anchor.diff:  (defmacro variable-level (x)
     `(car ,x))
   
  -(eval-when (eval compile load)
  +(eval-when (:compile-toplevel :load-toplevel :execute)
     (defmacro variable-value (x)
       #+include-name-in-variable `(cadr ,x)
       #-include-name-in-variable `(cdr ,x)))
  
positive.code: 
  (in-package #:pttpp)
  
  (eval-when (eval compile load)
    (setq *print-radix* nil))
  
  (eval-when (eval compile load)
    (defmacro stack-let (bindings &body body)
      ;; stack-let on the 3600 is like let except variable values are
      ;; consed on the stack, not in the heap thereby diminishing
  
negative.code: ;; for unbound variables this encoding assumes that integers will not be used
  ;; as functors
  
  ;;(eval-when (:compile-toplevel :load-toplevel :execute)
  ;;  (pushnew :include-name-in-variable *features*))
  
  (defun new-variable (var-name var-level)
  