From 6901769925657004254 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: f78e5,fe27635c57b20d94,start X-Google-Attributes: gidf78e5,public X-Google-ArrivalTime: 2002-03-05 20:40:08 PST Path: archiver1.google.com!news1.google.com!newsfeed.stanford.edu!newsfeeds.belnet.be!news.belnet.be!newsfeed00.sul.t-online.de!t-online.de!newsfeed.wirehub.nl!shale.ftech.net!news.ftech.net!dispose.news.demon.net!news.demon.co.uk!demon!mail2news.demon.co.uk!not-for-mail From: "Garry Lancaster" Newsgroups: comp.std.c++ Subject: Base class can't be typedef. Why? Date: Wed, 6 Mar 2002 04:39:35 GMT Organization: ntlworld News Service Approved: Fergus Henderson , moderator of comp.std.c++ Message-ID: X-Trace: mail2news.demon.co.uk 1015389579 mail2news:11089 mail2news mail2news.demon.co.uk X-Complaints-To: abuse@demon.net X-Mail2News-Path: news.demon.net!mulga.cs.mu.oz.au X-Authentication-Warning: mulga.cs.mu.OZ.AU: fjh set sender to devnull@stump.algebra.com using -f X-Robomod: STUMP, ichudov@algebra.com (Igor Chudov) X-Priority: 3 X-MSMail-Priority: Normal X-Newsreader: Microsoft Outlook Express 5.00.2615.200 X-MimeOLE: Produced By Microsoft MimeOLE V5.00.2615.200 NNTP-Posting-Date: Tue, 05 Mar 2002 18:00:23 GMT Lines: 55 Xref: archiver1.google.com comp.std.c++:9884 Dear All Am currently writing some somewhat hairy template code that involves me deriving from a class type that is buried deep within a load of templated and typedef'd code. And therein lies the problem. I want to use a typedef to simplify my base class type e.g. I want to write typedef my_incredibly_long_type_name short_name; class derived : public short_name {...}; rather than class derived : public my_incredibly_long_type_name {...}; (In reality the long name is even longer and I use it elsewhere making the typedef more beneficial than in this cut down example.) However para 7.1.3/4 of the standard says: "A typedef-name that names a class is a class-name (9.1). If a typedef-name is used following the class-key in an elaborated-type-specifier (7.1.5.3) or in the class-head of a class declaration...the program is ill-formed." ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ The class-head includes the part that specifies base classes. Therefore I am prevented from using my typedef name there. Is my interpretation of the standard correct? If so, what is the rationale behind this decision? It seems bizarre; after all, I can quite happily use my typedef name to declare a data member. And what is a base class in reality but a data member with a bit of extra compiler magic thrown in? Kind regards Garry Lancaster Codemill Ltd Visit our web site at http://www.codemill.net --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.research.att.com/~austern/csc/faq.html ]