Implement till 5.14

ex-5_07-13.scm

@@ -357,6 +357,14 @@
 (display "[ok]\n")
 
 (display "\nex-5.13 - dynamic-registers\n")
-;; (load "misc/sicp-regsim.scm")
 
-(display "TBD!\n")
+(define (lookup-register name)
+  (let ((val (assoc name register-table)))
+    (if val
+        (cadr val)
+        (begin  ;; Allocate register dynamically if needed
+          (allocate-register name)
+          (lookup-register name)))))
+
+(display "[ok]\n")
+