From -743379678526509633 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: f78e5,6d7908504577ecbe X-Google-Attributes: gidf78e5,public From: seitz@ix.netcom.com (Matt Seitz) Subject: Re: Why this behavior? Date: 1997/09/19 Message-ID: <5vsrmv$7u0@kane.ico.net>#1/1 X-Deja-AN: 273940715 References: X-Original-Date: Fri, 19 Sep 1997 03:29:53 GMT Originator: austern@isolde.mti.sgi.com Organization: ICOnetworks, Scotts Valley, CA. 408-461-4638 X-Auth: PGPMoose V1.1 PGP comp.std.c++ iQBVAwUBNCL/qUy4NqrwXLNJAQECAwIAqrVTH2qYvfRZxjXXK3df1iOy6AoAQxUS F0+DqbAbMPqQwJQm4cMqmqyqBdqIPJhtH25KgT0ueZsZnd0BbIkl7w== =nOLL Newsgroups: comp.std.c++ In article , Carl Mummert wrote: >I am curious about a behavior fo the vector class. > >What is the reasoning behind this not working: > >vector vec(3); >vec[5] = 2; //not correct; operator[] won't > //allocate space According to Stroustrup. the reason was efficiency (C++ PROGRAMMING LANGUAGE, 3rd Ed., section 16.3.3). In order for vec[n] to automatically allocate space, it would need to compare n to the current vector size every time vec[n] is used. In order to better match the speed of C arrays, it was decided that vectors would not do range checking when the subscript operator was used. --- [ comp.std.c++ is moderated. To submit articles: Try just posting with your newsreader. If that fails, use mailto:std-c++@ncar.ucar.edu comp.std.c++ FAQ: http://reality.sgi.com/austern/std-c++/faq.html Moderation policy: http://reality.sgi.com/austern/std-c++/policy.html Comments? mailto:std-c++-request@ncar.ucar.edu ]