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 /*
     pybind11/numpy.h: Basic NumPy support, vectorize() wrapper
 
     Copyright (c) 2016 Wenzel Jakob <wenzel.jakob@epfl.ch>
 
     All rights reserved. Use of this source code is governed by a
     BSD-style license that can be found in the LICENSE file.
 */
 
 #pragma once
 
 #include "pybind11.h"
 #include "detail/common.h"
 #include "complex.h"
 #include "gil_safe_call_once.h"
 #include "pytypes.h"
 
 #include <algorithm>
 #include <array>
 #include <cstdint>
 #include <cstdlib>
 #include <cstring>
 #include <functional>
 #include <numeric>
 #include <sstream>
 #include <string>
 #include <type_traits>
 #include <typeindex>
 #include <utility>
 #include <vector>
 
 #if defined(PYBIND11_NUMPY_1_ONLY) && !defined(PYBIND11_INTERNAL_NUMPY_1_ONLY_DETECTED)
 #    error PYBIND11_NUMPY_1_ONLY must be defined before any pybind11 header is included.
 #endif
 
 /* This will be true on all flat address space platforms and allows us to reduce the
    whole npy_intp / ssize_t / Py_intptr_t business down to just ssize_t for all size
    and dimension types (e.g. shape, strides, indexing), instead of inflicting this
    upon the library user.
    Note that NumPy 2 now uses ssize_t for `npy_intp` to simplify this. */
 static_assert(sizeof(::pybind11::ssize_t) == sizeof(Py_intptr_t), "ssize_t != Py_intptr_t");
 static_assert(std::is_signed<Py_intptr_t>::value, "Py_intptr_t must be signed");
 // We now can reinterpret_cast between py::ssize_t and Py_intptr_t (MSVC + PyPy cares)
 
 PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
 
 PYBIND11_WARNING_DISABLE_MSVC(4127)
 
 class dtype; // Forward declaration
 class array; // Forward declaration
 
 PYBIND11_NAMESPACE_BEGIN(detail)
 
 template <>
 struct handle_type_name<dtype> {
     static constexpr auto name = const_name("numpy.dtype");
 };
 
 template <>
 struct handle_type_name<array> {
     static constexpr auto name = const_name("numpy.ndarray");
 };
 
 template <typename type, typename SFINAE = void>
 struct npy_format_descriptor;
 
 /* NumPy 1 proxy (always includes legacy fields) */
 struct PyArrayDescr1_Proxy {
     PyObject_HEAD
     PyObject *typeobj;
     char kind;
     char type;
     char byteorder;
     char flags;
     int type_num;
     int elsize;
     int alignment;
     char *subarray;
     PyObject *fields;
     PyObject *names;
 };
 
 #ifndef PYBIND11_NUMPY_1_ONLY
 struct PyArrayDescr_Proxy {
     PyObject_HEAD
     PyObject *typeobj;
     char kind;
     char type;
     char byteorder;
     char _former_flags;
     int type_num;
     /* Additional fields are NumPy version specific. */
 };
 #else
 /* NumPy 1.x only, we can expose all fields */
 using PyArrayDescr_Proxy = PyArrayDescr1_Proxy;
 #endif
 
 /* NumPy 2 proxy, including legacy fields */
 struct PyArrayDescr2_Proxy {
     PyObject_HEAD
     PyObject *typeobj;
     char kind;
     char type;
     char byteorder;
     char _former_flags;
     int type_num;
     std::uint64_t flags;
     ssize_t elsize;
     ssize_t alignment;
     PyObject *metadata;
     Py_hash_t hash;
     void *reserved_null[2];
     /* The following fields only exist if 0 <= type_num < 2056 */
     char *subarray;
     PyObject *fields;
     PyObject *names;
 };
 
 struct PyArray_Proxy {
     PyObject_HEAD
     char *data;
     int nd;
     ssize_t *dimensions;
     ssize_t *strides;
     PyObject *base;
     PyObject *descr;
     int flags;
 };
 
 struct PyVoidScalarObject_Proxy {
     PyObject_VAR_HEAD char *obval;
     PyArrayDescr_Proxy *descr;
     int flags;
     PyObject *base;
 };
 
 struct numpy_type_info {
     PyObject *dtype_ptr;
     std::string format_str;
 };
 
 struct numpy_internals {
     std::unordered_map<std::type_index, numpy_type_info> registered_dtypes;
 
     numpy_type_info *get_type_info(const std::type_info &tinfo, bool throw_if_missing = true) {
         auto it = registered_dtypes.find(std::type_index(tinfo));
         if (it != registered_dtypes.end()) {
             return &(it->second);
         }
         if (throw_if_missing) {
             pybind11_fail(std::string("NumPy type info missing for ") + tinfo.name());
         }
         return nullptr;
     }
 
     template <typename T>
     numpy_type_info *get_type_info(bool throw_if_missing = true) {
         return get_type_info(typeid(typename std::remove_cv<T>::type), throw_if_missing);
     }
 };
 
 PYBIND11_NOINLINE void load_numpy_internals(numpy_internals *&ptr) {
     ptr = &get_or_create_shared_data<numpy_internals>("_numpy_internals");
 }
 
 inline numpy_internals &get_numpy_internals() {
     static numpy_internals *ptr = nullptr;
     if (!ptr) {
         load_numpy_internals(ptr);
     }
     return *ptr;
 }
 
 PYBIND11_NOINLINE module_ import_numpy_core_submodule(const char *submodule_name) {
     module_ numpy = module_::import("numpy");
     str version_string = numpy.attr("__version__");
 
     module_ numpy_lib = module_::import("numpy.lib");
     object numpy_version = numpy_lib.attr("NumpyVersion")(version_string);
     int major_version = numpy_version.attr("major").cast<int>();
 
 #ifdef PYBIND11_NUMPY_1_ONLY
     if (major_version >= 2) {
         throw std::runtime_error(
             "This extension was built with PYBIND11_NUMPY_1_ONLY defined, "
             "but NumPy 2 is used in this process. For NumPy2 compatibility, "
             "this extension needs to be rebuilt without the PYBIND11_NUMPY_1_ONLY define.");
     }
 #endif
     /* `numpy.core` was renamed to `numpy._core` in NumPy 2.0 as it officially
         became a private module. */
     std::string numpy_core_path = major_version >= 2 ? "numpy._core" : "numpy.core";
     return module_::import((numpy_core_path + "." + submodule_name).c_str());
 }
 
 template <typename T>
 struct same_size {
     template <typename U>
     using as = bool_constant<sizeof(T) == sizeof(U)>;
 };
 
 template <typename Concrete>
 constexpr int platform_lookup() {
     return -1;
 }
 
 // Lookup a type according to its size, and return a value corresponding to the NumPy typenum.
 template <typename Concrete, typename T, typename... Ts, typename... Ints>
 constexpr int platform_lookup(int I, Ints... Is) {
     return sizeof(Concrete) == sizeof(T) ? I : platform_lookup<Concrete, Ts...>(Is...);
 }
 
 struct npy_api {
     enum constants {
         NPY_ARRAY_C_CONTIGUOUS_ = 0x0001,
         NPY_ARRAY_F_CONTIGUOUS_ = 0x0002,
         NPY_ARRAY_OWNDATA_ = 0x0004,
         NPY_ARRAY_FORCECAST_ = 0x0010,
         NPY_ARRAY_ENSUREARRAY_ = 0x0040,
         NPY_ARRAY_ALIGNED_ = 0x0100,
         NPY_ARRAY_WRITEABLE_ = 0x0400,
         NPY_BOOL_ = 0,
         NPY_BYTE_,
         NPY_UBYTE_,
         NPY_SHORT_,
         NPY_USHORT_,
         NPY_INT_,
         NPY_UINT_,
         NPY_LONG_,
         NPY_ULONG_,
         NPY_LONGLONG_,
         NPY_ULONGLONG_,
         NPY_FLOAT_,
         NPY_DOUBLE_,
         NPY_LONGDOUBLE_,
         NPY_CFLOAT_,
         NPY_CDOUBLE_,
         NPY_CLONGDOUBLE_,
         NPY_OBJECT_ = 17,
         NPY_STRING_,
         NPY_UNICODE_,
         NPY_VOID_,
         // Platform-dependent normalization
         NPY_INT8_ = NPY_BYTE_,
         NPY_UINT8_ = NPY_UBYTE_,
         NPY_INT16_ = NPY_SHORT_,
         NPY_UINT16_ = NPY_USHORT_,
         // `npy_common.h` defines the integer aliases. In order, it checks:
         // NPY_BITSOF_LONG, NPY_BITSOF_LONGLONG, NPY_BITSOF_INT, NPY_BITSOF_SHORT, NPY_BITSOF_CHAR
         // and assigns the alias to the first matching size, so we should check in this order.
         NPY_INT32_
         = platform_lookup<std::int32_t, long, int, short>(NPY_LONG_, NPY_INT_, NPY_SHORT_),
         NPY_UINT32_ = platform_lookup<std::uint32_t, unsigned long, unsigned int, unsigned short>(
             NPY_ULONG_, NPY_UINT_, NPY_USHORT_),
         NPY_INT64_
         = platform_lookup<std::int64_t, long, long long, int>(NPY_LONG_, NPY_LONGLONG_, NPY_INT_),
         NPY_UINT64_
         = platform_lookup<std::uint64_t, unsigned long, unsigned long long, unsigned int>(
             NPY_ULONG_, NPY_ULONGLONG_, NPY_UINT_),
     };
 
     unsigned int PyArray_RUNTIME_VERSION_;
 
     struct PyArray_Dims {
         Py_intptr_t *ptr;
         int len;
     };
 
     static npy_api &get() {
         PYBIND11_CONSTINIT static gil_safe_call_once_and_store<npy_api> storage;
         return storage.call_once_and_store_result(lookup).get_stored();
     }
 
     bool PyArray_Check_(PyObject *obj) const {
         return PyObject_TypeCheck(obj, PyArray_Type_) != 0;
     }
     bool PyArrayDescr_Check_(PyObject *obj) const {
         return PyObject_TypeCheck(obj, PyArrayDescr_Type_) != 0;
     }
 
