ceph/src/boost/libs/metaparse/doc/get_position.qbk

   1 [#get_position]
   2 [section get_position]
   3
   4 [h1 Synopsis]
   5
   6   template <class D>
   7   struct get_position;
   8
   9 This is a [link lazy_metafunction lazy template metafunction].
  10
  11 [table Arguments
  12   [[Name] [Type]]
  13   [[`D`]  [[link accept accept] or [link reject reject] value]]
  14 ]
  15
  16 [h1 Description]
  17
  18 Returns the source position information of a parsing result.
  19
  20 [h1 Header]
  21
  22   #include <boost/metaparse/get_position.hpp>
  23
  24 [h1 Example]
  25
  26   #include <boost/metaparse/get_position.hpp>
  27   #include <boost/metaparse/start.hpp>
  28   #include <boost/metaparse/accept.hpp>
  29   #include <boost/metaparse/reject.hpp>
  30   #include <boost/metaparse/string.hpp>
  31   #include <boost/metaparse/define_error.hpp>
  32
  33   #include <type_traits>
  34
  35   using namespace boost::metaparse;
  36
  37   BOOST_METAPARSE_DEFINE_ERROR(sample_error, "Sample error message");
  38
  39   struct returns_reject
  40   {
  41     using type = reject<sample_error, start>;
  42   };
  43
  44   static_assert(
  45     std::is_same<
  46       start,
  47       get_position<reject<sample_error, start>>::type
  48     >::type::value,
  49     "It should return the position of a reject"
  50   );
  51
  52   static_assert(
  53     std::is_same<
  54       start,
  55       get_position<
  56         accept<sample_error, BOOST_METAPARSE_STRING("foo"), start>
  57       >::type
  58     >::type::value,
  59     "It should return the position of an accept"
  60   );
  61
  62   static_assert(
  63     std::is_same<start, get_position<returns_reject>::type>::type::value,
  64     "It should support lazy evaluation"
  65   );
  66
  67 [endsect]
  68