ExtensionDtype
==============

.. cpp:class:: numpy::ExtensionDtype

   numpy C++ class.

Example
-------

.. code-block:: cpp

   #include <numpy/np_ndarray.h>
   using namespace numpy;

   // Use ExtensionDtype
   ExtensionDtype obj;
   // ... operations ...

Indexing / Selection
--------------------

.. list-table::
   :widths: 40 20 15 25
   :header-rows: 1

   * - Signature
     - Return Type
     - Location
     - Example
   * - ``virtual size_t itemsize() const = 0``
     - virtual size_t
     - df_extension_dtype.h:42
     - :ref:`View <example-extensiondtype-itemsize-0>`

Type Checking
-------------

.. list-table::
   :widths: 40 20 15 25
   :header-rows: 1

   * - Signature
     - Return Type
     - Location
     - Example
   * - ``virtual bool is_nullable() const``
     - virtual bool
     - df_extension_dtype.h:55
     - 

Other Methods
-------------

.. list-table::
   :widths: 40 20 15 25
   :header-rows: 1

   * - Signature
     - Return Type
     - Location
     - Example
   * - ``virtual std::string kind() const = 0``
     - virtual std::string
     - df_extension_dtype.h:49
     - 
   * - ``virtual std::string name() const = 0``
     - virtual std::string
     - df_extension_dtype.h:30
     - :ref:`View <example-extensiondtype-name-1>`
   * - ``virtual numpy::DType numpy_dtype() const = 0``
     - virtual numpy::DType
     - df_extension_dtype.h:36
     - 
   * - ``virtual std::string repr() const``
     - virtual std::string
     - df_extension_dtype.h:80
     - 
   * - ``virtual const std::type_info& type() const = 0``
     - virtual const std::type_info&
     - df_extension_dtype.h:61
     - :ref:`View <example-extensiondtype-type-2>`


Code Examples
-------------

The following examples are extracted from the test suite.

.. _example-extensiondtype-itemsize-0:

.. dropdown:: itemsize (np_test_2_all.cpp:3540)
   :class-title: example-dropdown

   .. code-block:: cpp
      :linenos:
      :lineno-start: 3530
      :emphasize-lines: 11

            }
      
            // Test size
            if (!(size(arr) == 24)) {
                std::string description = std::string("testArrayInfo():") + __FILE__ + ":" + std::to_string(__LINE__) + ": !(size(arr) == 24)";
                std::cout << std::string("[FAIL] ") + description << std::endl;
                throw std::runtime_error(description);
            }
      
            // Test itemsize
            if (!(itemsize(arr) == sizeof(double))) {
                std::string description = std::string("testArrayInfo():") + __FILE__ + ":" + std::to_string(__LINE__) + ": !(itemsize(arr) == sizeof(double))";
                std::cout << std::string("[FAIL] ") + description << std::endl;
                throw std::runtime_error(description);
            }
      
            // Test nbytes
            if (!(nbytes(arr) == 24 * sizeof(double))) {
                std::string description = std::string("testArrayInfo():") + __FILE__ + ":" + std::to_string(__LINE__) + ": !(nbytes(arr) == 24 * sizeof(double))";
                std::cout << std::string("[FAIL] ") + description << std::endl;
                throw std::runtime_error(description);

.. _example-extensiondtype-name-1:

.. dropdown:: name (np_test_1_all.cpp:24865)
   :class-title: example-dropdown

   .. code-block:: cpp
      :linenos:
      :lineno-start: 24855
      :emphasize-lines: 11

            uint64_t before_restore = rng.next_uint64();
            rng.set_state(state);
            uint64_t after_restore = rng.next_uint64();
      
            if (before_restore != after_restore) {
              std::cout << "  [FAIL] : in np_test_bitgen_mt19937() : state restore failed";
              throw std::runtime_error("np_test_bitgen_mt19937 failed: state");
            }
      
            // Test name
            if (rng.name() != "MT19937") {
              std::cout << "  [FAIL] : in np_test_bitgen_mt19937() : incorrect name";
              throw std::runtime_error("np_test_bitgen_mt19937 failed: name");
            }
      
            std::cout << " -> tests passed" << std::endl;
          }
      
          // ============================================================================
          // PCG64 TESTS
          // ============================================================================

.. _example-extensiondtype-type-2:

.. dropdown:: type (np_test_1_all.cpp:2240)
   :class-title: example-dropdown

   .. code-block:: cpp
      :linenos:
      :lineno-start: 2230
      :emphasize-lines: 11

              std::string description = std::string("testArrayEdgeCases():") + __FILE__ + ":" + std::to_string(__LINE__) + ": !(multi_array.getElementAt({0, 1}).is_type<std::string>())";
              std::cout << std::string("[FAIL] ") + description << std::endl;
              throw std::runtime_error(description);
          }
          if (!(multi_array.getElementAt({0, 2}).is_type<double>())) {
              std::string description = std::string("testArrayEdgeCases():") + __FILE__ + ":" + std::to_string(__LINE__) + ": !(multi_array.getElementAt({0, 2}).is_type<double>())";
              std::cout << std::string("[FAIL] ") + description << std::endl;
              throw std::runtime_error(description);
          }
      
          // Test 4: Arrays with all same type (homogeneous)
          NDArray<object_> homo_array = createObjectZeros({5});
          for (size_t i = 0; i < 5; ++i) {
              homo_array.setElementAt({i}, object_(static_cast<int>(i * 10)));
          }
      
          // Verify all are same type
          for (size_t i = 0; i < 5; ++i) {
              object_ obj = homo_array.getElementAt({i});
              if (!(obj.is_type<int>())) {
                  std::string description = std::string("testArrayEdgeCases():") + __FILE__ + ":" + std::to_string(__LINE__) + ": !(obj.is_type<int>())";