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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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70
src/json.hpp
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@ -140,6 +140,7 @@ 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 {};
@ -149,68 +150,31 @@ struct disjunction<B1, Bn...>
/*!
@brief Helper to determine whether there's a key_type for T.
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
contains a `mapped_type`, whereas `std::vector` fails the test.
@sa http://stackoverflow.com/a/7728728/266378
@since version 1.0.0, overworked in version 2.0.6
*/
template<typename T>
struct has_mapped_type
{
private:
template <typename U, typename = typename U::mapped_type>
static int detect(U&&);
static void detect(...);
public:
static constexpr bool value =
std::is_integral<decltype(detect(std::declval<T>()))>::value;
#define NLOHMANN_JSON_HAS_HELPER(type) \
template <typename T> struct has_##type { \
private: \
template <typename U, typename = typename U::type> \
static int detect(U &&); \
\
static void detect(...); \
\
public: \
static constexpr bool value = \
std::is_integral<decltype(detect(std::declval<T>()))>::value; \
};
template <template <typename...> class T>
struct wrapper{};
NLOHMANN_JSON_HAS_HELPER(mapped_type)
NLOHMANN_JSON_HAS_HELPER(key_type)
NLOHMANN_JSON_HAS_HELPER(value_type)
NLOHMANN_JSON_HAS_HELPER(iterator)
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;
};
#undef NLOHMANN_JSON_HAS_HELPER
template <bool B, class RealType, class CompatibleObjectType>
struct is_compatible_object_type_impl : std::false_type{};