Newsgroups: comp.lang.c Path: utzoo!henry From: henry@utzoo.uucp (Henry Spencer) Subject: Re: array[-1] -- permitted? Message-ID: <1988Sep24.211146.26484@utzoo.uucp> Organization: U of Toronto Zoology References: <867@osupyr.mast.ohio-state.edu> <3200@geac.UUCP> <1430@ficc.uu.net> <1988Sep19.164701.11136@ateng.uucp> <2583@ingr.UUCP> <1237@imagine.PAWL.RPI.EDU> <69575@sun.uucp> Date: Sat, 24 Sep 88 21:11:46 GMT In article <69575@sun.uucp> swilson@sun.UUCP (Scott Wilson) writes: >I'm not quite sure what is being discussed. I assume the standard >says that the -1'th element on an array is not guaranteed to be >accessible, not that negative array indices are disallowed... More precisely, what it says is that even *computing* a pointer to the -1th element of an array can send you off into the Twilight Zone. This is not new -- if you read K&R, that's always been the rule. However, there is no objection to subtracting 1 from a pointer that already points to the Nth element of an array, where N > 0. (&a[1])[-1] is legal. -- NASA is into artificial | Henry Spencer at U of Toronto Zoology stupidity. - Jerry Pournelle | uunet!attcan!utzoo!henry henry@zoo.toronto.edu