Re: Is a std::map<> ordered?

From:
Rolf Magnus <ramagnus@t-online.de>
Newsgroups:
comp.lang.c++
Date:
Fri, 21 Nov 2008 12:34:27 +0100
Message-ID:
<gg66c2$k1q$01$1@news.t-online.com>
Pete Becker wrote:

On 2008-11-20 14:40:19 -0500, acehreli@gmail.com said:

On Nov 20, 7:48 am, Juha Nieminen <nos...@thanks.invalid> wrote:

joseph cook wrote:

A map is always sorted using std::less


Not always. By default, yes, but you can specify other comparators, e

g:

std::map<int, int, std::greater> reversedMap;


Or at runtime:

   std::map<int, int> myMap(myPredicate);


Not really. There's a third type argument to std::map which specifies
the map's predicate type, with a default of std::less<T>. This
constructor takes an argument with the same type as the template's
predicate argument, so you can't pass arbitrary predicate objects. This
constructor is only useful with a user-defined predicate type that can
be initialized with something other than its default constructor.


Well, basically that just does mean that it depends on a runtime value.
Otherwise, you wouldn't need those constructor arguments in the first place.

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