1[#repeated] 2[section repeated] 3 4[h1 Synopsis] 5 6 template <class P> 7 struct repeated; 8 9This 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 18It applies `P` on the input string repeatedly as long as `P` accepts the input. 19The result of parsing is a sequence of the results of the individual 20applications of `P`. 21 22When `P` rejects the input for the first time, `repeated` still accepts the 23input and the result of parsing is an empty sequence. 24 25Here is a diagram showing how `repeated` works by example: 26 27 using int_token = token<int_>; 28 29[$images/metaparse/repeated_diag1.png [width 70%]] 30 31Further details can be found in the [link repetition Repetition] section 32of the [link manual User Manual]. 33 34[h1 Header] 35 36 #include <boost/metaparse/repeated.hpp> 37 38[h1 Expression semantics] 39 40For any `p` parser the following are equivalent: 41 42 repeated<p> 43 44 foldl< 45 p, 46 /* unspecified empty sequence */, 47 boost::mpl::push_back<_2, _1> 48 > 49 50[h1 Example] 51 52 #include <boost/metaparse/repeated.hpp> 53 #include <boost/metaparse/digit_val.hpp> 54 #include <boost/metaparse/start.hpp> 55 #include <boost/metaparse/string.hpp> 56 #include <boost/metaparse/get_result.hpp> 57 58 #include <boost/mpl/equal.hpp> 59 #include <boost/mpl/vector.hpp> 60 #include <boost/mpl/int.hpp> 61 62 using namespace boost::metaparse; 63 64 using digits = repeated<digit_val>; 65 66 static_assert( 67 boost::mpl::equal< 68 get_result<digits::apply<BOOST_METAPARSE_STRING("1234"), start>>::type, 69 boost::mpl::vector< 70 boost::mpl::int_<1>, 71 boost::mpl::int_<2>, 72 boost::mpl::int_<3>, 73 boost::mpl::int_<4> 74 > 75 >::type::value, 76 "the result of parsing should be the list of digit values" 77 ); 78 79 static_assert( 80 boost::mpl::equal< 81 get_result<digits::apply<BOOST_METAPARSE_STRING("x"), start>>::type, 82 boost::mpl::vector<> 83 >::type::value, 84 "repeated should accept the input when it can't parse anything with digit_val" 85 ); 86 87[endsect] 88 89
