Example Usage
=============

First, we must include the exposed classes and functions:

.. code-block:: python
    
    from lazysignals import Signal, effect, derived

Let us define our first signal ``s``, holding the initial value ``1``:

.. code-block:: python

    s = Signal(1)

Next, derive a signal ``p`` that checks the parity of ``s``:

.. code-block:: python

    p = derived(lambda: s.value % 2 == 0)

Let us log the parity ``p`` to the console:

.. code-block:: python

    effect(lambda: print(f"parity:", "even" if p.value else "odd"))

Finally, perform some updates to ``s``:

.. code-block:: python

    s.value = 1  # no change (s.value was 1 already), no output
    s.value = 2  # output: "parity: even"
    s.value = 4  # output: "parity: odd"
    s.value = 5  # no change (p.value was False already), no output
    s.value = 6  # output: "parity: even"

.. note::
    We did not need to mention the dependency on ``s`` anywhere within in the effect.
    Yet changes to ``s.value`` caused ``p.value`` to update and the effect to run.
    
.. note::
    The effect only ran for those changes that mattered.
    Whenever ``p.value`` stayed the same (because ``s.value`` did not change or its parity did not flip), no effect was run.