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

   1 [#token]
   2 [section token]
   3
   4 [h1 Synopsis]
   5
   6   template <class P>
   7   struct token;
   8
   9 This is a [link parser_combinator parser combinator].
  10
  11 [table Arguments
  12   [[Name] [Type]]
  13   [[`P`]  [[link parser parser]]]
  14 ]
  15
  16 [h1 Description]
  17
  18 `token` parses the input using `P` when it succeeds, `token` consumes all
  19 whitespaces afterwards. The result of parsing is the result of `P`.
  20
  21 [h1 Header]
  22
  23   #include <boost/metaparse/token.hpp>
  24
  25 [h1 Expression semantics]
  26
  27 For any `p` parser the following are equivalent:
  28
  29   token<p>
  30
  31   first_of<p, spaces>
  32
  33 [h1 Example]
  34
  35   #include <boost/metaparse/token.hpp>
  36   #include <boost/metaparse/int_.hpp>
  37   #include <boost/metaparse/start.hpp>
  38   #include <boost/metaparse/get_result.hpp>
  39   #include <boost/metaparse/get_remaining.hpp>
  40   #include <boost/metaparse/is_error.hpp>
  41   #include <boost/metaparse/string.hpp>
  42
  43   #include <type_traits>
  44
  45   using namespace boost::metaparse;
  46
  47   using int_token = token<int_>;
  48
  49   static_assert(
  50     get_result<
  51       int_token::apply<BOOST_METAPARSE_STRING("13 "), start>
  52     >::type::value,
  53     "the result of int_token is the number"
  54   );
  55
  56   static_assert(
  57     std::is_same<
  58       BOOST_METAPARSE_STRING(""),
  59       get_remaining<int_token::apply<BOOST_METAPARSE_STRING("13 "), start>>::type
  60     >::type::value,
  61     "token consumes whitespaces after the number"
  62   );
  63
  64   static_assert(
  65     get_result<
  66       int_token::apply<BOOST_METAPARSE_STRING("13"), start>
  67     >::type::value,
  68     "whitespaces after the number are optional"
  69   );
  70
  71   static_assert(
  72     is_error<int_token::apply<BOOST_METAPARSE_STRING("foo"), start>>::type::value,
  73     "when there is no number, token fails"
  74   );
  75
  76 [endsect]
  77