A Lisp Production System for Translation into Roman Numerals

(defun to-roman () (let ((n nil))(loop (cond

((null n)

(setq n (read)))

((equal n 0)

(terpri) (setq n nil))

((and (numberp n)(> n 0)(< n 4))

(princ #\I)(decf n))

((and (numberp n)(= n 4))

(format t "IV")(decf n 4))

((and (numberp n)(< n 9))

(princ #\V)(decf n 5))

((and (numberp n)(> n 9)(< n 40))

(princ #\X)(decf n 10))

(t (format t "cannot handle ~S~%" n)(setq n nil))

) ) ) )

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