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• optimize 2D array in C++

  - by Hristo

  I'm dealing with a 2D array with the following characteristics: const int cols = 500; const int rows = 100; int arr[rows][cols]; I access array arr in the following manner to do some work: for(int k = 0; k < T; ++k) { // for each trainee myscore[k] = 0; for(int i = 0; i < N; ++i) { // for each sample for(int j = 0; j < E[i]; ++j) { // for each expert myscore[k] += delta(i, anotherArray[k][i], arr[j][i]); } } } So I am worried about the array 'arr' and not the other one. I need to make this more cache-friendly and also boost the speed. I was thinking perhaps transposing the array but I wasn't sure how to do that. My implementation turns out to only work for square matrices. How would I make it work for non-square matrices? Also, would mapping the 2D array into a 1D array boost the performance? If so, how would I do that? Finally, any other advice on how else I can optimize this... I've run out of ideas, but I know that arr[j][i] is the place where I need to make changes because I'm accessing columns by columns instead of rows by rows so that is not cache friendly at all. Thanks, Hristo

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• How to scale JPEG images with a non-standard sampling factor in Java?

  - by HRJ

  I am using Java AWT for scaling a JPEG image, to create thumbnails. The code works fine when the image has a normal sampling factor ( 2x2,1x1,1x1 ) However, an image which has this sampling factor ( 1x1, 1x1, 1x1 ) creates problem when scaled. The colors get corrupted though the features are recognizable. The original and the thumbnail: The code I am using is roughly equivalent to: static BufferedImage awtScaleImage(BufferedImage image, int maxSize, int hint) { // We use AWT Image scaling because it has far superior quality // compared to JAI scaling. It also performs better (speed)! System.out.println("AWT Scaling image to: " + maxSize); int w = image.getWidth(); int h = image.getHeight(); float scaleFactor = 1.0f; if (w > h) scaleFactor = ((float) maxSize / (float) w); else scaleFactor = ((float) maxSize / (float) h); w = (int)(w * scaleFactor); h = (int)(h * scaleFactor); // since this code can run both headless and in a graphics context // we will just create a standard rgb image here and take the // performance hit in a non-compatible image format if any Image i = image.getScaledInstance(w, h, hint); image = new BufferedImage(w, h, BufferedImage.TYPE_INT_RGB); Graphics2D g = image.createGraphics(); g.drawImage(i, null, null); g.dispose(); i.flush(); return image; } (Code courtesy of this page ) Is there a better way to do this? Here's a test image with sampling factor of [ 1x1, 1x1, 1x1 ].

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• FileNotFoundException Java

  - by Troels Hansen

  Hi, I'm trying to make a simple highscore system for a minesweeper game. However i keep getting a file not found exception, and i've tried to use the full path for the file aswell. package minesweeper; import java.io.*; import java.util.*; public class Highscore{ public static void submitHighscore(String difficulty) throws IOException{ int easy = 99999; int normal = 99999; int hard = 99999; //int newScore = (int) MinesweeperView.getTime(); int newScore = 10; File f = new File("Highscores.dat"); if (!f.exists()){ f.createNewFile(); } Scanner input = new Scanner(f); PrintStream output = new PrintStream(f); if (input.hasNextInt()){ easy = input.nextInt(); normal = input.nextInt(); hard = input.nextInt(); } output.flush(); if(difficulty.equals("easy")){ if (easy > newScore){ easy = newScore; } }else if (difficulty.equals("normal")){ if (normal > newScore){ normal = newScore; } }else if (difficulty.equals("hard")){ if (hard > newScore){ hard = newScore; } } output.println(easy); output.println(normal); output.println(hard); } //temporary main method used for debugging public static void main(String[] args) throws IOException { submitHighscore("easy"); } }

