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/Src/Dependencies/Boost/libs/iterator/doc/RandomAccessTraversal.rst

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 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
 5Random Access Traversal Concept
 6...............................
 7
 8A class or built-in type ``X`` models the *Random Access Traversal*
 9concept if the following expressions are valid and respect the stated
10semantics.  In the table below, ``Distance`` is
11``iterator_traits<X>::difference_type`` and ``n`` represents a
12constant object of type ``Distance``.
13
14+------------------------------------------------------------------------------------------------------------------+
15|Random Access Traversal Iterator Requirements (in addition to Bidirectional Traversal)                            |
16+-------------------------------+---------------------------------+-------------------------+----------------------+
17|Expression                     |Return Type                      |Operational Semantics    |Assertion/            |
18|                               |                                 |                         |Precondition          |
19+===============================+=================================+=========================+======================+
20|``r += n``                     |``X&``                           |::                       |                      |
21|                               |                                 |                         |                      |
22|                               |                                 | {                       |                      |
23|                               |                                 |   Distance m = n;       |                      |
24|                               |                                 |   if (m >= 0)           |                      |
25|                               |                                 |     while (m--)         |                      |
26|                               |                                 |       ++r;              |                      |
27|                               |                                 |   else                  |                      |
28|                               |                                 |     while (m++)         |                      |
29|                               |                                 |       --r;              |                      |
30|                               |                                 |   return r;             |                      |
31|                               |                                 | }                       |                      |
32+-------------------------------+---------------------------------+-------------------------+----------------------+
33|``a + n``, ``n + a``           |``X``                            |``{ X tmp = a; return tmp|                      |
34|                               |                                 |+= n; }``                |                      |
35|                               |                                 |                         |                      |
36+-------------------------------+---------------------------------+-------------------------+----------------------+
37|``r -= n``                     |``X&``                           |``return r += -n``       |                      |
38+-------------------------------+---------------------------------+-------------------------+----------------------+
39|``a - n``                      |``X``                            |``{ X tmp = a; return tmp|                      |
40|                               |                                 |-= n; }``                |                      |
41|                               |                                 |                         |                      |
42+-------------------------------+---------------------------------+-------------------------+----------------------+
43|``b - a``                      |``Distance``                     |``a < b ?  distance(a,b) |pre: there exists a   |
44|                               |                                 |: -distance(b,a)``       |value ``n`` of        |
45|                               |                                 |                         |``Distance`` such that|
46|                               |                                 |                         |``a + n == b``.  ``b  |
47|                               |                                 |                         |== a + (b - a)``.     |
48+-------------------------------+---------------------------------+-------------------------+----------------------+
49|``a[n]``                       |convertible to T                 |``*(a + n)``             |pre: a is a *Readable |
50|                               |                                 |                         |Iterator*             |
51+-------------------------------+---------------------------------+-------------------------+----------------------+
52|``a[n] = v``                   |convertible to T                 |``*(a + n) = v``         |pre: a is a *Writable |
53|                               |                                 |                         |iterator*             |
54+-------------------------------+---------------------------------+-------------------------+----------------------+
55|``a < b``                      |convertible to ``bool``          |``b - a > 0``            |``<`` is a total      |
56|                               |                                 |                         |ordering relation     |
57+-------------------------------+---------------------------------+-------------------------+----------------------+
58|``a > b``                      |convertible to ``bool``          |``b < a``                |``>`` is a total      |
59|                               |                                 |                         |ordering relation     |
60+-------------------------------+---------------------------------+-------------------------+----------------------+
61|``a >= b``                     |convertible to ``bool``          |``!(a < b)``             |                      |
62+-------------------------------+---------------------------------+-------------------------+----------------------+
63|``a <= b``                     |convertible to ``bool``          |``!(a > b)``             |                      |
64+-------------------------------+---------------------------------+-------------------------+----------------------+
65|``iterator_traversal<X>::type``|Convertible to                   |                         |                      |
66|                               |``random_access_traversal_tag``  |                         |                      |
67+-------------------------------+---------------------------------+-------------------------+----------------------+