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From: jsdy@hadron.UUCP (Joseph S. D. Yao)
Newsgroups: net.lang.c
Subject: Re: break, continue, return, goto (net.religion.c)
Message-ID: <70@hadron.UUCP>
Date: Thu, 14-Nov-85 00:49:40 EST
Article-I.D.: hadron.70
Posted: Thu Nov 14 00:49:40 1985
Date-Received: Fri, 15-Nov-85 08:29:46 EST
References: <771@whuxl.UUCP> <516@busch.UUCP> <779@whuxl.UUCP> <521@busch.UUCP>
Reply-To: jsdy@hadron.UUCP (Joseph S. D. Yao)
Distribution: net
Organization: Hadron, Inc., Fairfax, VA
Lines: 44
Keywords: argument, array, pointer, *sigh*
Summary: That was no array; that was my pointer!

In article <521@busch.UUCP> dcm@busch.UUCP (Craig Miller) writes:
>	Today's C question:  how come C won't let you increment a global,
>	static or automatic array name, but will let you increment an array
>	name that's a function argument?  Film at 11.

Craig, I hope you're not serious.  You've been around this newsgroup
(I thought) since the last time I wrote >= 100 ll on this subject.

For those who weren't, the problem is that when one seems to pass
an array as an argument in C:
	char name[128];
		...
	foofunc(name);
...
foofunc(str)
  char str[];
{
one isn't really.  This is one case where C violates the Rule of
saying what you mean.  For historical reasons (see diatribe in
archives), what is passed is the address of the first element of
the array -- a pointer instead of the array!  This is one reason
(of two basic ones) that there is the confusing statement somewhere
in K&R that pointers and array addresses are treated identically.
In this case, a correct declaration of str would be:
  char *str;
but I may just want to emphasize the array-ness of it [*sigh*].
In any case,
	an array is a set of values at a fixed location.  we
	cannot change the value of that fixed location (name++)
	any more than we can change any other fixed value
	(foofunc++ or foofunc()++) or constant (1++ ?????).

	a pointer is a single pointer-size (not necessarily word)
	location in memory in which can be placed an address, such
	as the address of the beginning of that array.  The pointer
	can be changed:  in particular, it can be incremented and
	decremented (str++).

More concisely:
	a pointer name represents an l-value.
	an array name doesn't.
-- 

	Joe Yao		hadron!jsdy@seismo.{CSS.GOV,ARPA,UUCP}