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• Need little assistance

  - by Umaid

  I am iterating in current days, so need little assistance for (int I=-1; I<30; I++) { for (int J=0; J=30; J++) { for (int K=1; K=30; K++) { SELECT rowid,Month, Day, Advice from MainCategory where Month= 'May ' and Day in ((cast(strftime('%d',date('now','I day')) as Integer)),(cast(strftime('%d',date('now','J day')) as Integer)),(cast(strftime('%d',date('now','K day')) as Integer))); } } } What if i want to go in reverse order also for (int I=-1; I<30; I--) { for (int J=0; J=30; J--) { for (int K=1; K=30; K--) { SELECT rowid,Month, Day, Advice from MainCategory where Month= 'May ' and Day in ((cast(strftime('%d',date('now','I day')) as Integer)),(cast(strftime('%d',date('now','J day')) as Integer)),(cast(strftime('%d',date('now','K day')) as Integer))); } } } On every previous click, i want to fetch 3 records so do i need to iterate till 3 or make it on all record 30 in a month from which i want to fetch.

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• C++ operator lookup rules / Koenig lookup

  - by John Bartholomew

  While writing a test suite, I needed to provide an implementation of operator<<(std::ostream&... for Boost unit test to use. This worked: namespace theseus { namespace core { std::ostream& operator<<(std::ostream& ss, const PixelRGB& p) { return (ss << "PixelRGB(" << (int)p.r << "," << (int)p.g << "," << (int)p.b << ")"); } }} This didn't: std::ostream& operator<<(std::ostream& ss, const theseus::core::PixelRGB& p) { return (ss << "PixelRGB(" << (int)p.r << "," << (int)p.g << "," << (int)p.b << ")"); } Apparently, the second wasn't included in the candidate matches when g++ tried to resolve the use of the operator. Why (what rule causes this)? The code calling operator<< is deep within the Boost unit test framework, but here's the test code: BOOST_AUTO_TEST_SUITE(core_image) BOOST_AUTO_TEST_CASE(test_output) { using namespace theseus::core; BOOST_TEST_MESSAGE(PixelRGB(5,5,5)); // only compiles with operator<< definition inside theseus::core std::cout << PixelRGB(5,5,5) << "\n"; // works with either definition BOOST_CHECK(true); // prevent no-assertion error } BOOST_AUTO_TEST_SUITE_END() For reference, I'm using g++ 4.4 (though for the moment I'm assuming this behaviour is standards-conformant).

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• Can a Generic Method handle both Reference and Nullable Value types?

  - by Adam Lassek

  I have a series of Extension methods to help with null-checking on IDataRecord objects, which I'm currently implementing like this: public static int? GetNullableInt32(this IDataRecord dr, int ordinal) { int? nullInt = null; return dr.IsDBNull(ordinal) ? nullInt : dr.GetInt32(ordinal); } public static int? GetNullableInt32(this IDataRecord dr, string fieldname) { int ordinal = dr.GetOrdinal(fieldname); return dr.GetNullableInt32(ordinal); } and so on, for each type I need to deal with. I'd like to reimplement these as a generic method, partly to reduce redundancy and partly to learn how to write generic methods in general. I've written this: public static Nullable<T> GetNullable<T>(this IDataRecord dr, int ordinal) { Nullable<T> nullValue = null; return dr.IsDBNull(ordinal) ? nullValue : (Nullable<T>) dr.GetValue(ordinal); } which works as long as T is a value type, but if T is a reference type it won't. This method would need to return either a Nullable type if T is a value type, and default(T) otherwise. How would I implement this behavior?

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• Most Elegant Way to write isPrime in java

