[Pyparsing] Is it possible to optimize this grammar?

[Gustavo N. <me...@gu...>]

Hello, everyone.

My Pyparsing grammar for boolean expressions [1] takes too much time to parse 
relatively complex expressions and I was wondering if it could be optimized 
somehow.

With it, my test suite takes ~1 hour to run, while the following individual 
expressions take the time specified on the right (in seconds):
 * 'user == "gustavo"' => 0.08
 * "weather:today_rains & (Pi > e | today_is_monday())" => 9.78
 * "W == 0   |   (X != 1   ^   (Y > 2   &   Z < 3))" => 676.20

Possibly the worst of all is that these are the results on a 64-bit, 2.50GHz, 
4GiB/RAM computer. So it will be many times slower on many computers. :(

Is there any way I could improve the performance of this parser?

Thanks in advance,

[1] I've excerpted the relevant code here (it's a simplified version of the 
actual code):
http://pyparsing.pastebin.com/f6a9c86ee
-- 
Gustavo Narea <xri://=Gustavo>.
| Tech blog: =Gustavo/(+blog)/tech  ~  About me: =Gustavo/about |