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• Multithreaded SDL error in C++

  - by wyatt

  I'm building a program in C++, using SDL, and am occasionally receiving this error: * glibc detected * ./assistant: double free or corruption (!prev) It's difficult to replicate, so I can't find exactly what's causing it, but I just added a second thread to the program, and neither thread run on its own seems to cause the error. The threads don't share any variables, though they both run the functions SDL_BlitSurface and SDL_Flip. Could running these concurrently throw up such an error, or am I barking up the wrong tree? If this is the cause, should I simply throw a mutex around all SDL calls? Thanks

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• C++: Where can I define the body for a private function?

  - by Martijn Courteaux

  Hi, I have a header like this (header guards not shown): class GameSystem { public: GameSystem(Game *pcGame); virtual ~GameSystem(); void Setup(); private: void InitGame(); void RunGame(); void ExitGame(); Game *m_pcGame; /* Properties */ int m_nWidth; int m_nHeight; int m_nFps; bool m_bFullscreen; }; Where can I define the body for InitGame(), RunGame() and ExitGame()? Can I define it in my .cpp file? If so, how? Or am I obliged to make their body in my .h file? I'm using Eclipse and I began typing: void GameSystem:: and then he doesn't suggest the private functions.

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• Initializing a array after declaration

  - by robUK

  Hello, gcc 4.4.3 c89 I have the following code as a sample of what I am trying to do. I don't know the actual size of the array, until I enter the function. However, I don't think I can set the array size after I have declared it. I need it global as some other functions will need to access the device names. Many thanks for any suggestions, /* global */ char *devices_names[]; void fill_devices(size_t num_devices) { devices_names[num_devices]; /* start filling */ }

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• Resizing Ubuntu x64 Server Partition with VirtualBox not reflected in OS

  - by daleyjem

  I've already resized my virtual disk with VirtualBox, but now need to extend the partition of my Ubuntu VM itself. I thought I was on my way with GParted live CD, but after I resize the "extended" filesystem partition, and then the child "lvm2 pv" filesystem partition to fill the unallocated space, df -h still shows the original disk size after I reboot into the VM. Any tips on this? I've scoured the webs tirelessly. Should I be resizing the boot (/dev/sda1) partition instead? Should I try to convert my lvm2 to ext4 or something? I'm lost on this. Note: VirtualBox hard disk is "dynamic". Specs: VBox 4.2.18 Ubuntu 12.04.2 amd64 Gparted 0.16.2-1b-i486

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• Why does the assignment operator return a value and not a reference?

  - by Nick Lowman

  I saw the example below explained on this site and thought both answers would be 20 and not the 10 that is returned. He wrote that both the comma and assignment returns a value, not a reference. I don't quite understand what that means. I understand it in relation to passing variables into functions or methods i.e primitive types are passed in by value and objects by reference but I'm not sure how it applies in this case. I also understand about context and the value of 'this' (after help from stackoverflow) but I thought in both cases I would still be invoking it as a method, foo.bar() which would mean foo is the context but it seems both result in a function call bar(). Why is that and what does it all mean? var x = 10; var foo = { x: 20, bar: function () {return this.x;} }; (foo.bar = foo.bar)();//returns 10 (foo.bar, foo.bar)();//returns 10

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• Is pthread_spin_trylock safe inside of sigsegv handler of multithreaded application?

  - by TWMouton

  I am trying to implement a handler that on SIGSEGV will collect some information such as process-id, thread-id and a backtrace and write this information to a file/pipe/socket. The problem lies in that there is the (probably pretty high) possibility that if one thread experienced a SIGSEGV that the others will shortly follow. If two threads happen to make it to the bit of code where they're writing their report out at the same time then they'll interleave their writing (to the same file). I know that I should only be using async-signal-safe functions as detailed in signal(7) I also have seen at least two cases here and video linked in top answer here where others have used pthread_spin_trylock to get around this problem. Is this a safe way to prevent the above problem?

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• Add a custom class name to Wordpress body tag?

  - by Scott B

  I'd like to place a directive in my theme's functions.php file which appends a classname to the wordpress body tag. Is there a built-in API method for this? For example, my body tag code is... <body <?php if(function_exists("body_class") && !is_404()){body_class();} else echo 'class="page default"'?>> And it results in the following being written to the body tag (depending on the context in which the page is presented (page, post, logged-in, etc) <body class="home blog logged-in"> Depending on the child theme I'm using at the time, I want it to be... <body class="home blog logged-in mychildthemename">

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• Implement abstract class as a local class? pros and cons

  - by sinec

  Hi, for some reason I'm thinking on implementing interface within a some function(method) as local class. Consider following: class A{ public: virtual void MethodToOverride() = 0; }; A * GetPtrToAImplementation(){ class B : public A { public: B(){} ~B(){} void MethodToOverride() { //do something } }; return static_cast<A *>(new B()); } int _tmain(int argc, _TCHAR* argv[]) { A * aInst = GetPtrToAImplementation(); aInst->MethodToOverride(); delete aInst; return 0; } the reason why I'm doing this are: I'm lazy to implement class (B) in separate files MethodToOverride just delegates call to other class Class B shouldn't be visible to other users no need to worry about deleting aInst since smart pointers are used in real implementation So my question is if I'm doing this right? Thanks in advance!

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• What is the smallest Windows header I can #include to define DWORD?

  - by j_random_hacker

  I have a small header file of my own which declares a couple of functions, one of which has a return type of DWORD. I'm reluctant to drag in windows.h just to get the official definition of this type since that file is huge, and my header will be used in a number of source modules that don't otherwise need it. Of course, in practice I know that DWORD is just unsigned int, but I'd prefer the more hygienic approach of including an official header file if possible. On this page it says that DWORD is defined in windef.h, but unfortunately including just this small file directly leads to compilation errors -- apparently it expects to be included by other headers. (Also, the fact that my file is a header file also means I can't just declare WIN32_LEAN_AND_MEAN, since the source file that #includes my file might need this to be left undefined.) Any ideas? I know it's not the end of the world -- I can just continue to #include <windows.h> -- but thought someone might have a better idea!

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• c++ compilation error

  - by clamp

  hello, i got a compile error which i do not understand. i have a h/cpp file combination that does not contain a class but just defines some utility functions. when i try to use a struct that is defined in another class i get the error: error C2027: use of undefined type so, stripped down to the problem, the h file looks like this namespace A { void foo(B::C::SStruct const & Var); } the definition of SStruct is in a class which is in another h-file, that is of course included. namespace B { Class C { struct SStruct { }; } } what am i missing here? thanks!

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