Implement till 5.8

ex-5_01-06.scm

@@ -119,11 +119,11 @@
         (goto (label expt-loop))
       after-expt
         (restore continue)
-        (assign val (op *) (reg b) (reg val))   ; val now contains n(n - 1)!
-        (goto (reg continue))                   ; return to caller
+        (assign val (op *) (reg b) (reg val))
+        (goto (reg continue))
       base-case
-        (assign val (const 1))                  ; base case: 1! = 1
-        (goto (reg continue))                   ; return to caller
+        (assign val (const 1))
+        (goto (reg continue))
       expt-done)))
 
 (set-register-contents! expt-rec-machine 'b 3)