     unsigned int (*PyArray_GetNDArrayCFeatureVersion_)();
     PyObject *(*PyArray_DescrFromType_)(int);
     PyObject *(*PyArray_NewFromDescr_)(PyTypeObject *,
                                        PyObject *,
                                        int,
                                        Py_intptr_t const *,
                                        Py_intptr_t const *,
                                        void *,
                                        int,
                                        PyObject *);
     // Unused. Not removed because that affects ABI of the class.
     PyObject *(*PyArray_DescrNewFromType_)(int);
     int (*PyArray_CopyInto_)(PyObject *, PyObject *);
     PyObject *(*PyArray_NewCopy_)(PyObject *, int);
     PyTypeObject *PyArray_Type_;
     PyTypeObject *PyVoidArrType_Type_;
     PyTypeObject *PyArrayDescr_Type_;
     PyObject *(*PyArray_DescrFromScalar_)(PyObject *);
     PyObject *(*PyArray_FromAny_)(PyObject *, PyObject *, int, int, int, PyObject *);
     int (*PyArray_DescrConverter_)(PyObject *, PyObject **);
     bool (*PyArray_EquivTypes_)(PyObject *, PyObject *);
 #ifdef PYBIND11_NUMPY_1_ONLY
     int (*PyArray_GetArrayParamsFromObject_)(PyObject *,
                                              PyObject *,
                                              unsigned char,
                                              PyObject **,
                                              int *,
                                              Py_intptr_t *,
                                              PyObject **,
                                              PyObject *);
 #endif
     PyObject *(*PyArray_Squeeze_)(PyObject *);
     // Unused. Not removed because that affects ABI of the class.
     int (*PyArray_SetBaseObject_)(PyObject *, PyObject *);
     PyObject *(*PyArray_Resize_)(PyObject *, PyArray_Dims *, int, int);
     PyObject *(*PyArray_Newshape_)(PyObject *, PyArray_Dims *, int);
     PyObject *(*PyArray_View_)(PyObject *, PyObject *, PyObject *);
 
 private:
     enum functions {
         API_PyArray_GetNDArrayCFeatureVersion = 211,
         API_PyArray_Type = 2,
         API_PyArrayDescr_Type = 3,
         API_PyVoidArrType_Type = 39,
         API_PyArray_DescrFromType = 45,
         API_PyArray_DescrFromScalar = 57,
         API_PyArray_FromAny = 69,
         API_PyArray_Resize = 80,
         // CopyInto was slot 82 and 50 was effectively an alias. NumPy 2 removed 82.
         API_PyArray_CopyInto = 50,
         API_PyArray_NewCopy = 85,
         API_PyArray_NewFromDescr = 94,
         API_PyArray_DescrNewFromType = 96,
         API_PyArray_Newshape = 135,
         API_PyArray_Squeeze = 136,
         API_PyArray_View = 137,
         API_PyArray_DescrConverter = 174,
         API_PyArray_EquivTypes = 182,
 #ifdef PYBIND11_NUMPY_1_ONLY
         API_PyArray_GetArrayParamsFromObject = 278,
 #endif
         API_PyArray_SetBaseObject = 282
     };
 
     static npy_api lookup() {
         module_ m = detail::import_numpy_core_submodule("multiarray");
         auto c = m.attr("_ARRAY_API");
         void **api_ptr = (void **) PyCapsule_GetPointer(c.ptr(), nullptr);
         if (api_ptr == nullptr) {
             raise_from(PyExc_SystemError, "FAILURE obtaining numpy _ARRAY_API pointer.");
             throw error_already_set();
         }
         npy_api api;
 #define DECL_NPY_API(Func) api.Func##_ = (decltype(api.Func##_)) api_ptr[API_##Func];
         DECL_NPY_API(PyArray_GetNDArrayCFeatureVersion);
         api.PyArray_RUNTIME_VERSION_ = api.PyArray_GetNDArrayCFeatureVersion_();
         if (api.PyArray_RUNTIME_VERSION_ < 0x7) {
             pybind11_fail("pybind11 numpy support requires numpy >= 1.7.0");
         }
         DECL_NPY_API(PyArray_Type);
         DECL_NPY_API(PyVoidArrType_Type);
         DECL_NPY_API(PyArrayDescr_Type);
         DECL_NPY_API(PyArray_DescrFromType);
         DECL_NPY_API(PyArray_DescrFromScalar);
         DECL_NPY_API(PyArray_FromAny);
         DECL_NPY_API(PyArray_Resize);
         DECL_NPY_API(PyArray_CopyInto);
         DECL_NPY_API(PyArray_NewCopy);
         DECL_NPY_API(PyArray_NewFromDescr);
         DECL_NPY_API(PyArray_DescrNewFromType);
         DECL_NPY_API(PyArray_Newshape);
         DECL_NPY_API(PyArray_Squeeze);
         DECL_NPY_API(PyArray_View);
         DECL_NPY_API(PyArray_DescrConverter);
         DECL_NPY_API(PyArray_EquivTypes);
 #ifdef PYBIND11_NUMPY_1_ONLY
         DECL_NPY_API(PyArray_GetArrayParamsFromObject);
 #endif
         DECL_NPY_API(PyArray_SetBaseObject);
 
 #undef DECL_NPY_API
         return api;
     }
 };
 
 inline PyArray_Proxy *array_proxy(void *ptr) { return reinterpret_cast<PyArray_Proxy *>(ptr); }
 
 inline const PyArray_Proxy *array_proxy(const void *ptr) {
     return reinterpret_cast<const PyArray_Proxy *>(ptr);
 }
 
 inline PyArrayDescr_Proxy *array_descriptor_proxy(PyObject *ptr) {
     return reinterpret_cast<PyArrayDescr_Proxy *>(ptr);
 }
 
 inline const PyArrayDescr_Proxy *array_descriptor_proxy(const PyObject *ptr) {
     return reinterpret_cast<const PyArrayDescr_Proxy *>(ptr);
 }
 
 inline const PyArrayDescr1_Proxy *array_descriptor1_proxy(const PyObject *ptr) {
     return reinterpret_cast<const PyArrayDescr1_Proxy *>(ptr);
 }
 
 inline const PyArrayDescr2_Proxy *array_descriptor2_proxy(const PyObject *ptr) {
     return reinterpret_cast<const PyArrayDescr2_Proxy *>(ptr);
 }
 
 inline bool check_flags(const void *ptr, int flag) {
     return (flag == (array_proxy(ptr)->flags & flag));
 }
 
 template <typename T>
 struct is_std_array : std::false_type {};
 template <typename T, size_t N>
 struct is_std_array<std::array<T, N>> : std::true_type {};
 template <typename T>
 struct is_complex : std::false_type {};
 template <typename T>
 struct is_complex<std::complex<T>> : std::true_type {};
 
 template <typename T>
 struct array_info_scalar {
     using type = T;
     static constexpr bool is_array = false;
     static constexpr bool is_empty = false;
     static constexpr auto extents = const_name("");
     static void append_extents(list & /* shape */) {}
 };
 // Computes underlying type and a comma-separated list of extents for array
 // types (any mix of std::array and built-in arrays). An array of char is
 // treated as scalar because it gets special handling.
 template <typename T>
 struct array_info : array_info_scalar<T> {};
 template <typename T, size_t N>
 struct array_info<std::array<T, N>> {
     using type = typename array_info<T>::type;
     static constexpr bool is_array = true;
     static constexpr bool is_empty = (N == 0) || array_info<T>::is_empty;
     static constexpr size_t extent = N;
 
     // appends the extents to shape
     static void append_extents(list &shape) {
         shape.append(N);
         array_info<T>::append_extents(shape);
     }
 
     static constexpr auto extents = const_name<array_info<T>::is_array>(
         ::pybind11::detail::concat(const_name<N>(), array_info<T>::extents), const_name<N>());
 };
 // For numpy we have special handling for arrays of characters, so we don't include
 // the size in the array extents.
 template <size_t N>
 struct array_info<char[N]> : array_info_scalar<char[N]> {};
 template <size_t N>
 struct array_info<std::array<char, N>> : array_info_scalar<std::array<char, N>> {};
 template <typename T, size_t N>
 struct array_info<T[N]> : array_info<std::array<T, N>> {};
 template <typename T>
 using remove_all_extents_t = typename array_info<T>::type;
 
 template <typename T>
 using is_pod_struct
     = all_of<std::is_standard_layout<T>, // since we're accessing directly in memory
                                          // we need a standard layout type
 #if defined(__GLIBCXX__)                                                                          \
     && (__GLIBCXX__ < 20150422 || __GLIBCXX__ == 20150426 || __GLIBCXX__ == 20150623              \
         || __GLIBCXX__ == 20150626 || __GLIBCXX__ == 20160803)
              // libstdc++ < 5 (including versions 4.8.5, 4.9.3 and 4.9.4 which were released after
              // 5) don't implement is_trivially_copyable, so approximate it
              std::is_trivially_destructible<T>,
              satisfies_any_of<T, std::has_trivial_copy_constructor, std::has_trivial_copy_assign>,
 #else
              std::is_trivially_copyable<T>,
 #endif
              satisfies_none_of<T,
                                std::is_reference,
                                std::is_array,
                                is_std_array,
                                std::is_arithmetic,
                                is_complex,
                                std::is_enum>>;
 
 // Replacement for std::is_pod (deprecated in C++20)
 template <typename T>
 using is_pod = all_of<std::is_standard_layout<T>, std::is_trivial<T>>;
 
 template <ssize_t Dim = 0, typename Strides>
 ssize_t byte_offset_unsafe(const Strides &) {
     return 0;
 }
 template <ssize_t Dim = 0, typename Strides, typename... Ix>
 ssize_t byte_offset_unsafe(const Strides &strides, ssize_t i, Ix... index) {
     return i * strides[Dim] + byte_offset_unsafe<Dim + 1>(strides, index...);
 }
 
 /**
  * Proxy class providing unsafe, unchecked const access to array data.  This is constructed through
  * the `unchecked<T, N>()` method of `array` or the `unchecked<N>()` method of `array_t<T>`. `Dims`
  * will be -1 for dimensions determined at runtime.
  */
 template <typename T, ssize_t Dims>
 class unchecked_reference {
 protected:
     static constexpr bool Dynamic = Dims < 0;
     const unsigned char *data_;
     // Storing the shape & strides in local variables (i.e. these arrays) allows the compiler to
     // make large performance gains on big, nested loops, but requires compile-time dimensions
     conditional_t<Dynamic, const ssize_t *, std::array<ssize_t, (size_t) Dims>> shape_, strides_;
     const ssize_t dims_;
 
     friend class pybind11::array;
     // Constructor for compile-time dimensions:
     template <bool Dyn = Dynamic>
     unchecked_reference(const void *data,
                         const ssize_t *shape,
                         const ssize_t *strides,
                         enable_if_t<!Dyn, ssize_t>)
         : data_{reinterpret_cast<const unsigned char *>(data)}, dims_{Dims} {
         for (size_t i = 0; i < (size_t) dims_; i++) {
             shape_[i] = shape[i];
             strides_[i] = strides[i];
         }
     }
     // Constructor for runtime dimensions:
     template <bool Dyn = Dynamic>
     unchecked_reference(const void *data,
                         const ssize_t *shape,
                         const ssize_t *strides,
                         enable_if_t<Dyn, ssize_t> dims)
         : data_{reinterpret_cast<const unsigned char *>(data)}, shape_{shape}, strides_{strides},
           dims_{dims} {}
 
 public:
     /**
      * Unchecked const reference access to data at the given indices.  For a compile-time known
      * number of dimensions, this requires the correct number of arguments; for run-time
      * dimensionality, this is not checked (and so is up to the caller to use safely).
      */
     template <typename... Ix>
     const T &operator()(Ix... index) const {
         static_assert(ssize_t{sizeof...(Ix)} == Dims || Dynamic,
                       "Invalid number of indices for unchecked array reference");
         return *reinterpret_cast<const T *>(data_
                                             + byte_offset_unsafe(strides_, ssize_t(index)...));
     }
     /**
      * Unchecked const reference access to data; this operator only participates if the reference
      * is to a 1-dimensional array.  When present, this is exactly equivalent to `obj(index)`.
      */
     template <ssize_t D = Dims, typename = enable_if_t<D == 1 || Dynamic>>
     const T &operator[](ssize_t index) const {
         return operator()(index);
     }
 
