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  • Java single Array best choice for accessing pixels for manipulation?

    - by Petrol
    I am just watching this tutorial https://www.youtube.com/watch?v=HwUnMy_pR6A and the guy (who seems to be pretty competent) is using a single array to store and access the pixels of his to-be-rendered image. I was wondering if this really is the best way to do this. The alternative of Multi-Array does have one pointer more, but Arrays do have an O(1) for accessing each index and calculating the index in a single array seems to take one addition and one multiplication operation per pixel. And if Multi-Arrays really are bad, can't you use something with Hashing to avoid those addition and multiplication operations? EDIT: here is his code... public class Screen { private int width, height; public int[] pixels; public Screen(int width, int height) { this.width = width; this.height = height; // creating array the size of one index/int for every pixel // single array has better performance than multi-array pixels = new int[width * height]; } public void render() { for (int y = 0; y < height; y++) { for (int x = 0; x < width; x++) { pixels[x + y * width] = 0xff00ff; } } } }

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  • Binary serialization/de-serialization in C++ and C#

    - by 6pack kid
    Hello. I am working on a distributed application which has two components. One is written in standard C++ (not managed C++) and the other one is written in C#. Both are communicating via a message bus. I have a situation in which I need to pass objects from C++ to C# application and for this I need to serialize those objects in C++ and de-serialize them in C# (something like marshaling/un-marshaling in .NET). I need to perform this serialization in binary and not in XML (due to performance reasons). I have used Boost.Serialization to do this when both ends were implemented in C++ but now that I have a .NET application on one end, Boost.Serialization is not a viable solution. I am looking for a solution that allows me to perform (de)serialization across C++ and .NET boundary i.e., cross platform binary serialization. I know I can implement the (de)serialization code in a C++ dll and use P/Invoke in the .NET application, but I want to keep that as a last resort. Also, I want to know if I use some standard like gzip, will that be efficient? Are there any other alternatives to gzip? What are the pros/cons of them? Thanks

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  • Performance degrades for more than 2 threads on Xeon X5355

    - by zoolii
    Hi All, I am writing an application using boost threads and using boost barriers to synchronize the threads. I have two machines to test the application. Machine 1 is a core2 duo (T8300) cpu machine (windows XP professional - 4GB RAM) where I am getting following performance figures : Number of threads :1 , TPS :21 Number of threads :2 , TPS :35 (66 % improvement) further increase in number of threads decreases the TPS but that is understandable as the machine has only two cores. Machine 2 is a 2 quad core ( Xeon X5355) cpu machine (windows 2003 server with 4GB RAM) and has 8 effective cores. Number of threads :1 , TPS :21 Number of threads :2 , TPS :27 (28 % improvement) Number of threads :4 , TPS :25 Number of threads :8 , TPS :24 As you can see, performance is degrading after 2 threads (though it has 8 cores). If the program has some bottle neck , then for 2 thread also it should have degraded. Any idea? , Explanations ? , Does the OS has some role in performance ? - It seems like the Core2duo (2.4GHz) scales better than Xeon X5355 (2.66GHz) though it has better clock speed. Thank you -Zoolii

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  • Looking to reimplement build toolchain from bash/grep/sed/awk/(auto)make/configure to something more

    - by wash
    I currently maintain a few boxes that house a loosely related cornucopia of coding projects, databases and repositories (ranging from a homebrew *nix distro to my class notes), maintained by myself and a few equally pasty-skinned nerdy friends (all of said cornucopia is stored in SVN). The vast majority of our code is in C/C++/assembly (a few utilities are in python/perl/php, we're not big java fans), compiled in gcc. Our build toolchain typically consists of a hodgepodge of make, bash, grep, sed and awk. Recent discovery of a Makefile nearly as long as the program it builds (as well as everyone's general anxiety with my cryptic sed and awking) has motivated me to seek a less painful build system. Currently, the strongest candidate I've come across is Boost Build/Bjam as a replacement for GNU make and python as a replacement for our build-related bash scripts. Are there any other C/C++/asm build systems out there worth looking into? I've browsed through a number of make alternatives, but I haven't found any that are developed by names I know aside from Boost's. (I should note that an ability to easily extract information from svn commandline tools such as svnversion is important, as well as enough flexibility to configure for builds of asm projects as easily as c/c++ projects)