  - by Anantha Kumaran

  public class Prime { public static boolean isPrime1(int n) { if (n <= 1) { return false; } if (n == 2) { return true; } for (int i = 2; i <= Math.sqrt(n) + 1; i++) { if (n % i == 0) { return false; } } return true; } public static boolean isPrime2(int n) { if (n <= 1) { return false; } if (n == 2) { return true; } if (n % 2 == 0) { return false; } for (int i = 3; i <= Math.sqrt(n) + 1; i = i + 2) { if (n % i == 0) { return false; } } return true; } } public class PrimeTest { public PrimeTest() { } @Test public void testIsPrime() throws IllegalArgumentException, IllegalAccessException, InvocationTargetException { Prime prime = new Prime(); TreeMap<Long, String> methodMap = new TreeMap<Long, String>(); for (Method method : Prime.class.getDeclaredMethods()) { long startTime = System.currentTimeMillis(); int primeCount = 0; for (int i = 0; i < 1000000; i++) { if ((Boolean) method.invoke(prime, i)) { primeCount++; } } long endTime = System.currentTimeMillis(); Assert.assertEquals(method.getName() + " failed ", 78498, primeCount); methodMap.put(endTime - startTime, method.getName()); } for (Entry<Long, String> entry : methodMap.entrySet()) { System.out.println(entry.getValue() + " " + entry.getKey() + " Milli seconds "); } } } I am trying to find the fastest way to check whether the given number is prime or not. This is what is finally came up with. Is there any better way than the second implementation(isPrime2).

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• Extend and Overload MS and Point Types

  - by dr d b karron

  Do I have make my own Point and Vector types to overload them ? Why does this not work ? namespace System . windows { public partial struct Point : IFormattable { public static Point operator * ( Point P , double D ) { Point Po = new Point ( ); return Po; } } } namespace SilverlightApplication36 { public partial class MainPage : UserControl { public static void ShrinkingRectangle ( WriteableBitmap wBM , int x1 , int y1 , int x2 , int y2 , Color C ) { wBM . DrawRectangle ( x1 , y1 , x2 , y2 , Colors . Red ); Point Center = Mean ( x1 , y1 , x2 , y2 ); wBM . SetPixel ( Center , Colors.Blue , 3 ); Point P1 = new Point ( x1 , y1 ); Point P2 = new Point ( x1 , y2 ); Point P3 = new Point ( x1 , y2 ); Point P4 = new Point ( x2 , y1 ); const int Steps = 10; for ( int i = 0 ; i < Steps ; i++ ) { double iF = (double)(i+1) / (double)Steps; double jF = ( 1.0 - iF ); Point P11 = **P1 * jF;** } }

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• How do I build a class that shares a table with multiple columns in MVC3?

  - by Barrett Kuethen

  I have a Job table public class Job { public int JobId { get; set; } public int SalesManagerId { get; set; } public int SalesRepId { get; set; } } and a Person table public class Person { public int PersonId { get; set; } public int FirstName { get; set; } public int LastName { get; set; } } My question is, how do I link the SalesManagerId to the Person (or PersonId) as well as the SalesRepId to the Person (PersonId)? The Sales Manager and Sales Rep are independent of each other. I just don't want to make 2 different lists to support the Sales Manager and Sales Rep roles. I'm new to MVC3, but it seems public virtual Person Person {get; set; } would be the way to go, but that doesn't work. Any help would be appreciated! Thanks!

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• Pointer arithmetic.

  - by Knowing me knowing you

  Having code: int** a = new int*[2]; a[0] = new int(1); a[1] = new int(2); cout << "a[0] " << a[0] << '\n'; cout << "a[1] " << a[1] << '\n'; cout << "a[2] " << a[2] << '\n'; cout << "a[0] + 1 " << a[0] + 1 << '\n';//WHY THIS ISN'T == a[1] ? cout << "*(a + 1): " << *(a + 1) << '\n'; //WHY THIS IS == a[1] ? cout << "a[0] - a[1] " << static_cast<int>(a[0] - a[1])<< '\n';//WHY THIS IS == 16 not 4? cout << sizeof(int**); Questions are included right next to relevant lines in code.

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• c++ Design pattern for CoW, inherited classes, and variable shared data?

