Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!utgpu!water!watmath!clyde!rutgers!ames!ucbcad!ucbvax!ulysses!hector!jss
From: jss@hector.UUCP
Newsgroups: news.software.b,comp.lang.c
Subject: Re: News for Xenix on PC AT ?
Message-ID: <2440@ulysses.homer.nj.att.com>
Date: Thu, 23-Apr-87 12:23:53 EST
Article-I.D.: ulysses.2440
Posted: Thu Apr 23 12:23:53 1987
Date-Received: Sat, 25-Apr-87 05:22:17 EST
References: <18346@ucbvax.BERKELEY.EDU> <145@sds.UUCP> <17005@sun.uucp> <146@sds.UUCP>
Sender: daemon@ulysses.homer.nj.att.com
Reply-To: jss@hector (Jerry Schwarz)
Organization: AT&T Bell Labs, Murray Hill
Lines: 18
Xref: utgpu news.software.b:506 comp.lang.c:1791

In article <146@sds.UUCP> dave@sds.UUCP writes:
>
>Why is "if (charptr == 0)" NOT identical to "if ((int)charptr == 0)" ???

Because the language definition says it isn't.  The relevant paragraphs
of K&R and ANSI proposal (I don't have H&S at hand)

K&R: A pointer may be compared to an integer, but the result is
machine dependent unless the integer is the constant 0.  A pointer to
which 0 has been assigned is guaranteed not to point to any object
and will appear to be equal to 0 ...

ANSI: An integral constand expression with the value 0, or such an
expression cast to type void *, is called a null pointer constant. If
a null pointer constant is assigned to or compared for equality to a
pointer, the constant is converted to a pointer of that type ...

Jerry Schwarz