     /// Pointer access to the data at the given indices.
     template <typename... Ix>
     const T *data(Ix... ix) const {
         return &operator()(ssize_t(ix)...);
     }
 
     /// Returns the item size, i.e. sizeof(T)
     constexpr static ssize_t itemsize() { return sizeof(T); }
 
     /// Returns the shape (i.e. size) of dimension `dim`
     ssize_t shape(ssize_t dim) const { return shape_[(size_t) dim]; }
 
     /// Returns the number of dimensions of the array
     ssize_t ndim() const { return dims_; }
 
     /// Returns the total number of elements in the referenced array, i.e. the product of the
     /// shapes
     template <bool Dyn = Dynamic>
     enable_if_t<!Dyn, ssize_t> size() const {
         return std::accumulate(
             shape_.begin(), shape_.end(), (ssize_t) 1, std::multiplies<ssize_t>());
     }
     template <bool Dyn = Dynamic>
     enable_if_t<Dyn, ssize_t> size() const {
         return std::accumulate(shape_, shape_ + ndim(), (ssize_t) 1, std::multiplies<ssize_t>());
     }
 
     /// Returns the total number of bytes used by the referenced data.  Note that the actual span
     /// in memory may be larger if the referenced array has non-contiguous strides (e.g. for a
     /// slice).
     ssize_t nbytes() const { return size() * itemsize(); }
 };
 
 template <typename T, ssize_t Dims>
 class unchecked_mutable_reference : public unchecked_reference<T, Dims> {
     friend class pybind11::array;
     using ConstBase = unchecked_reference<T, Dims>;
     using ConstBase::ConstBase;
     using ConstBase::Dynamic;
 
 public:
     // Bring in const-qualified versions from base class
     using ConstBase::operator();
     using ConstBase::operator[];
 
     /// Mutable, unchecked access to data at the given indices.
     template <typename... Ix>
     T &operator()(Ix... index) {
         static_assert(ssize_t{sizeof...(Ix)} == Dims || Dynamic,
                       "Invalid number of indices for unchecked array reference");
         return const_cast<T &>(ConstBase::operator()(index...));
     }
     /**
      * Mutable, unchecked access data at the given index; this operator only participates if the
      * reference is to a 1-dimensional array (or has runtime dimensions).  When present, this is
      * exactly equivalent to `obj(index)`.
      */
     template <ssize_t D = Dims, typename = enable_if_t<D == 1 || Dynamic>>
     T &operator[](ssize_t index) {
         return operator()(index);
     }
 
     /// Mutable pointer access to the data at the given indices.
     template <typename... Ix>
     T *mutable_data(Ix... ix) {
         return &operator()(ssize_t(ix)...);
     }
 };
 
 template <typename T, ssize_t Dim>
 struct type_caster<unchecked_reference<T, Dim>> {
     static_assert(Dim == 0 && Dim > 0 /* always fail */,
                   "unchecked array proxy object is not castable");
 };
 template <typename T, ssize_t Dim>
 struct type_caster<unchecked_mutable_reference<T, Dim>>
     : type_caster<unchecked_reference<T, Dim>> {};
 
 PYBIND11_NAMESPACE_END(detail)
 
 class dtype : public object {
 public:
     PYBIND11_OBJECT_DEFAULT(dtype, object, detail::npy_api::get().PyArrayDescr_Check_)
 
     explicit dtype(const buffer_info &info) {
         dtype descr(_dtype_from_pep3118()(pybind11::str(info.format)));
         // If info.itemsize == 0, use the value calculated from the format string
         m_ptr = descr.strip_padding(info.itemsize != 0 ? info.itemsize : descr.itemsize())
                     .release()
                     .ptr();
     }
 
     explicit dtype(const pybind11::str &format) : dtype(from_args(format)) {}
 
     explicit dtype(const std::string &format) : dtype(pybind11::str(format)) {}
 
     explicit dtype(const char *format) : dtype(pybind11::str(format)) {}
 
     dtype(list names, list formats, list offsets, ssize_t itemsize) {
         dict args;
         args["names"] = std::move(names);
         args["formats"] = std::move(formats);
         args["offsets"] = std::move(offsets);
         args["itemsize"] = pybind11::int_(itemsize);
         m_ptr = from_args(args).release().ptr();
     }
 
     /// Return dtype for the given typenum (one of the NPY_TYPES).
     /// https://numpy.org/devdocs/reference/c-api/array.html#c.PyArray_DescrFromType
     explicit dtype(int typenum)
         : object(detail::npy_api::get().PyArray_DescrFromType_(typenum), stolen_t{}) {
         if (m_ptr == nullptr) {
             throw error_already_set();
         }
     }
 
     /// This is essentially the same as calling numpy.dtype(args) in Python.
     static dtype from_args(const object &args) {
         PyObject *ptr = nullptr;
         if ((detail::npy_api::get().PyArray_DescrConverter_(args.ptr(), &ptr) == 0) || !ptr) {
             throw error_already_set();
         }
         return reinterpret_steal<dtype>(ptr);
     }
 
     /// Return dtype associated with a C++ type.
     template <typename T>
     static dtype of() {
         return detail::npy_format_descriptor<typename std::remove_cv<T>::type>::dtype();
     }
 
     /// Size of the data type in bytes.
 #ifdef PYBIND11_NUMPY_1_ONLY
     ssize_t itemsize() const { return detail::array_descriptor_proxy(m_ptr)->elsize; }
 #else
     ssize_t itemsize() const {
         if (detail::npy_api::get().PyArray_RUNTIME_VERSION_ < 0x12) {
             return detail::array_descriptor1_proxy(m_ptr)->elsize;
         }
         return detail::array_descriptor2_proxy(m_ptr)->elsize;
     }
 #endif
 
     /// Returns true for structured data types.
 #ifdef PYBIND11_NUMPY_1_ONLY
     bool has_fields() const { return detail::array_descriptor_proxy(m_ptr)->names != nullptr; }
 #else
     bool has_fields() const {
         if (detail::npy_api::get().PyArray_RUNTIME_VERSION_ < 0x12) {
             return detail::array_descriptor1_proxy(m_ptr)->names != nullptr;
         }
         const auto *proxy = detail::array_descriptor2_proxy(m_ptr);
         if (proxy->type_num < 0 || proxy->type_num >= 2056) {
             return false;
         }
         return proxy->names != nullptr;
     }
 #endif
 
     /// Single-character code for dtype's kind.
     /// For example, floating point types are 'f' and integral types are 'i'.
     char kind() const { return detail::array_descriptor_proxy(m_ptr)->kind; }
 
     /// Single-character for dtype's type.
     /// For example, ``float`` is 'f', ``double`` 'd', ``int`` 'i', and ``long`` 'l'.
     char char_() const {
         // Note: The signature, `dtype::char_` follows the naming of NumPy's
         // public Python API (i.e., ``dtype.char``), rather than its internal
         // C API (``PyArray_Descr::type``).
         return detail::array_descriptor_proxy(m_ptr)->type;
     }
 
     /// type number of dtype.
     int num() const {
         // Note: The signature, `dtype::num` follows the naming of NumPy's public
         // Python API (i.e., ``dtype.num``), rather than its internal
         // C API (``PyArray_Descr::type_num``).
         return detail::array_descriptor_proxy(m_ptr)->type_num;
     }
 
     /// Single character for byteorder
     char byteorder() const { return detail::array_descriptor_proxy(m_ptr)->byteorder; }
 
 /// Alignment of the data type
 #ifdef PYBIND11_NUMPY_1_ONLY
     int alignment() const { return detail::array_descriptor_proxy(m_ptr)->alignment; }
 #else
     ssize_t alignment() const {
         if (detail::npy_api::get().PyArray_RUNTIME_VERSION_ < 0x12) {
             return detail::array_descriptor1_proxy(m_ptr)->alignment;
         }
         return detail::array_descriptor2_proxy(m_ptr)->alignment;
     }
 #endif
 
 /// Flags for the array descriptor
 #ifdef PYBIND11_NUMPY_1_ONLY
     char flags() const { return detail::array_descriptor_proxy(m_ptr)->flags; }
 #else
     std::uint64_t flags() const {
         if (detail::npy_api::get().PyArray_RUNTIME_VERSION_ < 0x12) {
             return (unsigned char) detail::array_descriptor1_proxy(m_ptr)->flags;
         }
         return detail::array_descriptor2_proxy(m_ptr)->flags;
     }
 #endif
 
 private:
     static object &_dtype_from_pep3118() {
         PYBIND11_CONSTINIT static gil_safe_call_once_and_store<object> storage;
         return storage
             .call_once_and_store_result([]() {
                 return detail::import_numpy_core_submodule("_internal")
                     .attr("_dtype_from_pep3118");
             })
             .get_stored();
     }
 
     dtype strip_padding(ssize_t itemsize) {
         // Recursively strip all void fields with empty names that are generated for
         // padding fields (as of NumPy v1.11).
         if (!has_fields()) {
             return *this;
         }
 
         struct field_descr {
             pybind11::str name;
             object format;
             pybind11::int_ offset;
             field_descr(pybind11::str &&name, object &&format, pybind11::int_ &&offset)
                 : name{std::move(name)}, format{std::move(format)}, offset{std::move(offset)} {};
         };
         auto field_dict = attr("fields").cast<dict>();
         std::vector<field_descr> field_descriptors;
         field_descriptors.reserve(field_dict.size());
 
         for (auto field : field_dict.attr("items")()) {
             auto spec = field.cast<tuple>();
             auto name = spec[0].cast<pybind11::str>();
             auto spec_fo = spec[1].cast<tuple>();
             auto format = spec_fo[0].cast<dtype>();
             auto offset = spec_fo[1].cast<pybind11::int_>();
             if ((len(name) == 0u) && format.kind() == 'V') {
                 continue;
             }
             field_descriptors.emplace_back(
                 std::move(name), format.strip_padding(format.itemsize()), std::move(offset));
         }
 
         std::sort(field_descriptors.begin(),
                   field_descriptors.end(),
                   [](const field_descr &a, const field_descr &b) {
                       return a.offset.cast<int>() < b.offset.cast<int>();
                   });
 
         list names, formats, offsets;
         for (auto &descr : field_descriptors) {
             names.append(std::move(descr.name));
             formats.append(std::move(descr.format));
             offsets.append(std::move(descr.offset));
         }
         return dtype(std::move(names), std::move(formats), std::move(offsets), itemsize);
     }
 };
 
 class array : public buffer {
 public:
     PYBIND11_OBJECT_CVT(array, buffer, detail::npy_api::get().PyArray_Check_, raw_array)
 
     enum {
         c_style = detail::npy_api::NPY_ARRAY_C_CONTIGUOUS_,
         f_style = detail::npy_api::NPY_ARRAY_F_CONTIGUOUS_,
         forcecast = detail::npy_api::NPY_ARRAY_FORCECAST_
     };
 
     array() : array(0, static_cast<const double *>(nullptr)) {}
 
     using ShapeContainer = detail::any_container<ssize_t>;
     using StridesContainer = detail::any_container<ssize_t>;
 
