RosettaCodeData/Task/Runtime-evaluation-In-an-environment/Common-Lisp/runtime-evaluation-in-an-environment-3.lisp

(defun eval-with-x (program a b)
  (let* ((f (compile nil `(lambda (x) ,program)))
         (at-a (funcall f a))
         (at-b (funcall f b)))
    (- at-b at-a)))