Synopsis

template <class P, int N>
struct iterate_c;

This is a parser combinator.

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.

Header

#include <boost/metaparse/iterate_c.hpp>

Expression semantics

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

iterate_c<p, n>

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

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"
);