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  • C++ meta-splat function

    - by aaa
    hello. Is there an existing function (in boost mpl or fusion) to splat meta-vector to variadic template arguments? for example: splat<vector<T1, T2, ...>, function>::type same as function<T1, T2, ...> my search have not found one, and I do not want to reinvent one if it already exists. edit: after some tinkering, apparently it's next to impossible to accomplish this in general way, as it would require declaring full template template parameter list for all possible cases. only reasonable solution is to use macro: #define splat(name, function) \ template<class T, ...> struct name; \ template<class T> \ struct name<T,typename boost::enable_if_c< \ result_of::size<T>::value == 1>::type> { \ typedef function< \ typename result_of::value_at_c<T,0>::type \ > type; \ }; Oh well. thank you

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  • How to handle 'this' pointer in constructor?

    - by Kyle
    I have objects which create other child objects within their constructors, passing 'this' so the child can save a pointer back to its parent. I use boost::shared_ptr extensively in my programming as a safer alternative to std::auto_ptr or raw pointers. So the child would have code such as shared_ptr<Parent>, and boost provides the shared_from_this() method which the parent can give to the child. My problem is that shared_from_this() cannot be used in a constructor, which isn't really a crime because 'this' should not be used in a constructor anyways unless you know what you're doing and don't mind the limitations. Google's C++ Style Guide states that constructors should merely set member variables to their initial values. Any complex initialization should go in an explicit Init() method. This solves the 'this-in-constructor' problem as well as a few others as well. What bothers me is that people using your code now must remember to call Init() every time they construct one of your objects. The only way I can think of to enforce this is by having an assertion that Init() has already been called at the top of every member function, but this is tedious to write and cumbersome to execute. Are there any idioms out there that solve this problem at any step along the way?

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  • How do I make these inputs relate to each other?

    - by dmanexe
    I have a series of checkbox inputs and corresponding text area inputs to allow specification of quantity. Here's what the two fields look like when the item is static (i.e. only 1): <input type="checkbox" name="measure[checked][]" value="<?=$item->id?>"> <input type="hidden" name="measure[quantity][]" value="1" /> Here's what the input fields look like for all items that have a specifiable quantity: <input type="checkbox" name="measure[checked][]" value="<?=$item->id?>"> <input class="item_mult" value="0" type="text" name="measure[quantity][]" /> This would play nicely, if within the array, it didn't output like this, after collecting it with: $field = $this->input->post('measure',true); Array ( [quantity] => Array ( [0] => 1 [1] => 1 [2] => 1 [3] => 1 [4] => 1 [5] => 1 [6] => 25 [7] => 0 [8] => 0 [9] => 0 [10] => 1 [11] => 1 [12] => 1 [13] => 1 [14] => 1 [15] => 1 [16] => 1 [17] => 1 [18] => 1 [19] => 1 [20] => 1 [21] => 1 [22] => 0 [23] => 0 [24] => 0 [25] => 0 [26] => 0 [27] => 0 [28] => 0 [29] => 0 [30] => 0 [31] => 0 [32] => 0 [33] => 0 [34] => 0 [35] => 0 [36] => 0 [37] => 0 [38] => 0 [39] => 0 [40] => 0 [41] => 1 [42] => 1 [43] => 1 [44] => 1 [45] => 1 [46] => 1 [47] => 1 [48] => 1 [49] => 1 [50] => 1 [51] => 1 [52] => 0 [53] => 0 [54] => 0 ) [checked] => Array ( [0] => 4 [1] => 6 [2] => 13 ) ) I understand what the values in the checked array are, I just do not understand how to relate the first field to the second, later in the program. How do I incorporate the correct code to relate checked items to quantities?

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  • Is there a way to find out whether a class is a direct base of another class?

