Exercise 5.7 (define expt-a (make-machine '(continue n b val) (list (list '= =) (list '- -) (list '* *)) '(machine (assign continue (label expt-done)) expt-loop (test (op =) (reg n) (const 0)) (branch (label immediate-answer)) (save continue) (assign continue (label afterexpt)) (assign n (op -) (reg n) (const 1)) (goto (label expt-loop)) afterexpt (restore continue) (assign val (op *) (reg b) (reg