Exponentiation is one more case in the operator switch, computed with the host language’s power function. The single-line change is small, but the value it produces is the proof that the right-associative parsing from the earlier chapter was correct. 2 ^ 3 ^ 2 evaluates to 512, because the tree grouped it as 2 ^ (3 ^ 2), which is 2 ^ 9. Had it grouped the other way, you would get (2 ^ 3) ^ 2 = 64 instead.

This is the satisfying part of separating parsing from evaluation: the evaluator does nothing clever about associativity or precedence at all. It blindly walks whatever tree it is handed. All the difficult decisions were made once, in the binding powers, and every operator you evaluate simply inherits them.