| .. Sequences/Concepts//Forward Sequence |10 |
| |
| Forward Sequence |
| ================ |
| |
| Description |
| ----------- |
| |
| A |Forward Sequence| is an MPL concept representing a compile-time sequence of |
| elements. Sequence elements are |
| types, and are accessible through |iterators|. The |begin| and |end| metafunctions |
| provide iterators delimiting the range of the sequence |
| elements. A sequence guarantees that its elements are arranged in a definite, |
| but possibly unspecified, order. Every MPL sequence is a |Forward Sequence|. |
| |
| Definitions |
| ----------- |
| |
| * The *size* of a sequence is the number of elements it contains. The size is a |
| nonnegative number. |
| |
| * A sequence is *empty* if its size is zero. |
| |
| |
| Expression requirements |
| ----------------------- |
| |
| For any |Forward Sequence| ``s`` the following expressions must be valid: |
| |
| +---------------------------+-----------------------------------+---------------------------+ |
| | Expression | Type | Complexity | |
| +===========================+===================================+===========================+ |
| | ``begin<s>::type`` | |Forward Iterator| | Amortized constant time | |
| +---------------------------+-----------------------------------+---------------------------+ |
| | ``end<s>::type`` | |Forward Iterator| | Amortized constant time | |
| +---------------------------+-----------------------------------+---------------------------+ |
| | ``size<s>::type`` | |Integral Constant| | Unspecified | |
| +---------------------------+-----------------------------------+---------------------------+ |
| | ``empty<s>::type`` | Boolean |Integral Constant| | Constant time | |
| +---------------------------+-----------------------------------+---------------------------+ |
| | ``front<s>::type`` | Any type | Amortized constant time | |
| +---------------------------+-----------------------------------+---------------------------+ |
| |
| |
| Expression semantics |
| -------------------- |
| |
| +---------------------------+-----------------------------------------------------------------------+ |
| | Expression | Semantics | |
| +===========================+=======================================================================+ |
| | ``begin<s>::type`` | An iterator to the first element of the sequence; see |begin|. | |
| +---------------------------+-----------------------------------------------------------------------+ |
| | ``end<s>::type`` | A past-the-end iterator to the sequence; see |end|. | |
| +---------------------------+-----------------------------------------------------------------------+ |
| | ``size<s>::type`` | The size of the sequence; see |size|. | |
| +---------------------------+-----------------------------------------------------------------------+ |
| | ``empty<s>::type`` | |true if and only if| the sequence is empty; see |empty|. | |
| +---------------------------+-----------------------------------------------------------------------+ |
| | ``front<s>::type`` | The first element in the sequence; see |front|. | |
| +---------------------------+-----------------------------------------------------------------------+ |
| |
| |
| Invariants |
| ---------- |
| |
| For any |Forward Sequence| ``s`` the following invariants always hold: |
| |
| * [``begin<s>::type``, ``end<s>::type``) is always a valid range. |
| |
| * An algorithm that iterates through the range [``begin<s>::type``, ``end<s>::type``) |
| will pass through every element of ``s`` exactly once. |
| |
| * ``begin<s>::type`` is identical to ``end<s>::type`` if and only if ``s`` is empty. |
| |
| * Two different iterations through ``s`` will access its elements in the same order. |
| |
| |
| Models |
| ------ |
| |
| * |vector| |
| * |map| |
| * |range_c| |
| * |iterator_range| |
| * |filter_view| |
| |
| See also |
| -------- |
| |
| |Sequences|, |Bidirectional Sequence|, |Forward Iterator|, |begin| / |end|, |size|, |empty|, |front| |
| |
| |
| .. copyright:: Copyright © 2001-2009 Aleksey Gurtovoy and David Abrahams |
| Distributed under the Boost Software License, Version 1.0. (See accompanying |
| file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) |