  - by krunk

  I've designed a copy-on-write base class. The class holds the default set of data needed by all children in a shared data model/CoW model. The derived classes also have data that only pertains to them, but should be CoW between other instances of that derived class. I'm looking for a clean way to implement this. If I had a base class FooInterface with shared data FooDataPrivate and a derived object FooDerived. I could create a FooDerivedDataPrivate. The underlying data structure would not effect the exposed getters/setters API, so it's not about how a user interfaces with the objects. I'm just wondering if this is a typical MO for such cases or if there's a better/cleaner way? What peeks my interest, is I see the potential of inheritance between the the private data classes. E.g. FooDerivedDataPrivate : public FooDataPrivate, but I'm not seeing a way to take advantage of that polymorphism in my derived classes. class FooDataPrivate { public: Ref ref; // atomic reference counting object int a; int b; int c; }; class FooInterface { public: // constructors and such // .... // methods are implemented to be copy on write. void setA(int val); void setB(int val); void setC(int val); // copy constructors, destructors, etc. all CoW friendly private: FooDataPrivate *data; }; class FooDerived : public FooInterface { public: FooDerived() : FooInterface() {} private: // need more shared data for FooDerived // this is the ???, how is this best done cleanly? };

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• GUI Agent accepts statuses from Daemon and shows it using progress indicator

  - by Pavel

  Hi to all! My application is a GUI agent, which communicate with daemon through the unix domain socket, wrapped in CFSocket.... So there are main loop and added CFRunLoop source. Daemon sends statuses and agent shows it with a progress indicator. When there are any data on socket, callback function begin to work and at this time I have to immediately show the new window with progress indicator and increase counter. //this function initiate the runloop for listening socket - (int) AcceptDaemonConnection:(ConnectionRef)conn { int err = 0; conn->fSockCF = CFSocketCreateWithNative(NULL, (CFSocketNativeHandle) conn->fSockFD, kCFSocketAcceptCallBack, ConnectionGotData, NULL); if (conn->fSockCF == NULL) err = EINVAL; if (err == 0) { conn->fRunLoopSource = CFSocketCreateRunLoopSource(NULL, conn->fSockCF, 0); if (conn->fRunLoopSource == NULL) err = EINVAL; else CFRunLoopAddSource(CFRunLoopGetCurrent(), conn->fRunLoopSource, kCFRunLoopDefaultMode); CFRelease(conn->fRunLoopSource); } return err; } // callback function void ConnectionGotData(CFSocketRef s, CFSocketCallBackType type, CFDataRef address, const void * data, void * info) { #pragma unused(s) #pragma unused(address) #pragma unused(info) assert(type == kCFSocketAcceptCallBack); assert( (int *) data != NULL ); assert( (*(int *) data) != -1 ); TStatusUpdate status; int nativeSocket = *(int *) data; status = [agg AcceptPacket:nativeSocket]; // [stWindow InitNewWindow] inside [agg SendUpdateStatus:status.percent]; } AcceptPacket function receives packet from the socket and trying to show new window with progress indicator. Corresponding function is called, but nothing happens... I think, that I have to make work the main application loop with interrupting CFSocket loop... Or send a notification? No idea....

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• How to use Comparator in Java to sort

  - by Dan

  I learned how to use the comparable but I'm having difficulty with the Comparator. I am having a error in my code: Exception in thread "main" java.lang.ClassCastException: New.People cannot be cast to java.lang.Comparable at java.util.Arrays.mergeSort(Unknown Source) at java.util.Arrays.sort(Unknown Source) at java.util.Collections.sort(Unknown Source) at New.TestPeople.main(TestPeople.java:18) Here is my code: import java.util.Comparator; public class People implements Comparator{ private int id; private String info; private double price; public People(int newid, String newinfo, double newprice){ setid(newid); setinfo(newinfo); setprice(newprice); } public int getid() { return id; } public void setid(int id) { this.id = id; } public String getinfo() { return info; } public void setinfo(String info) { this.info = info; } public double getprice() { return price; } public void setprice(double price) { this.price = price; } public int compare(Object obj1, Object obj2) { Integer p1 = ((People)obj1).getid(); Integer p2 = ((People)obj2).getid(); if (p1 p2 ){ return 1; } else if (p1 < p2){ return -1; } else return 0; } } import java.util.ArrayList; import java.util.Collections; public class TestPeople { public static void main(String[] args) { ArrayList peps = new ArrayList(); peps.add(new People(123, "M", 14.25)); peps.add(new People(234, "M", 6.21)); peps.add(new People(362, "F", 9.23)); peps.add(new People(111, "M", 65.99)); peps.add(new People(535, "F", 9.23)); Collections.sort(peps); for(int i=0;i I believe it has to do something with the casting in the compare method but I was playing around with it and still could not find the solution

