ceph/src/boost/libs/mpl/doc/src/refmanual/copy_if.rst

   1 .. Algorithms/Transformation Algorithms//copy_if |20
   2
   3 copy_if
   4 =======
   5
   6 Synopsis
   7 --------
   8
   9 .. parsed-literal::
  10
  11     template<
  12           typename Sequence
  13         , typename Pred
  14         , typename In = |unspecified|
  15         >
  16     struct copy_if
  17     {
  18         typedef |unspecified| type;
  19     };
  20
  21
  22
  23 Description
  24 -----------
  25
  26 Returns a filtered copy of the original sequence containing the elements that satisfy
  27 the predicate ``Pred``.
  28
  29 |transformation algorithm disclaimer|
  30
  31 Header
  32 ------
  33
  34 .. parsed-literal::
  35
  36     #include <boost/mpl/copy_if.hpp>
  37
  38
  39 Model of
  40 --------
  41
  42 |Reversible Algorithm|
  43
  44
  45 Parameters
  46 ----------
  47
  48 +---------------+-------------------------------+-------------------------------+
  49 | Parameter     | Requirement                   | Description                   |
  50 +===============+===============================+===============================+
  51 | ``Sequence``  | |Forward Sequence|            | A sequence to copy.           |
  52 +---------------+-------------------------------+-------------------------------+
  53 | ``Pred``      | Unary |Lambda Expression|     | A copying condition.          |
  54 +---------------+-------------------------------+-------------------------------+
  55 | ``In``        | |Inserter|                    | An inserter.                  |
  56 +---------------+-------------------------------+-------------------------------+
  57
  58
  59 Expression semantics
  60 --------------------
  61
  62 |Semantics disclaimer...| |Reversible Algorithm|.
  63
  64 For any |Forward Sequence| ``s``, an unary |Lambda Expression| ``pred``, and
  65 an |Inserter| ``in``:
  66
  67
  68 .. parsed-literal::
  69
  70     typedef copy_if<s,pred,in>::type r;
  71
  72
  73 :Return type:
  74     A type.
  75
  76 :Semantics:
  77     Equivalent to
  78
  79     .. parsed-literal::
  80
  81         typedef lambda<pred>::type p;
  82         typedef lambda<in::operation>::type op;
  83
  84         typedef fold<
  85               s
  86             , in::state
  87             , eval_if<
  88                   apply_wrap\ ``1``\<p,_2>
  89                 , apply_wrap\ ``2``\<op,_1,_2>
  90                 , identity<_1>
  91                 >
  92             >::type r;
  93
  94
  95 Complexity
  96 ----------
  97
  98 Linear. Exactly ``size<s>::value`` applications of ``pred``, and at
  99 most ``size<s>::value`` applications of ``in::operation``.
 100
 101
 102 Example
 103 -------
 104
 105 .. parsed-literal::
 106
 107     typedef copy_if<
 108           range_c<int,0,10>
 109         , less< _1, int_<5> >
 110         , back_inserter< vector<> >
 111         >::type result;
 112
 113     BOOST_MPL_ASSERT_RELATION( size<result>::value, ==, 5 );
 114     BOOST_MPL_ASSERT(( equal<result,range_c<int,0,5> > ));
 115
 116
 117 See also
 118 --------
 119
 120 |Transformation Algorithms|, |Reversible Algorithm|, |reverse_copy_if|, |copy|, |remove_if|, |replace_if|
 121
 122
 123 .. copyright:: Copyright ©  2001-2009 Aleksey Gurtovoy and David Abrahams
 124    Distributed under the Boost Software License, Version 1.0. (See accompanying
 125    file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)