From 3603290070289094322 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: f78e5,7eaa8faac8da5016 X-Google-Attributes: gidf78e5,public From: postmast.root.admi.gov@iname.com (blargg) Subject: Re: Defect Report: member == in container iterators considered harmful Date: 1999/08/18 Message-ID: #1/1 X-Deja-AN: 514104403 X-NNTP-Posting-Host: aus-as5-186.io.com Approved: stephen.clamage@sun.com (comp.std.c++) References: <7p4nj8$n3u@enews4.newsguy.com> <37B98C2E.E3A1EA71@acm.org> <37B98D53.3B7@wanadoo.fr> <37B9A195.B7090C3C@acm.org> X-UID: 0000000001 X-Status: $$$T X-Complaints-To: abuse@io.com X-Trace: hiram.io.com 934956609 16068 208.2.105.186 (18 Aug 1999 06:10:09 GMT) Organization: e-mail address IS valid - but fools the spammers NNTP-Posting-Date: 18 Aug 1999 06:10:09 GMT Newsgroups: comp.std.c++ Originator: clamage@taumet In article <37B9A195.B7090C3C@acm.org>, Pete Becker wrote: > Valentin Bonnard wrote: > > > > Pete Becker wrote: > > > > > Darin Adler wrote: > > > > > > bool check_equal(std::deque::iterator i, > > > > std::deque::const_iterator ci) > > > > { > > > > return i == ci; > > > > } > > > > > > > > > > Agreed. But the begin and end iterators that you get from a container > > > are of the same type, and they work just fine for the standard STL > > > idioms. Why do you need to do this? What coding practices does it > > > support? > > > > Would you consider the following unatural or silly ? > > > > for (const_iterator it = begin(); it!=end(); ++it) > > foo (*it); > > Absolutely. The standard STL idiom is to put the loop in a template > function. Yeah. It's simpler for compiler writers to only allow one for loop per function :-) Ugh. What a mess, writing multiple functions like this. I'll pass. > That way you don't have to worry about getting the type of the > iterator right. But the mistake in that particular loop is the decision > to use a const_iterator without regard to the actual constness of the > container. I suppose if you were given a pointer-to-non-const, you wouldn't consider ever converting that to a pointer-to-const? > Write it this way: > > for (Container::iterator it = cont.begin(); it != cont.end(); ++it) > foo(*it); What if we only want to inspect the container, and enforce this decision by using a const iterator? [ 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 ]