     // Constructs an array taking shape/strides from arbitrary container types
     array(const pybind11::dtype &dt,
           ShapeContainer shape,
           StridesContainer strides,
           const void *ptr = nullptr,
           handle base = handle()) {
 
         if (strides->empty()) {
             *strides = detail::c_strides(*shape, dt.itemsize());
         }
 
         auto ndim = shape->size();
         if (ndim != strides->size()) {
             pybind11_fail("NumPy: shape ndim doesn't match strides ndim");
         }
         auto descr = dt;
 
         int flags = 0;
         if (base && ptr) {
             if (isinstance<array>(base)) {
                 /* Copy flags from base (except ownership bit) */
                 flags = reinterpret_borrow<array>(base).flags()
                         & ~detail::npy_api::NPY_ARRAY_OWNDATA_;
             } else {
                 /* Writable by default, easy to downgrade later on if needed */
                 flags = detail::npy_api::NPY_ARRAY_WRITEABLE_;
             }
         }
 
         auto &api = detail::npy_api::get();
         auto tmp = reinterpret_steal<object>(api.PyArray_NewFromDescr_(
             api.PyArray_Type_,
             descr.release().ptr(),
             (int) ndim,
             // Use reinterpret_cast for PyPy on Windows (remove if fixed, checked on 7.3.1)
             reinterpret_cast<Py_intptr_t *>(shape->data()),
             reinterpret_cast<Py_intptr_t *>(strides->data()),
             const_cast<void *>(ptr),
             flags,
             nullptr));
         if (!tmp) {
             throw error_already_set();
         }
         if (ptr) {
             if (base) {
                 api.PyArray_SetBaseObject_(tmp.ptr(), base.inc_ref().ptr());
             } else {
                 tmp = reinterpret_steal<object>(
                     api.PyArray_NewCopy_(tmp.ptr(), -1 /* any order */));
             }
         }
         m_ptr = tmp.release().ptr();
     }
 
     array(const pybind11::dtype &dt,
           ShapeContainer shape,
           const void *ptr = nullptr,
           handle base = handle())
         : array(dt, std::move(shape), {}, ptr, base) {}
 
     template <typename T,
               typename
               = detail::enable_if_t<std::is_integral<T>::value && !std::is_same<bool, T>::value>>
     array(const pybind11::dtype &dt, T count, const void *ptr = nullptr, handle base = handle())
         : array(dt, {{count}}, ptr, base) {}
 
     template <typename T>
     array(ShapeContainer shape, StridesContainer strides, const T *ptr, handle base = handle())
         : array(pybind11::dtype::of<T>(),
                 std::move(shape),
                 std::move(strides),
                 reinterpret_cast<const void *>(ptr),
                 base) {}
 
     template <typename T>
     array(ShapeContainer shape, const T *ptr, handle base = handle())
         : array(std::move(shape), {}, ptr, base) {}
 
     template <typename T>
     explicit array(ssize_t count, const T *ptr, handle base = handle())
         : array({count}, {}, ptr, base) {}
 
     explicit array(const buffer_info &info, handle base = handle())
         : array(pybind11::dtype(info), info.shape, info.strides, info.ptr, base) {}
 
     /// Array descriptor (dtype)
     pybind11::dtype dtype() const {
         return reinterpret_borrow<pybind11::dtype>(detail::array_proxy(m_ptr)->descr);
     }
 
     /// Total number of elements
     ssize_t size() const {
         return std::accumulate(shape(), shape() + ndim(), (ssize_t) 1, std::multiplies<ssize_t>());
     }
 
     /// Byte size of a single element
     ssize_t itemsize() const { return dtype().itemsize(); }
 
     /// Total number of bytes
     ssize_t nbytes() const { return size() * itemsize(); }
 
     /// Number of dimensions
     ssize_t ndim() const { return detail::array_proxy(m_ptr)->nd; }
 
     /// Base object
     object base() const { return reinterpret_borrow<object>(detail::array_proxy(m_ptr)->base); }
 
     /// Dimensions of the array
     const ssize_t *shape() const { return detail::array_proxy(m_ptr)->dimensions; }
 
     /// Dimension along a given axis
     ssize_t shape(ssize_t dim) const {
         if (dim >= ndim()) {
             fail_dim_check(dim, "invalid axis");
         }
         return shape()[dim];
     }
 
     /// Strides of the array
     const ssize_t *strides() const { return detail::array_proxy(m_ptr)->strides; }
 
     /// Stride along a given axis
     ssize_t strides(ssize_t dim) const {
         if (dim >= ndim()) {
             fail_dim_check(dim, "invalid axis");
         }
         return strides()[dim];
     }
 
     /// Return the NumPy array flags
     int flags() const { return detail::array_proxy(m_ptr)->flags; }
 
     /// If set, the array is writeable (otherwise the buffer is read-only)
     bool writeable() const {
         return detail::check_flags(m_ptr, detail::npy_api::NPY_ARRAY_WRITEABLE_);
     }
 
     /// If set, the array owns the data (will be freed when the array is deleted)
     bool owndata() const {
         return detail::check_flags(m_ptr, detail::npy_api::NPY_ARRAY_OWNDATA_);
     }
 
     /// Pointer to the contained data. If index is not provided, points to the
     /// beginning of the buffer. May throw if the index would lead to out of bounds access.
     template <typename... Ix>
     const void *data(Ix... index) const {
         return static_cast<const void *>(detail::array_proxy(m_ptr)->data + offset_at(index...));
     }
 
     /// Mutable pointer to the contained data. If index is not provided, points to the
     /// beginning of the buffer. May throw if the index would lead to out of bounds access.
     /// May throw if the array is not writeable.
     template <typename... Ix>
     void *mutable_data(Ix... index) {
         check_writeable();
         return static_cast<void *>(detail::array_proxy(m_ptr)->data + offset_at(index...));
     }
 
     /// Byte offset from beginning of the array to a given index (full or partial).
     /// May throw if the index would lead to out of bounds access.
     template <typename... Ix>
     ssize_t offset_at(Ix... index) const {
         if ((ssize_t) sizeof...(index) > ndim()) {
             fail_dim_check(sizeof...(index), "too many indices for an array");
         }
         return byte_offset(ssize_t(index)...);
     }
 
     ssize_t offset_at() const { return 0; }
 
     /// Item count from beginning of the array to a given index (full or partial).
     /// May throw if the index would lead to out of bounds access.
     template <typename... Ix>
     ssize_t index_at(Ix... index) const {
         return offset_at(index...) / itemsize();
     }
 
     /**
      * Returns a proxy object that provides access to the array's data without bounds or
      * dimensionality checking.  Will throw if the array is missing the `writeable` flag.  Use with
      * care: the array must not be destroyed or reshaped for the duration of the returned object,
      * and the caller must take care not to access invalid dimensions or dimension indices.
      */
     template <typename T, ssize_t Dims = -1>
     detail::unchecked_mutable_reference<T, Dims> mutable_unchecked() & {
         if (Dims >= 0 && ndim() != Dims) {
             throw std::domain_error("array has incorrect number of dimensions: "
                                     + std::to_string(ndim()) + "; expected "
                                     + std::to_string(Dims));
         }
         return detail::unchecked_mutable_reference<T, Dims>(
             mutable_data(), shape(), strides(), ndim());
     }
 
     /**
      * Returns a proxy object that provides const access to the array's data without bounds or
      * dimensionality checking.  Unlike `mutable_unchecked()`, this does not require that the
      * underlying array have the `writable` flag.  Use with care: the array must not be destroyed
      * or reshaped for the duration of the returned object, and the caller must take care not to
      * access invalid dimensions or dimension indices.
      */
     template <typename T, ssize_t Dims = -1>
     detail::unchecked_reference<T, Dims> unchecked() const & {
         if (Dims >= 0 && ndim() != Dims) {
             throw std::domain_error("array has incorrect number of dimensions: "
                                     + std::to_string(ndim()) + "; expected "
                                     + std::to_string(Dims));
         }
         return detail::unchecked_reference<T, Dims>(data(), shape(), strides(), ndim());
     }
 
     /// Return a new view with all of the dimensions of length 1 removed
     array squeeze() {
         auto &api = detail::npy_api::get();
         return reinterpret_steal<array>(api.PyArray_Squeeze_(m_ptr));
     }
 
     /// Resize array to given shape
     /// If refcheck is true and more that one reference exist to this array
     /// then resize will succeed only if it makes a reshape, i.e. original size doesn't change
     void resize(ShapeContainer new_shape, bool refcheck = true) {
         detail::npy_api::PyArray_Dims d
             = {// Use reinterpret_cast for PyPy on Windows (remove if fixed, checked on 7.3.1)
                reinterpret_cast<Py_intptr_t *>(new_shape->data()),
                int(new_shape->size())};
         // try to resize, set ordering param to -1 cause it's not used anyway
         auto new_array = reinterpret_steal<object>(
             detail::npy_api::get().PyArray_Resize_(m_ptr, &d, int(refcheck), -1));
         if (!new_array) {
             throw error_already_set();
         }
         if (isinstance<array>(new_array)) {
             *this = std::move(new_array);
         }
     }
 
     /// Optional `order` parameter omitted, to be added as needed.
     array reshape(ShapeContainer new_shape) {
         detail::npy_api::PyArray_Dims d
             = {reinterpret_cast<Py_intptr_t *>(new_shape->data()), int(new_shape->size())};
         auto new_array
             = reinterpret_steal<array>(detail::npy_api::get().PyArray_Newshape_(m_ptr, &d, 0));
         if (!new_array) {
             throw error_already_set();
         }
         return new_array;
     }
 
     /// Create a view of an array in a different data type.
     /// This function may fundamentally reinterpret the data in the array.
     /// It is the responsibility of the caller to ensure that this is safe.
     /// Only supports the `dtype` argument, the `type` argument is omitted,
     /// to be added as needed.
     array view(const std::string &dtype) {
         auto &api = detail::npy_api::get();
         auto new_view = reinterpret_steal<array>(api.PyArray_View_(
             m_ptr, dtype::from_args(pybind11::str(dtype)).release().ptr(), nullptr));
         if (!new_view) {
             throw error_already_set();
         }
         return new_view;
     }
 