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• tricky interview question for C++

  - by Alexander

  Given the code below. How would you create/implement SR.h so that it produces the correct output WITHOUT any asterix in your solution? I got bummed by this question #include <cstdio> #include "SR.h" int main() { int j = 5; int a[] = {10, 15}; { SR x(j), y(a[0]), z(a[1]); j = a[0]; a[0] = a[1]; a[1] = j; printf("j = %d, a = {%d, %d}\n", j, a[0], a[1]); } printf("j = %d, a = {%d, %d}\n", j, a[0], a[1]); } //output j = 10, a = {15, 10} j = 5, a = {10, 15} #include <cstdio> #include "SR.h" int main() { int sum = 0; for (int i = 1; i < 100; i++) { SR ii(i); while (i--) sum += i; } printf("sum = %d\n", sum); } //The output is "sum = 161700".

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• [C#] Linq doesn't insert associated entity on insert.

  - by Tomek

  Hello! I have simple mapping: [Table(Name="Person")] public class Person { private int id; private int state_id; private EntityRef<PersonState> state = new EntityRef<PersonState>(); [Column(IsPrimaryKey = true, Storage = "id", Name="id", IsDbGenerated = true, CanBeNull = false)] public int ID { get { return id; } set { id = value; } } [Column(Storage="state_id", Name="state_id")] public int StateID { get{ return state_id;} set{ state_id = value;} } [Association( Storage = "state", ThisKey = "StateID", IsForeignKey=true)] public PersonState State { get { return state.Entity; } set { state.Entity = value; } } } [Table(Name = "PersonState")] public class PersonState { private int id; private State state; [Column(Name="id", Storage="id", IsDbGenerated=true, IsPrimaryKey=true)] public int ID { get { return id; } set { id = value; } } [Column(Name = "date", Storage = "date")] public DateTime Date { get { return date; } set { date = value; } } [Column(Name = "type", Storage = "state")] public State State { get { return state; } set { state = value; } } } I use this code to insert new person with default state: private static Person NewPerson() { Person p = new Person(); p.State = DefaultState(p); return p; } private static PersonState DefaultState() { PersonState state = new PersonState(); state.Date = DateTime.Now; state.State = State.NotNotified; state.Comment = "Default State!"; return state; } Leater in code: db.Persons.InsertOnSubmit(NewPerson()); db.SubmitChanges(); In database(sqlite) I have all new persons, but state_id of all persons is set to 0, and PersonState table is empty. Why Linq did not insert any State object to database?

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• Linking a template class using another template class (error LNK2001)

  - by Luís Guilherme

  I implemented the "Strategy" design pattern using an Abstract template class, and two subclasses. Goes like this: template <class T> class Neighbourhood { public: virtual void alter(std::vector<T>& array, int i1, int i2) = 0; }; and template <class T> class Swap : public Neighbourhood<T> { public: virtual void alter(std::vector<T>& array, int i1, int i2); }; There's another subclass, just like this one, and alter is implemented in the cpp file. Ok, fine! Now I declare another method, in another class (including neighbourhood header file, of course), like this: void lSearch(/*parameters*/, Neighbourhood<LotSolutionInformation> nhood); It compiles fine and cleanly. When starting to link, I get the following error: 1>SolverFV.obj : error LNK2001: unresolved external symbol "public: virtual void __thiscall lsc::Neighbourhood<class LotSolutionInformation>::alter(class std::vector<class LotSolutionInformation,class std::allocator<class LotSolutionInformation> > &,int,int)" (?alter@?$Neighbourhood@VLotSolutionInformation@@@lsc@@UAEXAAV?$vector@VLotSolutionInformation@@V?$allocator@VLotSolutionInformation@@@std@@@std@@HH@Z)

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• NUnit doesn't work well with Assert.AreEqual

