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  • C# implicit conversions and == operator

    - by Arnis L.
    Some code for context: class a { } class b { public a a{get;set;} public static implicit operator a(b b) { return b.a; } } a a=null; b b=null; a = b; //compiler: cannot apply operator '==' to operands of type tralala... bool c = a == b; Is it possible to use == operator on different type instances, where one can implicitly convert to another? What did i miss? Edit: If types must be the same calling ==, then why int a=1; double b=1; bool c=a==b; works?

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  • How do I write an overload operator where both arguments are interface

    - by Eric Girard
    I'm using interface for most of my stuff. I can't find a way to create an overload operator + that would allow me to perform an addition on any objects implementing the IPoint interface Code interface IPoint { double X { get; set; } double Y { get; set; } } class Point : IPoint { double X { get; set; } double Y { get; set; } //How and where do I create this operator/extension ??? public static IPoint operator + (IPoint a,IPoint b) { return Add(a,b); } public static IPoint Add(IPoint a,IPoint b) { return new Point { X = a.X + b.X, Y = a.Y + b.Y }; } } //Dumb use case : public class Test { IPoint _currentLocation; public Test(IPoint initialLocation) { _currentLocation = intialLocation } public MoveOf(IPoint movement) { _currentLocation = _currentLocation + intialLocation; //Much cleaner/user-friendly than _currentLocation = Point.Add(_currentLocation,intialLocation); } }

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  • C++ operator overloading doubt

    - by avd
    I have a code base, in which for Matrix class, these two definitions are there for () operator: template <class T> T& Matrix<T>::operator() (unsigned row, unsigned col) { ...... } template <class T> T Matrix<T>::operator() (unsigned row, unsigned col) const { ...... } One thing I understand is that the second one does not return the reference but what does const mean in the second declaration. Also which function is called when I do say mat(i,j)

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  • Operator Overloading for Queue C++

    - by Josh
    I was trying to use the overload operator method to copy the entries of one queue into another, but I am going wrong with my function. I don't know how else to access the values of the queue "original" any other way than what I have below: struct Node { int item; Node* next; }; class Queue { public: [...] //Extra code here void operator = (const Queue &original); protected: Node *front, *end; } void Queue::operator=(const Queue &original) { //THIS IS WHERE IM GOING WRONG while(original.front->next != NULL) { front->item = original.front->item; front->next = new Node; front = front->next; original.front = original.front->next; } }

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  • signature output operator overload

    - by coubeatczech
    hi, do you know, how to write signature of a function or method for operator<< for template class in C++? I want something like: template <class A class MyClass{ public: friend ostream & operator<<(ostream & os, MyClass<A mc); } ostream & operator<<(ostream & os, MyClass<A mc){ // some code return os; } But this just won't compile. Do anyone know, how to write it correctly?

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  • Overloading assignment operator in C#

    - by Carson Myers
    I know the = operator can't be overloaded, but there must be a way to do what I want here: I'm just creating classes to represent quantitative units, since I'm doing a bit of physics. Apparently I can't just inherit from a primitive, but I want my classes to behave exactly like primitives -- I just want them typed differently. So I'd be able to go, Velocity ms = 0; ms = 17.4; ms += 9.8; etc. I'm not sure how to do this. I figured I'd just write some classes like so: class Power { private Double Value { get; set; } //operator overloads for +, -, /, *, =, etc } But apparently I can't overload the assignment operator. Is there any way I can get this behavior?

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  • C++ operator[] syntax.

    - by Lanissum
    Just a quick syntax question. I'm writing a map class (for school). If I define the following operator overload: template<typename Key, typename Val> class Map {... Val* operator[](Key k); What happens when a user writes: Map<int,int> myMap; map[10] = 3; Doing something like that will only overwrite a temporary copy of the [null] pointer at Key k. Is it even possible to do: map[10] = 3; printf("%i\n", map[10]); with the same operator overload?

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  • does overload operator-> a compile time action?

    - by Brent
    when I tried to compile the code: struct S { void func2() {} }; class O { public: inline S* operator->() const; private: S* ses; }; inline S* O::operator->() const { return ses; } int main() { O object; object->func(); return 0; } there is a compile error reported: D:\code>g++ operatorp.cpp -S -o operatorp.exe operatorp.cpp: In function `int main()': operatorp.cpp:27: error: 'struct S' has no member named 'func' it seems that invoke the overloaded function of "operator-" is done during compile time? I'd add "-S" option for compile only.

