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

   1 [#repeated_reject_incomplete]
   2 [section repeated_reject_incomplete]
   3
   4 [h1 Synopsis]
   5
   6   template <class P>
   7   struct repeated_reject_incomplete;
   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 The same as [link repeated `repeated`], but once `P` rejects the input,
  19 `repeated_reject_incomplete` checks if `P` consumes any characters before
  20 rejecting the input. If so, `repeated_reject_incomplete` rejects the input with
  21 the same error message this last application of `P` returned. Otherwise
  22 `repeated_reject_incomplete` accepts the input and gives the same result as
  23 [link repeated `repeated`].
  24
  25 Here is a diagram showing how `repeated_reject_incomplete` works by example:
  26
  27   using int_token = token<int_>;
  28   using plus_token = token<lit_c<'+'>>;
  29   using plus_int = last_of<plus_token, int_token>;
  30   using sum_op = mpl::lambda<mpl::plus<mpl::_1, mpl::_2>>::type;
  31
  32 [$images/metaparse/repeated_reject_incomplete_diag1.png [width 70%]]
  33
  34 [h1 Header]
  35
  36   #include <boost/metaparse/repeated_reject_incomplete.hpp>
  37
  38 [h1 Expression semantics]
  39
  40 For any `p` parser, `s` compile-time string and `pos` source position
  41
  42   repeated_reject_incomplete<p>::apply<s, pos>
  43
  44 is equivalent to
  45
  46   first_of<repeated<p>, fail_at_first_char_expected<p> >::apply<s, pos>
  47
  48 [h1 Example]
  49
  50   #include <boost/metaparse/repeated_reject_incomplete.hpp>
  51   #include <boost/metaparse/lit_c.hpp>
  52   #include <boost/metaparse/last_of.hpp>
  53   #include <boost/metaparse/token.hpp>
  54   #include <boost/metaparse/int_.hpp>
  55   #include <boost/metaparse/string.hpp>
  56   #include <boost/metaparse/start.hpp>
  57   #include <boost/metaparse/get_result.hpp>
  58   #include <boost/metaparse/is_error.hpp>
  59
  60   #include <boost/mpl/equal.hpp>
  61   #include <boost/mpl/vector_c.hpp>
  62
  63   using namespace boost::metaparse;
  64
  65   using int_token = token<int_>;
  66   using plus_token = token<lit_c<'+'>>;
  67   using plus_int = last_of<plus_token, int_token>;
  68
  69   using ints = repeated_reject_incomplete<plus_int>;
  70
  71   static_assert(
  72     boost::mpl::equal<
  73       boost::mpl::vector_c<int, 13, 3, 21>,
  74       get_result<
  75         ints::apply<BOOST_METAPARSE_STRING("+ 13 + 3 + 21"), start>
  76       >::type
  77     >::type::value,
  78     "ints should parse the numbers"
  79   );
  80
  81   static_assert(
  82     is_error<
  83       ints::apply<BOOST_METAPARSE_STRING("+ 13 + 3 +"), start>
  84     >::type::value,
  85     "when the last number is missing, it should be an error"
  86   );
  87
  88 [endsect]
  89