anchor.diff:    (cons x y))
   (defprimfun "cons?" (x)
     (consp x))
  +(defprimfun "list?" (x)
  +  (listp x))
   (defprimfun "car" (cons)
     (car cons))
   (defprimfun "cdr" (cons)
  
positive.code:       *true*
        *false*))
  
  (defprimop "set-var!" (*denv* env var value)
    (setf (lookup var (clutter-eval env *denv*)) (clutter-eval value *denv*)))
  
  (defprimop "def-var!" (*denv* env var value)
    (extend (clutter-eval env *denv*) var (clutter-eval value *denv*))
    var)
  
  
negative.code: (defprimfun "eval" (expression environment)
    (clutter-eval expression environment))
  
  (defprimfun "make-env" (&rest parents)
    (apply #'make-env parents))
  
  