    - by user176168
    Hi I'm wondering whether there is a way to find out whether a class is a direct base of another class i.e. in boost type trait terms a is_direct_base_of function. As far as I can see boost doesn't see to support this kind of functionality which leads me to think that its impossible with the current C++ standard. The reason I want it is to do some validation checking on two macro's that are used for a reflection system to specify that one class is derived from another e.g. header.h: #define BASE A #define DERIVED B class A {}; class B : public A { #include <rtti.h> }; rtti.h: // I want to check that the two macro's are correct with a compile time assert Rtti<BASE, DERIVED> m_rtti; Although the macro's seem unnecessary in this simple example in my real world scenario rtti.h is a lot more complex. One possible avenue would be to compare the size of the this pointer with the size of a this pointer cast to the base type and some how trying to figure out whether its the size of the base class itself away or something (yeah your right I don't know how that would work either! lol)

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  • A generic C++ library that provides QtConcurrent functionality?

    - by Lucas
    QtConcurrent is awesome. I'll let the Qt docs speak for themselves: QtConcurrent includes functional programming style APIs for parallel list processing, including a MapReduce and FilterReduce implementation for shared-memory (non-distributed) systems, and classes for managing asynchronous computations in GUI applications. For instance, you give QtConcurrent::map() an iterable sequence and a function that accepts items of the type stored in the sequence, and that function is applied to all the items in the collection. This is done in a multi-threaded manner, with a thread pool equal to the number of logical CPU's on the system. There are plenty of other function in QtConcurrent, like filter(), filteredReduced() etc. The standard CompSci map/reduce functions and the like. I'm totally in love with this, but I'm starting work on an OSS project that will not be using the Qt framework. It's a library, and I don't want to force others to depend on such a large framework like Qt. I'm trying to keep external dependencies to a minimum (it's the decent thing to do). I'm looking for a generic C++ framework that provides me with the same/similar high-level primitives that QtConcurrent does. AFAIK boost has nothing like this (I may be wrong though). boost::thread is very low-level compared to what I'm looking for. I know C# has something very similar with their Parallel Extensions so I know this isn't a Qt-only idea. What do you suggest I use?

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  • C++ variable to const expression

    - by user1344784
    template <typename Real> class A{ }; template <typename Real> class B{ }; //... a few dozen more similar template classes class Computer{ public slots: void setFrom(int from){ from_ = from; } void setTo(int to){ to_ = to; } private: template <int F, int T> void compute(){ using boost::fusion::vector; using boost::fusion::at_c; vector<A<float>, B<float>, ...> v; at_c<from_>(v).operator()(at_c<to_>(v)); //error; needs to be const-expression. }; This question isn't about Qt, but there is a line of Qt code in my example. The setFrom() and setTo() are functions that are called based on user selection via the GUI widget. The root of my problem is that 'from' and 'to' are variables. In my compute member function I need to pick a type (A, B, etc.) based on the values of 'from' and 'to'. The only way I know how to do what I need to do is to use switch statements, but that's extremely tedious in my case and I would like to avoid. Is there anyway to convert the error line to a constant-expression?

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  • template specialization for static member functions; howto?

    - by Rolle
    I am trying to implement a template function with handles void differently using template specialization. The following code gives me an "Explicit specialization in non-namespace scope" in gcc: template <typename T> static T safeGuiCall(boost::function<T ()> _f) { if (_f.empty()) throw GuiException("Function pointer empty"); { ThreadGuard g; T ret = _f(); return ret; } } // template specialization for functions wit no return value template <> static void safeGuiCall<void>(boost::function<void ()> _f) { if (_f.empty()) throw GuiException("Function pointer empty"); { ThreadGuard g; _f(); } } I have tried moving it out of the class (the class is not templated) and into the namespace but then I get the error "Explicit specialization cannot have a storage class". I have read many discussions about this, but people don't seem to agree how to specialize function templates. Any ideas?