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  • Binary operator overloading on a templated class (C++)

    - by GRB
    Hi all, I was recently trying to gauge my operator overloading/template abilities and as a small test, created the Container class below. While this code compiles fine and works correctly under MSVC 2008 (displays 11), both MinGW/GCC and Comeau choke on the operator+ overload. As I trust them more than MSVC, I'm trying to figure out what I'm doing wrong. Here is the code: #include <iostream> using namespace std; template <typename T> class Container { friend Container<T> operator+ <> (Container<T>& lhs, Container<T>& rhs); public: void setobj(T ob); T getobj(); private: T obj; }; template <typename T> void Container<T>::setobj(T ob) { obj = ob; } template <typename T> T Container<T>::getobj() { return obj; } template <typename T> Container<T> operator+ <> (Container<T>& lhs, Container<T>& rhs) { Container<T> temp; temp.obj = lhs.obj + rhs.obj; return temp; } int main() { Container<int> a, b; a.setobj(5); b.setobj(6); Container<int> c = a + b; cout << c.getobj() << endl; return 0; } This is the error Comeau gives: Comeau C/C++ 4.3.10.1 (Oct 6 2008 11:28:09) for ONLINE_EVALUATION_BETA2 Copyright 1988-2008 Comeau Computing. All rights reserved. MODE:strict errors C++ C++0x_extensions "ComeauTest.c", line 27: error: an explicit template argument list is not allowed on this declaration Container<T> operator+ <> (Container<T>& lhs, Container<T>& rhs) ^ 1 error detected in the compilation of "ComeauTest.c". I'm having a hard time trying to get Comeau/MingGW to play ball, so that's where I turn to you guys. It's been a long time since my brain has melted this much under the weight of C++ syntax, so I feel a little embarrassed ;). Thanks in advance. EDIT: Eliminated an (irrelevant) lvalue error listed in initial Comeau dump.

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  • Windows batch file to delete .svn files and folders

    - by Marco Demaio
    Hi,in order to delete all ".svn" files/folders/subfolders in "myfolder" I use this simple line in a batch file: FOR /R myfolder %%X IN (.svn) DO (RD /S /Q "%%X") This works, but if there are no ".svn" files/folders the batch file shows a warning saying: "The system cannot find the file specified." This warning is very noisy so I was wondering how to make it understand that if it doesn't find any ".svn" files/folders he must skip the RD command. Usually using wild cards would suffice, but in this case I don't know how to use them, because I don't want to delete files/folders with .svn extension, but I want to delete the files/folders named exactly ".svn", so if I do this: FOR /R myfolder %%X IN (*.svn) DO (RD /S /Q "%%X") it would NOT delete files/folders named extaclty ".svn" anymore. I tried also this: FOR /R myfolder %%X IN (.sv*) DO (RD /S /Q "%%X") but it doesn't work either, he deletes nothing. Thanks for any help!

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  • Java == operator. "Invalid assignment operator"

    - by Tom
    Hi, I was trying to write a simple method boolean validate(MyObject o) { return o.getPropertyA() == null && o.getPropertyB()==null; } And got a strange error on the == null part. Maybe my Java is rusty after a season in PLSQL. Consider this: Integer i = 4; i ==null; //compile error: Syntax error on token ==. Invalid assignment operator. Integer i2 = 4; if (i==null); //No problem How can this be ? Any explanation ? Im using jdk160_05.

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  • DELETE from two tables with one OUTPUT clause?

    - by lance
    This deletes the document from the Document table and outputs information about the deleted document into the FinishedDocument table. DELETE FROM Document OUTPUT Deleted.DocumentId , Deleted.DocumentDescription INTO FinishedDocument WHERE DocumentId = @DocumentId I need to delete the document not just from the Document table, but also from the DocumentBackup table. Meanwhile, I need to maintain insertion into FinishedDocument. Is all of this possible with only one statement? If not, is a second DELETE (against DocumentBackup), with all of it wrapped in a transaction, the way to go?

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  • Delete throws "deleted object would be re-saved by cascade"

    - by Greg
    I have following model: <class name="Person" table="Person" optimistic-lock="version"> <id name="Id" type="Int32" unsaved-value="0"> <generator class="native" /> </id> <!-- plus some properties here --> </class> <class name="Event" table="Event" optimistic-lock="version"> <id name="Id" type="Int32" unsaved-value="0"> <generator class="native" /> </id> <!-- plus some properties here --> </class> <class name="PersonEventRegistration" table="PersonEventRegistration" optimistic-lock="version"> <id name="Id" type="Int32" unsaved-value="0"> <generator class="native" /> </id> <property name="IsComplete" type="Boolean" not-null="true" /> <property name="RegistrationDate" type="DateTime" not-null="true" /> <many-to-one name="Person" class="Person" column="PersonId" foreign-key="FK_PersonEvent_PersonId" cascade="all-delete-orphan" /> <many-to-one name="Event" class="Event" column="EventId" foreign-key="FK_PersonEvent_EventId" cascade="all-delete-orphan" /> </class> There are no properties pointing to PersonEventRegistration either in Person nor in Event. When I try to delete an entry from PersonEventRegistration, I get the following error: "deleted object would be re-saved by cascade" The problem is, I don't store this object in any other collection - the delete code looks like this: public bool UnregisterFromEvent(Person person, Event entry) { var registrationEntry = this.session .CreateCriteria<PersonEventRegistration>() .Add(Restrictions.Eq("Person", person)) .Add(Restrictions.Eq("Event", entry)) .Add(Restrictions.Eq("IsComplete", false)) .UniqueResult<PersonEventRegistration>(); bool result = false; if (null != registrationEntry) { using (ITransaction tx = this.session.BeginTransaction()) { this.session.Delete(registrationEntry); tx.Commit(); result = true; } } return result; } What am I doing wrong here?