     /// Ensure that the argument is a NumPy array
     /// In case of an error, nullptr is returned and the Python error is cleared.
     static array ensure(handle h, int ExtraFlags = 0) {
         auto result = reinterpret_steal<array>(raw_array(h.ptr(), ExtraFlags));
         if (!result) {
             PyErr_Clear();
         }
         return result;
     }
 
 protected:
     template <typename, typename>
     friend struct detail::npy_format_descriptor;
 
     void fail_dim_check(ssize_t dim, const std::string &msg) const {
         throw index_error(msg + ": " + std::to_string(dim) + " (ndim = " + std::to_string(ndim())
                           + ')');
     }
 
     template <typename... Ix>
     ssize_t byte_offset(Ix... index) const {
         check_dimensions(index...);
         return detail::byte_offset_unsafe(strides(), ssize_t(index)...);
     }
 
     void check_writeable() const {
         if (!writeable()) {
             throw std::domain_error("array is not writeable");
         }
     }
 
     template <typename... Ix>
     void check_dimensions(Ix... index) const {
         check_dimensions_impl(ssize_t(0), shape(), ssize_t(index)...);
     }
 
     void check_dimensions_impl(ssize_t, const ssize_t *) const {}
 
     template <typename... Ix>
     void check_dimensions_impl(ssize_t axis, const ssize_t *shape, ssize_t i, Ix... index) const {
         if (i >= *shape) {
             throw index_error(std::string("index ") + std::to_string(i)
                               + " is out of bounds for axis " + std::to_string(axis)
                               + " with size " + std::to_string(*shape));
         }
         check_dimensions_impl(axis + 1, shape + 1, index...);
     }
 
     /// Create array from any object -- always returns a new reference
     static PyObject *raw_array(PyObject *ptr, int ExtraFlags = 0) {
         if (ptr == nullptr) {
             set_error(PyExc_ValueError, "cannot create a pybind11::array from a nullptr");
             return nullptr;
         }
         return detail::npy_api::get().PyArray_FromAny_(
             ptr, nullptr, 0, 0, detail::npy_api::NPY_ARRAY_ENSUREARRAY_ | ExtraFlags, nullptr);
     }
 };
 
 template <typename T, int ExtraFlags = array::forcecast>
 class array_t : public array {
 private:
     struct private_ctor {};
     // Delegating constructor needed when both moving and accessing in the same constructor
     array_t(private_ctor,
             ShapeContainer &&shape,
             StridesContainer &&strides,
             const T *ptr,
             handle base)
         : array(std::move(shape), std::move(strides), ptr, base) {}
 
 public:
     static_assert(!detail::array_info<T>::is_array, "Array types cannot be used with array_t");
 
     using value_type = T;
 
     array_t() : array(0, static_cast<const T *>(nullptr)) {}
     array_t(handle h, borrowed_t) : array(h, borrowed_t{}) {}
     array_t(handle h, stolen_t) : array(h, stolen_t{}) {}
 
     PYBIND11_DEPRECATED("Use array_t<T>::ensure() instead")
     array_t(handle h, bool is_borrowed) : array(raw_array_t(h.ptr()), stolen_t{}) {
         if (!m_ptr) {
             PyErr_Clear();
         }
         if (!is_borrowed) {
             Py_XDECREF(h.ptr());
         }
     }
 
     // NOLINTNEXTLINE(google-explicit-constructor)
     array_t(const object &o) : array(raw_array_t(o.ptr()), stolen_t{}) {
         if (!m_ptr) {
             throw error_already_set();
         }
     }
 
     explicit array_t(const buffer_info &info, handle base = handle()) : array(info, base) {}
 
     array_t(ShapeContainer shape,
             StridesContainer strides,
             const T *ptr = nullptr,
             handle base = handle())
         : array(std::move(shape), std::move(strides), ptr, base) {}
 
     explicit array_t(ShapeContainer shape, const T *ptr = nullptr, handle base = handle())
         : array_t(private_ctor{},
                   std::move(shape),
                   (ExtraFlags & f_style) != 0 ? detail::f_strides(*shape, itemsize())
                                               : detail::c_strides(*shape, itemsize()),
                   ptr,
                   base) {}
 
     explicit array_t(ssize_t count, const T *ptr = nullptr, handle base = handle())
         : array({count}, {}, ptr, base) {}
 
     constexpr ssize_t itemsize() const { return sizeof(T); }
 
     template <typename... Ix>
     ssize_t index_at(Ix... index) const {
         return offset_at(index...) / itemsize();
     }
 
     template <typename... Ix>
     const T *data(Ix... index) const {
         return static_cast<const T *>(array::data(index...));
     }
 
     template <typename... Ix>
     T *mutable_data(Ix... index) {
         return static_cast<T *>(array::mutable_data(index...));
     }
 
     // Reference to element at a given index
     template <typename... Ix>
     const T &at(Ix... index) const {
         if ((ssize_t) sizeof...(index) != ndim()) {
             fail_dim_check(sizeof...(index), "index dimension mismatch");
         }
         return *(static_cast<const T *>(array::data())
                  + byte_offset(ssize_t(index)...) / itemsize());
     }
 
     // Mutable reference to element at a given index
     template <typename... Ix>
     T &mutable_at(Ix... index) {
         if ((ssize_t) sizeof...(index) != ndim()) {
             fail_dim_check(sizeof...(index), "index dimension mismatch");
         }
         return *(static_cast<T *>(array::mutable_data())
                  + byte_offset(ssize_t(index)...) / itemsize());
     }
 
     /**
      * Returns a proxy object that provides access to the array's data without bounds or
      * dimensionality checking.  Will throw if the array is missing the `writeable` flag.  Use with
      * care: the array must not be destroyed or reshaped for the duration of the returned object,
      * and the caller must take care not to access invalid dimensions or dimension indices.
      */
     template <ssize_t Dims = -1>
     detail::unchecked_mutable_reference<T, Dims> mutable_unchecked() & {
         return array::mutable_unchecked<T, Dims>();
     }
 
     /**
      * Returns a proxy object that provides const access to the array's data without bounds or
      * dimensionality checking.  Unlike `mutable_unchecked()`, this does not require that the
      * underlying array have the `writable` flag.  Use with care: the array must not be destroyed
      * or reshaped for the duration of the returned object, and the caller must take care not to
      * access invalid dimensions or dimension indices.
      */
     template <ssize_t Dims = -1>
     detail::unchecked_reference<T, Dims> unchecked() const & {
         return array::unchecked<T, Dims>();
     }
 
     /// Ensure that the argument is a NumPy array of the correct dtype (and if not, try to convert
     /// it).  In case of an error, nullptr is returned and the Python error is cleared.
     static array_t ensure(handle h) {
         auto result = reinterpret_steal<array_t>(raw_array_t(h.ptr()));
         if (!result) {
             PyErr_Clear();
         }
         return result;
     }
 
     static bool check_(handle h) {
         const auto &api = detail::npy_api::get();
         return api.PyArray_Check_(h.ptr())
                && api.PyArray_EquivTypes_(detail::array_proxy(h.ptr())->descr,
                                           dtype::of<T>().ptr())
                && detail::check_flags(h.ptr(), ExtraFlags & (array::c_style | array::f_style));
     }
 
 protected:
     /// Create array from any object -- always returns a new reference
     static PyObject *raw_array_t(PyObject *ptr) {
         if (ptr == nullptr) {
             set_error(PyExc_ValueError, "cannot create a pybind11::array_t from a nullptr");
             return nullptr;
         }
         return detail::npy_api::get().PyArray_FromAny_(ptr,
                                                        dtype::of<T>().release().ptr(),
                                                        0,
                                                        0,
                                                        detail::npy_api::NPY_ARRAY_ENSUREARRAY_
                                                            | ExtraFlags,
                                                        nullptr);
     }
 };
 
 template <typename T>
 struct format_descriptor<T, detail::enable_if_t<detail::is_pod_struct<T>::value>> {
     static std::string format() {
         return detail::npy_format_descriptor<typename std::remove_cv<T>::type>::format();
     }
 };
 
 template <size_t N>
 struct format_descriptor<char[N]> {
     static std::string format() { return std::to_string(N) + 's'; }
 };
 template <size_t N>
 struct format_descriptor<std::array<char, N>> {
     static std::string format() { return std::to_string(N) + 's'; }
 };
 
 template <typename T>
 struct format_descriptor<T, detail::enable_if_t<std::is_enum<T>::value>> {
     static std::string format() {
         return format_descriptor<
             typename std::remove_cv<typename std::underlying_type<T>::type>::type>::format();
     }
 };
 
 template <typename T>
 struct format_descriptor<T, detail::enable_if_t<detail::array_info<T>::is_array>> {
     static std::string format() {
         using namespace detail;
         static constexpr auto extents = const_name("(") + array_info<T>::extents + const_name(")");
         return extents.text + format_descriptor<remove_all_extents_t<T>>::format();
     }
 };
 
 PYBIND11_NAMESPACE_BEGIN(detail)
 template <typename T, int ExtraFlags>
 struct pyobject_caster<array_t<T, ExtraFlags>> {
     using type = array_t<T, ExtraFlags>;
 
     bool load(handle src, bool convert) {
         if (!convert && !type::check_(src)) {
             return false;
         }
         value = type::ensure(src);
         return static_cast<bool>(value);
     }
 
     static handle cast(const handle &src, return_value_policy /* policy */, handle /* parent */) {
         return src.inc_ref();
     }
     PYBIND11_TYPE_CASTER(type, handle_type_name<type>::name);
 };
 
 template <typename T>
 struct compare_buffer_info<T, detail::enable_if_t<detail::is_pod_struct<T>::value>> {
     static bool compare(const buffer_info &b) {
         return npy_api::get().PyArray_EquivTypes_(dtype::of<T>().ptr(), dtype(b).ptr());
     }
 };
 
 template <typename T, typename = void>
 struct npy_format_descriptor_name;
 
 template <typename T>
 struct npy_format_descriptor_name<T, enable_if_t<std::is_integral<T>::value>> {
     static constexpr auto name = const_name<std::is_same<T, bool>::value>(
         const_name("bool"),
         const_name<std::is_signed<T>::value>("numpy.int", "numpy.uint")
             + const_name<sizeof(T) * 8>());
 };
 
 template <typename T>
 struct npy_format_descriptor_name<T, enable_if_t<std::is_floating_point<T>::value>> {
     static constexpr auto name = const_name < std::is_same<T, float>::value
                                  || std::is_same<T, const float>::value
                                  || std::is_same<T, double>::value
                                  || std::is_same<T, const double>::value
                                         > (const_name("numpy.float") + const_name<sizeof(T) * 8>(),
                                            const_name("numpy.longdouble"));
 };
 