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  • Confused about std::runtime_error vs. std::logic_error

    - by David Gladfelter
    I recently saw that the boost program_options library throws a logic_error if the command-line input was un-parsable. That challenged my assumptions about logic_error vs. runtime_error. I assumed that logic errors (logic_error and its derived classes) were problems that resulted from internal failures to adhere to program invariants, often in the form of illegal arguments to internal API's. In that sense they are largely equivalent to ASSERT's, but meant to be used in released code (unlike ASSERT's which are not usually compiled into released code.) They are useful in situations where it is infeasible to integrate separate software components in debug/test builds or the consequences of a failure are such that it is important to give runtime feedback about the invalid invariant condition to the user. Similarly, I thought that runtime_errors resulted exclusively from runtime conditions outside of the control of the programmer: I/O errors, invalid user input, etc. However, program_options is obviously heavily (primarily?) used as a means of parsing end-user input, so under my mental model it certainly should throw a runtime_error in the case of bad input. Where am I going wrong? Do you agree with the boost model of exception typing?

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  • Is it possible to create ostream object, which outputs to multiple destinations?

    - by fiktor
    In 0-th approximation I have a class class MyClass{ public: ... std::ostream & getOStream(){return f;} private: ofstream f; ... }; Which is used sometimes in the following way: MyClass myclass; myclass.getOStream()<<some<<information<<printed<<here; But now I want to change the class MyClass, so that information will be printed both to f and to std::out, i.e. I want the above line to be equivalent to myclass.f<<some<<information<<printed<<here; std::cout<<some<<information<<printed<<here; I don't know any good way to do that. Do you? Is there any standard solution (for example in stl or in boost)? P.S. I tried to search on this, but it seems that I don't know good keywords. Words multiple, output, ostream, C++, boost seem to be too general.

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  • Change value of adjacent vertices and remove self loop

    - by StereoMatching
    Try to write a Karger’s algorithm with boost::graph example (first column is vertice, other are adjacent vertices): 1 2 3 2 1 3 4 3 1 2 4 4 2 3 assume I merge 2 to 1, I get the result 1 2 3 2 1 1 3 4 2 1 3 4 3 1 2 4 4 2 3 first question : How could I change the adjacent vertices("2" to "1") of vertice 1? my naive solution template<typename Vertex, typename Graph> void change_adjacent_vertices_value(Vertex input, Vertex value, Graph &g) { for (auto it = boost::adjacent_vertices(input, g); it.first != it.second; ++it.first){ if(*it.first == value){ *(it.first) = input; //error C2106: '=' : left operand must be l-value } } } Apparently, I can't set the value of the adjacent vertices to "1" by this way The result I want after "change_adjacent_vertices_value" 1 1 3 1 1 1 3 4 2 1 3 4 3 1 2 4 4 2 3 second question : How could I pop out the adjacent vertices? Assume I want to pop out the consecutive 1 from the vertice 1 The result I expected 1 1 3 1 3 4 2 1 3 4 3 1 2 4 4 2 3 any function like "pop_adjacent_vertex" could use?

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  • curl multiple requests cookie issue

    - by embedded
    I'm using curl multi API for multiple curl requests. first I'm using a single request to login to a site and save the cookie file. then I'm using the curl multi API to get some data from that site. The problem I'm facing is that from some reason the cookie file does not get read and I'm redirecting to the main login page. I must say that this work once in awhile so I can't point what went wrong. Any help would be much appreciated. Thanks

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  • WPF Manipulation and Touch events not firing, but mouse events do?

    - by Smetad Anarkist
    I have a Samsung LD220Z multi touch monitor, and when I'm experimenting with some WPF and touch features the touch events arent firing. The mouse down event seems to be firing however. Does this mean that I have to take into account that not all touch screen behave the same, and how do I get the touch inputs on my screen? I've tried the Windows 7 Touch pack that microsoft released. And the multi touch features seems to work there. Any suggestion on how to proceed with this?

