From -8441578401696501421 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: f78e5,c6e0f35f0f156cba X-Google-Attributes: gidf78e5,public From: Christopher Eltschka Subject: Re: Viewing the contents of a const map& Date: 1999/03/20 Message-ID: <36F217C4.4A668F7@physik.tu-muenchen.de>#1/1 X-Deja-AN: 456791043 Content-Transfer-Encoding: 7bit Approved: Fergus Henderson References: <36eff78c.407264815@news1.occa.home.net> <7cq66i$4fc$1@remarQ.com> X-Original-Date: Fri, 19 Mar 1999 10:24:20 +0100 Content-Type: text/plain; charset=us-ascii X-Complaints-To: news@news.unimelb.edu.au X-Trace: izvestia.its.unimelb.edu.au 921905193 20237 128.250.29.17 (20 Mar 1999 04:46:33 GMT) Organization: [posted via] Leibniz-Rechenzentrum, Muenchen (Germany) X-Auth: PGPMoose V1.1 PGP comp.std.c++ iQBFAgUANvMoD+EDnX0m9pzZAQESewF9EwjIz1wb5+09JG/XrxgiTSADuqMEQWg6 u9kAgKvWAV7VbPVQ24z2rdkbkJA2aTCs =2Gt3 Mime-Version: 1.0 NNTP-Posting-Date: 20 Mar 1999 04:46:33 GMT Newsgroups: comp.std.c++ Joe Buck wrote: > > sean.shubin@www.anything.com (Sean Shubin) writes: > >Since the map operator [] can be used for both reading and writing > >values to a map, what should I use to access a given value of a map > >that is const? > > The reason you can't use [] with a const map is because there isn't > anything that can be done if the key is not present in the map > (well, OK, you could throw an exception). If the const operator[] returned by value, it could also return a default constructed value. This is what the non-const operator[] does as well, except that it puts that into the map as well. If you use only the operator[] interface, you even won't see the difference at all. If you are using the iterator interface, you'll see the difference, of course - but since it's logical that a const operator[] won't change the map, I don't see a problem with this. [...] --- [ 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://reality.sgi.com/austern_mti/std-c++/faq.html ]