EQ2EMu/EQ2/source/depends/boost_1_72_0/libs/metaparse/doc/iterate.qbk

[#iterate]
[section iterate]

[h1 Synopsis]

  template <class P, class N>
  struct iterate;

This is a [link parser_combinator parser combinator].

[table Arguments
  [[Name] [Type]]
  [[`P`]  [[link parser parser]]]
  [[`N`]  [[link boxed_value boxed] non-negative integer value]]
]

[h1 Description]

It applies `P` on the input string `N` times. The result of parsing is a
sequence of the results of the individual applications of `P`. `P` has to accept
the input `N` times for `iterate` to accept it.

[h1 Header]

  #include <boost/metaparse/iterate.hpp>

[h1 Expression semantics]

For any `p` parser, `n` wrapped integer the following are equivalent:

  iterate<p, n>
  
  iterate_c<p, n::type::value>

[h1 Example]

  #include <boost/metaparse/iterate.hpp>
  #include <boost/metaparse/digit.hpp>
  #include <boost/metaparse/string.hpp>
  #include <boost/metaparse/start.hpp>
  #include <boost/metaparse/get_result.hpp>
  #include <boost/metaparse/is_error.hpp>
  
  #include <boost/mpl/vector.hpp>
  #include <boost/mpl/equal.hpp>
  #include <boost/mpl/char.hpp>
  
  #include <type_traits>
  
  using namespace boost::metaparse;
  
  static_assert(
    boost::mpl::equal<
      boost::mpl::vector<
        boost::mpl::char_<'1'>,
        boost::mpl::char_<'2'>,
        boost::mpl::char_<'3'>
      >,
      get_result<
        iterate<digit, std::integral_constant<int, 3>>::apply<
          BOOST_METAPARSE_STRING("123"),
          start
        >
      >::type
    >::type::value,
    "the result should be the sequence of the individual applications of digit"
  );
  
  static_assert(
    boost::mpl::equal<
      boost::mpl::vector<
        boost::mpl::char_<'1'>,
        boost::mpl::char_<'2'>,
        boost::mpl::char_<'3'>
      >,
      get_result<
        iterate<digit, std::integral_constant<int, 3>>::apply<
          BOOST_METAPARSE_STRING("1234"),
          start
        >
      >::type
    >::type::value,
    "only three iterations should be made"
  );
  
  static_assert(
    is_error<
      iterate<digit, std::integral_constant<int, 3>>::apply<
        BOOST_METAPARSE_STRING("12"),
        start
      >
    >::type::value,
    "it should fail when digit can not be applied three times"
  );
  

[endsect]