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

[#iterate_c]
[section iterate_c]

[h1 Synopsis]

  template <class P, int N>
  struct iterate_c;

This is a [link parser_combinator parser combinator].

[table Arguments
  [[Name] [Type]]
  [[`P`]  [[link parser parser]]]
  [[`N`]  [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_c` to accept it.

[h1 Header]

  #include <boost/metaparse/iterate_c.hpp>

[h1 Expression semantics]

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

  iterate_c<p, n>
  
  sequence<
    p, // 1.
    p, // 2.
    // ...
    p  // n.
  >

[h1 Example]

  #include <boost/metaparse/iterate_c.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>
  
  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_c<digit, 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_c<digit, 3>::apply<BOOST_METAPARSE_STRING("1234"), start>
      >::type
    >::type::value,
    "only three iterations should be made"
  );
  
  static_assert(
    is_error<
      iterate_c<digit, 3>::apply<BOOST_METAPARSE_STRING("12"), start>
    >::type::value,
    "it should fail when digit can not be applied three times"
  );

[endsect]