TITLE: References, const pointers, and storage (more)

[ Continued discusssion about the difference between references
  and const pointers. -adc ]


PROBLEM: thp@PROBLEM_WITH_INEWS_DOMAIN_FILE (Tom Payne)

What capability would an automatically dereferenced const pointer have
that reference does not?  Or vice versa?


RESPONSE: kanze@lts.sel.alcatel.de (James Kanze), 17 Aug 95

In C++, pointers are objects: they have identity, manifested by a
unique address.  References are *not* objects, and do not have
identity.  References define a name equivalence; semantically, they
are more closely related to the Fortran `equivalence' statement than
they are to pointers.

A simple example:

	struct A { int &a1 ; int &a2 ; } a ;
	struct B { int *b1 ; int *b2 ; } b ;

What is guaranteed by the standard:  first, sizeof( A ) >= 1 (since A
is an object, although it contains no objects), whereas sizeof( B ) >=
2, since B contains two objects, each of which must have a positive
size.  Second: &b.b1 != &b.b2, since b1 and b2 are objects, and must
have an identity manifested by a distinct address.  There is no such
guarantee concerning a1 and a2.