Re: Small question about operator overloading

From:

Victor Bazarov <v.Abazarov@comAcast.net>

Newsgroups:

comp.lang.c++

Date:

Thu, 29 May 2008 17:47:50 -0400

Message-ID:

<g1n8a6$vgg$1@news.datemas.de>

Alex Snast wrote:

I'm wondering if it common to return a const reference to an object

const BinSearchTree& operator= (const BinSearchTree& rhs)
throw(bad_alloc);

or

BinSearchTree& operator= (const BinSearchTree& rhs)
throw(bad_alloc);

is there any standard on those

There is no standard, but we know that the built-in operator= has the
signature such that it returns a reference to *non-const* object. That
can be used as a hint. The point in most cases is that if you can
assign to that object, you should be able to call a non-const member
function. Example:

     struct NormalAssignment
     {
         void foo() {}
     };

     struct OpAssReturnsConst
     {
         OpAssReturnsConst const& operator=(OpAssReturnsConst const&)
         { return *this; }
         void foo() {}
     };

     int main()
     {
         NormalAssignment n1, n2;
         (n1 = n2).foo(); // assign to n1, then call foo() for it.
         OpAssReturnsConst c1, c2;
         (c1 = c2).foo(); /// OOPS
     }

V
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