.. _Operator_Functions:

#########
Functions
#########

The class is equipped with two types of :ref:`Constructors<Operator_Functions_Constructors>` that refer to the cases if it uses the number-conserving :ref:`Basis class<BasisU1>` or the **not** number-conserving :ref:`State class<State>`.

Arbitrary terms in form of local tensor products can be added with :ref:`add_operator(...)<Operator_Functions_add_operator>` in :ref:`Input Functions<Operator_Functions_Input>`.
The function :ref:`define_operator(...)<Operator_Functions_define_operator>` allows to create arbitrary matrices acting on the local Hilbert space of dimension :math:`Q`.
A few :ref:`default operators<Operator_Functions_add_default_operators>` are included.

Full access to the :ref:`states<State>` forming the basis of the operator -- independent of the used template class **T** -- are listed in :ref:`State Handling<Operator_Functions_State_Handling>`.
The functions :ref:`get_index(state)<Operator_Functions_get_index>`, :ref:`get_state(index)<Operator_Functions_get_state>`, and :ref:`increment(state)<Operator_Functions_increment>` provide full access to the basis states.
The function :ref:`apply(state)<Operator_Functions_apply>` is used to generate the matrix representation of this operator.

Finally, the operator can represented in different matrix formats using the functions in :ref:`Matrix Formats<Operator_Functions_Frontends>`.
We provide native **cpp** container but also frontends for different linear algebra libraries like :ref:`Eigen<Eigen_setup>` and :ref:`Petsc<Petsc_setup>`.


.. toctree::
    :maxdepth: 1
    :titlesonly:

    Functions/Miscellaneous.rst
    Functions/Input.rst
    Functions/State_Handling.rst
    Functions/Frontends.rst