.. Algorithms/Querying Algorithms//contains |30

contains

Synopsis

.. parsed-literal::

template<
      typename Sequence
    , typename T
    >
struct contains
{
    typedef |unspecified| type;
};

Description

Returns a true-valued |Integral Constant| if one or more elements in Sequence are identical to T.

Header

.. parsed-literal::

#include <boost/mpl/contains.hpp>

Parameters

+---------------+---------------------------+-----------------------------------+ | Parameter | Requirement | Description | +===============+===========================+===================================+ | Sequence | |Forward Sequence| | A sequence to be examined. | +---------------+---------------------------+-----------------------------------+ | T | Any type | A type to search for. | +---------------+---------------------------+-----------------------------------+

Expression semantics

For any |Forward Sequence| s and arbitrary type t:

.. parsed-literal::

typedef contains<s,t>::type r;

:Return type: |Integral Constant|.

:Semantics: Equivalent to

.. parsed-literal::
    
    typedef not_< is_same< 
          find<s,t>::type
        , end<s>::type
        > >::type r;

Complexity

Linear. At most size<s>::value comparisons for identity.

Example

.. parsed-literal::

typedef vector<char,int,unsigned,long,unsigned long> types;
BOOST_MPL_ASSERT_NOT(( contains<types,bool> ));

See also

|Querying Algorithms|, |find|, |find_if|, |count|, |lower_bound|

.. 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)