.. _section-Typed Variables:

Typed Variables
---------------

A common pattern is to add a type check for variables in a rule. We saw this in our bachelor rule in [negation]:

.. code-block:: flora

    ?Person[bachelor] :-
      ?Person : Man,
      \+ ?Person [spouse -> ?Spouse].

Flora has a convenient shorthand syntax for that is equivalent to this:

.. code-block:: flora

    ?Person^^Man[bachelor] :-
      \+ ?Person [spouse -> ?Spouse].

This doesn’t save any typing, but it documents more clearly the intended types of arguments to a rule.