31 lines
864 B
Common Lisp
31 lines
864 B
Common Lisp
; prints recursive list structure
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;(let (seen-list)
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(setf seenlist nil)
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(defun seenp (l) (member l seenlist :test 'eq))
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(defun make-seen (l) (setf seenlist (cons l seenlist)))
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(defun printrec (l) (printrec-any l) (setf seenlist nil))
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(defun printrec-any (l)
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(cond ((atom l) (prin1 l) (princ " "))
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((seenp l) (princ "<...> "))
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(t
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(make-seen l)
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(princ "(")
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(printrec-list l)
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(princ ") ")))
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nil)
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(defun printrec-list (l)
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(printrec-any (car l))
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(cond ((cdr l)
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(cond ((seenp (cdr l))
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(princ "<...> "))
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((atom (cdr l))
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(princ ". ")
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(prin1 (cdr l))
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(princ " "))
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(t
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(make-seen (cdr l))
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(printrec-list (cdr l))))))
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nil)
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; )
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