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::indirect_array

std::indirect_array< _Tp >(3)				     Library Functions Manual				     std::indirect_array< _Tp >(3)

NAME

       std::indirect_array< _Tp > -

SYNOPSIS

   Public Types
       typedef _Tp value_type

   Public Member Functions
       indirect_array (const indirect_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
       indirect_array & operator= (const indirect_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 gslice_array< _Tp >
       class valarray< _Tp >

Detailed Description
   template<class _Tp>class std::indirect_array< _Tp >
       Reference to arbitrary subset of an array.

       An indirect_array is a reference to the actual elements of an array specified by an ordered array of indices. The way to get an
       indirect_array is to call operator[](valarray<size_t>) on a valarray. The returned indirect_array then permits carrying operations out on
       the referenced subset of elements in the original valarray.

       For example, if an indirect_array is obtained using the array (4,2,0) as an argument, and then assigned to an array containing (1,2,3),
       then the underlying array will have array[0]==3, array[2]==2, and array[4]==1.

       Parameters:
	   Tp Element type.

       Definition at line 84 of file valarray.

Author
       Generated automatically by Doxygen for libstdc++ from the source code.

libstdc++							  Tue Jun 10 2014				     std::indirect_array< _Tp >(3)