.. Algorithms/Transformation Algorithms//partition |85

partition

Synopsis

.. parsed-literal::

template<
      typename Seq
    , typename Pred
    , typename In1 = |unspecified|
    , typename In2 = |unspecified|
    >
struct partition
{
    typedef |unspecified| type;
};

Description

Returns a pair of sequences together containing all elements in the range |begin/end<Seq>| split into two groups based on the predicate Pred. partition is a synonym for |stable_partition|.

|transformation algorithm disclaimer|

Header

.. parsed-literal::

#include <boost/mpl/partition.hpp>

Model of

|Reversible Algorithm|

Parameters

+-------------------+-----------------------------------+-------------------------------+ | Parameter | Requirement | Description | +===================+===================================+===============================+ | Seq | |Forward Sequence| | An original sequence. | +-------------------+-----------------------------------+-------------------------------+ | Pred | Unary |Lambda Expression| | A partitioning predicate. | +-------------------+-----------------------------------+-------------------------------+ | In1, In2 | |Inserter| | Output inserters. | +-------------------+-----------------------------------+-------------------------------+

Expression semantics

|Semantics disclaimer...| |Reversible Algorithm|.

For any |Forward Sequence| s, an unary |Lambda Expression| pred, and |Inserter|\ s in1 and in2:

.. parsed-literal::

typedef partition<s,pred,in1,in2>::type r;

:Return type: A |pair|.

:Semantics: Equivalent to

.. parsed-literal::

    typedef stable_partition<s,pred,in1,in2>::type r;

Complexity

Linear. Exactly size<s>::value applications of pred, and size<s>::value of summarized in1::operation / in2::operation applications.

Example

.. parsed-literal::

template< typename N > struct is_odd : bool_<(N::value % 2)> {};

typedef partition<
      range_c<int,0,10> 
    , is_odd<_1>
    , back_inserter< vector<> >
    , back_inserter< vector<> >
    >::type r;

BOOST_MPL_ASSERT(( equal< r::first, vector_c<int,1,3,5,7,9> > ));
BOOST_MPL_ASSERT(( equal< r::second, vector_c<int,0,2,4,6,8> > ));

See also

|Transformation Algorithms|, |Reversible Algorithm|, |reverse_partition|, |stable_partition|, |sort|

.. 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)