.. Algorithms/Querying Algorithms//count |40

count

Synopsis

.. parsed-literal::

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

Description

Returns the number of elements in a Sequence that are identical to T.

Header

.. parsed-literal::

#include <boost/mpl/count.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 count<s,t>::type n;

:Return type: |Integral Constant|.

:Semantics: Equivalent to

.. parsed-literal::

    typedef count_if< s,is_same<_,T> >::type n;

Complexity

Linear. Exactly size<s>::value comparisons for identity.

Example

.. parsed-literal::

typedef vector<int,char,long,short,char,short,double,long> types;
typedef count<types, short>::type n;

BOOST_MPL_ASSERT_RELATION( n::value, ==, 2 );

See also

|Querying Algorithms|, |count_if|, |find|, |find_if|, |contains|, |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)