def enablePackrat():
if not ParserElement._packratEnabled:<EOL><INDENT>ParserElement._packratEnabled = True<EOL>ParserElement._parse = ParserElement._parseCache<EOL><DEDENT>
Enables "packrat" parsing, which adds memoizing to the parsing logic.
           Repeated parse attempts at the same string location (which happens
           often in many complex grammars) can immediately return a cached value,
           instead of re-executing parsing/validating code.  Memoizing is done of
           both valid results and parsing exceptions.

           This speedup may break existing programs that use parse actions that
           have side-effects.  For this reason, packrat parsing is disabled when
           you first import pyparsing.  To activate the packrat feature, your
           program must call the class method ParserElement.enablePackrat().  If
           your program uses psyco to "compile as you go", you must call
           enablePackrat before calling psyco.full().  If you do not do this,
           Python will crash.  For best results, call enablePackrat() immediately
           after importing pyparsing.