Path: utzoo!attcan!uunet!cs.utexas.edu!rutgers!att!cbnewsl!strange
From: strange@cbnewsl.ATT.COM (philip.e.brown)
Newsgroups: comp.lang.c++
Subject: Re: Ambiguity and Access Control
Message-ID: <2944@cbnewsl.ATT.COM>
Date: 19 Nov 89 18:02:46 GMT
References: <4051@cadillac.CAD.MCC.COM>
Reply-To: strange@cbnewsl.ATT.COM (philip.e.brown,sf,)
Distribution: na
Organization: AT&T Bell Laboratories
Lines: 47


	In article <4051@cadillac.CAD.MCC.COM> dsouza@mcc.com writes:
	>
	>
	>In 2.0, is ambiguity checked independently (before) access control.
	>If so, WHY ?

Yes.

Access could easily be checked before ambiguity if C++ only
supported class data members (one name, one member).  However,
C++ also has function members (one name, many members).

Currently, lookup applies to a name, whereas access control
applies to a member.  Bridging this gap are the rules for
overloaded function matching.

So, you have something like
    (1) name lookup
    (2) matching
    (3) access control

where "matching" for a data member is a no-op.  The ambiguity
check currently happens at the end of (1).

The question is then,
    "Why can't all three steps be combined into one to avoid ambiguities?"

Basically, you can't always do the matching before the
ambiguity check.  Consider

    class C {
	int f(int);
    public:
	int f(double);
    };

    int (C::*pmf)(int) = &C::f;

The expression "C::f" must provide an unambiguous name even
though the matching and access check cannot be done until
the initialization of "pmf".

--------

Phil Brown
strange@attunix.att.com