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  • How to delete refClass record in Doctrine?

    - by terrani
    Hi all! I have many-to-many relations with the following tables. post tag post_tag I created three classes with Doctrine, so I have the following classes as well. BasePost BaseTag BasePostTag in the setUp() method, I defined relations. I like to delete tag record when I delete post record. So I simply put cascade as descirbed on Doctrine document. $this->hasMany("Tag as Tags",array( 'refClass' => 'PostTag', 'local'=>'object_id', 'foreign'=>'tag_id', 'cascade'=> array('delete') )); it works without a problem. My questions is, how do I delete a record from post_tag table? Do I need to create a query myself?

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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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  • Oracle: delete suddenly taking a long time

    - by Damo
    Hi We have a feed process which runs every day of the year. As part of that we delete every row from a table (approx 1 million rows) every day, repopulate it using 5 different stored procedures and then commit the transaction. This is the only commit statement that we call. All of a sudden the delete has started takign about 2 hours to complete. The delete is also very simple (delete from T_PROFILE_WORK) This has worked perfectly well for the past year, but in the past week i have noticed this issue. Any help on this is greatly appreciated Thanks Damien

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  • What is the most efficient way to delete all selected items in a ListViewItem collection

    - by Andrew
    My user is able to select multiple items in a ListView collection that is configured to show details (that is, a list of rows). What I want to do is add a Delete button that will delete all of the selected items from the ListViewItem collection associated with the ListView. The collection of selected items is available in ListView.SelectedItems, but ListView.Items doesn't appear to have a single method that lets me delete the entire range. I have to iterate through the range and delete them one by one, which will potentially modify a collection I'm iterating over. Any hints? Edit: What I'm basically after is the opposite of AddRange().

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  • Oracle 10g multiple DELETE statements

    - by bmw0128
    I'm building a dml file that first deletes records that may be in the table, then inserts records. Example: DELETE from foo where field1='bar'; DELETE from foo where fields1='bazz'; INSERT ALL INTO foo(field1, field2) values ('bar', 'x') INTO foo(field1, field2) values ('bazz', 'y') SELECT * from DUAL; When I run the insert statement by itself, it runs fine. When I run the deletes, only the last delete runs. Also, it seems to be necessary to end the multiple insert with the select, is that so? If so, why is that necessary? In the past, when using MySQL, I could just list multiple delete and insert statements, all individually ending with a semicolon, and it would run fine.

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  • MySQL: LOAD DATA reclaim disk space after delete

    - by Michael
    I have a DB schema composed of MYISAM tables, i am interested to delete old records from time to time from some of the tables. I know that delete does not reclaim the memory space, but as i found in a description of DELETE command, inserts may reuse the space deleted In MyISAM tables, deleted rows are maintained in a linked list and subsequent INSERT operations reuse old row positions. I am interested if LOAD DATA command also reuses the deleted space? UPDATE I am also interested how the index space reclaimed?

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  • The difference between delete and delete [] in C++

    - by Ilya Melamed
    I've written a class that contains two pointers, one is char* color_ and one in vertexesset* vertex_ where vertexesset is a class I created. In the destractor I've written at start delete [] color_; delete [] vertex_; When It came to the destructor it gave me a segmentation fault. Then I changed the destructor to: delete [] color_; delete vertex_; And now it works fine. What is the difference between the two?

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  • Const operator overloading problems in C++

    - by steigers
    Hello everybody, I'm having trouble with overloading operator() with a const version: #include <iostream> #include <vector> using namespace std; class Matrix { public: Matrix(int m, int n) { vector<double> tmp(m, 0.0); data.resize(n, tmp); } ~Matrix() { } const double & operator()(int ii, int jj) const { cout << " - const-version was called - "; return data[ii][jj]; } double & operator()(int ii, int jj) { cout << " - NONconst-version was called - "; if (ii!=1) { throw "Error: you may only alter the first row of the matrix."; } return data[ii][jj]; } protected: vector< vector<double> > data; }; int main() { try { Matrix A(10,10); A(1,1) = 8.8; cout << "A(1,1)=" << A(1,1) << endl; cout << "A(2,2)=" << A(2,2) << endl; double tmp = A(3,3); } catch (const char* c) { cout << c << endl; } } This gives me the following output: NONconst-version was called - - NONconst-version was called - A(1,1)=8.8 NONconst-version was called - Error: you may only alter the first row of the matrix. How can I achieve that C++ call the const-version of operator()? I am using GCC 4.4.0. Thanks for your help! Sebastian

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  • C# what does the == operator do in detail?

    - by clamp
    in c# what does exactly happen in the background when you do a comparison with the "==" operator on two objects? does it just compare the addresses? or does it something like Equals() or CompareTo() ? PS: what about the "==" operator in java? does it behave the same?

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