From 9097899573987642520 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: f78e5,add62e0f5e586127 X-Google-Attributes: gidf78e5,public X-Google-ArrivalTime: 1994-09-26 12:18:45 PST Newsgroups: comp.std.c++ Path: bga.com!news.sprintlink.net!howland.reston.ans.net!xlink.net!slsv6bt!slsv6bt!kanze From: kanze@us-es.sel.de (James Kanze US/ESC 60/3/164 #71425) Subject: Re: compile time consts In-Reply-To: rfg@netcom.com's message of Sat, 24 Sep 1994 07:54:40 GMT Message-ID: Sender: news@lts.sel.alcatel.de Organization: SEL References: <1994Sep19.110228.3591@fmrco.uucp> Date: 26 Sep 1994 19:09:45 GMT Lines: 45 In article rfg@netcom.com (Ronald F. Guilmette) writes: |> In article weissman@netcom.com (Bob Weissman) writes: |> >In article <1994Sep19.110228.3591@fmrco.uucp>, |> >David Binderman wrote: |> >>I claim the following is legal code. Three compilers disagree with me. |> >>Who is correct ? |> >The compilers are. |> >>#include |> >>const int N = 1000; |> >>const int Q = (int) sqrt( (double) N); |> >>int a[ Q]; |> >See ARM 8.2.4, then see ARM 5.19. The expression inside the brackets |> >must be a constant-expression. |> This part, I believe. |> >Because "(int) sqrt((double) N)" is not a constant-expression, neither is "Q". |> Can _anyone_ provide a chapter and verse citation to support this conclusion? |> If so, I would greatly appreciate it. Thanks. In the ARM, section 5.19: "A constant-expression can involve only literals, enumerators, const values of integral types initialized with constant expressions, and sizeof expressions." No mention of function calls, so the initialization expression of Q is not a constant expression. And since Q is not initialized with a constant expression, an expression containing Q is not a constant expression. And of course, in section 8.2.4, the syntax for an array declaration requires a constant-expression. -- James Kanze Tel.: (+33) 88 14 49 00 email: kanze@lts.sel.alcatel.de GABI Software, Sarl., 8 rue des Francs-Bourgeois, F-67000 Strasbourg, France Conseils en informatique industrielle -- -- Beratung in industrieller Datenverarbeitung