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add a macro for has_xxx types

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Théo Delrieu 2016-11-17 18:15:40 +01:00 committed by Théo DELRIEU
parent e2dbe7a69f
commit 9b401972a0
1 changed files with 18 additions and 54 deletions
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72
src/json.hpp
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@ -140,6 +140,7 @@ template <class B1> struct conjunction<B1> : B1 {};
template <class B1, class... Bn> template <class B1, class... Bn>
struct conjunction<B1, Bn...> struct conjunction<B1, Bn...>
: conditional_t<bool(B1::value), conjunction<Bn...>, B1> {}; : conditional_t<bool(B1::value), conjunction<Bn...>, B1> {};
template <class B> struct negation : std::integral_constant<bool, !B::value> {}; template <class B> struct negation : std::integral_constant<bool, !B::value> {};
template <class...> struct disjunction : std::false_type {}; template <class...> struct disjunction : std::false_type {};
template <class B1> struct disjunction<B1> : B1 {}; template <class B1> struct disjunction<B1> : B1 {};
@ -149,68 +150,31 @@ struct disjunction<B1, Bn...>
/*! /*!
@brief Helper to determine whether there's a key_type for T. @brief Helper to determine whether there's a key_type for T.
Thus helper is used to tell associative containers apart from other containers Thus helper is used to tell associative containers apart from other containers
such as sequence containers. For instance, `std::map` passes the test as it such as sequence containers. For instance, `std::map` passes the test as it
contains a `mapped_type`, whereas `std::vector` fails the test. contains a `mapped_type`, whereas `std::vector` fails the test.
@sa http://stackoverflow.com/a/7728728/266378 @sa http://stackoverflow.com/a/7728728/266378
@since version 1.0.0, overworked in version 2.0.6 @since version 1.0.0, overworked in version 2.0.6
*/ */
template<typename T> #define NLOHMANN_JSON_HAS_HELPER(type) \
struct has_mapped_type template <typename T> struct has_##type { \
{ private: \
private: template <typename U, typename = typename U::type> \
template <typename U, typename = typename U::mapped_type> static int detect(U &&); \
static int detect(U&&); \
static void detect(...); \
\
public: \
static constexpr bool value = \
std::is_integral<decltype(detect(std::declval<T>()))>::value; \
};
static void detect(...); NLOHMANN_JSON_HAS_HELPER(mapped_type)
public: NLOHMANN_JSON_HAS_HELPER(key_type)
static constexpr bool value = NLOHMANN_JSON_HAS_HELPER(value_type)
std::is_integral<decltype(detect(std::declval<T>()))>::value; NLOHMANN_JSON_HAS_HELPER(iterator)
};
template <template <typename...> class T> #undef NLOHMANN_JSON_HAS_HELPER
struct wrapper{};
template<typename T>
struct has_key_type
{
private:
template <typename U, typename = typename U::key_type>
static int detect(U&&);
static void detect(...);
public:
static constexpr bool value =
std::is_integral<decltype(detect(std::declval<T>()))>::value;
};
template<typename T>
struct has_value_type
{
private:
template <typename U, typename = typename U::value_type>
static int detect(U&&);
static void detect(...);
public:
static constexpr bool value =
std::is_integral<decltype(detect(std::declval<T>()))>::value;
};
template<typename T>
struct has_iterator
{
private:
template <typename U, typename = typename U::iterator>
static int detect(U&&);
static void detect(...);
public:
static constexpr bool value =
std::is_integral<decltype(detect(std::declval<T>()))>::value;
};
template <bool B, class RealType, class CompatibleObjectType> template <bool B, class RealType, class CompatibleObjectType>
struct is_compatible_object_type_impl : std::false_type{}; struct is_compatible_object_type_impl : std::false_type{};