Re: How does the == operator for multimaps behave ?

From:

Pete Becker <pete@versatilecoding.com>

Newsgroups:

comp.lang.c++

Date:

Sat, 30 Aug 2008 07:41:17 -0400

Message-ID:

<2008083007411716807-pete@versatilecodingcom>

On 2008-08-30 00:46:55 -0400, Nikhil.S.Ketkar@gmail.com said:

How does the == operator for multimap in STL behave ? I was under the
impression that this is supposed to properly compare multimaps for
equality. It seems that what it actually does is just check if each
member in location L in one multimap is equal to the the member in
location L in the other multimap.

Yes, that's what "equality" means for a multimap. The thing to keep in
mind is that STL containers manage sequences; two containers are equal
if the sequences [container1.begin(), container1.end()) and
[container2.begin(), container2.end()) are equal. Multimaps preserve
order; when you insert an element with the same key as another element,
the new element goes into the sequence after any others with the same
key. So insert(make_pair(0, 2)) followed by insert(make_pair(0, 4))
creates a different sequence from the one created by
insert(make_pair(0, 4)) followed by insert(make_pair(0, 2)).

--
Pete
Roundhouse Consulting, Ltd. (www.versatilecoding.com) Author of "The
Standard C++ Library Extensions: a Tutorial and Reference
(www.petebecker.com/tr1book)