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From: mcdaniel@uicsrd.UUCP
Newsgroups: comp.lang.c
Subject: Re: Literal strings in C
Message-ID: <44200002@uicsrd>
Date: Sun, 14-Jun-87 00:37:00 EDT
Article-I.D.: uicsrd.44200002
Posted: Sun Jun 14 00:37:00 1987
Date-Received: Wed, 17-Jun-87 00:44:57 EDT
References: <212@inco.UUCP>
Lines: 42
Nf-ID: #R:inco.UUCP:212:uicsrd:44200002:000:1155
Nf-From: uicsrd.CSRD.UIUC.EDU!mcdaniel    Jun 13 23:37:00 1987


> 	pointing out a couple of real peculiarities. Both of the
> 	following statements are legal, executable C, at least to
> 	the Sun 3.2 C compiler, which is presumably based on PCC.
>
> 	c = "literal string"[i];
>
> 	"literal string"[i] = c;

It's worse than that.  According to K&R, "[]" is not really an
operator;  it is an abbreviation:
	a[b] is equivalent to *(a+b)
and vice versa.  In other words, it's an abbreviation for pointer
arithmetic.  In C's arithmetic model + is commutative, so
	a[b] is equivalent to b[a]
I just compiled and ran this program:
	#include <stdio.h>
	main()
	{
		int i;
		i = 5;
		fprintf(stderr, "%c\n", "0123456789"[i]);
		fprintf(stderr, "%c\n", "0123456789"[5]);
		fprintf(stderr, "%c\n", i["0123456789"]);
		fprintf(stderr, "%c\n", 5["0123456789"]);
	}
and got output of
	5
	5
	5
	5
as expected.

--
Tim, the Bizarre and Oddly-Dressed Enchanter
Center for Supercomputing Research and Development
at the University of Illinois at Urbana-Champaign

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