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support polymorphic visitor (variant)

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bolero-MURAKAMI 2012-12-19 23:06:08 +09:00
parent 9ee3e03ddd
commit f01382e3e5
8 changed files with 204 additions and 24 deletions
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85
sprout/variant/variant.hpp
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@ -14,6 +14,8 @@
#include <sprout/tuple/functions.hpp>
#include <sprout/type/type_tuple.hpp>
#include <sprout/type/algorithm/find_index.hpp>
#include <sprout/functional/type_traits/has_type.hpp>
#include <sprout/functional/type_traits/weak_result_type.hpp>
namespace sprout {
template<typename... Types>
@ -72,6 +74,52 @@ namespace sprout {
typedef typename impl_type::uncvref_tuple_type uncvref_tuple_type;
public:
typedef typename impl_type::tuple_type tuple_type;
private:
template<typename Visitor, typename Tuple, typename IndexTuple>
struct visitor_result_impl_1;
template<typename Visitor, typename Tuple, sprout::index_t... Indexes>
struct visitor_result_impl_1<Visitor, Tuple, sprout::index_tuple<Indexes...> > {
public:
typedef typename std::decay<
typename std::common_type<
decltype((std::declval<Visitor>())(sprout::tuples::get<Indexes>(std::declval<Tuple>())))...
>::type
>::type type;
};
template<typename Visitor, typename Tuple, typename = void>
struct visitor_result_impl;
template<typename Visitor, typename Tuple>
struct visitor_result_impl<
Visitor, Tuple,
typename std::enable_if<!sprout::has_result_type<sprout::weak_result_type<Visitor> >::value>::type
>
: public visitor_result_impl_1<Visitor, Tuple, typename sprout::index_range<0, sprout::tuples::tuple_size<Tuple>::value>::type>
{};
template<typename Visitor, typename Tuple>
struct visitor_result_impl<
Visitor, Tuple,
typename std::enable_if<sprout::has_result_type<sprout::weak_result_type<Visitor> >::value>::type
> {
public:
typedef typename sprout::weak_result_type<Visitor>::result_type type;
};
public:
template<typename Visitor, typename Visitable>
struct visitor_result
: public visitor_result_impl<Visitor, typename Visitable::tuple_type>
{};
template<typename Visitor, typename Visitable>
struct visitor_result<Visitor, Visitable const>
: public visitor_result_impl<Visitor, typename Visitable::tuple_type const>
{};
template<typename Visitor, typename Visitable>
struct visitor_result<Visitor, Visitable volatile>
: public visitor_result_impl<Visitor, typename Visitable::tuple_type volatile>
{};
template<typename Visitor, typename Visitable>
struct visitor_result<Visitor, Visitable const volatile>
: public visitor_result_impl<Visitor, typename Visitable::tuple_type const volatile>
{};
private:
template<int I>
static SPROUT_CONSTEXPR typename std::enable_if<
@ -124,21 +172,24 @@ namespace sprout {
: output<I + 1>(os, t, which)
;
}
template<int I, typename Tuple, typename Visitor>
template<typename Result, int I, typename Tuple, typename Visitor>
static SPROUT_CONSTEXPR typename std::enable_if<
I == sizeof...(Types),
typename std::decay<Visitor>::type::result_type
>::type visit(Tuple&& t, Visitor&& v, int which) {
return typename std::decay<Visitor>::type::result_type();
}
template<int I, typename Tuple, typename Visitor>
static SPROUT_CONSTEXPR typename std::enable_if<
I != sizeof...(Types),
typename std::decay<Visitor>::type::result_type
I == sizeof...(Types) - 1,
Result
>::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)
: throw std::domain_error("variant<>: bad visit")
;
}
template<typename Result, int I, typename Tuple, typename Visitor>
static SPROUT_CONSTEXPR typename std::enable_if<
I != sizeof...(Types) - 1,
Result
>::type visit(Tuple&& t, Visitor&& v, int which) {
return I == which
? sprout::forward<Visitor>(v)(sprout::tuples::get<I>(sprout::forward<Tuple>(t)))
: visit<Result, I + 1>(sprout::forward<Tuple>(t), sprout::forward<Visitor>(v), which)
;
}
private:
@ -249,12 +300,16 @@ namespace sprout {
}
// visitation support
template<typename Visitor>
SPROUT_CONSTEXPR typename std::decay<Visitor>::type::result_type apply_visitor(Visitor&& visitor) const {
return visit<0>(tuple_, sprout::forward<Visitor>(visitor), which_);
SPROUT_CONSTEXPR typename visitor_result<typename std::remove_reference<Visitor>::type, variant const>::type
apply_visitor(Visitor&& visitor) const {
typedef typename visitor_result<typename std::remove_reference<Visitor>::type, variant const>::type result_type;
return visit<result_type, 0>(tuple_, sprout::forward<Visitor>(visitor), which_);
}
template<typename Visitor>
typename std::decay<Visitor>::type::result_type apply_visitor(Visitor&& visitor) {
return visit<0>(tuple_, sprout::forward<Visitor>(visitor), which_);
typename visitor_result<typename std::remove_reference<Visitor>::type, variant>::type
apply_visitor(Visitor&& visitor) {
typedef typename visitor_result<typename std::remove_reference<Visitor>::type, variant>::type result_type;
return visit<result_type, 0>(tuple_, sprout::forward<Visitor>(visitor), which_);
}
};