ceph/src/boost/libs/range/include/boost/range/detail/default_constructible_unary_fn.hpp

   1 // Boost.Range library
   2 //
   3 //  Copyright Neil Groves 2014. Use, modification and
   4 //  distribution is subject to the Boost Software License, Version
   5 //  1.0. (See accompanying file LICENSE_1_0.txt or copy at
   6 //  http://www.boost.org/LICENSE_1_0.txt)
   7 //
   8 // For more information, see http://www.boost.org/libs/range/
   9 //
  10 #ifndef BOOST_RANGE_DETAIL_DEFAULT_CONSTRUCTIBLE_UNARY_FN_HPP_INCLUDED
  11 #define BOOST_RANGE_DETAIL_DEFAULT_CONSTRUCTIBLE_UNARY_FN_HPP_INCLUDED
  12
  13 #include <boost/optional/optional.hpp>
  14 #include <boost/mpl/if.hpp>
  15 #include <boost/type_traits/has_trivial_constructor.hpp>
  16
  17 namespace boost
  18 {
  19     namespace range_detail
  20     {
  21
  22 template<typename F, typename R>
  23 class default_constructible_unary_fn_wrapper
  24 {
  25 public:
  26     typedef R result_type;
  27
  28     default_constructible_unary_fn_wrapper()
  29     {
  30     }
  31     default_constructible_unary_fn_wrapper(const F& source)
  32         : m_impl(source)
  33     {
  34     }
  35     template<typename Arg>
  36     R operator()(const Arg& arg) const
  37     {
  38         BOOST_ASSERT(m_impl);
  39         return (*m_impl)(arg);
  40     }
  41     template<typename Arg>
  42     R operator()(Arg& arg) const
  43     {
  44         BOOST_ASSERT(m_impl);
  45         return (*m_impl)(arg);
  46     }
  47 private:
  48     boost::optional<F> m_impl;
  49 };
  50
  51 template<typename F, typename R>
  52 struct default_constructible_unary_fn_gen
  53 {
  54     typedef typename boost::mpl::if_<
  55         boost::has_trivial_default_constructor<F>,
  56         F,
  57         default_constructible_unary_fn_wrapper<F,R>
  58     >::type type;
  59 };
  60
  61     } // namespace range_detail
  62 } // namespace boost
  63
  64 #endif // include guard