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

   1 [#iterate]
   2 [section iterate]
   3
   4 [h1 Synopsis]
   5
   6   template <class P, class N>
   7   struct iterate;
   8
   9 This is a [link parser_combinator parser combinator].
  10
  11 [table Arguments
  12   [[Name] [Type]]
  13   [[`P`]  [[link parser parser]]]
  14   [[`N`]  [[link boxed_value boxed] non-negative integer value]]
  15 ]
  16
  17 [h1 Description]
  18
  19 It applies `P` on the input string `N` times. The result of parsing is a
  20 sequence of the results of the individual applications of `P`. `P` has to accept
  21 the input `N` times for `iterate` to accept it.
  22
  23 [h1 Header]
  24
  25   #include <boost/metaparse/iterate.hpp>
  26
  27 [h1 Expression semantics]
  28
  29 For any `p` parser, `n` wrapped integer the following are equivalent:
  30
  31   iterate<p, n>
  32
  33   iterate_c<p, n::type::value>
  34
  35 [h1 Example]
  36
  37   #include <boost/metaparse/iterate.hpp>
  38   #include <boost/metaparse/digit.hpp>
  39   #include <boost/metaparse/string.hpp>
  40   #include <boost/metaparse/start.hpp>
  41   #include <boost/metaparse/get_result.hpp>
  42   #include <boost/metaparse/is_error.hpp>
  43
  44   #include <boost/mpl/vector.hpp>
  45   #include <boost/mpl/equal.hpp>
  46   #include <boost/mpl/char.hpp>
  47
  48   #include <type_traits>
  49
  50   using namespace boost::metaparse;
  51
  52   static_assert(
  53     boost::mpl::equal<
  54       boost::mpl::vector<
  55         boost::mpl::char_<'1'>,
  56         boost::mpl::char_<'2'>,
  57         boost::mpl::char_<'3'>
  58       >,
  59       get_result<
  60         iterate<digit, std::integral_constant<int, 3>>::apply<
  61           BOOST_METAPARSE_STRING("123"),
  62           start
  63         >
  64       >::type
  65     >::type::value,
  66     "the result should be the sequence of the individual applications of digit"
  67   );
  68
  69   static_assert(
  70     boost::mpl::equal<
  71       boost::mpl::vector<
  72         boost::mpl::char_<'1'>,
  73         boost::mpl::char_<'2'>,
  74         boost::mpl::char_<'3'>
  75       >,
  76       get_result<
  77         iterate<digit, std::integral_constant<int, 3>>::apply<
  78           BOOST_METAPARSE_STRING("1234"),
  79           start
  80         >
  81       >::type
  82     >::type::value,
  83     "only three iterations should be made"
  84   );
  85
  86   static_assert(
  87     is_error<
  88       iterate<digit, std::integral_constant<int, 3>>::apply<
  89         BOOST_METAPARSE_STRING("12"),
  90         start
  91       >
  92     >::type::value,
  93     "it should fail when digit can not be applied three times"
  94   );
  95
  96
  97 [endsect]
  98