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

   1 [#letter]
   2 [section letter]
   3
   4 [h1 Synopsis]
   5
   6   struct letter;
   7
   8 This is a [link parser parser].
   9
  10 [h1 Description]
  11
  12 Parser accepting one character in the range `a-z` or `A-Z`. The result of the
  13 parser is the accepted character.
  14
  15 [h1 Header]
  16
  17   #include <boost/metaparse/letter.hpp>
  18
  19 [h1 Expression semantics]
  20
  21 The following are equivalent:
  22
  23   letter
  24
  25   accept_when<one_char, util::is_letter<>, error::letter_expected>
  26
  27 [h1 Example]
  28
  29   #include <boost/metaparse/letter.hpp>
  30   #include <boost/metaparse/start.hpp>
  31   #include <boost/metaparse/string.hpp>
  32   #include <boost/metaparse/is_error.hpp>
  33   #include <boost/metaparse/get_result.hpp>
  34
  35   using namespace boost::metaparse;
  36
  37   static_assert(
  38     !is_error<letter::apply<BOOST_METAPARSE_STRING("a"), start>>::type::value,
  39     "letter should accept a letter"
  40   );
  41
  42   static_assert(
  43     is_error<letter::apply<BOOST_METAPARSE_STRING("0"), start>>::type::value,
  44     "letter should reject a digit"
  45   );
  46
  47   static_assert(
  48     get_result<
  49       letter::apply<BOOST_METAPARSE_STRING("z"), start>
  50     >::type::value == 'z',
  51     "the result of parsing should be the character value"
  52   );
  53
  54 [endsect]
  55