ceph/src/boost/libs/iterator/doc/BidirectionalTraversal.rst

   1 .. Copyright David Abrahams 2006. Distributed under the Boost
   2 .. Software License, Version 1.0. (See accompanying
   3 .. file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
   4
   5 Bidirectional Traversal Concept
   6 ...............................
   7
   8 A class or built-in type ``X`` models the *Bidirectional Traversal*
   9 concept if, in addition to ``X`` meeting the requirements of Forward
  10 Traversal Iterator, the following expressions are valid and respect
  11 the stated semantics.
  12
  13 +--------------------------------------------------------------------------------------+
  14 |Bidirectional Traversal Iterator Requirements (in addition to Forward Traversal       |
  15 |Iterator)                                                                             |
  16 +--------------------------------+-------------------------------+---------------------+
  17 |Expression                      |Return Type                    |Assertion/Semantics /|
  18 |                                |                               |Pre-/Post-condition  |
  19 +================================+===============================+=====================+
  20 |``--r``                         |``X&``                         |pre: there exists    |
  21 |                                |                               |``s`` such that ``r  |
  22 |                                |                               |== ++s``.  post:     |
  23 |                                |                               |``s`` is             |
  24 |                                |                               |dereferenceable.     |
  25 |                                |                               |``--(++r) == r``.    |
  26 |                                |                               |``--r == --s``       |
  27 |                                |                               |implies ``r ==       |
  28 |                                |                               |s``. ``&r == &--r``. |
  29 +--------------------------------+-------------------------------+---------------------+
  30 |``r--``                         |convertible to ``const X&``    |::                   |
  31 |                                |                               |                     |
  32 |                                |                               | {                   |
  33 |                                |                               |   X tmp = r;        |
  34 |                                |                               |   --r;              |
  35 |                                |                               |   return tmp;       |
  36 |                                |                               | }                   |
  37 +--------------------------------+-------------------------------+---------------------+
  38 |``iterator_traversal<X>::type`` |Convertible to                 |                     |
  39 |                                |``bidirectional_traversal_tag``|                     |
  40 |                                |                               |                     |
  41 +--------------------------------+-------------------------------+---------------------+