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X3: constexprize attr from array types

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This commit is contained in:
Nikita Kniazev
2020-03-07 00:31:46 +03:00
parent 8e94d8d783
commit f569990d10
2 changed files with 32 additions and 29 deletions
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54
include/boost/spirit/home/x3/auxiliary/attr.hpp
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@@ -16,13 +16,35 @@
#include <boost/type_traits/is_same.hpp>
#include <boost/type_traits/remove_cv.hpp>
#include <boost/type_traits/remove_reference.hpp>
#include <algorithm>
#include <cstddef>
#include <string>
#include <utility>
namespace boost { namespace spirit { namespace x3
{
namespace detail
{
template <typename Value, std::size_t N
, typename = std::make_index_sequence<N>>
struct array_helper;
template <typename Value, std::size_t N, std::size_t... Is>
struct array_helper<Value, N, std::index_sequence<Is...>>
{
constexpr array_helper(Value const (&value)[N])
: value_{ value[Is]... } {}
constexpr array_helper(Value (&&value)[N])
: value_{ static_cast<Value&&>(value[Is])... } {}
// silence MSVC warning C4512: assignment operator could not be generated
array_helper& operator= (array_helper const&) = delete;
Value value_[N];
};
}
template <typename Value>
struct attr_parser : parser<attr_parser<Value>>
{
@@ -56,22 +78,15 @@ namespace boost { namespace spirit { namespace x3
template <typename Value, std::size_t N>
struct attr_parser<Value[N]> : parser<attr_parser<Value[N]>>
, detail::array_helper<Value, N>
{
using detail::array_helper<Value, N>::array_helper;
typedef Value attribute_type[N];
static bool const has_attribute =
!is_same<unused_type, attribute_type>::value;
static bool const handles_container = true;
attr_parser(Value const (&value)[N])
{
std::copy(value + 0, value + N, value_ + 0);
}
attr_parser(Value (&&value)[N])
{
std::move(value + 0, value + N, value_ + 0);
}
template <typename Iterator, typename Context
, typename RuleContext, typename Attribute>
@@ -79,12 +94,10 @@ namespace boost { namespace spirit { namespace x3
, Context const& /* context */, RuleContext&, Attribute& attr_) const
{
// $$$ Change to copy_to once we have it $$$
traits::move_to(value_ + 0, value_ + N, attr_);
traits::move_to(this->value_ + 0, this->value_ + N, attr_);
return true;
}
Value value_[N];
// silence MSVC warning C4512: assignment operator could not be generated
attr_parser& operator= (attr_parser const&) = delete;
};
@@ -108,19 +121,6 @@ namespace boost { namespace spirit { namespace x3
{
return { std::forward<Value>(value) };
}
template <typename Value, std::size_t N>
attr_parser<typename remove_cv<Value>::type[N]>
operator()(Value (&value)[N]) const
{
return { value };
}
template <typename Value, std::size_t N>
attr_parser<typename remove_cv<Value>::type[N]>
operator()(Value (&&value)[N]) const
{
return { value };
}
};
constexpr auto attr = attr_gen{};

7
test/x3/attr.cpp
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@@ -20,8 +20,11 @@ int main()
BOOST_SPIRIT_ASSERT_CONSTEXPR_CTORS(attr);
BOOST_SPIRIT_ASSERT_CONSTEXPR_CTORS(attr(1));
// TODO: Currently is not constexpr
//BOOST_SPIRIT_ASSERT_CONSTEXPR_CTORS(attr("asd"));
BOOST_SPIRIT_ASSERT_CONSTEXPR_CTORS(attr("asd"));
{
constexpr char s[] = "asd";
BOOST_SPIRIT_ASSERT_CONSTEXPR_CTORS(attr(s));
}
{
int d = 0;