Re: Reference is not a member of class?

From:
James Dennett <jdennett@acm.org>
Newsgroups:
comp.lang.c++.moderated
Date:
28 Jun 2006 06:38:03 -0400
Message-ID:
<xmdog.7689$6w.7502@fed1read11>
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?


It isn't.

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

                void f() const
                {
                        m_i = 0;


This modifies the int referred to by the reference.
It's not a reference-to-const, so that's legal, just
as it would be legal to write *m_pi = 0; if you had
a member m_pi of type int* instead of your reference
member. Constness isn't transitive; the fact that
the test object is const means that its members are
const, but things they point/refer to don't become
const because of that. It's the difference between
a pointer that can't be changed, and a pointer-to-const.

                }

        private :
                int& m_i;
        };

int main()
{
  int i = 1;
  const test t(i);
  t.f(); // set i to 0
}


Hope this helps,

James

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