Can somebody direct me to a part/facility inside the Spirit library to do the following:

I need to pre-parce a boolean expression (once) and save it somewhere. Then I need to evaluate this expression (many times, performance important) based on different values of tokens.

Will Spirit.Classic do? Or do I need to use any of the newer libraries inside Spirit?

I belive you'll get more responses on Spirit-specific list: http://www.boost.org/community/groups.html#spirit