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  • curl multiple request session issue

    - by embedded
    I'm using curl multi API for multiple curl requests. first I'm using a single request to login to a site and save the cookie file. then I'm using the curl multi API to get some data from that site. The problem I'm facing is that from some reason the cookie file does not get read and I'm redirecting to the main login page. I must say that this work once in awhile so I can't point what went wrong. Any help would be much appreciated. Thanks

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  • Using Array Variables For FILE_GET_CONTENTS

    - by Whoshooter
    I have a script all done now and everything has been debugged and it works, except for the last hurdle. This script grabs pertinent information on bank web sites, takes that data and uses it to populate a template and then it's all posted to Wordpress - BUT I get an error because the file_get_contents function fails taking each url from the Array. I've var_dumped the array and all the URLS are there in the [0] key, so this is what I tried. master data is the scraped URL source the script uses urlscrape_array is the collection of URLS $master_data = file_get_contents($urlscrape_array[0]); When I run the script using a URL like below it works beautifully every time; $master_data = file_get_contents("http://www.somesite/somepage.html"); This is the error I get when I try to use the first example' Warning: file_get_contents() expects parameter 1 to be string, array given in /home3/path/public_html/mysite.com/boise_project/scriptmainpage.php on line 13 As requested here is a sample of the var_dump on $urlscrape_array[0] array(504) { [0]=> string(56) "http://www.somepage.com/somepage-3178.html" [1]=> string(54) "http://www.somepage.com/somepage-16.html" [2]=> string(56) "http://www.somepage.com/somepage-3202.html" [3]=> string(56) "http://www.somepage.com/somepage-4324.html" [4]=> string(56) "http://www.somepage.com/somepage-4777.html" [5]=> string(56) "http://www.somepage.com/somepage-5140.html" [6]=> string(56) "http://www.somepage.com/somepage-5220.html" [7]=> string(56) "http://www.somepage.com/somepage-9205.html" [8]=> string(56) "http://www.somepage.com/somepage-3251.html" [9]=> string(56) "http://www.somepage.com/somepage-3323.html" [10]=> string(56) "http://www.somepage.com/some-page-3797.html" [11]=> string(56) "http://www.somepage.com/some-page-4145.html" [12]=> string(56) "http://www.somepage.com/some-page-3191.html" [13]=> string(55) "http://www.somepage.com/some-page-329.html" [14]=> string(56) etc.... Error as per the foreach statement provided by Uptown Warning: Invalid argument supplied for foreach() in /home3/bettyt45/public_html/bdbud.com/boise_project/boise-wordpress.php on line 12 NULL print_r resulst below; Array ( [0] => Array ( [0] => http://www.somesite.com/some-page-3178.html [1] => http://www.somesite.com/some-page-16.html [2] => http://www.somesite.com/some-page-3202.html [3] => http://www.somesite.com/some-page-4324.html [4] => http://www.somesite.com/some-page-4777.html [5] => http://www.somesite.com/some-page-5140.html [6] => http://www.somesite.com/some-page-5220.html [7] => http://www.somesite.com/some-page-9205.html [8] => http://www.somesite.com/some-page-3251.html [9] => http://www.somesite.com/some-page-3323.html [10] => http://www.somesite.com/some-page-3797.html [11] => http://www.somesite.com/some-page-4145.html [12] => http://www.somesite.com/some-page-3191.html [13] => http://www.somesite.com/some-page-329.html [14] => http://www.somesite.com/some-page-3341.html [15] => http://www.somesite.com/some-page-3758.html [16] => http://www.somesite.com/some-page-4180.html [17] => http://www.somesite.com/some-page-9014.html [18] => http://www.somesite.com/some-page-5987.html [19] => http://www.somesite.com/some-page-1542.html [20] => http://www.somesite.com/some-page-3004.html [21] => http://www.somesite.com/some-page-9034.html [22] => http://www.somesite.com/some-page-3385.html [23] => http://www.somesite.com/some-page-3435.html [24] => http://www.somesite.com/some-page-6389.html [25] => http://www.somesite.com/some-page-6992.html [26] => http://www.somesite.com/some-page-7051.html HERE IS THE CODE I USED TO CREATE THE ARRAY ABOVE; $urlscrape_data = file_get_contents('http://www.bdbud.com/boise_project/boise-urls.htm'); preg_match_all('~http\:\/\/www.creditunionsonline.com\/credit\-union\-\d{1,4}?\.html~', $urlscrape_data, $urlscrape_matches); $urlscrape_array = $urlscrape_matches;

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  • Do Android/webOS devices support multi-touch Javascript events?

