ceph/src/boost/boost/spirit/home/x3/support/unused.hpp

   1 /*=============================================================================
   2     Copyright (c) 2001-2014 Joel de Guzman
   3     Copyright (c) 2001-2011 Hartmut Kaiser
   4
   5     Distributed under the Boost Software License, Version 1.0. (See accompanying
   6     file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
   7 ==============================================================================*/
   8 #if !defined(BOOST_SPIRIT_X3_UNUSED_APRIL_16_2006_0616PM)
   9 #define BOOST_SPIRIT_X3_UNUSED_APRIL_16_2006_0616PM
  10
  11 #include <iosfwd>
  12
  13 ///////////////////////////////////////////////////////////////////////////////
  14 namespace boost { namespace spirit { namespace x3
  15 {
  16     struct unused_type
  17     {
  18         unused_type() = default;
  19
  20         template <typename T>
  21         unused_type(T const&)
  22         {
  23         }
  24
  25         template <typename T>
  26         unused_type const&
  27         operator=(T const&) const
  28         {
  29             return *this;
  30         }
  31
  32         template <typename T>
  33         unused_type&
  34         operator=(T const&)
  35         {
  36             return *this;
  37         }
  38
  39         // unused_type can also masquerade as an empty context (see context.hpp)
  40
  41         template <typename ID>
  42         unused_type get(ID) const
  43         {
  44             return {};
  45         }
  46     };
  47
  48     auto const unused = unused_type{};
  49
  50     inline std::ostream& operator<<(std::ostream& out, unused_type const&)
  51     {
  52         return out;
  53     }
  54
  55     inline std::istream& operator>>(std::istream& in, unused_type&)
  56     {
  57         return in;
  58     }
  59 }}}
  60
  61 #endif