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  • IList<T> and IReadOnlyList<T>

    - by Safak Gür
    My problem is that I have a method that can take a collection as parameter that, Has a Count property Has an integer indexer (get-only) And I don't know what type should this parameter be. I would choose IList<T> before .NET 4.5 since there is no other indexable collection interface for this and arrays implement it, which is a big plus. But .NET 4.5 introduces the new IReadOnlyList<T> interface and I want my method to support that, too. How can I write this method to support both IList<T> and IReadOnlyList<T> without violating the basic principles like DRY? Can I convert IList<T> to IReadOnlyList<T> somehow in an overload? What is the way to go here? Edit: Daniel's answer gave me some pretty ideas, I guess I'll go with this: public void Do<T>(IList<T> collection) { DoInternal(collection, collection.Count, i => collection[i]); } public void Do<T>(IReadOnlyList<T> collection) { DoInternal(collection, collection.Count, i => collection[i]); } private void DoInternal<T>(IEnumerable<T> collection, int count, Func<int, T> indexer) { // Stuff } Or I could just accept a ReadOnlyList<T> and provide an helper like this: public static class CollectionEx { public static IReadOnlyList<T> AsReadOnly<T>(this IList<T> collection) { if (collection == null) throw new ArgumentNullException("collection"); return new ReadOnlyWrapper<T>(collection); } private sealed class ReadOnlyWrapper<T> : IReadOnlyList<T> { private readonly IList<T> _Source; public int Count { get { return _Source.Count; } } public T this[int index] { get { return _Source[index]; } } public ReadOnlyWrapper(IList<T> source) { _Source = source; } public IEnumerator<T> GetEnumerator() { return _Source.GetEnumerator(); } IEnumerator IEnumerable.GetEnumerator() { return GetEnumerator(); } } } Then I could call Do(array.AsReadOnly())

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  • How do I output installation status using gtk in c?

    - by Runner
    int main( int argc, char *argv[] ) { GtkWidget *window; gtk_init (&argc, &argv); window = gtk_window_new (GTK_WINDOW_TOPLEVEL); gtk_widget_show (window); gtk_main (); return 0; } The above is just a empty winform,I want to output dynamic information in it(not editable), how should I do that?

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  • C/C++ pragma in define macro

    - by aaa
    is there some way to embed pragma statement in macro with other statements? I am trying to achieve something like: #define DEFINE_DELETE_OBJECT(type) \ void delete_ ## type_(int handle); \ void delete_ ## type(int handle); \ #pragma weak delete_ ## type_ = delete_ ## type I am okay with boost solutions (save for wave) if one exists. thank you

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  • Convert multiquery to a query using group by and so on

    - by ffffff
    -schema CREATE TABLE `ratings` ( `id` int(11) NOT NULL default '0', `rating` int(11) NOT NULL default '1', `rating_start` datetime NOT NULL default '0000-00-00 00:00:00', PRIMARY KEY (`id`) ) TYPE=MyISAM -myprogram.php foreach($ids as $id){ $sql = "SELECT rating FROM ratings WHERE id = '$id' AND rating_start >= NOW()"; $sql .= "ORDER BY rating_start DESC LIMIT 1;" $ret = $db->execute($id); } Can I teke same date from a Query? by using id IN (".implode(",",$ids).") and GROUP BY id

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  • Java serialization problem

    - by stefan89
    I have two classes X and Y, like this: class X implements Serializable { int val1; Y val2; } class Y implements Serializable { int val; } I want to transmit an object of type X from a client to server but i can't because the class X has a field of type Y. I replaced the field of type Y with a field of type X in class X and it works.

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  • Optimizing sparse dot-product in C#

    - by Haggai
    Hello. I'm trying to calculate the dot-product of two very sparse associative arrays. The arrays contain an ID and a value, so the calculation should be done only on those IDs that are common to both arrays, e.g. <(1, 0.5), (3, 0.7), (12, 1.3) * <(2, 0.4), (3, 2.3), (12, 4.7) = 0.7*2.3 + 1.3*4.7 . My implementation (call it dict) currently uses Dictionaries, but it is too slow to my taste. double dot_product(IDictionary<int, double> arr1, IDictionary<int, double> arr2) { double res = 0; double val2; foreach (KeyValuePair<int, double> p in arr1) if (arr2.TryGetValue(p.Key, out val2)) res += p.Value * val2; return res; } The full arrays have about 500,000 entries each, while the sparse ones are only tens to hundreds entries each. I did some experiments with toy versions of dot products. First I tried to multiply just two double arrays to see the ultimate speed I can get (let's call this "flat"). Then I tried to change the implementation of the associative array multiplication using an int[] ID array and a double[] values array, walking together on both ID arrays and multiplying when they are equal (let's call this "double"). I then tried to run all three versions with debug or release, with F5 or Ctrl-F5. The results are as follows: debug F5: dict: 5.29s double: 4.18s (79% of dict) flat: 0.99s (19% of dict, 24% of double) debug ^F5: dict: 5.23s double: 4.19s (80% of dict) flat: 0.98s (19% of dict, 23% of double) release F5: dict: 5.29s double: 3.08s (58% of dict) flat: 0.81s (15% of dict, 26% of double) release ^F5: dict: 4.62s double: 1.22s (26% of dict) flat: 0.29s ( 6% of dict, 24% of double) I don't understand these results. Why isn't the dictionary version optimized in release F5 as do the double and flat versions? Why is it only slightly optimized in the release ^F5 version while the other two are heavily optimized? Also, since converting my code into the "double" scheme would mean lots of work - do you have any suggestions how to optimize the dictionary one? Thanks! Haggai

