.. Sequences/Classes//map |50

map

Description

map is a |variadic|, associative, extensible sequence of type pairs that supports constant-time insertion and removal of elements, and testing for membership. A map may contain at most one element for each key.

__ Associative Sequence_ __ Extensible Associative Sequence_

Header

+-------------------+-------------------------------------------------------+ | Sequence form | Header | +===================+=======================================================+ | Variadic | #include <boost/mpl/map.hpp> | +-------------------+-------------------------------------------------------+ | Numbered | #include <boost/mpl/map/map\ n\ .hpp> | +-------------------+-------------------------------------------------------+

Model of

• |Variadic Sequence|
• |Associative Sequence|
• |Extensible Associative Sequence|

Expression semantics

|In the following table...| m is an instance of map, pos is an iterator into m, x and |p1...pn| are pair\ s, and k is an arbitrary type.

+---------------------------------------+-----------------------------------------------------------+ | Expression | Semantics | +=======================================+===========================================================+ | .. parsed-literal:: | map of elements |p1...pn|; see | | | |Variadic Sequence|. | | map<|p1...pn|> | | | map\ n\ <|p1...pn|> | | +---------------------------------------+-----------------------------------------------------------+ | .. parsed-literal:: | Identical to map\ n\ <\ |p1...pn|\ >; | | | see |Variadic Sequence|. | | map<|p1...pn|>::type | | | map\ n\ <|p1...pn|>::type | | +---------------------------------------+-----------------------------------------------------------+ | begin<m>::type | An iterator pointing to the beginning of m; | | | see |Associative Sequence|. | +---------------------------------------+-----------------------------------------------------------+ | end<m>::type | An iterator pointing to the end of m; | | | see |Associative Sequence|. | +---------------------------------------+-----------------------------------------------------------+ | size<m>::type | The size of m; see |Associative Sequence|. | +---------------------------------------+-----------------------------------------------------------+ | empty<m>::type | |true if and only if| m is empty; see | | | |Associative Sequence|. | +---------------------------------------+-----------------------------------------------------------+ | front<m>::type | The first element in m; see | | | |Associative Sequence|. | +---------------------------------------+-----------------------------------------------------------+ | has_key<m,k>::type | Queries the presence of elements with the key k in | | | m; see |Associative Sequence|. | +---------------------------------------+-----------------------------------------------------------+ | count<m,k>::type | The number of elements with the key k in m; | | | see |Associative Sequence|. | +---------------------------------------+-----------------------------------------------------------+ | order<m,k>::type | A unique unsigned |Integral Constant| associated with | | | the key k in m; see |Associative Sequence|. | +---------------------------------------+-----------------------------------------------------------+ | .. parsed-literal:: | The element associated with the key k in | | | m; see |Associative Sequence|. | | at<m,k>::type | | | at<m,k,default>::type | | +---------------------------------------+-----------------------------------------------------------+ | key_type<m,x>::type | Identical to x::first; see |Associative Sequence|. | +---------------------------------------+-----------------------------------------------------------+ | value_type<m,x>::type | Identical to x::second; see |Associative Sequence|. | +---------------------------------------+-----------------------------------------------------------+ | insert<m,x>::type | A new map, t, equivalent to m except that | | | :: | | | | | | at< t, key_type<m,x>::type >::type | | | | | | is identical to value_type<m,x>::type. | +---------------------------------------+-----------------------------------------------------------+ | insert<m,pos,x>::type | Equivalent to insert<m,x>::type; pos is ignored. | +---------------------------------------+-----------------------------------------------------------+ | erase_key<m,k>::type | A new map, t, equivalent to m except that | | | has_key<t, k>::value == false. | +---------------------------------------+-----------------------------------------------------------+ | erase<m,pos>::type | Equivalent to erase<m, deref<pos>::type >::type. | +---------------------------------------+-----------------------------------------------------------+ | clear<m>::type | An empty map; see |clear|. | +---------------------------------------+-----------------------------------------------------------+

Example

.. parsed-literal::

typedef map<
      pair<int,unsigned>
    , pair<char,unsigned char>
    , pair<long_<5>,char[17]>
    , pair<int[42],bool>
    > m;

BOOST_MPL_ASSERT_RELATION( size<m>::value, ==, 4 );
BOOST_MPL_ASSERT_NOT(( empty<m> ));

BOOST_MPL_ASSERT(( is_same< at<m,int>::type, unsigned > ));
BOOST_MPL_ASSERT(( is_same< at<m,long_<5> >::type, char[17] > ));
BOOST_MPL_ASSERT(( is_same< at<m,int[42]>::type, bool > ));
BOOST_MPL_ASSERT(( is_same< at<m,long>::type, void\_ > ));

See also

|Sequences|, |Variadic Sequence|, |Associative Sequence|, |Extensible Associative Sequence|, |set|, |vector|

.. copyright:: Copyright 2001-2009 Aleksey Gurtovoy and David Abrahams Distributed under the Boost Software License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)