application/octet-stream
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910 B
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34 lines
;; The biggest product of 2 3-digit numbers that is a palindrome
;; https://projecteuler.net/problem=4
(defun reverse-num (a)
(declare (fixnum a))
(let ((ret 0))
(declare (fixnum ret))
(loop while (> a 0) do
(progn (setf ret (+ (* ret 10) (rem a 10)))
(setf a (floor a 10))))
ret))
(defun palindrome? (a)
(declare (fixnum a))
(eq a (reverse-num a)))
(defun start-search ()
(let ((max 0))
(declare (fixnum max))
(dotimes (a 1000 max)
(declare (fixnum a))
(dotimes (b 1000)
(declare (fixnum b))
(let ((p (* a b)))
(declare (fixnum p))
(when (and (palindrome? p)
(> p max))
(setf max p)))))))
(compile 'reverse-num)
(compile 'palindrome?)
(compile 'start-search)
(format T "The biggest product of 2 3-digit numbers that is a palindrome is: ~a~%" (start-search))
(quit)
