.. Sequences/Intrinsic Metafunctions//erase

erase

Synopsis

.. parsed-literal::

template<
      typename Sequence
    , typename First
    , typename Last = |unspecified|
    >
struct erase
{
    typedef |unspecified| type;
};

Description

erase performs a removal of one or more adjacent elements in the sequence starting from an arbitrary position.

Header

.. parsed-literal::

#include <boost/mpl/erase.hpp>

Model of

|Tag Dispatched Metafunction|

Parameters

+---------------+-----------------------------------+-----------------------------------------------+ | Parameter | Requirement | Description | +===============+===================================+===============================================+ | Sequence | |Extensible Sequence| or | A sequence to erase from. | | | |Extensible Associative Sequence| | | +---------------+-----------------------------------+-----------------------------------------------+ | First | |Forward Iterator| | An iterator to the beginning of the range to | | | | be erased. | +---------------+-----------------------------------+-----------------------------------------------+ | Last | |Forward Iterator| | An iterator past-the-end of the range to be | | | | erased. | +---------------+-----------------------------------+-----------------------------------------------+

Expression semantics

.. compound:: :class: expression-semantics

For any |Extensible Sequence| ``s``, and iterators ``pos``, ``first`` and ``last`` into ``s``:


.. parsed-literal::

    typedef erase<s,first,last>::type r; 

:Return type:
    |Extensible Sequence|.

:Precondition:
    ``[first,last)`` is a valid range in ``s``. 
 
:Semantics:
    ``r`` is a new sequence, |concept-identical| to ``s``, of the following elements:
    [``begin<s>::type``, ``pos``), [``last``, ``end<s>::type``).

:Postcondition:
    The relative order of the elements in ``r`` is the same as in ``s``;

    .. parsed-literal::

       size<r>::value == size<s>::value - distance<first,last>::value


.. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

.. parsed-literal::

    typedef erase<s,pos>::type r;

:Return type:
    |Extensible Sequence|.
    
:Precondition:
    ``pos`` is a dereferenceable iterator in ``s``.

:Semantics:
    Equivalent to 
    
    .. parsed-literal::

       typedef erase< s,pos,next<pos>::type >::type r;

.. compound:: :class: expression-semantics

For any |Extensible Associative Sequence| ``s``, and iterator ``pos`` into ``s``:

.. parsed-literal::

    typedef erase<s,pos>::type r;

:Return type:
    |Extensible Sequence|.
    
:Precondition:
    ``pos`` is a dereferenceable iterator to ``s``.

:Semantics:
    Erases the element at a specific position ``pos``; equivalent to
    ``erase_key<s, deref<pos>::type >::type``.

:Postcondition:
    ``size<r>::value == size<s>::value - 1``. 

Complexity

+---------------------------------------+-----------------------------------------------+ | Sequence archetype | Complexity (the range form) | +=======================================+===============================================+ | |Extensible Associative Sequence| | Amortized constant time. | +---------------------------------------+-----------------------------------------------+ | |Extensible Sequence| | Quadratic in the worst case, linear at best. | +---------------------------------------+-----------------------------------------------+

Example

.. parsed-literal::

typedef vector_c<int,1,0,5,1,7,5,0,5> values;
typedef find< values, integral_c<int,7> >::type pos;
typedef erase<values,pos>::type result;

BOOST_MPL_ASSERT_RELATION( size<result>::value, ==, 7 );

typedef find<result, integral_c<int,7> >::type iter;
BOOST_MPL_ASSERT(( is_same< iter, end<result>::type > ));

See also

|Extensible Sequence|, |Extensible Associative Sequence|, |erase_key|, |pop_front|, |pop_back|, |insert|

.. 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)