Need to understand the overloaded assignment operator behavior Post: 302777457

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Top Forums Programming Need to understand the overloaded assignment operator behavior Post 302777457 by royalibrahim on Friday 8th of March 2013 02:27:30 AM

03-08-2013

Registered User

Quote:

Originally Posted by Corona688

If the B class was descended from the A class, that would be overloading, if you overloaded its copy constructor.

@Corona688, thank you for the reply. But even in the case when class B is not derived/inherited from A, and having the custom assignment operator implemented (like in the below code), then the B's overloaded assignment (only) is called.

Code:

class A {
public:
    void operator=(const A& rhs) {
        if (this == &rhs) cout << "self-assigned";
    }
};

class B {
    A a; // should not be a pointer member, (i.e) A* a
public:
    void operator=(const B& rhs) {
        cout << "B's" << endl;
    }
};

int main() {
    B b;
    b = b;  // Ans: B's
}

my understanding was the user implemented overloaded assignment operator function will be invoked at the time when that class's object is assigned. If there is no such implementation in that class then the compiler provided default assignment operator will be called, theoretically. Also, in class B there is just a containment member object and my doubt is why the class A's assignment operator is invoked when instance of B is assigned? Is this a compiler's optimization technique?

Last edited by royalibrahim; 03-08-2013 at 06:49 AM..

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std::slice_array

std::slice_array< _Tp >(3cxx)											     std::slice_array< _Tp >(3cxx)

NAME

       std::slice_array< _Tp > -

SYNOPSIS

   Public Types
       typedef _Tp value_type

   Public Member Functions
       slice_array (const slice_array &)
       void operator%= (const valarray< _Tp > &) const
       template<class _Dom > void operator%= (const _Expr< _Dom, _Tp > &) const
       void operator&= (const valarray< _Tp > &) const
       template<class _Dom > void operator&= (const _Expr< _Dom, _Tp > &) const
       void operator*= (const valarray< _Tp > &) const
       template<class _Dom > void operator*= (const _Expr< _Dom, _Tp > &) const
       void operator+= (const valarray< _Tp > &) const
       template<class _Dom > void operator+= (const _Expr< _Dom, _Tp > &) const
       void operator-= (const valarray< _Tp > &) const
       template<class _Dom > void operator-= (const _Expr< _Dom, _Tp > &) const
       void operator/= (const valarray< _Tp > &) const
       template<class _Dom > void operator/= (const _Expr< _Dom, _Tp > &) const
       void operator<<= (const valarray< _Tp > &) const
       template<class _Dom > void operator<<= (const _Expr< _Dom, _Tp > &) const
       slice_array & operator= (const slice_array &)
       void operator= (const valarray< _Tp > &) const
       void operator= (const _Tp &) const
       template<class _Dom > void operator= (const _Expr< _Dom, _Tp > &) const
       void operator>>= (const valarray< _Tp > &) const
       template<class _Dom > void operator>>= (const _Expr< _Dom, _Tp > &) const
       void operator^= (const valarray< _Tp > &) const
       template<class _Dom > void operator^= (const _Expr< _Dom, _Tp > &) const
       void operator|= (const valarray< _Tp > &) const
       template<class _Dom > void operator|= (const _Expr< _Dom, _Tp > &) const

   Friends
       class valarray< _Tp >

Detailed Description
   template<typename _Tp>class std::slice_array< _Tp >
       Reference to one-dimensional subset of an array.

       A slice_array is a reference to the actual elements of an array specified by a slice. The way to get a slice_array is to call
       operator[](slice) on a valarray. The returned slice_array then permits carrying operations out on the referenced subset of elements in the
       original valarray. For example, operator+=(valarray) will add values to the subset of elements in the underlying valarray this slice_array
       refers to.

       Parameters:
	   Tp Element type.

       Definition at line 124 of file slice_array.h.

Author
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libstdc++							  Tue Nov 27 2012				     std::slice_array< _Tp >(3cxx)