| .. Sequences/Intrinsic Metafunctions//back |
| |
| back |
| ==== |
| |
| Synopsis |
| -------- |
| |
| .. parsed-literal:: |
| |
| template< |
| typename Sequence |
| > |
| struct back |
| { |
| typedef |unspecified| type; |
| }; |
| |
| |
| |
| Description |
| ----------- |
| |
| Returns the last element in the sequence. |
| |
| |
| Header |
| ------ |
| |
| .. parsed-literal:: |
| |
| #include <boost/mpl/back.hpp> |
| |
| |
| Model of |
| -------- |
| |
| |Tag Dispatched Metafunction| |
| |
| |
| Parameters |
| ---------- |
| |
| +---------------+---------------------------+-----------------------------------+ |
| | Parameter | Requirement | Description | |
| +===============+===========================+===================================+ |
| | ``Sequence`` | |Bidirectional Sequence| | A sequence to be examined. | |
| +---------------+---------------------------+-----------------------------------+ |
| |
| |
| Expression semantics |
| -------------------- |
| |
| For any |Bidirectional Sequence| ``s``: |
| |
| .. parsed-literal:: |
| |
| typedef back<s>::type t; |
| |
| :Return type: |
| A type. |
| |
| :Precondition: |
| ``empty<s>::value == false``. |
| |
| :Semantics: |
| Equivalent to |
| |
| .. parsed-literal:: |
| |
| typedef deref< prior< end<s>::type >::type >::type t; |
| |
| |
| |
| Complexity |
| ---------- |
| |
| Amortized constant time. |
| |
| |
| Example |
| ------- |
| |
| .. parsed-literal:: |
| |
| typedef range_c<int,0,1> range1; |
| typedef range_c<int,0,10> range2; |
| typedef range_c<int,-10,0> range3; |
| |
| BOOST_MPL_ASSERT_RELATION( back<range1>::value, ==, 0 ); |
| BOOST_MPL_ASSERT_RELATION( back<range2>::value, ==, 9 ); |
| BOOST_MPL_ASSERT_RELATION( back<range3>::value, ==, -1 ); |
| |
| |
| See also |
| -------- |
| |
| |Bidirectional Sequence|, |front|, |push_back|, |end|, |deref|, |at| |
| |
| |
| .. 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) |