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

   1 .. Metafunctions/Miscellaneous//inherit |30
   2
   3 inherit
   4 =======
   5
   6 Synopsis
   7 --------
   8
   9 .. parsed-literal::
  10
  11     template<
  12           typename T1, typename T2
  13         >
  14     struct inherit\ ``2``
  15     {
  16         typedef |unspecified| type;
  17     };
  18
  19     |...|
  20
  21     template<
  22           typename T1, typename T2,\ |...| typename T\ *n*
  23         >
  24     struct inherit\ *n*
  25     {
  26         typedef |unspecified| type;
  27     };
  28
  29     template<
  30           typename T1
  31         , typename T2
  32         |...|
  33         , typename T\ *n* = |unspecified|
  34         >
  35     struct inherit
  36     {
  37         typedef |unspecified| type;
  38     };
  39
  40
  41 Description
  42 -----------
  43
  44 Returns an unspecified class type publically derived from |T1...Tn|.
  45 Guarantees that derivation from |empty_base| is always a no-op,
  46 regardless of the position and number of |empty_base| classes in
  47 |T1...Tn|.
  48
  49
  50 Header
  51 ------
  52
  53 .. parsed-literal::
  54
  55     #include <boost/mpl/inherit.hpp>
  56
  57
  58 Model of
  59 --------
  60
  61 |Metafunction|
  62
  63
  64 Parameters
  65 ----------
  66
  67 +---------------+-------------------+-----------------------------------+
  68 | Parameter     | Requirement       | Description                       |
  69 +===============+===================+===================================+
  70 | |T1...Tn|     | A class type      | Classes to derived from.          |
  71 +---------------+-------------------+-----------------------------------+
  72
  73
  74 Expression semantics
  75 --------------------
  76
  77 For artibrary class types |t1...tn|:
  78
  79 .. parsed-literal::
  80
  81     typedef inherit2<t1,t2>::type r;
  82
  83 :Return type:
  84     A class type.
  85
  86 :Precondition:
  87     ``t1`` and ``t2`` are complete types.
  88
  89 :Semantics:
  90     If both ``t1`` and ``t2`` are identical to ``empty_base``, equivalent to
  91
  92     .. parsed-literal::
  93
  94         typedef empty_base r;
  95
  96
  97     otherwise, if ``t1`` is identical to ``empty_base``, equivalent to
  98
  99     .. parsed-literal::
 100
 101         typedef t2 r;
 102
 103
 104     otherwise, if ``t2`` is identical to ``empty_base``, equivalent to
 105
 106     .. parsed-literal::
 107
 108         typedef t1 r;
 109
 110
 111     otherwise equivalent to
 112
 113     .. parsed-literal::
 114
 115         struct r : t1, t2 {};
 116
 117 .. ...........................................................................
 118
 119 .. parsed-literal::
 120
 121     typedef inherit\ *n*\<t1,t2,\ |...|\ t\ *n*\ >::type r;
 122
 123 :Return type:
 124     A class type.
 125
 126 :Precondition:
 127     |t1...tn| are complete types.
 128
 129 :Semantics:
 130     Equivalent to
 131
 132     .. parsed-literal::
 133
 134         struct r
 135             : inherit\ ``2``\<
 136                   inherit\ *n-1*\<t1,t2,\ |...|\ t\ *n-1*\>::type
 137                 , t\ *n*
 138                 >
 139         {
 140         };
 141
 142
 143 .. ...........................................................................
 144
 145
 146 .. parsed-literal::
 147
 148     typedef inherit<t1,t2,\ |...|\ t\ *n*\ >::type r;
 149
 150 :Precondition:
 151     |t1...tn| are complete types.
 152
 153 :Return type:
 154     A class type.
 155
 156 :Semantics:
 157     Equivalent to
 158
 159     .. parsed-literal::
 160
 161         typedef inherit\ *n*\<t1,t2,\ |...|\ t\ *n*\ >::type r;
 162
 163
 164
 165 Complexity
 166 ----------
 167
 168 Amortized constant time.
 169
 170
 171 Example
 172 -------
 173
 174 .. parsed-literal::
 175
 176     struct udt1 { int n; };
 177     struct udt2 {};
 178
 179     typedef inherit<udt1,udt2>::type r1;
 180     typedef inherit<empty_base,udt1>::type r2;
 181     typedef inherit<empty_base,udt1,empty_base,empty_base>::type r3;
 182     typedef inherit<udt1,empty_base,udt2>::type r4;
 183     typedef inherit<empty_base,empty_base>::type r5;
 184
 185     BOOST_MPL_ASSERT(( is_base_and_derived< udt1, r1> ));
 186     BOOST_MPL_ASSERT(( is_base_and_derived< udt2, r1> ));
 187     BOOST_MPL_ASSERT(( is_same< r2, udt1> ));
 188     BOOST_MPL_ASSERT(( is_same< r3, udt1 > ));
 189     BOOST_MPL_ASSERT(( is_base_and_derived< udt1, r4 > ));
 190     BOOST_MPL_ASSERT(( is_base_and_derived< udt2, r4 > ));
 191     BOOST_MPL_ASSERT(( is_same< r5, empty_base > ));
 192
 193
 194 See also
 195 --------
 196
 197 |Metafunctions|, |empty_base|, |inherit_linearly|, |identity|
 198
 199
 200 .. copyright:: Copyright ©  2001-2009 Aleksey Gurtovoy and David Abrahams
 201    Distributed under the Boost Software License, Version 1.0. (See accompanying
 202    file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)