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

   1 [#space]
   2 [section space]
   3
   4 [h1 Synopsis]
   5
   6   struct space;
   7
   8 This is a [link parser parser].
   9
  10 [h1 Description]
  11
  12 `space` accepts one white space character. The result of parsing is the parsed
  13 character.
  14
  15 [h1 Header]
  16
  17   #include <boost/metaparse/space.hpp>
  18
  19 [h1 Expression semantics]
  20
  21 The following are equivalent:
  22
  23   space
  24
  25   accept_when<one_char, util::is_whitespace<>, errors::whitespace_expected>
  26
  27 [h1 Example]
  28
  29   #include <boost/metaparse/space.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_remaining.hpp>
  34
  35   #include <type_traits>
  36
  37   using namespace boost::metaparse;
  38
  39   static_assert(
  40     std::is_same<
  41       BOOST_METAPARSE_STRING(" foo"),
  42       get_remaining<space::apply<BOOST_METAPARSE_STRING("  foo"), start>>::type
  43     >::type::value,
  44     "it should consume the first space of the input"
  45   );
  46
  47   static_assert(
  48     is_error<space::apply<BOOST_METAPARSE_STRING("x"), start>>::type::value,
  49     "it should return an error when the input does not begin with a whitespace"
  50   );
  51
  52 [endsect]
  53