 template <typename T>
 struct npy_format_descriptor_name<T, enable_if_t<is_complex<T>::value>> {
     static constexpr auto name = const_name < std::is_same<typename T::value_type, float>::value
                                  || std::is_same<typename T::value_type, const float>::value
                                  || std::is_same<typename T::value_type, double>::value
                                  || std::is_same<typename T::value_type, const double>::value
                                         > (const_name("numpy.complex")
                                                + const_name<sizeof(typename T::value_type) * 16>(),
                                            const_name("numpy.longcomplex"));
 };
 
 template <typename T>
 struct npy_format_descriptor<
     T,
     enable_if_t<satisfies_any_of<T, std::is_arithmetic, is_complex>::value>>
     : npy_format_descriptor_name<T> {
 private:
     // NB: the order here must match the one in common.h
     constexpr static const int values[15] = {npy_api::NPY_BOOL_,
                                              npy_api::NPY_BYTE_,
                                              npy_api::NPY_UBYTE_,
                                              npy_api::NPY_INT16_,
                                              npy_api::NPY_UINT16_,
                                              npy_api::NPY_INT32_,
                                              npy_api::NPY_UINT32_,
                                              npy_api::NPY_INT64_,
                                              npy_api::NPY_UINT64_,
                                              npy_api::NPY_FLOAT_,
                                              npy_api::NPY_DOUBLE_,
                                              npy_api::NPY_LONGDOUBLE_,
                                              npy_api::NPY_CFLOAT_,
                                              npy_api::NPY_CDOUBLE_,
                                              npy_api::NPY_CLONGDOUBLE_};
 
 public:
     static constexpr int value = values[detail::is_fmt_numeric<T>::index];
 
     static pybind11::dtype dtype() { return pybind11::dtype(/*typenum*/ value); }
 };
 
 template <typename T>
 struct npy_format_descriptor<T, enable_if_t<is_same_ignoring_cvref<T, PyObject *>::value>> {
     static constexpr auto name = const_name("object");
 
     static constexpr int value = npy_api::NPY_OBJECT_;
 
     static pybind11::dtype dtype() { return pybind11::dtype(/*typenum*/ value); }
 };
 
 #define PYBIND11_DECL_CHAR_FMT                                                                    \
     static constexpr auto name = const_name("S") + const_name<N>();                               \
     static pybind11::dtype dtype() {                                                              \
         return pybind11::dtype(std::string("S") + std::to_string(N));                             \
     }
 template <size_t N>
 struct npy_format_descriptor<char[N]> {
     PYBIND11_DECL_CHAR_FMT
 };
 template <size_t N>
 struct npy_format_descriptor<std::array<char, N>> {
     PYBIND11_DECL_CHAR_FMT
 };
 #undef PYBIND11_DECL_CHAR_FMT
 
 template <typename T>
 struct npy_format_descriptor<T, enable_if_t<array_info<T>::is_array>> {
 private:
     using base_descr = npy_format_descriptor<typename array_info<T>::type>;
 
 public:
     static_assert(!array_info<T>::is_empty, "Zero-sized arrays are not supported");
 
     static constexpr auto name
         = const_name("(") + array_info<T>::extents + const_name(")") + base_descr::name;
     static pybind11::dtype dtype() {
         list shape;
         array_info<T>::append_extents(shape);
         return pybind11::dtype::from_args(
             pybind11::make_tuple(base_descr::dtype(), std::move(shape)));
     }
 };
 
 template <typename T>
 struct npy_format_descriptor<T, enable_if_t<std::is_enum<T>::value>> {
 private:
     using base_descr = npy_format_descriptor<typename std::underlying_type<T>::type>;
 
 public:
     static constexpr auto name = base_descr::name;
     static pybind11::dtype dtype() { return base_descr::dtype(); }
 };
 
 struct field_descriptor {
     const char *name;
     ssize_t offset;
     ssize_t size;
     std::string format;
     dtype descr;
 };
 
 PYBIND11_NOINLINE void register_structured_dtype(any_container<field_descriptor> fields,
                                                  const std::type_info &tinfo,
                                                  ssize_t itemsize,
                                                  bool (*direct_converter)(PyObject *, void *&)) {
 
     auto &numpy_internals = get_numpy_internals();
     if (numpy_internals.get_type_info(tinfo, false)) {
         pybind11_fail("NumPy: dtype is already registered");
     }
 
     // Use ordered fields because order matters as of NumPy 1.14:
     // https://docs.scipy.org/doc/numpy/release.html#multiple-field-indexing-assignment-of-structured-arrays
     std::vector<field_descriptor> ordered_fields(std::move(fields));
     std::sort(
         ordered_fields.begin(),
         ordered_fields.end(),
         [](const field_descriptor &a, const field_descriptor &b) { return a.offset < b.offset; });
 
     list names, formats, offsets;
     for (auto &field : ordered_fields) {
         if (!field.descr) {
             pybind11_fail(std::string("NumPy: unsupported field dtype: `") + field.name + "` @ "
                           + tinfo.name());
         }
         names.append(pybind11::str(field.name));
         formats.append(field.descr);
         offsets.append(pybind11::int_(field.offset));
     }
     auto *dtype_ptr
         = pybind11::dtype(std::move(names), std::move(formats), std::move(offsets), itemsize)
               .release()
               .ptr();
 
     // There is an existing bug in NumPy (as of v1.11): trailing bytes are
     // not encoded explicitly into the format string. This will supposedly
     // get fixed in v1.12; for further details, see these:
     // - https://github.com/numpy/numpy/issues/7797
     // - https://github.com/numpy/numpy/pull/7798
     // Because of this, we won't use numpy's logic to generate buffer format
     // strings and will just do it ourselves.
     ssize_t offset = 0;
     std::ostringstream oss;
     // mark the structure as unaligned with '^', because numpy and C++ don't
     // always agree about alignment (particularly for complex), and we're
     // explicitly listing all our padding. This depends on none of the fields
     // overriding the endianness. Putting the ^ in front of individual fields
     // isn't guaranteed to work due to https://github.com/numpy/numpy/issues/9049
     oss << "^T{";
     for (auto &field : ordered_fields) {
         if (field.offset > offset) {
             oss << (field.offset - offset) << 'x';
         }
         oss << field.format << ':' << field.name << ':';
         offset = field.offset + field.size;
     }
     if (itemsize > offset) {
         oss << (itemsize - offset) << 'x';
     }
     oss << '}';
     auto format_str = oss.str();
 
     // Smoke test: verify that NumPy properly parses our buffer format string
     auto &api = npy_api::get();
     auto arr = array(buffer_info(nullptr, itemsize, format_str, 1));
     if (!api.PyArray_EquivTypes_(dtype_ptr, arr.dtype().ptr())) {
         pybind11_fail("NumPy: invalid buffer descriptor!");
     }
 
     auto tindex = std::type_index(tinfo);
     numpy_internals.registered_dtypes[tindex] = {dtype_ptr, std::move(format_str)};
     with_internals([tindex, &direct_converter](internals &internals) {
         internals.direct_conversions[tindex].push_back(direct_converter);
     });
 }
 
 template <typename T, typename SFINAE>
 struct npy_format_descriptor {
     static_assert(is_pod_struct<T>::value,
                   "Attempt to use a non-POD or unimplemented POD type as a numpy dtype");
 
     static constexpr auto name = make_caster<T>::name;
 
     static pybind11::dtype dtype() { return reinterpret_borrow<pybind11::dtype>(dtype_ptr()); }
 
     static std::string format() {
         static auto format_str = get_numpy_internals().get_type_info<T>(true)->format_str;
         return format_str;
     }
 
     static void register_dtype(any_container<field_descriptor> fields) {
         register_structured_dtype(std::move(fields),
                                   typeid(typename std::remove_cv<T>::type),
                                   sizeof(T),
                                   &direct_converter);
     }
 
 private:
     static PyObject *dtype_ptr() {
         static PyObject *ptr = get_numpy_internals().get_type_info<T>(true)->dtype_ptr;
         return ptr;
     }
 
     static bool direct_converter(PyObject *obj, void *&value) {
         auto &api = npy_api::get();
         if (!PyObject_TypeCheck(obj, api.PyVoidArrType_Type_)) {
             return false;
         }
         if (auto descr = reinterpret_steal<object>(api.PyArray_DescrFromScalar_(obj))) {
             if (api.PyArray_EquivTypes_(dtype_ptr(), descr.ptr())) {
                 value = ((PyVoidScalarObject_Proxy *) obj)->obval;
                 return true;
             }
         }
         return false;
     }
 };
 
 #ifdef __CLION_IDE__ // replace heavy macro with dummy code for the IDE (doesn't affect code)
 #    define PYBIND11_NUMPY_DTYPE(Type, ...) ((void) 0)
 #    define PYBIND11_NUMPY_DTYPE_EX(Type, ...) ((void) 0)
 #else
 
 #    define PYBIND11_FIELD_DESCRIPTOR_EX(T, Field, Name)                                          \
         ::pybind11::detail::field_descriptor {                                                    \
             Name, offsetof(T, Field), sizeof(decltype(std::declval<T>().Field)),                  \
                 ::pybind11::format_descriptor<decltype(std::declval<T>().Field)>::format(),       \
                 ::pybind11::detail::npy_format_descriptor<                                        \
                     decltype(std::declval<T>().Field)>::dtype()                                   \
         }
 
 // Extract name, offset and format descriptor for a struct field
 #    define PYBIND11_FIELD_DESCRIPTOR(T, Field) PYBIND11_FIELD_DESCRIPTOR_EX(T, Field, #Field)
 
