1 files changed, 54 insertions, 0 deletions
diff --git a/sources/shiboken6/doc/typesystem_specialfunctions.rst b/sources/shiboken6/doc/typesystem_specialfunctions.rst
new file mode 100644
index 000000000..78a6ff489
--- /dev/null
+++ b/sources/shiboken6/doc/typesystem_specialfunctions.rst
@@ -0,0 +1,54 @@
+.. _special-functions:
+
+Special functions
+-----------------
+
+.. _sequence-protocol:
+
+Sequence Protocol
+^^^^^^^^^^^^^^^^^
+
+Support for the sequence protocol is achieved adding functions with special
+names, this is done using the :ref:`add-function` tag.
+
+The special function names are:
+
+============= =============================================== ==================== ===================
+Function name Parameters                                      Return type          CPython equivalent
+============= =============================================== ==================== ===================
+__len__       PyObject* self                                  Py_ssize_t           PySequence_Size
+__getitem__   PyObject* self, Py_ssize_t _i                   PyObject*            PySequence_GetItem
+__setitem__   PyObject* self, Py_ssize_t _i, PyObject* _value int                  PySequence_SetItem
+__contains__  PyObject* self, PyObject* _value                int                  PySequence_Contains
+__concat__    PyObject* self, PyObject* _other                PyObject*            PySequence_Concat
+============= =============================================== ==================== ===================
+
+You just need to inform the function name to the :ref:`add-function` tag, without any
+parameter or return type information, when you do it, |project| will create a C
+function with parameters and return type defined by the table above.
+
+The function needs to follow the same semantics of the *CPython equivalent*
+function, the only way to do it is using the
+:ref:`inject-code <codeinjectionsemantics>` tag.
+
+A concrete example how to add sequence protocol support to a class can be found
+on shiboken tests, more precisely in the definition of the Str class in
+``tests/samplebinding/typesystem_sample.xml``.
+
+.. _bool-cast:
+
+Bool Cast
+^^^^^^^^^
+
+Implementing bool casts enables using values which have a concept of validity
+in boolean expressions. In C++, this is commonly implemented as
+``operator bool() const``. In Qt, relevant classes have a
+``bool isNull() const`` function.
+
+In Python, the function ``__bool__`` is used for this. shiboken can generate
+this functions depending on the command line options
+:ref:`--use-operator-bool-as-nb-bool <use-operator-bool-as-nb-bool>`
+and :ref:`--use-isnull-as-nb-bool <use-isnull-as-nb-bool>`,
+which can be overridden by specifying the boolean attributes
+**isNull** or **operator-bool** on the :ref:`value-type` or :ref:`object-type`
+elements in typesystem XML.