ceph/src/boost/boost/parameter/aux_/default.hpp

   1 // Copyright Daniel Wallin, David Abrahams 2005. Use, modification and
   2 // distribution is subject to the Boost Software License, Version 1.0. (See
   3 // accompanying file LICENSE_1_0.txt or copy at
   4 // http://www.boost.org/LICENSE_1_0.txt)
   5
   6 #ifndef DEFAULT_050329_HPP
   7 # define DEFAULT_050329_HPP
   8
   9 # include <boost/detail/workaround.hpp>
  10
  11 namespace boost { namespace parameter { namespace aux {
  12
  13 // A wrapper for the default value passed by the user when resolving
  14 // the value of the parameter with the given Keyword
  15 template <class Keyword, class Value>
  16 struct default_
  17 {
  18     default_(Value& x)
  19       : value(x)
  20     {}
  21
  22     Value& value;
  23 };
  24
  25 //
  26 // lazy_default --
  27 //
  28 //    A wrapper for the default value computation function passed by
  29 //    the user when resolving the value of the parameter with the
  30 //    given keyword
  31 //
  32 # if BOOST_WORKAROUND(__EDG_VERSION__, <= 300)
  33 // These compilers need a little extra help with overload
  34 // resolution; we have empty_arg_list's operator[] accept a base
  35 // class to make that overload less preferable.
  36 template <class KW, class DefaultComputer>
  37 struct lazy_default_base
  38 {
  39     lazy_default_base(DefaultComputer const& x)
  40       : compute_default(x)
  41     {}
  42     DefaultComputer const& compute_default;
  43 };
  44
  45 template <class KW, class DefaultComputer>
  46 struct lazy_default
  47   : lazy_default_base<KW,DefaultComputer>
  48   {
  49       lazy_default(DefaultComputer const & x)
  50         : lazy_default_base<KW,DefaultComputer>(x)
  51       {}
  52   };
  53 #  define BOOST_PARAMETER_lazy_default_fallback lazy_default_base
  54 # else
  55 template <class KW, class DefaultComputer>
  56 struct lazy_default
  57 {
  58     lazy_default(const DefaultComputer& x)
  59       : compute_default(x)
  60     {}
  61     DefaultComputer const& compute_default;
  62 };
  63 #  define BOOST_PARAMETER_lazy_default_fallback lazy_default
  64 # endif
  65
  66 }}} // namespace boost::parameter::aux
  67
  68 #endif // DEFAULT_050329_HPP
  69