anchor.diff:  (definitial |t| *true*)
   (definitial |f| *false*)
   (definitial |nil| '())
  +(defprimitive |not| (lambda (x) (if (eq x *false*) *true* *false*)) 1)
   (defprimitive |cons| #'cons 2)
   (defprimitive |car| #'car 1)
   (defprimitive |cdr| #'cdr 1)
  
positive.code:     (loop
        (princ "> ")
        (with-simple-restart (abort "Return to Clutter's toplevel")
          (princ (evaluate (read) *global-env* *global-fenv*)))
        (fresh-line))))
  
  (defun eprogn (exps env fenv)
  
negative.code: (defprimitive |rplacd| #'rplacd 2)
  (defprimitive |eq?| (lambda (x y) (if (eq x y) *true* *false*)) 2)
  (defprimitive |eql?| (lambda (x y) (if (eql x y) *true* *false*)) 2)
  (defprimitive |symbol?| (lambda (x) (if (symbolp x) *true* *false*)) 1)
  (defprimitive |<| (lambda (x y) (if (< x y) *true* *false*)) 2)
  (defprimitive |>| (lambda (x y) (if (> x y) *true* *false*)) 2)
  (defprimitive |=| (lambda (x y) (if (= x y) *true* *false*)) 2)
  