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

   1 .. Iterators/Iterator Metafunctions//distance |20
   2
   3 distance
   4 ========
   5
   6 Synopsis
   7 --------
   8
   9 .. parsed-literal::
  10
  11     template<
  12           typename First
  13         , typename Last
  14         >
  15     struct distance
  16     {
  17         typedef |unspecified| type;
  18     };
  19
  20
  21
  22 Description
  23 -----------
  24
  25 Returns the distance between ``First`` and ``Last`` iterators, that is, an
  26 |Integral Constant| ``n`` such that ``advance<First,n>::type`` is
  27 identical to ``Last``.
  28
  29
  30 Header
  31 ------
  32
  33 .. parsed-literal::
  34
  35     #include <boost/mpl/distance.hpp>
  36
  37
  38 Parameters
  39 ----------
  40
  41 +---------------+---------------------------+-----------------------------------+
  42 | Parameter     | Requirement               | Description                       |
  43 +===============+===========================+===================================+
  44 | ``First``,    | |Forward Iterator|        | Iterators to compute a            |
  45 | ``Last``      |                           | distance between.                 |
  46 +---------------+---------------------------+-----------------------------------+
  47
  48 Model Of
  49 --------
  50
  51 |Tag Dispatched Metafunction|
  52
  53
  54 Expression semantics
  55 --------------------
  56
  57 For any |Forward Iterator|\ s ``first`` and ``last``:
  58
  59 .. parsed-literal::
  60
  61     typedef distance<first,last>::type n;
  62
  63 :Return type:
  64     |Integral Constant|.
  65
  66 :Precondition:
  67     [``first``, ``last``) is a valid range.
  68
  69 :Semantics:
  70     Equivalent to
  71
  72     .. parsed-literal::
  73
  74         typedef iter_fold<
  75               iterator_range<first,last>
  76             , long_<0>
  77             , next<_1>
  78             >::type n;
  79
  80
  81 :Postcondition:
  82     ``is_same< advance<first,n>::type, last >::value == true``.
  83
  84
  85 Complexity
  86 ----------
  87
  88 Amortized constant time if ``first`` and ``last`` are |Random Access Iterator|\ s,
  89 otherwise linear time.
  90
  91
  92 Example
  93 -------
  94
  95 .. parsed-literal::
  96
  97     typedef range_c<int,0,10>::type range;
  98     typedef begin<range>::type first;
  99     typedef end<range>::type last;
 100
 101     BOOST_MPL_ASSERT_RELATION( (distance<first,last>::value), ==, 10);
 102
 103
 104 See also
 105 --------
 106
 107 |Iterators|, |Tag Dispatched Metafunction|, |advance|, |next|, |prior|
 108
 109
 110 .. copyright:: Copyright ©  2001-2009 Aleksey Gurtovoy and David Abrahams
 111    Distributed under the Boost Software License, Version 1.0. (See accompanying
 112    file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)