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From: chris@umcp-cs.UUCP (Chris Torek)
Newsgroups: net.lang.c
Subject: Re: if(p)
Message-ID: <1778@umcp-cs.UUCP>
Date: Tue, 8-Oct-85 03:28:00 EDT
Article-I.D.: umcp-cs.1778
Posted: Tue Oct  8 03:28:00 1985
Date-Received: Thu, 10-Oct-85 06:01:53 EDT
References: <1960@brl-tgr.ARPA>
Organization: U of Maryland, Computer Science Dept., College Park, MD
Lines: 22

> In [K&R, section] 9.3 ``the expression is 0'' cannot mean the
> constant 0, but rather that the expression evaluates to zero.
> There are plenty of uses of ``0'', ``zero'', and ``non-zero''
> referring to what an expression evaluates to, and only three
> references that I've found (7.7, 7.13 and 7.14) to the special
> meaning of the constant 0. [...]
> 
> In Sum:  it seems to me that ``if (p != NULL)'' is portable (NULL
> being 0) but ``if (p)'' is not.
> 
> Please correct me if I be wrong, before I mislead countless others.

Consider yourself corrected.  This rather loose definition in K&R
is one of the reasons there is an ANSI standard in the works.

In general, if K&R says `<x> is so', then you can be pretty darn
sure that <x> is so; but if they do not say `<y> is not', you will
just have to make your best guess.
-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 4251)
UUCP:	seismo!umcp-cs!chris
CSNet:	chris@umcp-cs		ARPA:	chris@mimsy.umd.edu