trytond: Add doc about type of PYSON (issue 901002)

[cedric...@b2ck.com]

Reviewers: ,

Description:
trytond: Add doc about type of PYSON

Please review this at http://codereview.tryton.org/901002/

Affected files:
M doc/ref/pyson.rst
M doc/topics/pyson.rst


Index: doc/ref/pyson.rst
===================================================================
--- a/doc/ref/pyson.rst
+++ b/doc/ref/pyson.rst
@@ -74,6 +74,11 @@
evaluation context, otherwise the ``default`` value (empty
string by default). Returns an instance of itself.

+.. note::
+
+ The default value determines the type of the statement.
+..
+
.. class:: Not(value)

A :class:`Not` object represents the PYSON ``Not()``
Index: doc/topics/pyson.rst
===================================================================
--- a/doc/topics/pyson.rst
+++ b/doc/topics/pyson.rst
@@ -13,9 +13,9 @@
So third party softwares do not need to depend on Python to be able to
fully communicate with the Tryton server.

-PYSON is a `deterministic algorithm`_ which will always
-succeed to evaluate statements. There is a default behavior for
-unknown values.
+PYSON is a `deterministic algorithm`_ which will always succeed to evaluate
+statements. There is a default behavior for unknown values. It is
statically
+typed and checked on instantiation.

There is also a :ref:`reference documentation of the API <ref-pyson>`.