boost/spirit/home/x3/directive/skip.hpp
/*=============================================================================
Copyright (c) 2001-2014 Joel de Guzman
Copyright (c) 2013 Agustin Berge
Copyright (c) 2024 Nana Sakisaka
Distributed under the Boost Software License, Version 1.0. (See accompanying
file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
=============================================================================*/
#if !defined(BOOST_SPIRIT_X3_SKIP_JANUARY_26_2008_0422PM)
#define BOOST_SPIRIT_X3_SKIP_JANUARY_26_2008_0422PM
#include <boost/spirit/home/x3/support/context.hpp>
#include <boost/spirit/home/x3/support/unused.hpp>
#include <boost/spirit/home/x3/support/expectation.hpp>
#include <boost/spirit/home/x3/core/skip_over.hpp>
#include <boost/spirit/home/x3/core/parser.hpp>
#include <boost/utility/enable_if.hpp>
namespace boost { namespace spirit { namespace x3
{
template <typename Subject>
struct reskip_directive : unary_parser<Subject, reskip_directive<Subject>>
{
typedef unary_parser<Subject, reskip_directive<Subject>> base_type;
static bool const is_pass_through_unary = true;
static bool const handles_container = Subject::handles_container;
constexpr reskip_directive(Subject const& subject)
: base_type(subject) {}
template <typename Iterator, typename Context
, typename RContext, typename Attribute>
typename disable_if<has_skipper<Context>, bool>::type
parse(Iterator& first, Iterator const& last
, Context& context, RContext& rcontext, Attribute& attr) const
{
auto const& skipper =
detail::get_unused_skipper(x3::get<skipper_tag>(context));
auto const local_ctx = make_context<skipper_tag>(skipper, context);
bool const r = this->subject.parse(first, last, local_ctx, rcontext, attr);
#if !BOOST_SPIRIT_X3_THROW_EXPECTATION_FAILURE
if (has_expectation_failure(local_ctx))
{
set_expectation_failure(get_expectation_failure(local_ctx), context);
}
#endif
return r;
}
template <typename Iterator, typename Context
, typename RContext, typename Attribute>
typename enable_if<has_skipper<Context>, bool>::type
parse(Iterator& first, Iterator const& last
, Context const& context, RContext& rcontext, Attribute& attr) const
{
return this->subject.parse(first, last, context, rcontext, attr);
}
};
template <typename Subject, typename Skipper>
struct skip_directive : unary_parser<Subject, skip_directive<Subject, Skipper>>
{
typedef unary_parser<Subject, skip_directive<Subject, Skipper>> base_type;
static bool const is_pass_through_unary = true;
static bool const handles_container = Subject::handles_container;
constexpr skip_directive(Subject const& subject, Skipper const& skipper)
: base_type(subject)
, skipper(skipper)
{}
template <typename Iterator, typename RContext, typename Attribute>
bool parse(Iterator& first, Iterator const& last
, unused_type const&, RContext& rcontext, Attribute& attr) const
{
// It is perfectly fine to omit the expectation_failure context
// even in non-throwing mode if and only if the skipper itself
// is expectation-less.
//
// For example:
// skip(a > b) [lit('foo')]
// skip(c >> d)[lit('foo')]
// `a > b` should require non-`unused_type` context, but
// `c >> d` should NOT require non-`unused_type` context
//
// However, it's impossible right now to detect whether
// `this->subject` actually is expectation-less, so we just
// call the parse function to see what will happen. If the
// subject turns out to lack the expectation context,
// static_assert will be engaged in other locations.
//
// Anyways, we don't need to repack the expectation context
// into our brand new skipper context, in contrast to the
// repacking process done in `x3::skip_over`.
return this->subject.parse(first, last,
make_context<skipper_tag>(skipper), rcontext, attr);
}
template <typename Iterator, typename Context, typename RContext, typename Attribute>
bool parse(Iterator& first, Iterator const& last
, Context const& context, RContext& rcontext, Attribute& attr) const
{
#if BOOST_SPIRIT_X3_THROW_EXPECTATION_FAILURE
return this->subject.parse(first, last, make_context<skipper_tag>(skipper, context), rcontext, attr);
#else
static_assert(
!std::is_same_v<expectation_failure_t<Context>, unused_type>,
"Context type was not specified for x3::expectation_failure_tag. "
"You probably forgot: `x3::with<x3::expectation_failure_tag>(failure)[p]`. "
"Note that you must also bind the context to your skipper.");
// This logic is heavily related to the instantiation chain;
// see `x3::skip_over` for details.
auto const local_ctx = make_context<skipper_tag>(skipper, context);
bool const r = this->subject.parse(first, last, local_ctx, rcontext, attr);
if (has_expectation_failure(local_ctx))
{
set_expectation_failure(get_expectation_failure(local_ctx), context);
}
return r;
#endif
}
Skipper const skipper;
};
struct reskip_gen
{
template <typename Skipper>
struct skip_gen
{
constexpr skip_gen(Skipper const& skipper)
: skipper_(skipper) {}
template <typename Subject>
constexpr skip_directive<typename extension::as_parser<Subject>::value_type, Skipper>
operator[](Subject const& subject) const
{
return { as_parser(subject), skipper_ };
}
Skipper skipper_;
};
template <typename Skipper>
constexpr skip_gen<Skipper> const operator()(Skipper const& skipper) const
{
return { skipper };
}
template <typename Subject>
constexpr reskip_directive<typename extension::as_parser<Subject>::value_type>
operator[](Subject const& subject) const
{
return { as_parser(subject) };
}
};
constexpr auto skip = reskip_gen{};
}}}
#endif
