1 // Copyright 2002, Fernando Luis Cacciola Carballal.

     2 //

     3 // Distributed under the Boost Software License, Version 1.0. (See

     4 // accompanying file LICENSE_1_0.txt or copy at

     5 // http://www.boost.org/LICENSE_1_0.txt)

     6 //

     7 // 21 Ago 2002 (Created) Fernando Cacciola

     8 //

     9 #ifndef BOOST_UTILITY_VALUE_INIT_21AGO2002_HPP

    10 #define BOOST_UTILITY_VALUE_INIT_21AGO2002_HPP

    11 

    12 #include "boost/detail/select_type.hpp"

    13 #include "boost/type_traits/cv_traits.hpp"

    14 

    15 namespace boost {

    16 

    17 namespace vinit_detail {

    18 

    19 template<class T>

    20 class const_T_base

    21 {

    22   protected :

    23 

    24    const_T_base() : x() {}

    25 

    26    T x ;

    27 } ;

    28 

    29 template<class T>

    30 struct non_const_T_base

    31 {

    32   protected :

    33 

    34    non_const_T_base() : x() {}

    35 

    36    mutable T x ;

    37 } ;

    38 

    39 template<class T>

    40 struct select_base

    41 {

    42   typedef typename

    43     boost::detail::if_true< ::boost::is_const<T>::value >

    44       ::template then< const_T_base<T>, non_const_T_base<T> >::type type ;

    45 } ;

    46 

    47 } // namespace vinit_detail

    48 

    49 template<class T>

    50 class value_initialized : private vinit_detail::select_base<T>::type

    51 {

    52   public :

    53 

    54     value_initialized() {}

    55 

    56     operator T&() const { return this->x ; }

    57 

    58     T& data() const { return this->x ; }

    59 

    60 } ;

    61 

    62 template<class T>

    63 T const& get ( value_initialized<T> const& x )

    64 {

    65   return x.data() ;

    66 }

    67 template<class T>

    68 T& get ( value_initialized<T>& x )

    69 {

    70   return x.data() ;

    71 }

    72 

    73 } // namespace boost

    74 

    75 

    76 #endif

    77