16 lines
658 B
Common Lisp
16 lines
658 B
Common Lisp
(defun all-subsequences2 (list)
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(labels ((recurse (s list)
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(if (endp list)
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(if (>= s 3)
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'(())
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'())
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(let ((x (car list))
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(xs (cdr list)))
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(if (evenp s)
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(append (mapcar (lambda (ys) (cons x ys))
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(recurse (+ s 1) xs))
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(recurse s xs))
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(append (mapcar (lambda (ys) (cons x ys))
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(recurse s xs))
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(recurse (+ s 1) xs)))))))
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(recurse 0 list)))
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