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  • Can I use the [] operator in C++ to create virtual arrays

    - by Shane MacLaughlin
    I have a large code base, originally C ported to C++ many years ago, that is operating on a number of large arrays of spatial data. These arrays contain structs representing point and triangle entities that represent surface models. I need to refactor the code such that the specific way these entities are stored internally varies for specific scenarios. For example if the points lie on a regular flat grid, I don't need to store the X and Y coordinates, as they can be calculated on the fly, as can the triangles. Similarly, I want to take advantage of out of core tools such as STXXL for storage. The simplest way of doing this is replacing array access with put and get type functions, e.g. point[i].x = XV; becomes Point p = GetPoint(i); p.x = XV; PutPoint(i,p); As you can imagine, this is a very tedious refactor on a large code base, prone to all sorts of errors en route. What I'd like to do is write a class that mimics the array by overloading the [] operator. As the arrays already live on the heap, and move around with reallocs, the code already assumes that references into the array such as point *p = point + i; may not be used. Is this class feasible to write? For example writing the methods below in terms of the [] operator; void MyClass::PutPoint(int Index, Point p) { if (m_StorageStrategy == RegularGrid) { int xoffs,yoffs; ComputeGridFromIndex(Index,xoffs,yoffs); StoreGridPoint(xoffs,yoffs,p.z); } else m_PointArray[Index] = p; } } Point MyClass::GetPoint(int Index) { if (m_StorageStrategy == RegularGrid) { int xoffs,yoffs; ComputeGridFromIndex(Index,xoffs,yoffs); return GetGridPoint(xoffs,yoffs); // GetGridPoint returns Point } else return m_PointArray[Index]; } } My concern is that all the array classes I've seen tend to pass by reference, whereas I think I'll have to pass structs by value. I think it should work put other than performance, can anyone see any major pitfalls with this approach. n.b. the reason I have to pass by value is to get point[a].z = point[b].z + point[c].z to work correctly where the underlying storage type varies.

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  • deteminant of matrix

    - by davit-datuashvili
    suppose there is given two dimensional array int a[][]=new int[4][4]; i am trying to find determinant of matrices please help i know how find it mathematical but i am trying to find it in programaticaly

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  • MySQL function to compare values in a db table against the previous

    - by Stuart
    Iam quite new to functions in SQL and I would like to create a function to compare values in a MySQL table against previous and I am not sure how to do this. For example (iId is the input value) DECLARE pVal INT(20); DECLARE val INT(20); SELECT price INTO pVal FROM products WHERE Id=iId; SELECT price FROM products; IF price == pVal THEN SET val = price; END IF; Thanks

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  • Android OnKeyListener

    - by user346665
    Why I can't implement OnKeyListener with parameter View such as on example where parameters are (View v, int keyCode, KeyEvent event) I'm forced to use parameters (DialogInterface dialog, int keyCode, KeyEvent event) but not the View as I want.

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  • T-SQL get SELECTed value of stored procedure

    - by David
    In T-SQL, this is allowed: DECLARE @SelectedValue int SELECT @SelectedValue = MyIntField FROM MyTable WHERE MyPrimaryKeyField = 1 So, it's possible to get the value of a SELECT and stuff it in a variable (provided it's scalar, obviously). If I put the same select logic in a stored procedure: CREATE PROCEDURE GetMyInt AS SELECT MyIntField FROM MyTable WHERE MyPrimaryKeyField = 1 Can I get the output of this stored procedure and stuff it in a variable? Something like: DECLARE @SelectedValue int SELECT @SelectedValue = EXEC GetMyInt (I know the syntax above is not allowed because I tried it!)

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  • Focus process window, ShowWindow vs System Tray

    - by ais
    I try open process window, this code work if window state is minimize, but if program in system tray window isn't opened. [DllImport("User32")] private static extern int SetForegroundWindow(IntPtr hwnd); [DllImport("User32")] private static extern bool ShowWindow(IntPtr hWnd, int nCmdShow); private static void ShowWindow(Process process) { ShowWindow(process.MainWindowHandle, SW_RESTORE); SetForegroundWindow(process.MainWindowHandle); }

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  • c++/boost: use tuple ctors when subclassing

    - by bbb
    Hi there, is there some way to use a boost tuple's ctors as an addition to the subclass methods (and ctors) like here? // typedef boost::tuple<int, SomeId, SomeStatus> Conn; // Conn(1); // works and initializes using default ctors of Some* struct Conn : boost::tuple<int, AsynchId, AccDevRetStatus> {}; Conn(1); // "no matching function call" (but i want it so much) T.H.X.