  - by stasal

  Hi! I'm new to unit-testing and NUit in particular. I'm just typing some examples from the book which refers to Java and JUnit. But I'm using C# instead. The problem is: I've got a class with overriden methods such as Equals() and GetHashCode(), but when I am trying to compare two objects of this class with Assert.AreEqual() my code is not called, so I get an exception. Assert.True(MyClass.Equals(MyClass2)) does work well. But I don't wanna use this construction instead of Assert.AreEqual(). Where the problem can be? Here is the class: public class Money { public int amount; protected string currency; public Money(int amount, string currency) { this.amount = amount; this.currency = currency; } public new bool Equals(object obj) { if (obj == null) return false; Money money = (Money)obj; return (amount == money.amount) && (Currency().Equals(money.Currency())); } public new int GetHashCode() { return (string.Format("{0}{1}", amount, currency)).GetHashCode(); } public static Money Dollar(int amount) { return new Money(amount, "USD"); } public static Money Franc(int amount) { return new Money(amount, "CHF"); } public Money Times(int multiplier) { return new Money(amount * multiplier, currency); } public string Currency() { return currency; } } And the test method itself: [TestFixture] public class DollarTest { [Test] public void TestMultiplication() { Money five = Money.Dollar(5); Assert.True(Money.Dollar(10).Equals(five.Times(2))); // ok Assert.AreEqual(Money.Dollar(10), five.Times(2)); // fails } } Thanks.

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• how to Solve the "Digg" problem in MongoDB

  - by user193116

  A while back,a Digg developer had posted this blog ,"http://about.digg.com/blog/looking-future-cassandra", where the he described one of the issues that were not optimally solved in MySQL. This was cited as one of the reasons for their move to Cassandra. I have been playing with MongoDB and I would like to understand how to implement the MongoDB collections for this problem From the article, the schema for this information in MySQL : CREATE TABLE Diggs ( id INT(11), itemid INT(11), userid INT(11), digdate DATETIME, PRIMARY KEY (id), KEY user (userid), KEY item (itemid) ) ENGINE=InnoDB DEFAULT CHARSET=utf8; CREATE TABLE Friends ( id INT(10) AUTO_INCREMENT, userid INT(10), username VARCHAR(15), friendid INT(10), friendname VARCHAR(15), mutual TINYINT(1), date_created DATETIME, PRIMARY KEY (id), UNIQUE KEY Friend_unique (userid,friendid), KEY Friend_friend (friendid) ) ENGINE=InnoDB DEFAULT CHARSET=utf8; This problem is ubiquitous in social networking scenario implementation. People befriend a lot of people and they in turn digg a lot of things. Quickly showing a user what his/her friends are up to is very critical. I understand that several blogs have since then provided a pure RDBMs solution with indexes for this issue; however I am curious as to how this could be solved in MongoDB.

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• C++ Header file questions

  - by Karl

  So I'm trying to learn C++ and I've gotten as far as using header files. They really make no sense to me. I've tried many combinations of this but nothing so far has worked: Main.cpp: #include "test.h" int main() { testClass Player1; return 0; } test.h: #ifndef TEST_H_INCLUDED #define TEST_H_INCLUDED class testClass { private: int health; public: testClass(); ~testClass(); int getHealth(); void setHealth(int inH); }; #endif // TEST_H_INCLUDED test.cpp: #include "test.h" testClass::testClass() { health = 100; } testClass::~testClass() {} int testClass::getHealth() { return(health); } void testClass::setHealth(int inH) { health = inH; } What I'm trying to do is pretty simple, but the way the header files work just makes no sense to me at all. Code blocks returns the following on build: obj\Debug\main.o(.text+0x131)||In function main':| *voip*\test\main.cpp |6|undefined reference totestClass::testClass()'| obj\Debug\main.o(.text+0x13c):voip\test\main.cpp|7|undefined reference to `testClass::~testClass()'| ||=== Build finished: 2 errors, 0 warnings ===| I'd appreciate any help. Or if you have a decent tutorial for it, that would be fine too (most of the tutorials I've googled haven't helped)

