RosettaCodeData/Task/Runtime-evaluation-In-an-environment/TXR/runtime-evaluation-in-an-environment-1.txr

(defun eval-subtract-for-two-values-of-x (code-fragment x1 x0)
  (- (eval ^(let ((x ,x1)) ,code-fragment))
     (eval ^(let ((x ,x0)) ,code-fragment))))

(eval-subtract-for-two-values-of-x 1 2) ;; yields -4.67077427047161