Path: utzoo!attcan!uunet!lll-winken!lll-tis!ames!oliveb!peritus!preston
From: preston@peritus.UUCP (Preston Gardner)
Newsgroups: comp.lang.c
Subject: const in array bound expression
Keywords: const ANSI constant expression array
Message-ID: <123@peritus.UUCP>
Date: 1 Aug 88 22:08:20 GMT
Organization: Peritus International, 10201 Torre, Cupertino, CA.
Lines: 26

What constitutes a constant expression under the new ANSI standard?  The
following should be legal:

    const int i = 5;
    int a[i];

But what about this?  This offers a big opportunity for headaches.

    const int agg[] = { 1, 1, 2, 3, 5, 8, 13, 21, 34 };
    int a[agg[4]];

I could not find anything in the ANSI draft I have (May 13, 1988) to help
with this.

C++ allows the first case but the AT&T C++ preprocessor we have rejects
the second.


Does anybody out there have any experience with this?  I believe the correct
thing is to allow scalar const vars (whose value is known in this module --
not externs) to be used in array bound expressions.  But I don't see it
in the ANSI standard, and I don't have any ANSI standard compilers (except the
one I'm writing) to try it out on right now.
-- 
				-- Preston Gardner
				   Peritus International, Inc.
				   ..{pyramid,sun}!oliveb!peritus!preston