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  • What is the meaning of client coordinates in SetWindowPos

    - by user1775315
    The documentation for SetWindowPos says the following for the X and Y parameters: X [in] Type: int The new position of the left side of the window, in client coordinates. Y [in] Type: int The new position of the top of the window, in client coordinates. By "client coordinates", does it mean that the parameters specify the position of the client area of the window, or that they specify the position of the window (not the client area) relative to the parent window's client area? Or something else?

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  • Xerces conflicts string.h

    - by Velthune
    Compiling my program I have this error: /usr/include/xercesc/util/Compilers/GCCDefs.hpp:133:60: error: declaration of ‘int strcasecmp(const char*, const char*)’ has a different exception specifier /usr/include/string.h:536:12: error: from previous declaration ‘int strcasecmp(const char*, const char*) throw ()’ make: *** [src/test/VFTImageMaterial.o] Error 1 Any idea about this conflict with string.h?

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  • Get rid of Trailing Numbers in C

    - by Tech163
    For example, #include <stdio.h> int main (int argc, const char * argv[]) { char out = printf("teststring"); printf("%d\n", out); return 0; } will return teststring10. Anyone has an idea how to get rid of the 10? Thanks in advance.

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  • Why is this undefined behaviour?

    - by xryl669
    Here's the sample code: X * makeX(int index) { return new X(index); } struct Tmp { mutable int count; Tmp() : count(0) {} const X ** getX() const { static const X* x[] = { makeX(count++), makeX(count++) }; return x; } }; This reports Undefined Behaviour on CLang version 500 in the static array construction. For sake of simplication for this post, the count is not static, but it does not change anything.

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  • Refactor the following two C++ methods to move out duplicate code

    - by ossandcad
    I have the following two methods that (as you can see) are similar in most of its statements except for one (see below for details) unsigned int CSWX::getLineParameters(const SURFACE & surface, vector<double> & params) { VARIANT varParams; surface->getPlaneParams(varParams); // this is the line of code that is different SafeDoubleArray sdParams(varParams); for( int i = 0 ; i < sdParams.getSize() ; ++i ) { params.push_back(sdParams[i]); } if( params.size() > 0 ) return 0; return 1; } unsigned int CSWX::getPlaneParameters(const CURVE & curve, vector<double> & params) { VARIANT varParams; curve->get_LineParams(varParams); // this is the line of code that is different SafeDoubleArray sdParams(varParams); for( int i = 0 ; i < sdParams.getSize() ; ++i ) { params.push_back(sdParams[i]); } if( params.size() > 0 ) return 0; return 1; } Is there any technique that I can use to move the common lines of code of the two methods out to a separate method, that could be called from the two variations - OR - possibly combine the two methods to a single method? The following are the restrictions: The classes SURFACE and CURVE are from 3rd party libraries and hence unmodifiable. (If it helps they are both derived from IDispatch) There are even more similar classes (e.g. FACE) that could fit into this "template" (not C++ template, just the flow of lines of code) I know the following could (possibly?) be implemented as solutions but am really hoping there is a better solution: I could add a 3rd parameter to the 2 methods - e.g. an enum - that identifies the 1st parameter (e.g. enum::input_type_surface, enum::input_type_curve) I could pass in an IDispatch and try dynamic_cast< and test which cast is NON_NULL and do an if-else to call the right method (e.g. getPlaneParams() vs. get_LineParams()) The following is not a restriction but would be a requirement because of my teammates resistance: Not implement a new class that inherits from SURFACE/CURVE etc. (They would much prefer to solve it using the enum solution I stated above)

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  • Advanced Model Binding vs 2010

    - by user281180
    Can I have an example of advanced model binding using ajaxpost? I have two classes Person and Test as follows: public class person{ public ArrayList Name = new ArrayList(); public Test []test {get;set;} } public class Test { public int ID{get;set;} public int mark{get;set;} } My Controller could be [HttpPost] public EmptyResult CaseTest(Person person) { return new EmptyResult(); } How do I post the values from the view?

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  • how to pass an integeter array from a asp.net mvc controller action back to javascript using jquery

    - by oo
    Here is my jQuery code: $.get('/Home/GetList', function(data) { debugger; $('#myMultiSelect').val(data); }); Here is my controller code: public ActionResult GetList(int id) { int[] bodyParts = _repository.GetList(id); //how do i return this as an array back to javascript ?? } if I have the GetList function return an array of integers, how do I return this to the jQuery function?

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  • how to pass an array from a asp.net mvc controller action back to javascript using jquery / ajax

    - by oo
    Here is my jQuery code: $.get('/Home/GetList', function(data) { debugger; $('#myMultiSelect').val(values); }); Here is my controller code: public ActionResult GetList(int id) { int[] bodyParts = _repository.GetList(id); //how do i return this as an array back to javascript ?? } if I have the GetList function return an array of integers, how do I return this to the jQuery function?

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