Sprout/sprout/variant/variant.hpp
2012-10-06 00:58:56 +09:00

267 lines
8.6 KiB
C++

#ifndef SPROUT_VARIANT_VARIANT_HPP
#define SPROUT_VARIANT_VARIANT_HPP
#include <cstddef>
#include <utility>
#include <stdexcept>
#include <type_traits>
#include <sprout/config.hpp>
#include <sprout/index_tuple.hpp>
#include <sprout/utility/forward.hpp>
#include <sprout/utility/move.hpp>
#include <sprout/utility/swap.hpp>
#include <sprout/tuple/tuple.hpp>
#include <sprout/tuple/functions.hpp>
#include <sprout/type/type_tuple.hpp>
#include <sprout/type/algorithm/find_index.hpp>
namespace sprout {
namespace detail {
template<typename... Types>
class variant_impl {
protected:
typedef sprout::tuples::tuple<Types...> tuple_type;
typedef sprout::types::type_tuple<typename std::decay<Types>::type...> uncvref_tuple_type;
private:
template<typename T, sprout::index_t... Indexes>
static SPROUT_CONSTEXPR tuple_type init(T&& operand, sprout::index_tuple<Indexes...>) {
return sprout::tuples::make<tuple_type>(
typename sprout::tuples::tuple_element<Indexes, tuple_type>::type()...,
sprout::forward<T>(operand)
);
}
protected:
tuple_type tuple_;
int which_;
protected:
SPROUT_CONSTEXPR variant_impl()
: tuple_()
, which_()
{}
template<typename T, typename Index>
SPROUT_CONSTEXPR variant_impl(T&& operand, Index)
: tuple_(init(sprout::forward<T>(operand), sprout::index_range<0, Index::value>::make()))
, which_(Index::value)
{
static_assert(Index::value < sizeof...(Types), "variant<>: invalid operand");
}
void swap(variant_impl& other)
SPROUT_NOEXCEPT_EXPR(SPROUT_NOEXCEPT_EXPR(sprout::swap(tuple_, other.tuple_)))
{
sprout::swap(tuple_, other.tuple_);
sprout::swap(which_, other.which_);
}
variant_impl& operator=(variant_impl const&) = default;
};
} // namespace detail
//
// variant
//
template<typename... Types>
class variant
: private sprout::detail::variant_impl<Types...>
{
private:
typedef sprout::detail::variant_impl<Types...> impl_type;
typedef typename impl_type::uncvref_tuple_type uncvref_tuple_type;
public:
typedef typename impl_type::tuple_type tuple_type;
private:
template<int I>
static SPROUT_CONSTEXPR typename std::enable_if<
I == sizeof...(Types),
bool
>::type eq(tuple_type const& l, tuple_type const& r, int which) {
return false;
}
template<int I>
static SPROUT_CONSTEXPR typename std::enable_if<
I != sizeof...(Types),
bool
>::type eq(tuple_type const& l, tuple_type const& r, int which) {
return I == which
? sprout::tuples::get<I>(l) == sprout::tuples::get<I>(r)
: eq<I + 1>(l, r, which)
;
}
template<int I>
static SPROUT_CONSTEXPR typename std::enable_if<
static_cast<std::size_t>(I) == sizeof...(Types),
bool
>::type lt(tuple_type const& l, tuple_type const& r, int which) {
return false;
}
template<int I>
static SPROUT_CONSTEXPR typename std::enable_if<
static_cast<std::size_t>(I) != sizeof...(Types),
bool
>::type lt(tuple_type const& l, tuple_type const& r, int which) {
return I == which
? sprout::tuples::get<I>(l) < sprout::tuples::get<I>(r)
: lt<I + 1>(l, r, which)
;
}
template<int I, typename Elem, typename Traits>
static typename std::enable_if<
static_cast<std::size_t>(I) == sizeof...(Types),
std::basic_ostream<Elem, Traits>&
>::type output(std::basic_ostream<Elem, Traits>& os, tuple_type const& t, int which) {
return os;
}
template<int I, typename Elem, typename Traits>
static typename std::enable_if<
static_cast<std::size_t>(I) != sizeof...(Types),
std::basic_ostream<Elem, Traits>&
>::type output(std::basic_ostream<Elem, Traits>& os, tuple_type const& t, int which) {
return I == which
? os << sprout::tuples::get<I>(t)
: output<I + 1>(os, t, which)
;
}
template<int I, typename Tuple, typename Visitor>
static SPROUT_CONSTEXPR typename std::enable_if<
I == sizeof...(Types),
typename Visitor::result_type
>::type visit(Tuple&& t, Visitor&& v, int which) {
return typename Visitor::result_type();
}
template<int I, typename Tuple, typename Visitor>
static SPROUT_CONSTEXPR typename std::enable_if<
I != sizeof...(Types),
typename Visitor::result_type