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• Dependency Properties, change notification and setting values in the constructor

  - by stefan.at.wpf

  Hello, I have a clas with 3 dependency properties A,B,C. The values of these properties are set by the constructor and every time one of the properties A, B or C changes, the method recalculate() is called. Now during execution of the constructor these method is called 3 times, because the 3 properties A, B, C are changed. Hoewever this isn't necessary as the method recalculate() can't do anything really useful without all 3 properties set. So what's the best way for property change notification but circumventing this change notification in the constructor? I thought about adding the property changed notification in the constructor, but then each object of the DPChangeSample class would always add more and more change notifications. Thanks for any hint! class DPChangeSample : DependencyObject { public static DependencyProperty AProperty = DependencyProperty.Register("A", typeof(int), typeof(DPChangeSample), new PropertyMetadata(propertyChanged)); public static DependencyProperty BProperty = DependencyProperty.Register("B", typeof(int), typeof(DPChangeSample), new PropertyMetadata(propertyChanged)); public static DependencyProperty CProperty = DependencyProperty.Register("C", typeof(int), typeof(DPChangeSample), new PropertyMetadata(propertyChanged)); private static void propertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e) { ((DPChangeSample)d).recalculate(); } private void recalculate() { // Using A, B, C do some cpu intensive caluclations } public DPChangeSample(int a, int b, int c) { SetValue(AProperty, a); SetValue(BProperty, b); SetValue(CProperty, c); } }

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• vector <T *> destructor

  - by Daniel.Z

  I have a class defined like: Class A { public: int num; A *parent; vector<A *> children; ... // constructor without parameters A(void) { this->num = 3; this->parent = 0; for (int i=0;i<num;++i) children.push_back(new A(this,num-1)); } // constructor with parameters A(A *a,int n) { this->num = n; this->children->parent = a; for (int i=0;i<num;++i) this->children.push_back(new A(this,this->num-1)); } }; now, the constructor works fine. there are some problem with destructor. currently, the destructor is defined as: A::~A(void) { if (this->parent!=0) this->parent = 0; for (int i=0;i<(int)children.size();++i) this->children[i]->~A(); vector <A *> ().swap(this->children); } but every time when I debug it, it will break at: void deallocate(pointer _Ptr, size_type) { // deallocate object at _Ptr, ignore size ::operator delete(_Ptr); } it looks like I cannot delete the pointer in the vector of this-children, is there any way that I can de-construct the class successfully?

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• Update table without using cursor and on date

  - by Muhammad Kashif Nadeem

  Please copy and run following script DECLARE @Customers TABLE (CustomerId INT) DECLARE @Orders TABLE ( OrderId INT, CustomerId INT, OrderDate DATETIME ) DECLARE @Calls TABLE (CallId INT, CallTime DATETIME, CallToId INT, OrderId INT) ----------------------------------------------------------------- INSERT INTO @Customers SELECT 1 INSERT INTO @Customers SELECT 2 ----------------------------------------------------------------- INSERT INTO @Orders SELECT 10, 1, DATEADD(d, -20, GETDATE()) INSERT INTO @Orders SELECT 11, 1, DATEADD(d, -10, GETDATE()) ----------------------------------------------------------------- INSERT INTO @Calls SELECT 101, DATEADD(d, -19, GETDATE()), 1, NULL INSERT INTO @Calls SELECT 102, DATEADD(d, -17, GETDATE()), 1, NULL INSERT INTO @Calls SELECT 103, DATEADD(d, -9, GETDATE()), 1, NULL INSERT INTO @Calls SELECT 104, DATEADD(d, -6, GETDATE()), 1, NULL INSERT INTO @Calls SELECT 105, DATEADD(d, -5, GETDATE()), 1, NULL ----------------------------------------------------------------- I want to update @Calls table and need following results. I am using the following query UPDATE @Calls SET OrderId = ( CASE WHEN (s.CallTime > e.OrderDate) THEN e.OrderId END ) FROM @Calls s INNER JOIN @Orders e ON s.CallToId = e.CustomerId and the result of my query is not what I need. Requirement: As you can see there are two orders. One is on 2010-12-12 and one is on 2010-12-22. I want to update @Calls table with relevant OrderId with respect to CallTime. In short If subsequent Orders are added, and there are further calls then we assume that a new call is associated with the most recent Order Note: This is sample data so this is not the case that I always have two Orders. There might be 10+ Orders and 100+ calls. Note2 I could not find good title for this question. Please change it if you think of any better. Thanks.

