ceph/src/boost/libs/metaparse/doc/repeated1.qbk

   1 [#repeated1]
   2 [section repeated1]
   3
   4 [h1 Synopsis]
   5
   6   template <class P>
   7   struct repeated1;
   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 It applies `P` on the input string repeatedly as long as the parser accepts the
  19 input. The result of parsing is a sequence of the results of the individual
  20 applications of `P`.
  21
  22 When `P` rejects the input for the first time, `repeated1` rejects it as well.
  23 At least one successful application of `P` is required for `repeated1` to accept
  24 the input.
  25
  26 [h1 Header]
  27
  28   #include <boost/metaparse/repeated1.hpp>
  29
  30 [h1 Expression semantics]
  31
  32 For any `p` parser the following are equivalent:
  33
  34   repeated1<p>
  35
  36   last_of<look_ahead<p>, repeated<p>>
  37
  38 [h1 Example]
  39
  40   #include <boost/metaparse/repeated1.hpp>
  41   #include <boost/metaparse/digit_val.hpp>
  42   #include <boost/metaparse/start.hpp>
  43   #include <boost/metaparse/string.hpp>
  44   #include <boost/metaparse/get_result.hpp>
  45   #include <boost/metaparse/is_error.hpp>
  46
  47   #include <boost/mpl/equal.hpp>
  48   #include <boost/mpl/vector.hpp>
  49   #include <boost/mpl/int.hpp>
  50
  51   using namespace boost::metaparse;
  52
  53   using digits = repeated1<digit_val>;
  54
  55   static_assert(
  56     boost::mpl::equal<
  57       get_result<digits::apply<BOOST_METAPARSE_STRING("1234"), start>>::type,
  58       boost::mpl::vector<
  59         boost::mpl::int_<1>,
  60         boost::mpl::int_<2>,
  61         boost::mpl::int_<3>,
  62         boost::mpl::int_<4>
  63       >
  64     >::type::value,
  65     "the result of parsing should be the list of digit values"
  66   );
  67
  68   static_assert(
  69     is_error<digits::apply<BOOST_METAPARSE_STRING("x"), start>>::type::value,
  70     "repeated1 should reject the input when it can't parse anything with digit_val"
  71   );
  72
  73 [endsect]
  74