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

   1 .. Algorithms/Concepts//Inserter
   2
   3 Inserter
   4 ========
   5
   6 Description
   7 -----------
   8
   9 An |Inserter| is a compile-time substitute for STL |Output Iterator|.
  10 Under the hood, it's simply a type holding
  11 two entities: a *state* and an *operation*. When passed to a
  12 |transformation algorithm|, the inserter's binary operation is
  13 invoked for every element that would normally be written into the
  14 output iterator, with the element itself (as the second
  15 argument) and the result of the previous operation's invocation |--| or,
  16 for the very first element, the inserter's initial state.
  17
  18 Technically, instead of taking a single inserter parameter,
  19 |transformation algorithms| could accept the state and the "output"
  20 operation separately. Grouping these in a single parameter entity,
  21 however, brings the algorithms semantically and syntactically closer to
  22 their STL counterparts, significantly simplifying many of the common
  23 use cases.
  24
  25
  26 Valid expressions
  27 -----------------
  28
  29 |In the following table...| ``in`` is a model of |Inserter|.
  30
  31 +-----------------------+-------------------------------+
  32 | Expression            | Type                          |
  33 +=======================+===============================+
  34 | ``in::state``         | Any type                      |
  35 +-----------------------+-------------------------------+
  36 | ``in::operation``     | Binary |Lambda Expression|    |
  37 +-----------------------+-------------------------------+
  38
  39
  40 Expression semantics
  41 --------------------
  42
  43 +-----------------------+-------------------------------------------+
  44 | Expression            | Semantics                                 |
  45 +=======================+===========================================+
  46 | ``in::state``         | The inserter's initial state.             |
  47 +-----------------------+-------------------------------------------+
  48 | ``in::operation``     | The inserter's "output" operation.        |
  49 +-----------------------+-------------------------------------------+
  50
  51
  52 Example
  53 -------
  54
  55 .. parsed-literal::
  56
  57     typedef transform<
  58           range_c<int,0,10>
  59         , plus<_1,_1>
  60         , back_inserter< vector0<> >
  61         >::type result;
  62
  63
  64 Models
  65 ------
  66
  67 * |[inserter]|
  68 * |front_inserter|
  69 * |back_inserter|
  70
  71 See also
  72 --------
  73
  74 |Algorithms|, |Transformation Algorithms|, |[inserter]|, |front_inserter|, |back_inserter|
  75
  76
  77 .. copyright:: Copyright ©  2001-2009 Aleksey Gurtovoy and David Abrahams
  78    Distributed under the Boost Software License, Version 1.0. (See accompanying
  79    file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)