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• Processing velocity-vectors during collision as neatly as possible

  - by DevEight

  Hello. I'm trying to create a good way to handle all possible collisions between two objects. Typically one will be moving and hitting the other, and should then "bounce" away. What I've done so far (I'm creating a typical game where you have a board and bounce a ball at bricks) is to check if the rectangles intersect and if they do, invert the Y-velocity. This is a really ugly and temporary solution that won't work in the long haul and since this is kind of processing is very common in games I'd really like to find a great way of doing this for future projects aswell. Any links or helpful info is appreciated. Below is what my collision-handling function looks like right now. protected void collision() { #region Boundaries if (bal.position.X + bal.velocity.X >= viewportRect.Width || bal.position.X + bal.velocity.X <= 0) { bal.velocity.X *= -1; } if (bal.position.Y + bal.velocity.Y <= 0) { bal.velocity.Y *= -1; } #endregion bal.rect = new Rectangle((int)bal.position.X+(int)bal.velocity.X-bal.sprite.Width/2, (int)bal.position.Y-bal.sprite.Height/2+(int)bal.velocity.Y, bal.sprite.Width, bal.sprite.Height); player.rect = new Rectangle((int)player.position.X-player.sprite.Width/2, (int)player.position.Y-player.sprite.Height/2, player.sprite.Width, player.sprite.Height); if (bal.rect.Intersects(player.rect)) { bal.position.Y = player.position.Y - player.sprite.Height / 2 - bal.sprite.Height / 2; if (player.position.X != player.prevPos.X) { bal.velocity.X -= (player.prevPos.X - player.position.X) / 2; } bal.velocity.Y *= -1; } foreach (Brick b in brickArray.list) { b.rect.X = Convert.ToInt32(b.position.X-b.sprite.Width/2); b.rect.Y = Convert.ToInt32(b.position.Y-b.sprite.Height/2); if (bal.rect.Intersects(b.rect)) { b.recieveHit(); bal.velocity.Y *= -1; } } brickArray.removeDead(); }

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• Segmentation Fault?

  - by user336808

  Hello, when I run this program while inputting a number greater than 46348, I get a segmentation fault. For any values below it, the program works perfectly. I am using CodeBlocks 8.02 on Ubuntu 10.04 64-bit. The code is as follows: int main() { int number = 46348; vector<bool> sieve(number+1,false); vector<int> primes; sieve[0] = true; sieve[1] = true; for(int i = 2; i <= number; i++) { if(sieve[i]==false) { primes.push_back(i); int temp = i*i; while(temp <= number) { sieve[temp] = true; temp = temp + i; } } } for(int i = 0; i < primes.size(); i++) cout << primes[i] << " "; return 0; }

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• Why do I get errors when using unsigned integers in an expression with C++?

  - by neuviemeporte

  Given the following piece of (pseudo-C++) code: float x=100, a=0.1; unsigned int height = 63, width = 63; unsigned int hw=31; for (int row=0; row < height; ++row) { for (int col=0; col < width; ++col) { float foo = x + col - hw + a * (col - hw); cout << foo << " "; } cout << endl; } The values of foo are screwed up for half of the array, in places where (col - hw) is negative. I figured because col is int and comes first, that this part of the expression is converted to int and becomes negative. Unfortunately, apparently it doesn't, I get an overflow of an unsigned value and I've no idea why. How should I resolve this problem? Use casts for the whole or part of the expression? What type of casts (C-style or static_cast<...)? Is there any overhead to using casts (I need this to work fast!)? EDIT: I changed all my unsigned ints to regular ones, but I'm still wondering why I got that overflow in this situation.

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