ceph/src/boost/libs/mpl/doc/src/refmanual/back.rst

   1 .. Sequences/Intrinsic Metafunctions//back
   2
   3 back
   4 ====
   5
   6 Synopsis
   7 --------
   8
   9 .. parsed-literal::
  10
  11     template<
  12           typename Sequence
  13         >
  14     struct back
  15     {
  16         typedef |unspecified| type;
  17     };
  18
  19
  20
  21 Description
  22 -----------
  23
  24 Returns the last element in the sequence.
  25
  26
  27 Header
  28 ------
  29
  30 .. parsed-literal::
  31
  32     #include <boost/mpl/back.hpp>
  33
  34
  35 Model of
  36 --------
  37
  38 |Tag Dispatched Metafunction|
  39
  40
  41 Parameters
  42 ----------
  43
  44 +---------------+---------------------------+-----------------------------------+
  45 | Parameter     | Requirement               | Description                       |
  46 +===============+===========================+===================================+
  47 | ``Sequence``  | |Bidirectional Sequence|  | A sequence to be examined.        |
  48 +---------------+---------------------------+-----------------------------------+
  49
  50
  51 Expression semantics
  52 --------------------
  53
  54 For any |Bidirectional Sequence| ``s``:
  55
  56 .. parsed-literal::
  57
  58     typedef back<s>::type t;
  59
  60 :Return type:
  61     A type.
  62
  63 :Precondition:
  64     ``empty<s>::value == false``.
  65
  66 :Semantics:
  67     Equivalent to
  68
  69     .. parsed-literal::
  70
  71        typedef deref< prior< end<s>::type >::type >::type t;
  72
  73
  74
  75 Complexity
  76 ----------
  77
  78 Amortized constant time.
  79
  80
  81 Example
  82 -------
  83
  84 .. parsed-literal::
  85
  86     typedef range_c<int,0,1> range1;
  87     typedef range_c<int,0,10> range2;
  88     typedef range_c<int,-10,0> range3;
  89
  90     BOOST_MPL_ASSERT_RELATION( back<range1>::value, ==, 0 );
  91     BOOST_MPL_ASSERT_RELATION( back<range2>::value, ==, 9 );
  92     BOOST_MPL_ASSERT_RELATION( back<range3>::value, ==, -1 );
  93
  94
  95 See also
  96 --------
  97
  98 |Bidirectional Sequence|, |front|, |push_back|, |end|, |deref|, |at|
  99
 100
 101 .. copyright:: Copyright ©  2001-2009 Aleksey Gurtovoy and David Abrahams
 102    Distributed under the Boost Software License, Version 1.0. (See accompanying
 103    file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)