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Internet Message Format | 1996-08-05 | 1.2 KB

Path: keats.ugrad.cs.ubc.ca!not-for-mail
From: [e-mail] (Kazimir Kylheku)
Newsgroups: comp.lang.c
Subject: Re: Combine zero-offset with unit-offset arrays ?
Date: 4 Mar 1996 10:00:31 -0800
Organization: Computer Science, University of B.C., Vancouver, B.C., Canada
Message-ID: <[e-mail]>
References: <4hes0h$[e-mail]> <[e-mail]>
NNTP-Posting-Host: keats.ugrad.cs.ubc.ca

In article <[e-mail]>,
Kazimir Kylheku <[e-mail]> wrote:
>#define fa(x) (fa[x-1])
>{
>    int foo = fa(1);
>}

By the way, that should be

#define fa(x) (fa[(x)-1])

since there are many expressions with lower precedence than -, but higher than
comma, such as shift and and bitwise logic operators.

>which now gives you fa[1-1], which is *((fa) + 1 - 1). This is defined. The
>standard allows you generate a pointer which references one element past the
>end of the array, thus if you put in the subscript 10,  you would have
>*((fa) + 10 - 1). ANSI condones the generation of a pointer to the non-existant
>element of the array that is conceptually one index past the last one, in
>order to support certain common coding idioms.
>--
>


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