    - by Rufo Sanchez
    On iPhone, iPod touch and (presumably) iPad, Apple has multi-touch event handling available via JavaScript in Mobile Safari. I know the Nexus One recently added multi-touch support via an update, and I believe webOS is also multi-touch enabled. Do Android 2.1 and/or webOS have access to multi-touch in the browser, or is this currently exclusive to Apple devices?

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  • Blackberry Development, adding dynamic number of buttons and setting Fieldchangelistener() for them

    - by Nikesh Yadav
    Hi, I am adding dynamic number of buttons in a Blackberry application and trying to get different events on each button click. I am not able to apply the setchangelistener() for these array of buttons as once the loop finishes after adding all the buttons, the events gets generated only for the last indexed button. If I make us of getIndex(), it runs fine only if I am not adding any other fields on my screen, but if I add other fields along with these array of buttons, the getIndex() function count them in the indexing as well. Can anyone please help me out in setting FieldChangeListener to array of ButtonField? Here is a sample code of the way I am using the array of ButtonField. I the code I have added two test LabelField at the top of the screen, if I remove them the code will run fine and I will get different result for each button click, but if I keep them active, the indexing gets effected and the Button wont work. package buttonclickloop; import net.rim.device.api.ui.DrawStyle; import net.rim.device.api.ui.Field; import net.rim.device.api.ui.FieldChangeListener; import net.rim.device.api.ui.component.ButtonField; import net.rim.device.api.ui.component.LabelField; import net.rim.device.api.ui.container.HorizontalFieldManager; import net.rim.device.api.ui.container.MainScreen; public class ButtoncClickLoop extends MainScreen { int i = 0; private ButtonField[] btn = new ButtonField[50]; public ButtoncClickLoop() { // TODO Auto-generated constructor stub LabelField Field1 = new LabelField("Field1"); LabelField Field2 = new LabelField("Field2",DrawStyle.RIGHT | ButtonField.USE_ALL_WIDTH); HorizontalFieldManager FieldHmgr = new HorizontalFieldManager(); FieldHmgr.add(Field1); FieldHmgr.add(Field2); FieldHmgr.setMargin(0,0,10,5); add(FieldHmgr); while (i < 3){ FieldChangeListener listener = new FieldChangeListener() { public void fieldChanged(Field field, int context) { context = field.getIndex(); if (field == btn[context]){ add(new LabelField("Label" + context + "")); } } }; btn[i] = new ButtonField("Button" + i + ""); btn[i].setChangeListener(listener); add(btn[i]); i = i + 1; } } } Thanks, Nikesh

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  • Java ArrayList initialization

    - by Jonathan
    I am aware that you can initialize an array during instantiation as follows: String[] names = new String[] {"Ryan", "Julie", "Bob"}; Is there a way to do the same thing with an ArrayList? Or must I add the contents individually with array.add()? Thanks, Jonathan

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  • Sorting Numbers ins a Object.

    - by user133611
    Hi I have an NSMutableArray of objects, let's say 'Person' Objects. I want to sort the NSMutable Array by person.savings i.e if suppose person having savings 1000,1050,500,1200,2000,1050 i want the Array in the ascending order. Thank You.

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  • Why is System.arraycopy native in Java?

    - by James B
    I was surprised to see in the Java source that System.arraycopy is a native method. Of course the reason is because it's faster. But what native tricks is the code able to employ that make it faster? Why not just loop over the original array and copy each pointer to the new array - surely this isn't that slow and cumbersome? Thanks, -James

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  • C++ delete[] operator

    - by Betamoo
    Is this the right way to use delete[] operator? int* a=new int[size]; delete[] a; If yes, Who (compiler or GC or whoever) will determine the size of the newly created array? and where will it store the array size? Thanks

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