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template <class P, class State, class BackwardOp> struct foldr_reject_incomplete1;
This is a parser combinator.
The same as foldr1
,
but once P
rejects the
input, foldr_reject_incomplete1
checks if P
consumes any
characters before rejecting the input. If so, foldr_reject_incomplete1
rejects the input with the same error message this last application of
P
returned. Otherwise
foldr_reject_incomplete1
accepts the input and gives the same result as foldr1
.
#include <boost/metaparse/foldr_reject_incomplete1.hpp>
For any p
parser, t
class, f
metafunction class taking two arguments, s
compile-time string and pos
source position
foldr_reject_incomplete1<p, t, f>::apply<s, pos>
is equivalent to
first_of<foldr1<p, t, f>, fail_at_first_char_expected<p> >::apply<s, pos>
#include <boost/metaparse/foldr_reject_incomplete1.hpp> #include <boost/metaparse/lit_c.hpp> #include <boost/metaparse/last_of.hpp> #include <boost/metaparse/token.hpp> #include <boost/metaparse/int_.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/lambda.hpp> #include <boost/mpl/plus.hpp> #include <boost/mpl/int.hpp> using namespace boost::metaparse; using int_token = token<int_>; using plus_token = token<lit_c<'+'>>; using plus_int = last_of<plus_token, int_token>; using sum_op = boost::mpl::lambda<boost::mpl::plus<boost::mpl::_1, boost::mpl::_2>>::type; using ints = foldr_reject_incomplete1<plus_int, boost::mpl::int_<11>, sum_op>; static_assert( get_result< ints::apply<BOOST_METAPARSE_STRING("+ 13 + 3 + 21"), start> >::type::value == 48, "ints should sum the numbers" ); static_assert( is_error< ints::apply<BOOST_METAPARSE_STRING("+ 13 + 3 +"), start> >::type::value, "when the last number is missing, it should be an error" ); static_assert( is_error<ints::apply<BOOST_METAPARSE_STRING(""), start>>::type::value, "when no numbers are provided, it should be an error" );