.. _`yaml representation`:

YAML representation
===================

When |symfer| serializes factor expressions from Python memory to a file, it uses
the `YAML <http://yaml.org>`_ format. YAML is like
`JSON <http://en.wikipedia.org/wiki/JSON>`_, only:

- You're allowed to leave out some of the brackets, braces and quotes.
- More importantly, you can define *shared* sub-structures within your
  document by placing an anchor such as ``&f`` at the
  first occurence, and a link ``*f`` at subsequent occurrences.
- An object can be preceded by a ``!tag`` defining its type.

The translation is as follows.

.. table::
    :widths: 1 1
    :column-alignment: left left

    +----------------------------------+----------------------------+
    | Python constructor               | YAML                       |
    +==================================+============================+
    |::                                |::                          |
    |                                  |                            |
    |    SumProd(['A','B'],[f,g])      |    !sumprod                |
    |                                  |    arg: [A,B]              |
    |                                  |    fac: [*f,*g]            |
    +----------------------------------+----------------------------+
    |::                                |::                          |
    |                                  |                            |
    |   f = Multinom([{'A':[0,1]},..], |    &f !multinom            |
    |                [0.25,0.75,..])   |    dom: [A: [0,0],..]      |
    |                                  |    par: [0.25,0.75,..]     |
    +----------------------------------+----------------------------+
    |::                                |::                          |
    |                                  |                            |
    |   d = Fun([{'C':[False,True]}],  |    &d !fun                 |
    |           [{'A':[0,1],..],       |    cod: [C: [False,True]]  |
    |           [1,0,..])              |    dom: [A: [0,1],..]      |
    |                                  |    par: [1,0,..]           |
    +----------------------------------+----------------------------+
    |::                                |::                          |
    |                                  |                            |
    |    Index([d],[h])                |    !index                  |
    |                                  |    det: [*d]               |
    |                                  |    fac: [*h]               |
    +----------------------------------+----------------------------+
    |::                                |::                          |
    |                                  |                            |
    |    I()                           |    !i {}                   |
    +----------------------------------+----------------------------+
    |::                                |::                          |
    |                                  |                            |
    |    Embed([d])                    |    !embed                  |
    |                                  |    det: [*d]               |
    +----------------------------------+----------------------------+
    |::                                |::                          |
    |                                  |                            |
    |    Reorder([{'newB':'B'},        |    !reorder                |
    |             {'newA':'A'}],       |    dic: [newB: B, newA: A] |
    |            [f])                  |    fac: [*f]               |
    +----------------------------------+----------------------------+