.. $Id: other_functions.txt 988349d92208 2010-03-12 mtnyogi $
.. 
.. Copyright © 2007-2010 Bruce Frederiksen
.. 
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.. of this software and associated documentation files (the "Software"), to deal
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.. furnished to do so, subject to the following conditions:
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.. The above copyright notice and this permission notice shall be included in
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.. IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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.. THE SOFTWARE.

restindex
    crumb: Other functions
    page-description:
        Other miscellaneous functions available that you might be interested
        in, such as tracing rules and smart error tracebacks that show lines
        from your .krb files.
    /description
    format: rest
    encoding: utf8
    output-encoding: utf8
    include: yes
    initialheaderlevel: 2
/restindex

uservalues
    filedate: $Id: other_functions.txt 988349d92208 2010-03-12 mtnyogi $
/uservalues

===============
Other Functions
===============

Running and Pickling Plans
==========================

.. this code is hidden and will set __file__ to the doc/examples directory.
   >>> import os
   >>> __file__ = \
   ...   os.path.join(os.path.dirname(os.path.dirname(os.getcwd())),
   ...                'examples')
   >>> from pyke import knowledge_engine
   >>> my_engine = knowledge_engine.engine(__file__)
   >>> my_engine.add_universal_fact('family', 'son_of', ('bruce', 'thomas'))
   >>> my_engine.add_universal_fact('family', 'son_of', ('david', 'bruce'))
   >>> my_engine.activate('bc_related0')

Once you've obtained a plan_ from `prove_goal`_ or `prove_1_goal`_, you just
call it like a normal Python function.  The arguments required are simply those
specified, if any, in the `taking clause`_ of the rule__ proving the top-level
goal.

You may call the plan function any number of times.  You may even pickle
the plan for later use.  The plans are constructed out of `functools.partial`_
functions, which needed to be registered with copy_reg_ in Python 2.x; but
this is no longer needed in Python 3.x.

No special code is required to unpickle a plan.  Just unpickle and call it.
(Unpickling the plan only imports one small Pyke module to be able to run
the plan).

.. __: ../pyke_syntax/krb_syntax/bc_rule.html


Tracing Rules
=============

Individual rules may be traced to aid in debugging.  The ``trace`` function
takes two arguments: the rule base name, and the name of the rule to trace:

    >>> my_engine.trace('bc_related0', 'grand_father_son')
    >>> my_engine.prove_1_goal('bc_related0.father_son(thomas, david, $depth)')
    bc_related0.grand_father_son('thomas', 'david', '$depth')
    bc_related0.grand_father_son succeeded with ('thomas', 'david', ('grand',))
    ({'depth': ('grand',)}, None)

This can be done either before or after rule base activation and will remain
in effect until you call ``untrace``:

    >>> my_engine.untrace('bc_related0', 'grand_father_son')
    >>> my_engine.prove_1_goal('bc_related0.father_son(thomas, david, $depth)')
    ({'depth': ('grand',)}, None)


Krb_traceback
=============

A handy traceback module is provided to convert Python functions, lines and
line numbers to the `.krb file`_ rule names, lines and line numbers in a
Python traceback.  This makes it much easier to read the tracebacks that occur
during proofs.

The ``krb_traceback`` module has exactly the same functions as the standard
Python traceback_ module, but they convert the generated Python function
information into .krb file information.  They also delete the intervening
Python functions between subgoal proofs.

    >>> import sys
    >>> from pyke import knowledge_engine
    >>> from pyke import krb_traceback
    >>>
    >>> my_engine = knowledge_engine.engine(__file__)
    >>> my_engine.activate('error_test')
    >>> try:                                            # doctest: +ELLIPSIS
    ...     my_engine.prove_1_goal('error_test.goal()')
    ... except:
    ...     krb_traceback.print_exc(None, sys.stdout)   # sys.stdout needed for doctest
    Traceback (most recent call last):
      File "<doctest other_functions.txt[16]>", line 2, in <module>
        my_engine.prove_1_goal('error_test.goal()')
      File "...knowledge_engine.py", line 367, in prove_1_goal
        return goal.compile(goal_str).prove_1(self, **args)
      File "...goal.py", line 47, in prove_1
        return next(iter(it))
      File "...rule_base.py", line 50, in __next__
        return next(self.iterator)
      File "...error_test.krb", line 26, in rule1
        goal2()
      File "...error_test.krb", line 31, in rule2
        goal3()
      File "...error_test.krb", line 36, in rule3
        goal4()
      File "...error_test.krb", line 41, in rule4
        check $bar > 0
      File "...contexts.py", line 231, in lookup_data
        raise KeyError("$%s not bound" % var_name)
    KeyError: '$bar not bound'


Miscellaneous
=============

There are a few more functions that may be useful in special situations.

*some_engine*.add_case_specific_fact(kb_name, fact_name, args)
    This is an alternate to the ``assert_`` function.
*some_engine*.get_kb(kb_name)
    Finds and returns the `knowledge base`_ by the name ``kb_name``.  Raises
    ``KeyError`` if not found.  Note that for `rule bases`_, this returns the
    active `rule base`_ where ``kb_name`` is the `rule base category`_ name.
    Thus, not all `rule bases`_ are accessible through this call.
*some_engine*.get_rb(rb_name)
    Finds and returns the `rule base`_ by the name ``rb_name``.  Raises
    ``KeyError`` if not found.  This works for any `rule base`_, whether it
    is active_ or not.
*some_engine*.print_stats([f = sys.stdout])
    Prints a brief set of statistics for each knowledge base to file ``f``.
    These are reset by the ``reset`` function.  This will show how many facts
    were asserted, and counts of how many forward-chaining rules were fired
    and rerun, as well as counts of how many backward-chaining goals were
    tried, and how many backward-chaining rules matched, succeeded and failed.
    Note that one backward-chaining rule may succeed many times through
    backtracking.

