I made some rather major changes to the parent node. I'm creating this new node so people interested in the topic notice the change.
Most of the changes were made to improve clarity. Despite the scope of the changes, the node is very similar to it's previous incarnation. (That's why I didn't create a new node.)
The most important change is the new section discussing the elimination of the very inefficient duplication in rules such as
pow : NUM '**' pow
In the spirit of the node in which it is contained, I refered to this as the "improving right-recursion", but the concepts can be applied to any rule with productions with a common prefix.