State machines
==============

.. currentmodule:: ansys.scadeone.core.swan

The Swan language has two syntax to express state machines:

- a state machine is a collection of states, each state having strong and weak transitions;
- a state machine is a collection of:

  - states, where states do not have transitions;
  - transition declarations, which describe the transitions as separate items.

A :py:class:`StateMachine` contains therefore a list of states and possibly transition declarations, all
as instances of :py:class:`StateMachineItem`.

The following figure shows the classes hierarchy when one uses states with transitions syntax. 

.. figure:: states_with_transitions.svg
    
    States with transitions

The following figure shows the classes hierarchy when one uses states without transitions and
separate transition declaration syntax. 

.. figure:: states_and_transitions.svg

    States and transition declarations

.. note::

    Both representations are not exclusive, though it is not expected to have a mixed definition of
    a state machine with states and their transitions, and separate transitions.


.. autoclass:: StateMachine

.. autoclass:: StateMachineItem

States
------

.. autoclass:: State

.. autoclass:: StateRef

Transitions
-----------

.. autoclass:: TransitionDecl

.. autoclass:: Transition 

.. autoclass:: Arrow

.. autoclass:: Target

Forks
-----

Forks are transitions which split into several branches.

.. .. autoclass:: Fork

State with transitions
~~~~~~~~~~~~~~~~~~~~~~

A fork a succession of *if then else* with :py:class:`Arrow`.

.. autoclass:: ForkTree

Separate transitions
~~~~~~~~~~~~~~~~~~~~

Fork is a list of *if* and one *else* arrows with priorities.

.. autoclass:: ForkWithPriority

.. autoclass:: ForkPriorityList