 // The main idea of this macro is borrowed from https://github.com/swansontec/map-macro
 // (C) William Swanson, Paul Fultz
 #    define PYBIND11_EVAL0(...) __VA_ARGS__
 #    define PYBIND11_EVAL1(...) PYBIND11_EVAL0(PYBIND11_EVAL0(PYBIND11_EVAL0(__VA_ARGS__)))
 #    define PYBIND11_EVAL2(...) PYBIND11_EVAL1(PYBIND11_EVAL1(PYBIND11_EVAL1(__VA_ARGS__)))
 #    define PYBIND11_EVAL3(...) PYBIND11_EVAL2(PYBIND11_EVAL2(PYBIND11_EVAL2(__VA_ARGS__)))
 #    define PYBIND11_EVAL4(...) PYBIND11_EVAL3(PYBIND11_EVAL3(PYBIND11_EVAL3(__VA_ARGS__)))
 #    define PYBIND11_EVAL(...) PYBIND11_EVAL4(PYBIND11_EVAL4(PYBIND11_EVAL4(__VA_ARGS__)))
 #    define PYBIND11_MAP_END(...)
 #    define PYBIND11_MAP_OUT
 #    define PYBIND11_MAP_COMMA ,
 #    define PYBIND11_MAP_GET_END() 0, PYBIND11_MAP_END
 #    define PYBIND11_MAP_NEXT0(test, next, ...) next PYBIND11_MAP_OUT
 #    define PYBIND11_MAP_NEXT1(test, next) PYBIND11_MAP_NEXT0(test, next, 0)
 #    define PYBIND11_MAP_NEXT(test, next) PYBIND11_MAP_NEXT1(PYBIND11_MAP_GET_END test, next)
 #    if defined(_MSC_VER)                                                                         \
         && !defined(__clang__) // MSVC is not as eager to expand macros, hence this workaround
 #        define PYBIND11_MAP_LIST_NEXT1(test, next)                                               \
             PYBIND11_EVAL0(PYBIND11_MAP_NEXT0(test, PYBIND11_MAP_COMMA next, 0))
 #    else
 #        define PYBIND11_MAP_LIST_NEXT1(test, next)                                               \
             PYBIND11_MAP_NEXT0(test, PYBIND11_MAP_COMMA next, 0)
 #    endif
 #    define PYBIND11_MAP_LIST_NEXT(test, next)                                                    \
         PYBIND11_MAP_LIST_NEXT1(PYBIND11_MAP_GET_END test, next)
 #    define PYBIND11_MAP_LIST0(f, t, x, peek, ...)                                                \
         f(t, x) PYBIND11_MAP_LIST_NEXT(peek, PYBIND11_MAP_LIST1)(f, t, peek, __VA_ARGS__)
 #    define PYBIND11_MAP_LIST1(f, t, x, peek, ...)                                                \
         f(t, x) PYBIND11_MAP_LIST_NEXT(peek, PYBIND11_MAP_LIST0)(f, t, peek, __VA_ARGS__)
 // PYBIND11_MAP_LIST(f, t, a1, a2, ...) expands to f(t, a1), f(t, a2), ...
 #    define PYBIND11_MAP_LIST(f, t, ...)                                                          \
         PYBIND11_EVAL(PYBIND11_MAP_LIST1(f, t, __VA_ARGS__, (), 0))
 
 #    define PYBIND11_NUMPY_DTYPE(Type, ...)                                                       \
         ::pybind11::detail::npy_format_descriptor<Type>::register_dtype(                          \
             ::std::vector<::pybind11::detail::field_descriptor>{                                  \
                 PYBIND11_MAP_LIST(PYBIND11_FIELD_DESCRIPTOR, Type, __VA_ARGS__)})
 
 #    if defined(_MSC_VER) && !defined(__clang__)
 #        define PYBIND11_MAP2_LIST_NEXT1(test, next)                                              \
             PYBIND11_EVAL0(PYBIND11_MAP_NEXT0(test, PYBIND11_MAP_COMMA next, 0))
 #    else
 #        define PYBIND11_MAP2_LIST_NEXT1(test, next)                                              \
             PYBIND11_MAP_NEXT0(test, PYBIND11_MAP_COMMA next, 0)
 #    endif
 #    define PYBIND11_MAP2_LIST_NEXT(test, next)                                                   \
         PYBIND11_MAP2_LIST_NEXT1(PYBIND11_MAP_GET_END test, next)
 #    define PYBIND11_MAP2_LIST0(f, t, x1, x2, peek, ...)                                          \
         f(t, x1, x2) PYBIND11_MAP2_LIST_NEXT(peek, PYBIND11_MAP2_LIST1)(f, t, peek, __VA_ARGS__)
 #    define PYBIND11_MAP2_LIST1(f, t, x1, x2, peek, ...)                                          \
         f(t, x1, x2) PYBIND11_MAP2_LIST_NEXT(peek, PYBIND11_MAP2_LIST0)(f, t, peek, __VA_ARGS__)
 // PYBIND11_MAP2_LIST(f, t, a1, a2, ...) expands to f(t, a1, a2), f(t, a3, a4), ...
 #    define PYBIND11_MAP2_LIST(f, t, ...)                                                         \
         PYBIND11_EVAL(PYBIND11_MAP2_LIST1(f, t, __VA_ARGS__, (), 0))
 
 #    define PYBIND11_NUMPY_DTYPE_EX(Type, ...)                                                    \
         ::pybind11::detail::npy_format_descriptor<Type>::register_dtype(                          \
             ::std::vector<::pybind11::detail::field_descriptor>{                                  \
                 PYBIND11_MAP2_LIST(PYBIND11_FIELD_DESCRIPTOR_EX, Type, __VA_ARGS__)})
 
 #endif // __CLION_IDE__
 
 class common_iterator {
 public:
     using container_type = std::vector<ssize_t>;
     using value_type = container_type::value_type;
     using size_type = container_type::size_type;
 
     common_iterator() : m_strides() {}
 
     common_iterator(void *ptr, const container_type &strides, const container_type &shape)
         : p_ptr(reinterpret_cast<char *>(ptr)), m_strides(strides.size()) {
         m_strides.back() = static_cast<value_type>(strides.back());
         for (size_type i = m_strides.size() - 1; i != 0; --i) {
             size_type j = i - 1;
             auto s = static_cast<value_type>(shape[i]);
             m_strides[j] = strides[j] + m_strides[i] - strides[i] * s;
         }
     }
 
     void increment(size_type dim) { p_ptr += m_strides[dim]; }
 
     void *data() const { return p_ptr; }
 
 private:
     char *p_ptr{nullptr};
     container_type m_strides;
 };
 
 template <size_t N>
 class multi_array_iterator {
 public:
     using container_type = std::vector<ssize_t>;
 
     multi_array_iterator(const std::array<buffer_info, N> &buffers, const container_type &shape)
         : m_shape(shape.size()), m_index(shape.size(), 0), m_common_iterator() {
 
         // Manual copy to avoid conversion warning if using std::copy
         for (size_t i = 0; i < shape.size(); ++i) {
             m_shape[i] = shape[i];
         }
 
         container_type strides(shape.size());
         for (size_t i = 0; i < N; ++i) {
             init_common_iterator(buffers[i], shape, m_common_iterator[i], strides);
         }
     }
 
     multi_array_iterator &operator++() {
         for (size_t j = m_index.size(); j != 0; --j) {
             size_t i = j - 1;
             if (++m_index[i] != m_shape[i]) {
                 increment_common_iterator(i);
                 break;
             }
             m_index[i] = 0;
         }
         return *this;
     }
 
     template <size_t K, class T = void>
     T *data() const {
         return reinterpret_cast<T *>(m_common_iterator[K].data());
     }
 
 private:
     using common_iter = common_iterator;
 
     void init_common_iterator(const buffer_info &buffer,
                               const container_type &shape,
                               common_iter &iterator,
                               container_type &strides) {
         auto buffer_shape_iter = buffer.shape.rbegin();
         auto buffer_strides_iter = buffer.strides.rbegin();
         auto shape_iter = shape.rbegin();
         auto strides_iter = strides.rbegin();
 
         while (buffer_shape_iter != buffer.shape.rend()) {
             if (*shape_iter == *buffer_shape_iter) {
                 *strides_iter = *buffer_strides_iter;
             } else {
                 *strides_iter = 0;
             }
 
             ++buffer_shape_iter;
             ++buffer_strides_iter;
             ++shape_iter;
             ++strides_iter;
         }
 
         std::fill(strides_iter, strides.rend(), 0);
         iterator = common_iter(buffer.ptr, strides, shape);
     }
 
     void increment_common_iterator(size_t dim) {
         for (auto &iter : m_common_iterator) {
             iter.increment(dim);
         }
     }
 
     container_type m_shape;
     container_type m_index;
     std::array<common_iter, N> m_common_iterator;
 };
 
 enum class broadcast_trivial { non_trivial, c_trivial, f_trivial };
 
 // Populates the shape and number of dimensions for the set of buffers.  Returns a
 // broadcast_trivial enum value indicating whether the broadcast is "trivial"--that is, has each
 // buffer being either a singleton or a full-size, C-contiguous (`c_trivial`) or Fortran-contiguous
 // (`f_trivial`) storage buffer; returns `non_trivial` otherwise.
 template <size_t N>
 broadcast_trivial
 broadcast(const std::array<buffer_info, N> &buffers, ssize_t &ndim, std::vector<ssize_t> &shape) {
     ndim = std::accumulate(
         buffers.begin(), buffers.end(), ssize_t(0), [](ssize_t res, const buffer_info &buf) {
             return std::max(res, buf.ndim);
         });
 
     shape.clear();
     shape.resize((size_t) ndim, 1);
 
     // Figure out the output size, and make sure all input arrays conform (i.e. are either size 1
     // or the full size).
     for (size_t i = 0; i < N; ++i) {
         auto res_iter = shape.rbegin();
         auto end = buffers[i].shape.rend();
         for (auto shape_iter = buffers[i].shape.rbegin(); shape_iter != end;
              ++shape_iter, ++res_iter) {
             const auto &dim_size_in = *shape_iter;
             auto &dim_size_out = *res_iter;
 
             // Each input dimension can either be 1 or `n`, but `n` values must match across
             // buffers
             if (dim_size_out == 1) {
                 dim_size_out = dim_size_in;
             } else if (dim_size_in != 1 && dim_size_in != dim_size_out) {
                 pybind11_fail("pybind11::vectorize: incompatible size/dimension of inputs!");
             }
         }
     }
 
     bool trivial_broadcast_c = true;
     bool trivial_broadcast_f = true;
     for (size_t i = 0; i < N && (trivial_broadcast_c || trivial_broadcast_f); ++i) {
         if (buffers[i].size == 1) {
             continue;
         }
 
         // Require the same number of dimensions:
         if (buffers[i].ndim != ndim) {
             return broadcast_trivial::non_trivial;
         }
 
         // Require all dimensions be full-size:
         if (!std::equal(buffers[i].shape.cbegin(), buffers[i].shape.cend(), shape.cbegin())) {
             return broadcast_trivial::non_trivial;
         }
 
         // Check for C contiguity (but only if previous inputs were also C contiguous)
         if (trivial_broadcast_c) {
             ssize_t expect_stride = buffers[i].itemsize;
             auto end = buffers[i].shape.crend();
             for (auto shape_iter = buffers[i].shape.crbegin(),
                       stride_iter = buffers[i].strides.crbegin();
                  trivial_broadcast_c && shape_iter != end;
                  ++shape_iter, ++stride_iter) {
                 if (expect_stride == *stride_iter) {
                     expect_stride *= *shape_iter;
                 } else {
                     trivial_broadcast_c = false;
                 }
             }
         }
 
