Path: utzoo!mnetor!uunet!lll-winken!lll-lcc!lll-tis!ames!rutgers!princeton!udel!burdvax!sdcrdcf!ism780c!news
From: news@ism780c.UUCP (News system)
Newsgroups: comp.lang.c
Subject: Re: Pointers and Arrays (was: C machine)
Message-ID: <8823@ism780c.UUCP>
Date: 2 Feb 88 00:08:36 GMT
References: <461@auvax.UUCP> <28700025@ccvaxa> <7159@brl-smoke.ARPA> <8728@ism780c.UUCP> <3546@ihlpf.ATT.COM> <1329@laidbak.UUCP>
Reply-To: marv@ism780.UUCP (Marvin Rubenstein)
Organization: Interactive Systems Corp., Santa Monica CA
Lines: 29

I got lost in all the >'s

I (Marv Rubinstein) wrote:
BTW, the definition of pointer difference in K&R is "if p and q point to
members of the same array , p-q is the number of elements between p and q."

Some one else wrote:
>I opened up my K&R, skimmed all of chapter 5 (Pointers and Arrays), and could
>not find this anywhere!  (Maybe I didn't look hard enough :-))  I don't think
>this is how K&R defined it (see more comments below).

You didn't :-)  Perhaps you should have looked in the index first.  In the
index on page 226 one finds the entry:

    "pointer subtraction 98"

On page 98 one finds in the last paragraph:
          "Pointer subtraction is also valid:  if p and q point to members
	   of the same array , p-q is the number of elements between p and q."

My reason for bring up this whole issue was to point out the the term
"between" used here is fuzzy and could lead one to confusion.  I was just
asking if the language in the standard was less ambigious. (Doug answered
that it is less ambigious).  Also I once had to correct a compiler that was
implemented such that p-q was the same as q-p (p and q pointers to the same
array).  When I found the wording on page 98 I asked several colleagues "how
many integers are there between 1 and 3 and how many integers are there
between 3 and 1?" most answered "one" to both questions.

       Marv Rubinstein.  -- Interactive Systeme