.. Sequences/Intrinsic Metafunctions//clear

clear

Synopsis

.. parsed-literal::

template<
      typename Sequence
    >
struct clear
{
    typedef |unspecified| type;
};

Description

Returns an empty sequence |concept-identical| to Sequence.

Header

.. parsed-literal::

#include <boost/mpl/clear.hpp>

Model of

|Tag Dispatched Metafunction|

Parameters

+---------------+-----------------------------------+---------------------------------------+ | Parameter | Requirement | Description | +===============+===================================+=======================================+ | Sequence | |Extensible Sequence| or | A sequence to get an empty "copy" of. | | | |Extensible Associative Sequence| | | +---------------+-----------------------------------+---------------------------------------+

Expression semantics

For any |Extensible Sequence| or |Extensible Associative Sequence| s:

.. parsed-literal::

typedef clear<s>::type t; 

:Return type: |Extensible Sequence| or |Extensible Associative Sequence|.

:Semantics: Equivalent to

.. parsed-literal::

   typedef erase< s, begin<s>::type, end<s>::type >::type t;

:Postcondition: empty<s>::value == true.

Complexity

Amortized constant time.

Example

.. parsed-literal::

typedef vector_c<int,1,3,5,7,9,11> odds;
typedef clear<odds>::type nothing;

BOOST_MPL_ASSERT(( empty<nothing> ));

See also

|Extensible Sequence|, |Extensible Associative Sequence|, |erase|, |empty|, |begin|, |end|

.. 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)