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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<title>Other Functions</title>
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<div class="document" id="other-functions">
<h1 class="title">Other Functions</h1>
<div class="section" id="running-and-pickling-plans">
<h2>Running and Pickling Plans</h2>
<!-- 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') -->
<p>Once you've obtained a <a class="reference external" href="../logic_programming/plans.html">plan</a> from <a class="reference external" href="proving_goals.html">prove_goal</a> or <a class="reference external" href="proving_goals.html">prove_1_goal</a>, you just
call it like a normal Python function. The arguments required are simply those
specified, if any, in the <a class="reference external" href="../pyke_syntax/krb_syntax/bc_rule.html#taking-clause">taking clause</a> of the <a class="reference external" href="../pyke_syntax/krb_syntax/bc_rule.html">rule</a> proving the top-level
goal.</p>
<p>You may call the plan function any number of times. You may even pickle
the plan for later use. But the plans are constructed out of
<a class="reference external" href="http://docs.python.org/library/functools.html">functools.partial</a> functions, that need to be registered with <a class="reference external" href="http://docs.python.org/library/copy_reg.html">copy_reg</a>
if you are running Python 2.x:</p>
<blockquote>
<pre class="doctest-block">
&gt;&gt;&gt; import copy_reg
&gt;&gt;&gt; import functools
&gt;&gt;&gt; copy_reg.pickle(functools.partial,
... lambda p: (functools.partial, (p.func,) + p.args))
</pre>
</blockquote>
<p>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).</p>
</div>
<div class="section" id="tracing-rules">
<h2>Tracing Rules</h2>
<p>Individual rules may be traced to aid in debugging. The <tt class="docutils literal">trace</tt> function
takes two arguments: the rule base name, and the name of the rule to trace:</p>
<blockquote>
<pre class="doctest-block">
&gt;&gt;&gt; my_engine.trace('bc_related0', 'grand_father_son')
&gt;&gt;&gt; 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)
</pre>
</blockquote>
<p>This can be done either before or after rule base activation and will remain
in effect until you call <tt class="docutils literal">untrace</tt>:</p>
<blockquote>
<pre class="doctest-block">
&gt;&gt;&gt; my_engine.untrace('bc_related0', 'grand_father_son')
&gt;&gt;&gt; my_engine.prove_1_goal('bc_related0.father_son(thomas, david, $depth)')
({'depth': ('grand',)}, None)
</pre>
</blockquote>
</div>
<div class="section" id="krb-traceback">
<h2>Krb_traceback</h2>
<p>A handy traceback module is provided to convert Python functions, lines and
line numbers to the <a class="reference external" href="../pyke_syntax/krb_syntax/index.html">.krb file</a> rule names, lines and line numbers in a
Python traceback. This makes it much easier to read the tracebacks that occur
during proofs.</p>
<p>The <tt class="docutils literal">krb_traceback</tt> module has exactly the same functions as the standard
Python <a class="reference external" href="http://docs.python.org/library/traceback.html">traceback</a> module, but they convert the generated Python function
information into .krb file information. They also delete the intervening
Python functions between subgoal proofs.</p>
<blockquote>
<pre class="doctest-block">
&gt;&gt;&gt; import sys
&gt;&gt;&gt; from pyke import knowledge_engine
&gt;&gt;&gt; from pyke import krb_traceback
&gt;&gt;&gt;
&gt;&gt;&gt; my_engine = knowledge_engine.engine(__file__)
&gt;&gt;&gt; my_engine.activate('error_test')
&gt;&gt;&gt; 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 &quot;&lt;doctest other_functions.txt[19]&gt;&quot;, line 2, in &lt;module&gt;
my_engine.prove_1_goal('error_test.goal()')
File &quot;...knowledge_engine.py&quot;, line 366, in prove_1_goal
return goal.compile(goal_str).prove_1(self, **args)
File &quot;...goal.py&quot;, line 47, in prove_1
return iter(it).next()
File &quot;...rule_base.py&quot;, line 50, in next
return self.iterator.next()
File &quot;...knowledge_engine.py&quot;, line 41, in from_iterable
for x in iterable: yield x
File &quot;...knowledge_engine.py&quot;, line 41, in from_iterable
for x in iterable: yield x
File &quot;...error_test.krb&quot;, line 26, in rule1
goal2()
File &quot;...error_test.krb&quot;, line 31, in rule2
goal3()
File &quot;...error_test.krb&quot;, line 36, in rule3
goal4()
File &quot;...error_test.krb&quot;, line 41, in rule4
check $bar &gt; 0
File &quot;...contexts.py&quot;, line 231, in lookup_data
raise KeyError(&quot;$%s not bound&quot; % var_name)
KeyError: '$bar not bound'
</pre>
</blockquote>
</div>
<div class="section" id="miscellaneous">
<h2>Miscellaneous</h2>
<p>There are a few more functions that may be useful in special situations.</p>
<dl class="docutils">
<dt><em>some_engine</em>.add_case_specific_fact(kb_name, fact_name, args)</dt>
<dd>This is an alternate to the <tt class="docutils literal">assert_</tt> function.</dd>
<dt><em>some_engine</em>.get_kb(kb_name)</dt>
<dd>Finds and returns the <a class="reference external" href="../knowledge_bases/index.html">knowledge base</a> by the name <tt class="docutils literal">kb_name</tt>. Raises
<tt class="docutils literal">KeyError</tt> if not found. Note that for <a class="reference external" href="../knowledge_bases/rule_bases.html">rule bases</a>, this returns the
active <a class="reference external" href="../knowledge_bases/rule_bases.html">rule base</a> where <tt class="docutils literal">kb_name</tt> is the <a class="reference external" href="../knowledge_bases/rule_bases.html#rule-base-categories">rule base category</a> name.
Thus, not all <a class="reference external" href="../knowledge_bases/rule_bases.html">rule bases</a> are accessible through this call.</dd>
<dt><em>some_engine</em>.get_rb(rb_name)</dt>
<dd>Finds and returns the <a class="reference external" href="../knowledge_bases/rule_bases.html">rule base</a> by the name <tt class="docutils literal">rb_name</tt>. Raises
<tt class="docutils literal">KeyError</tt> if not found. This works for any <a class="reference external" href="../knowledge_bases/rule_bases.html">rule base</a>, whether it
is <a class="reference external" href="../knowledge_bases/rule_bases.html#rule-base-activation">active</a> or not.</dd>
<dt><em>some_engine</em>.print_stats([f = sys.stdout])</dt>
<dd>Prints a brief set of statistics for each knowledge base to file <tt class="docutils literal">f</tt>.
These are reset by the <tt class="docutils literal">reset</tt> 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.</dd>
</dl>
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<h3>More:</h3>
<div class="right-item"><a href="creating_engine.html">Creating an Inference Engine Object</a><p>How to create a Pyke <em>inference engine</em> object.</p>
</div>
<div class="right-item"><a href="adding_facts.html">Asserting New Facts</a><p>How to dynamically assert new <em>facts</em> from your Python program.</p>
</div>
<div class="right-item"><a href="proving_goals.html">Proving Goals</a><p>Using Pyke's API to prove goals from your Python program.</p>
</div>
<div class="right-item"><a href="other_functions.html">Other Functions</a><p>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.</p>
</div>
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Copyright &copy; 2007-2009 Bruce Frederiksen
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Page last modified
Fri, Mar 12 2010.
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