From -2699724164613004416 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: f78e5,c0e61b6a667823c0 X-Google-Attributes: gidf78e5,public From: hinnant@_anti-spam_lightlink.com (Howard Hinnant) Subject: Re: no const operator[] in STL map? Date: 1999/01/24 Message-ID: #1/1 X-Deja-AN: 436366901 X-NNTP-Posting-Host: 205.232.34.48 Approved: stephen.clamage@sun.com (comp.std.c++) References: <916993358.766341@aloomba.aaii.oz.au> <36AA5AA6.2CC30DA4@ibm.net> X-UID: 0000000001 X-Status: $$$T X-Trace: 24 Jan 1999 10:53:59 -0500, 205.232.34.48 Organization: Lightlink Internet Newsgroups: comp.std.c++ Originator: clamage@taumet In article <36AA5AA6.2CC30DA4@ibm.net>, bijuthom@ibm.net wrote: > Does it mean that the mapped_type stored in a map should always have a > default constructor? Yes, if you want to use operator[]. > If I don't have a default constructor for the > mapped_type, is there any way for me to specify the value from which the > mapped_type object can be copy-constructed. (For example, like in the > constructor for vector.) No. Here is the standard-suggested implementation: T& operator[](const key_type& x); -1- Returns: (*((insert(make_pair(x, T()))).first)).second. -Howard [ 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 ]