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From: ark@alice.UUCP (Andrew Koenig)
Newsgroups: comp.lang.c
Subject: Re: Enumerated types
Message-ID: <9297@alice.UUCP>
Date: 4 May 89 13:41:07 GMT
References: <1152@unh.UUCP>
Distribution: usa
Organization: AT&T Bell Laboratories, Liberty Corner NJ
Lines: 34

In article <1152@unh.UUCP>, al712@unh.UUCP (Anthony   Lapadula) writes:
> Are you allowed to 'forward reference' enumerated types?  In other
> words, is this legal?

> 	enum a b;		/* 'enum a' is not yet defined */

> Does 'b' end up as an int, or is this an error?

It's an error, both in C++ and ANSI C.


> Also, how about this?

> 	char *ptr;
> 	enum a { b };		/* 'b' has value 0 in expressions, right? */

Right.

> 	if (ptr == b)		/* Same as (ptr == NULL) ? */
> 		foo();

Yes, if NULL==0, by virtue of the fact that b is 0.
However, the following is illegal:

	enum a1 {b1, c1};

	if (ptr == c1)
		foo();

because the only integral value that may be meaningfully
compared to a pointer is 0.
-- 
				--Andrew Koenig
				  ark@europa.att.com