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

   1 [#lit_c]
   2 [section lit_c]
   3
   4 [h1 Synopsis]
   5
   6   template <char C>
   7   struct lit;
   8
   9 This is a [link parser parser].
  10
  11 [table Arguments
  12   [[Name] [Type]]
  13   [[`C`]  [`char` value]]
  14 ]
  15
  16 [h1 Description]
  17
  18 Parser accepting only the `C` character. The result of parsing is the accepted
  19 character.
  20
  21 [h1 Header]
  22
  23   #include <boost/metaparse/lit_c.hpp>
  24
  25 [h1 Expression semantics]
  26
  27 For any `c` character the following are equivalent:
  28
  29   lit_c<c>
  30
  31   lit<boost::mpl::char_<c>>
  32
  33 [h1 Example]
  34
  35   #include <boost/metaparse/lit_c.hpp>
  36   #include <boost/metaparse/start.hpp>
  37   #include <boost/metaparse/string.hpp>
  38   #include <boost/metaparse/is_error.hpp>
  39   #include <boost/metaparse/get_result.hpp>
  40
  41   using namespace boost::metaparse;
  42
  43   static_assert(
  44     is_error<lit_c<'x'>::apply<BOOST_METAPARSE_STRING("a"), start>>::type::value,
  45     "a different character should be an error"
  46   );
  47
  48   static_assert(
  49     is_error<lit_c<'x'>::apply<BOOST_METAPARSE_STRING(""), start>>::type::value,
  50     "empty input should be an error"
  51   );
  52
  53   static_assert(
  54     get_result<
  55       lit_c<'x'>::apply<BOOST_METAPARSE_STRING("x"), start>
  56     >::type::value == 'x',
  57     "result of parsing should be the accepted character"
  58   );
  59
  60 [endsect]
  61