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

   1 [#repeated_one_of]
   2 [section repeated_one_of]
   3
   4 [h1 Synopsis]
   5
   6   template <class P1, class P2, /* ... */, class Pn>
   7   struct repeated_one_of1;
   8
   9 [table Arguments
  10   [[Name]         [Type]]
  11   [[`P1` .. `Pn`][[link parser parser]s]]
  12 ]
  13
  14 This is a [link parser_combinator parser combinator].
  15
  16 [h1 Description]
  17
  18 It applies the `P1` ... `Pn` parsers repeatedly as long as any of them accepts
  19 the input. In each iteration the parsers are tried in order and the first one
  20 accepting the input is used, therefore in case of ambiguous grammars the result
  21 of parsing depends on the order of the `P1` ... `Pn` parsers. The result of
  22 parsing with this [link parser_combinator parser combinator] is a sequence of
  23 the individual parsing results.
  24
  25 When none of the `P1` ... `Pn` parsers accept the input in the first iteration,
  26 `repeated_one_of` accepts the input and the result of parsing is an empty
  27 sequence.
  28
  29 The maximum number of accepted parsers is defined by the
  30 `BOOST_METAPARSE_LIMIT_ONE_OF_SIZE` macro. Its default value is 20.
  31
  32 [h1 Header]
  33
  34   #include <boost/metaparse/repeated_one_of.hpp>
  35
  36 [h1 Expression semantics]
  37
  38 For any `p1`, ..., `pn` parsers
  39
  40   repeated_one_of<p1, /* ... */, pn>
  41
  42 is equivalent to
  43
  44   repeated<one_of<p1, /* ... */, pn>>
  45
  46 [h1 Example]
  47
  48   #include <boost/metaparse/repeated_one_of.hpp>
  49   #include <boost/metaparse/lit_c.hpp>
  50   #include <boost/metaparse/start.hpp>
  51   #include <boost/metaparse/string.hpp>
  52   #include <boost/metaparse/get_result.hpp>
  53
  54   #include <boost/mpl/equal.hpp>
  55   #include <boost/mpl/vector.hpp>
  56   #include <boost/mpl/char.hpp>
  57
  58   using namespace boost::metaparse;
  59
  60   using as_and_bs = repeated_one_of<lit_c<'a'>, lit_c<'b'>>;
  61
  62   static_assert(
  63     boost::mpl::equal<
  64       get_result<as_and_bs::apply<BOOST_METAPARSE_STRING("abaab"), start>>::type,
  65       boost::mpl::vector<
  66         boost::mpl::char_<'a'>,
  67         boost::mpl::char_<'b'>,
  68         boost::mpl::char_<'a'>,
  69         boost::mpl::char_<'a'>,
  70         boost::mpl::char_<'b'>
  71       >
  72     >::type::value,
  73     "the result of parsing should be the list of results"
  74   );
  75
  76   static_assert(
  77     boost::mpl::equal<
  78       get_result<as_and_bs::apply<BOOST_METAPARSE_STRING("x"), start>>::type,
  79       boost::mpl::vector<>
  80     >::type::value,
  81     "repeated_one_of should accept the input when it"
  82     " can't parse anything with digit_val"
  83   );
  84
  85 [endsect]
  86