>::type visit(Tuple&& t, Visitor&& v, int which) {
return I == which
? sprout::forward<Visitor>(v)(sprout::tuples::get<I>(sprout::forward<Tuple>(t)))
: visit<I + 1>(sprout::forward<Tuple>(t), sprout::forward<Visitor>(v), which)
;
}
private:
using impl_type::tuple_;
using impl_type::which_;
public:
// construct/copy/destruct
SPROUT_CONSTEXPR variant()
: impl_type()
{}
variant(variant const&) = default;
variant(variant&&) = default;
template<typename T>
SPROUT_CONSTEXPR variant(T&& operand)
: impl_type(
sprout::forward<T>(operand),
sprout::types::find_index<uncvref_tuple_type, typename std::decay<T>::type>()
)
{}
// modifiers
void swap(variant& other)
SPROUT_NOEXCEPT_EXPR(SPROUT_NOEXCEPT_EXPR(impl_type::swap(other)))
{
impl_type::swap(other);
}
variant& operator=(variant const& rhs) {
static_cast<impl_type&>(*this) = rhs;
return *this;
}
variant& operator=(variant&& rhs)
SPROUT_NOEXCEPT_EXPR(std::is_nothrow_move_assignable<impl_type>::value)
{
static_cast<impl_type&>(*this) = sprout::move(rhs);
return *this;
}
template<typename T>
variant& operator=(T&& rhs) {
static_cast<impl_type&>(*this) = variant(sprout::forward<T>(rhs));
return *this;
}
// queries
SPROUT_CONSTEXPR int which() const {
return which_;
}
SPROUT_CONSTEXPR bool empty() const {
return false;
}
// relational
friend SPROUT_CONSTEXPR bool operator==(variant const& lhs, variant const& rhs) {
return lhs.which_ == rhs.which_ && eq<0>(lhs.tuple_, rhs.tuple_, lhs.which_);
}
friend SPROUT_CONSTEXPR bool operator!=(variant const& lhs, variant const& rhs) {
return !(lhs == rhs);
}
friend SPROUT_CONSTEXPR bool operator<(variant const& lhs, variant const& rhs) {
return lhs.which_ < rhs.which_
|| (lhs.which_ == rhs.which_ && lt<0>(lhs.tuple_, rhs.tuple_, lhs.which_))
;
}
friend SPROUT_CONSTEXPR bool operator>(variant const& lhs, variant const& rhs) {
return rhs < lhs;
}
friend SPROUT_CONSTEXPR bool operator<=(variant const& lhs, variant const& rhs) {
return !(rhs < lhs);
}
friend SPROUT_CONSTEXPR bool operator>=(variant const& lhs, variant const& rhs) {
return !(lhs < rhs);
}
template<typename Elem, typename Traits>
friend std::basic_ostream<Elem, Traits>& operator<<(std::basic_ostream<Elem, Traits>& lhs, variant const& rhs) {
return output<0>(lhs, rhs.tuple_, rhs.which_);
}
// get support
template<std::size_t I>
SPROUT_CONSTEXPR typename std::enable_if<
I != sizeof...(Types),
typename sprout::tuples::tuple_element<I, tuple_type>::type const&
>::type get_at() const {
return I == static_cast<std::size_t>(which_)
? sprout::tuples::get<I>(tuple_)
: (throw std::domain_error("variant<>: bad get"), sprout::tuples::get<I>(tuple_))
;
}
template<std::size_t I>
typename std::enable_if<
I != sizeof...(Types),
typename sprout::tuples::tuple_element<I, tuple_type>::type&
>::type get_at() {
return I == which_
? sprout::tuples::get<I>(tuple_)
: (throw std::domain_error("variant<>: bad get"), sprout::tuples::get<I>(tuple_))
;
}
template<typename U>
SPROUT_CONSTEXPR typename std::enable_if<
sprout::types::find_index<tuple_type, U>::value != sizeof...(Types),
U const&
>::type get() const {
return get_at<sprout::types::find_index<tuple_type, U>::value>();
}
template<typename U>
typename std::enable_if<
sprout::types::find_index<tuple_type, U>::value != sizeof...(Types),
U&
>::type get() {
return get_at<sprout::types::find_index<tuple_type, U>::value>();
}
// visitation support
template<typename Visitor>
SPROUT_CONSTEXPR typename Visitor::result_type apply_visitor(Visitor&& visitor) const {
return visit(tuple_, sprout::forward<Visitor>(visitor), which_);
}
template<typename Visitor>
typename Visitor::result_type apply_visitor(Visitor&& visitor) {
return visit(tuple_, sprout::forward<Visitor>(visitor), which_);
}
};
//
// swap
//
template<typename... Types>
inline void
swap(sprout::variant<Types...>& lhs, sprout::variant<Types...>& rhs)
SPROUT_NOEXCEPT_EXPR(SPROUT_NOEXCEPT_EXPR(lhs.swap(rhs)))
{
lhs.swap(rhs);
}
} // namespace sprout
#endif // #ifndef SPROUT_VARIANT_VARIANT_HPP