1.. Sequences/Concepts//Bidirectional Sequence |20 2 3Bidirectional Sequence 4====================== 5 6Description 7----------- 8 9A |Bidirectional Sequence| is a |Forward Sequence| whose iterators model 10|Bidirectional Iterator|. 11 12Refinement of 13------------- 14 15|Forward Sequence| 16 17 18Expression requirements 19----------------------- 20 21In addition to the requirements defined in |Forward Sequence|, 22for any |Bidirectional Sequence| ``s`` the following must be met: 23 24+---------------------------+-----------------------------------+---------------------------+ 25| Expression | Type | Complexity | 26+===========================+===================================+===========================+ 27| ``begin<s>::type`` | |Bidirectional Iterator| | Amortized constant time | 28+---------------------------+-----------------------------------+---------------------------+ 29| ``end<s>::type`` | |Bidirectional Iterator| | Amortized constant time | 30+---------------------------+-----------------------------------+---------------------------+ 31| ``back<s>::type`` | Any type | Amortized constant time | 32+---------------------------+-----------------------------------+---------------------------+ 33 34 35Expression semantics 36-------------------- 37 38|Semantics disclaimer...| |Forward Sequence|. 39 40+---------------------------+-----------------------------------------------------------------------+ 41| Expression | Semantics | 42+===========================+=======================================================================+ 43| ``back<s>::type`` | The last element in the sequence; see |back|. | 44+---------------------------+-----------------------------------------------------------------------+ 45 46 47Models 48------ 49 50* |vector| 51* |range_c| 52 53 54See also 55-------- 56 57|Sequences|, |Forward Sequence|, |Random Access Sequence|, |Bidirectional Iterator|, |begin| / |end|, |back| 58 59 60.. copyright:: Copyright � 2001-2009 Aleksey Gurtovoy and David Abrahams 61 Distributed under the Boost Software License, Version 1.0. (See accompanying 62 file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) 63