         // Check for Fortran contiguity (if previous inputs were also F contiguous)
         if (trivial_broadcast_f) {
             ssize_t expect_stride = buffers[i].itemsize;
             auto end = buffers[i].shape.cend();
             for (auto shape_iter = buffers[i].shape.cbegin(),
                       stride_iter = buffers[i].strides.cbegin();
                  trivial_broadcast_f && shape_iter != end;
                  ++shape_iter, ++stride_iter) {
                 if (expect_stride == *stride_iter) {
                     expect_stride *= *shape_iter;
                 } else {
                     trivial_broadcast_f = false;
                 }
             }
         }
     }
 
     return trivial_broadcast_c   ? broadcast_trivial::c_trivial
            : trivial_broadcast_f ? broadcast_trivial::f_trivial
                                  : broadcast_trivial::non_trivial;
 }
 
 template <typename T>
 struct vectorize_arg {
     static_assert(!std::is_rvalue_reference<T>::value,
                   "Functions with rvalue reference arguments cannot be vectorized");
     // The wrapped function gets called with this type:
     using call_type = remove_reference_t<T>;
     // Is this a vectorized argument?
     static constexpr bool vectorize
         = satisfies_any_of<call_type, std::is_arithmetic, is_complex, is_pod>::value
           && satisfies_none_of<call_type,
                                std::is_pointer,
                                std::is_array,
                                is_std_array,
                                std::is_enum>::value
           && (!std::is_reference<T>::value
               || (std::is_lvalue_reference<T>::value && std::is_const<call_type>::value));
     // Accept this type: an array for vectorized types, otherwise the type as-is:
     using type = conditional_t<vectorize, array_t<remove_cv_t<call_type>, array::forcecast>, T>;
 };
 
 // py::vectorize when a return type is present
 template <typename Func, typename Return, typename... Args>
 struct vectorize_returned_array {
     using Type = array_t<Return>;
 
     static Type create(broadcast_trivial trivial, const std::vector<ssize_t> &shape) {
         if (trivial == broadcast_trivial::f_trivial) {
             return array_t<Return, array::f_style>(shape);
         }
         return array_t<Return>(shape);
     }
 
     static Return *mutable_data(Type &array) { return array.mutable_data(); }
 
     static Return call(Func &f, Args &...args) { return f(args...); }
 
     static void call(Return *out, size_t i, Func &f, Args &...args) { out[i] = f(args...); }
 };
 
 // py::vectorize when a return type is not present
 template <typename Func, typename... Args>
 struct vectorize_returned_array<Func, void, Args...> {
     using Type = none;
 
     static Type create(broadcast_trivial, const std::vector<ssize_t> &) { return none(); }
 
     static void *mutable_data(Type &) { return nullptr; }
 
     static detail::void_type call(Func &f, Args &...args) {
         f(args...);
         return {};
     }
 
     static void call(void *, size_t, Func &f, Args &...args) { f(args...); }
 };
 
 template <typename Func, typename Return, typename... Args>
 struct vectorize_helper {
 
 // NVCC for some reason breaks if NVectorized is private
 #ifdef __CUDACC__
 public:
 #else
 private:
 #endif
 
     static constexpr size_t N = sizeof...(Args);
     static constexpr size_t NVectorized = constexpr_sum(vectorize_arg<Args>::vectorize...);
     static_assert(
         NVectorized >= 1,
         "pybind11::vectorize(...) requires a function with at least one vectorizable argument");
 
 public:
     template <typename T,
               // SFINAE to prevent shadowing the copy constructor.
               typename = detail::enable_if_t<
                   !std::is_same<vectorize_helper, typename std::decay<T>::type>::value>>
     explicit vectorize_helper(T &&f) : f(std::forward<T>(f)) {}
 
     object operator()(typename vectorize_arg<Args>::type... args) {
         return run(args...,
                    make_index_sequence<N>(),
                    select_indices<vectorize_arg<Args>::vectorize...>(),
                    make_index_sequence<NVectorized>());
     }
 
 private:
     remove_reference_t<Func> f;
 
     // Internal compiler error in MSVC 19.16.27025.1 (Visual Studio 2017 15.9.4), when compiling
     // with "/permissive-" flag when arg_call_types is manually inlined.
     using arg_call_types = std::tuple<typename vectorize_arg<Args>::call_type...>;
     template <size_t Index>
     using param_n_t = typename std::tuple_element<Index, arg_call_types>::type;
 
     using returned_array = vectorize_returned_array<Func, Return, Args...>;
 
     // Runs a vectorized function given arguments tuple and three index sequences:
     //     - Index is the full set of 0 ... (N-1) argument indices;
     //     - VIndex is the subset of argument indices with vectorized parameters, letting us access
     //       vectorized arguments (anything not in this sequence is passed through)
     //     - BIndex is a incremental sequence (beginning at 0) of the same size as VIndex, so that
     //       we can store vectorized buffer_infos in an array (argument VIndex has its buffer at
     //       index BIndex in the array).
     template <size_t... Index, size_t... VIndex, size_t... BIndex>
     object run(typename vectorize_arg<Args>::type &...args,
                index_sequence<Index...> i_seq,
                index_sequence<VIndex...> vi_seq,
                index_sequence<BIndex...> bi_seq) {
 
         // Pointers to values the function was called with; the vectorized ones set here will start
         // out as array_t<T> pointers, but they will be changed them to T pointers before we make
         // call the wrapped function.  Non-vectorized pointers are left as-is.
         std::array<void *, N> params{{reinterpret_cast<void *>(&args)...}};
 
         // The array of `buffer_info`s of vectorized arguments:
         std::array<buffer_info, NVectorized> buffers{
             {reinterpret_cast<array *>(params[VIndex])->request()...}};
 
         /* Determine dimensions parameters of output array */
         ssize_t nd = 0;
         std::vector<ssize_t> shape(0);
         auto trivial = broadcast(buffers, nd, shape);
         auto ndim = (size_t) nd;
 
         size_t size
             = std::accumulate(shape.begin(), shape.end(), (size_t) 1, std::multiplies<size_t>());
 
         // If all arguments are 0-dimension arrays (i.e. single values) return a plain value (i.e.
         // not wrapped in an array).
         if (size == 1 && ndim == 0) {
             PYBIND11_EXPAND_SIDE_EFFECTS(params[VIndex] = buffers[BIndex].ptr);
             return cast(
                 returned_array::call(f, *reinterpret_cast<param_n_t<Index> *>(params[Index])...));
         }
 
         auto result = returned_array::create(trivial, shape);
 
         PYBIND11_WARNING_PUSH
 #ifdef PYBIND11_DETECTED_CLANG_WITH_MISLEADING_CALL_STD_MOVE_EXPLICITLY_WARNING
         PYBIND11_WARNING_DISABLE_CLANG("-Wreturn-std-move")
 #endif
 
         if (size == 0) {
             return result;
         }
 
         /* Call the function */
         auto *mutable_data = returned_array::mutable_data(result);
         if (trivial == broadcast_trivial::non_trivial) {
             apply_broadcast(buffers, params, mutable_data, size, shape, i_seq, vi_seq, bi_seq);
         } else {
             apply_trivial(buffers, params, mutable_data, size, i_seq, vi_seq, bi_seq);
         }
 
         return result;
         PYBIND11_WARNING_POP
     }
 
     template <size_t... Index, size_t... VIndex, size_t... BIndex>
     void apply_trivial(std::array<buffer_info, NVectorized> &buffers,
                        std::array<void *, N> &params,
                        Return *out,
                        size_t size,
                        index_sequence<Index...>,
                        index_sequence<VIndex...>,
                        index_sequence<BIndex...>) {
 
         // Initialize an array of mutable byte references and sizes with references set to the
         // appropriate pointer in `params`; as we iterate, we'll increment each pointer by its size
         // (except for singletons, which get an increment of 0).
         std::array<std::pair<unsigned char *&, const size_t>, NVectorized> vecparams{
             {std::pair<unsigned char *&, const size_t>(
                 reinterpret_cast<unsigned char *&>(params[VIndex] = buffers[BIndex].ptr),
                 buffers[BIndex].size == 1 ? 0 : sizeof(param_n_t<VIndex>))...}};
 
         for (size_t i = 0; i < size; ++i) {
             returned_array::call(
                 out, i, f, *reinterpret_cast<param_n_t<Index> *>(params[Index])...);
             for (auto &x : vecparams) {
                 x.first += x.second;
             }
         }
     }
 
     template <size_t... Index, size_t... VIndex, size_t... BIndex>
     void apply_broadcast(std::array<buffer_info, NVectorized> &buffers,
                          std::array<void *, N> &params,
                          Return *out,
                          size_t size,
                          const std::vector<ssize_t> &output_shape,
                          index_sequence<Index...>,
                          index_sequence<VIndex...>,
                          index_sequence<BIndex...>) {
 
         multi_array_iterator<NVectorized> input_iter(buffers, output_shape);
 
         for (size_t i = 0; i < size; ++i, ++input_iter) {
             PYBIND11_EXPAND_SIDE_EFFECTS((params[VIndex] = input_iter.template data<BIndex>()));
             returned_array::call(
                 out, i, f, *reinterpret_cast<param_n_t<Index> *>(std::get<Index>(params))...);
         }
     }
 };
 
 template <typename Func, typename Return, typename... Args>
 vectorize_helper<Func, Return, Args...> vectorize_extractor(const Func &f, Return (*)(Args...)) {
     return detail::vectorize_helper<Func, Return, Args...>(f);
 }
 
 template <typename T, int Flags>
 struct handle_type_name<array_t<T, Flags>> {
     static constexpr auto name
         = const_name("numpy.ndarray[") + npy_format_descriptor<T>::name + const_name("]");
 };
 
 PYBIND11_NAMESPACE_END(detail)
 
 // Vanilla pointer vectorizer:
 template <typename Return, typename... Args>
 detail::vectorize_helper<Return (*)(Args...), Return, Args...> vectorize(Return (*f)(Args...)) {
     return detail::vectorize_helper<Return (*)(Args...), Return, Args...>(f);
 }
 
 // lambda vectorizer:
 template <typename Func, detail::enable_if_t<detail::is_lambda<Func>::value, int> = 0>
 auto vectorize(Func &&f)
     -> decltype(detail::vectorize_extractor(std::forward<Func>(f),
                                             (detail::function_signature_t<Func> *) nullptr)) {
     return detail::vectorize_extractor(std::forward<Func>(f),
                                        (detail::function_signature_t<Func> *) nullptr);
 }
 
 // Vectorize a class method (non-const):
 template <typename Return,
           typename Class,
           typename... Args,
           typename Helper = detail::vectorize_helper<
               decltype(std::mem_fn(std::declval<Return (Class::*)(Args...)>())),
               Return,
               Class *,
               Args...>>
 Helper vectorize(Return (Class::*f)(Args...)) {
     return Helper(std::mem_fn(f));
 }
 
 // Vectorize a class method (const):
 template <typename Return,
           typename Class,
           typename... Args,
           typename Helper = detail::vectorize_helper<
               decltype(std::mem_fn(std::declval<Return (Class::*)(Args...) const>())),
               Return,
               const Class *,
               Args...>>
 Helper vectorize(Return (Class::*f)(Args...) const) {
     return Helper(std::mem_fn(f));
 }
 
 PYBIND11_NAMESPACE_END(PYBIND11_NAMESPACE)

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