Re: Reference is not a member of class?

From:

"Maxim Yegorushkin" <maxim.yegorushkin@gmail.com>

Newsgroups:

comp.lang.c++.moderated

Date:

29 Jun 2006 04:38:04 -0400

Message-ID:

<1151478579.501952.274880@75g2000cwc.googlegroups.com>

Oleg wrote:

This code compiles on Test Drive Comeau C++ Online and on VC 7.1. So, I
assume that it is standard compliant. but why it is allowed to modify
non-const reference in const method?

Refrences are constant. Once initialized they can not be made refer
another object. But references can refer const and non-const objects.

        class test
        {
        public :
                test(int& i) :
                        m_i(i) {}

                void f() const
                {
                        m_i = 0;
                }

        private :
                int& m_i;
        };

In const member functions a top-level const qualifier is appied to all
members, unless a member is declared mutable. So, in f() m_i is int&
const, which is the same as int& because references are constant.

Consider this:

struct S
{
     int i, *p;
     S() : p(&i) {}
     void f() const { *p = 1; }
};

Here in f() p is int* const. It is the pointer what is const, not the
object it points to. This makes possible to still modify the object
pointed to.

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