Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!uwvax!tank!eecae!shadooby!sharkey!mcf!mibte!gamma!thumper!ulysses!andante!alice!ark
From: ark@alice.UUCP (Andrew Koenig)
Newsgroups: comp.lang.c++
Subject: Re: Any interest in making C++ a real superset of ANSI C?
Message-ID: <9406@alice.UUCP>
Date: 29 May 89 14:34:38 GMT
References: <7435@hoptoad.uucp> <9395@alice.UUCP> <1989May28.235216.29243@utzoo.uucp>
Organization: AT&T Bell Laboratories, Liberty Corner NJ
Lines: 46

First of all, I should point out that I think the
ability to have a struct with the same name as an
object was put into C as a compatibility hack in
the first place -- C did not always have structures and
keeping their names separate from other names was a
good way to avoid breaking existing code.  Old habits
die hard.  Personally, I've always found things like

	struct A A;

a little confusing.

However, if you're trying to translate C programs that
do this sort of thing into C++ programs, I think you
will find that C++ 2.0 is a lot more compatible with C
in this sense than previous versions.

For example, the following is legal in 2.0:

	struct A { int a; };
	extern void f(A);
	struct A A;		// `struct' optional here

	main()
	{
		struct A b;	// `struct' or `class' needed here
		A.a = 3;
		b = A;
		f(A);
	};

This works if `struct' is replaced by `class', too, provided
that the definition of A is changed slightly:

	class A { public: int a; };

Otherwise A::a would be private and inaccessible to `main.'


None of this introduces any new differences between `struct'
and `class.'  Instead, a class that does not have any constructors
is considered to be enough like C that the C++ translator will
go out of its way to allow C usages it would otherwise reject.
-- 
				--Andrew Koenig
				  ark@europa.att.com