E&S CVS Commit: PEAK-Rules - Added a generic version of the Chambers & Chen algorithm, with tests.

[pje at eby-sarna.com]

Author: pje
Date: Mon Jul  3 19:25:26 2006
New Revision: 2201

URL: http://svn.eby-sarna.com?rev=2201&view=rev
Log:
Added a generic version of the Chambers & Chen algorithm, with tests.  
Unlike the RuleDispatch implementation, this one doesn't care how 
indexes or criteria or expressions actually work, and it has a much 
simpler way of dealing with inter-expression constraints.  The tree 
building algorithm can also be easily revised to produce any kind of 
dispatch tree, either eagerly or lazily, and whether in the form of 
bytecode, source code, or an actual object tree.  (RuleDispatch only 
supports lazy creation of an object tree; it can't do anything else.)

Of course, this core algorithm is useless without some concrete types to 
represent expressions, criteria, and indexes -- not to mention some 
actual tree-generating code to go along with it.  But this algorithm for
generating decision trees will be at the heart of the main rule engine 
for predicate dispatching.

At this point, about 2/3rds of the code in the ``dispatch.functions``
module of RuleDispatch has been mapped to ``peak.rules.core`` and 
``peak.rules.indexing``.  About 1/6th of ``dispatch.strategy`` has also
been translated.  ``dispatch.ast_builder`` will not require any code
changes, but it will probably get some new tests.  The remaining modules,
however, (including ``strategy``, ``combiners``, and  ``predicates``)
will be changed substantially.

The good news is that these changes should mostly be simplifications, 
since most of the ``predicates`` module will become calls to 
BytecodeAssembler APIs.  But the remaining parts of ``strategy`` and 
``functions`` will likely become more complex, because they will need 
to know how to generate decision-making bytecode, deal with rule 
removals, and a few other odds and ends.  Some additional code will also 
be needed to ensure that the core implementation is sufficiently 
extensible to allow new features (like predicate abstractions and 
classifiers) to be implemented.

Added:
    PEAK-Rules/Indexing.txt   (with props)
    PEAK-Rules/peak/rules/indexing.py   (with props)
Modified:
    PEAK-Rules/test_rules.py