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add negation, disjunction, and conjunction from C++17

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Théo DELRIEU 2016-11-21 00:22:47 +01:00 committed by Théo DELRIEU
parent 88819449c2
commit 0d91113ccf
1 changed files with 39 additions and 9 deletions
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48
src/json.hpp
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@ -119,6 +119,9 @@ using remove_reference_t = typename std::remove_reference<T>::type;
template <typename T>
using uncvref_t = remove_cv_t<remove_reference_t<T>>;
template <bool If, typename Then, typename Else>
using conditional_t = typename std::conditional<If, Then, Else>::type;
// TODO update this doc
/*!
@brief unnamed namespace with internal helper functions
@ -127,6 +130,23 @@ using uncvref_t = remove_cv_t<remove_reference_t<T>>;
namespace detail
{
// implementation of 3 C++17 constructs: conjunction, disjunction, negation.
// This is needed to avoid evaluating all the traits, MSVC cannot compile due
// to std::is_constructible<basic_json_t, void> being instantiated
// (void -> back_insert_iterator::value_type)
// this could slow down compilation, since this implementation is taken from the example in cppreference...
template <class...> struct conjunction : std::true_type {};
template <class B1> struct conjunction<B1> : B1 {};
template <class B1, class... Bn>
struct conjunction<B1, Bn...>
: conditional_t<bool(B1::value), conjunction<Bn...>, B1> {};
template <class B> struct negation : std::integral_constant<bool, !B::value> {};
template <class...> struct disjunction : std::false_type {};
template <class B1> struct disjunction<B1> : B1 {};
template <class B1, class... Bn>
struct disjunction<B1, Bn...>
: conditional_t<bool(B1::value), B1, disjunction<Bn...>> {};
/*!
@brief Helper to determine whether there's a key_type for T.
@ -206,7 +226,12 @@ struct is_compatible_object_type_impl<true, RealType, CompatibleObjectType>
template<class RealType, class CompatibleObjectType>
struct is_compatible_object_type
{
static auto constexpr value = is_compatible_object_type_impl<has_mapped_type<CompatibleObjectType>::value and has_key_type<CompatibleObjectType>::value, RealType, CompatibleObjectType>::value;
static auto constexpr value = is_compatible_object_type_impl<
conjunction<negation<std::is_same<void, CompatibleObjectType>>,
has_mapped_type<CompatibleObjectType>,
has_key_type<CompatibleObjectType>>::value,
RealType, CompatibleObjectType>::value;
};
template <bool B, class BasicJson, class CompatibleArrayType>
@ -216,20 +241,25 @@ template <class BasicJson, class CompatibleArrayType>
struct is_compatible_array_type_impl<true, BasicJson, CompatibleArrayType>
{
static constexpr auto value =
not std::is_same<CompatibleArrayType, typename BasicJson::iterator>::value and
not std::is_same<CompatibleArrayType, typename BasicJson::const_iterator>::value and
not std::is_same<CompatibleArrayType, typename BasicJson::reverse_iterator>::value and
not std::is_same<CompatibleArrayType, typename BasicJson::const_reverse_iterator>::value and
not std::is_same<CompatibleArrayType, typename BasicJson::array_t::iterator>::value and
not std::is_same<CompatibleArrayType, typename BasicJson::array_t::const_iterator>::value and
std::is_constructible<BasicJson, typename CompatibleArrayType::value_type>::value;
conjunction<
negation<disjunction<
std::is_same<CompatibleArrayType, typename BasicJson::iterator>,
std::is_same<CompatibleArrayType, typename BasicJson::const_iterator>,
std::is_same<CompatibleArrayType, typename BasicJson::reverse_iterator>,
std::is_same<CompatibleArrayType, typename BasicJson::const_reverse_iterator>,
std::is_same<CompatibleArrayType, typename BasicJson::array_t::iterator>,
std::is_same<CompatibleArrayType, typename BasicJson::array_t::const_iterator>>>,
std::is_constructible<BasicJson, typename CompatibleArrayType::value_type>>::value;
};
template <class BasicJson, class CompatibleArrayType>
struct is_compatible_array_type
{
static auto constexpr value = is_compatible_array_type_impl<not is_compatible_object_type<typename BasicJson::object_t, CompatibleArrayType>::value and has_value_type<CompatibleArrayType>::value and has_iterator<CompatibleArrayType>::value, BasicJson, CompatibleArrayType>::value;
static auto constexpr value = is_compatible_array_type_impl<
conjunction<negation<is_compatible_object_type<typename BasicJson::object_t, CompatibleArrayType>>,
has_value_type<CompatibleArrayType>,
has_iterator<CompatibleArrayType>>::value, BasicJson, CompatibleArrayType>::value;
};
template <bool, typename, typename>