What is the purpose of the Visiter(s)?

Jan 31, 2009 at 7:35 PM
I am pretty familiar with all programming patterns (especially the visitor), however, I can't seem to understand what this visitor is actually doing?  Is there something under the hood that is translating all the "visit" methods?  Why have both a visitor and a translator?  Wouldn't the translator be the visitor while it parses through the Expression tree?  I guess it's probably from the lack of documentation that this part just isn't clear to me.