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

   1 .. Iterators/Iterator Metafunctions//deref |50
   2
   3 deref
   4 =====
   5
   6 Synopsis
   7 --------
   8
   9 .. parsed-literal::
  10
  11     template<
  12           typename Iterator
  13         >
  14     struct deref
  15     {
  16         typedef |unspecified| type;
  17     };
  18
  19
  20
  21 Description
  22 -----------
  23
  24 Dereferences an iterator.
  25
  26
  27 Header
  28 ------
  29
  30 .. parsed-literal::
  31
  32     #include <boost/mpl/deref.hpp>
  33
  34
  35
  36 Parameters
  37 ----------
  38
  39 +---------------+---------------------------+-----------------------------------+
  40 | Parameter     | Requirement               | Description                       |
  41 +===============+===========================+===================================+
  42 | ``Iterator``  | |Forward Iterator|        | The iterator to dereference.      |
  43 +---------------+---------------------------+-----------------------------------+
  44
  45
  46 Expression semantics
  47 --------------------
  48
  49 For any |Forward Iterator|\ s ``iter``:
  50
  51
  52 .. parsed-literal::
  53
  54     typedef deref<iter>::type t;
  55
  56 :Return type:
  57     A type.
  58
  59 :Precondition:
  60     ``iter`` is dereferenceable.
  61
  62 :Semantics:
  63     ``t`` is identical to the element referenced by ``iter``. If ``iter`` is
  64     a user-defined iterator, the library-provided default implementation is
  65     equivalent to
  66
  67     .. parsed-literal::
  68
  69         typedef iter::type t;
  70
  71
  72
  73
  74 Complexity
  75 ----------
  76
  77 Amortized constant time.
  78
  79
  80 Example
  81 -------
  82
  83 .. parsed-literal::
  84
  85     typedef vector<char,short,int,long> types;
  86     typedef begin<types>::type iter;
  87
  88     BOOST_MPL_ASSERT(( is_same< deref<iter>::type, char > ));
  89
  90
  91 See also
  92 --------
  93
  94 |Iterators|, |begin| / |end|, |next|
  95
  96
  97 .. copyright:: Copyright ©  2001-2009 Aleksey Gurtovoy and David Abrahams
  98    Distributed under the Boost Software License, Version 1.0. (See accompanying
  99    file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)