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

   1 .. Metafunctions/Composition and Argument Binding//quote |40
   2
   3 quote
   4 =====
   5
   6 Synopsis
   7 --------
   8
   9 .. parsed-literal::
  10
  11     template<
  12           template< typename P1 > class F
  13         , typename Tag = |unspecified|
  14         >
  15     struct quote1
  16     {
  17         // |unspecified|
  18         // |...|
  19     };
  20
  21     |...|
  22
  23     template<
  24           template< typename P1,\ |...| typename P\ *n* > class F
  25         , typename Tag = |unspecified|
  26         >
  27     struct quote\ *n*
  28     {
  29         // |unspecified|
  30         // |...|
  31     };
  32
  33
  34 Description
  35 -----------
  36
  37 ``quote``\ *n* is a higher-order primitive that wraps an *n*-ary |Metafunction| to create
  38 a corresponding |Metafunction Class|.
  39
  40
  41 Header
  42 ------
  43
  44 .. parsed-literal::
  45
  46     #include <boost/mpl/quote.hpp>
  47
  48
  49 Model of
  50 --------
  51
  52 |Metafunction Class|
  53
  54
  55 Parameters
  56 ----------
  57
  58 +---------------+-----------------------+-----------------------------------------------+
  59 | Parameter     | Requirement           | Description                                   |
  60 +===============+=======================+===============================================+
  61 | ``F``         | |Metafunction|        | A metafunction to wrap.                       |
  62 +---------------+-----------------------+-----------------------------------------------+
  63 | ``Tag``       | Any type              | A tag determining wrap semantics.             |
  64 +---------------+-----------------------+-----------------------------------------------+
  65
  66
  67 Expression semantics
  68 --------------------
  69
  70 For any *n*-ary |Metafunction| ``f`` and arbitrary type ``tag``:
  71
  72
  73 .. parsed-literal::
  74
  75     typedef quote\ *n*\ <f> g;
  76     typedef quote\ *n*\ <f,tag> g;
  77
  78 :Return type:
  79     |Metafunction Class|
  80
  81 :Semantics:
  82     Equivalent to
  83
  84     .. parsed-literal::
  85
  86         struct g
  87         {
  88             template< typename A1,\ |...| typename A\ *n* > struct apply
  89                 : f<A1,\ |...|\ A\ *n*\ >
  90             {
  91             };
  92         };
  93
  94     if ``f<A1,...An>`` has a nested type member ``::type``, and to
  95
  96     .. parsed-literal::
  97
  98         struct g
  99         {
 100             template< typename A1,\ |...| typename A\ *n* > struct apply
 101             {
 102                 typedef f<A1,\ |...|\ A\ *n*\ > type;
 103             };
 104         };
 105
 106     otherwise.
 107
 108
 109 Example
 110 -------
 111
 112 .. parsed-literal::
 113
 114     template< typename T > struct f1
 115     {
 116         typedef T type;
 117     };
 118
 119     template<
 120         typename T1, typename T2, typename T3, typename T4, typename T5
 121         >
 122     struct f5
 123     {
 124         // no 'type' member!
 125     };
 126
 127     typedef quote\ ``1``\<f1>::apply<int>::type t1;
 128     typedef quote\ ``5``\<f5>::apply<char,short,int,long,float>::type t5;
 129
 130     BOOST_MPL_ASSERT(( is_same< t1, int > ));
 131     BOOST_MPL_ASSERT(( is_same< t5, f5<char,short,int,long,float> > ));
 132
 133
 134 See also
 135 --------
 136
 137 |Composition and Argument Binding|, |Invocation|, |bind|, |lambda|, |protect|, |apply|
 138
 139
 140 .. copyright:: Copyright ©  2001-2009 Aleksey Gurtovoy and David Abrahams
 141    Distributed under the Boost Software License, Version 1.0. (See accompanying
 142    file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)