8 lines
342 B
Common Lisp
8 lines
342 B
Common Lisp
(defun december-31-weekday (year)
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(mod (+ year (floor year 4) (- (floor year 100)) (floor year 400)) 7))
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(defun iso-long-year-p (year)
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(or (= 4 (december-31-weekday year)) (= 3 (december-31-weekday (1- year)))))
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(format t "Long years between 1800 and 2100:~&~a~%"
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(loop for y from 1800 to 2100 if (iso-long-year-p y) collect y))
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