boost/spirit/home/x3/auxiliary/eps.hpp
/*=============================================================================
Copyright (c) 2001-2014 Joel de Guzman
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_EPS_MARCH_23_2007_0454PM)
#define BOOST_SPIRIT_X3_EPS_MARCH_23_2007_0454PM
#include <boost/spirit/home/x3/core/skip_over.hpp>
#include <boost/spirit/home/x3/core/parser.hpp>
#include <boost/spirit/home/x3/support/unused.hpp>
namespace boost { namespace spirit { namespace x3
{
struct rule_context_tag;
struct semantic_predicate : parser<semantic_predicate>
{
typedef unused_type attribute_type;
static bool const has_attribute = false;
constexpr semantic_predicate(bool predicate)
: predicate(predicate) {}
template <typename Iterator, typename Context, typename Attribute>
bool parse(Iterator& first, Iterator const& last
, Context const& context, unused_type, Attribute&) const
{
x3::skip_over(first, last, context);
return predicate;
}
bool predicate;
};
template <typename F>
struct lazy_semantic_predicate : parser<lazy_semantic_predicate<F>>
{
typedef unused_type attribute_type;
static bool const has_attribute = false;
constexpr lazy_semantic_predicate(F f)
: f(f) {}
template <typename Iterator, typename Context, typename Attribute>
bool parse(Iterator& first, Iterator const& last
, Context const& context, unused_type, Attribute& /* attr */) const
{
x3::skip_over(first, last, context);
return f(x3::get<rule_context_tag>(context));
}
F f;
};
struct eps_parser : parser<eps_parser>
{
typedef unused_type attribute_type;
static bool const has_attribute = false;
template <typename Iterator, typename Context
, typename RuleContext, typename Attribute>
bool parse(Iterator& first, Iterator const& last
, Context const& context, RuleContext&, Attribute&) const
{
x3::skip_over(first, last, context);
return true;
}
constexpr semantic_predicate operator()(bool predicate) const
{
return { predicate };
}
template <typename F>
constexpr lazy_semantic_predicate<F> operator()(F f) const
{
return { f };
}
};
constexpr auto eps = eps_parser{};
}}}
#endif