Function: avy--de-bruijn

avy--de-bruijn is a natively compiled function defined in avy.el.

Signature

(avy--de-bruijn KEYS N)

Documentation

De Bruijn sequence for alphabet KEYS and subsequences of length N.

Source Code

;; Defined in /nix/store/015952xhg9b72ira1qyjvb30bn11jiv3-emacs-packages-deps/share/emacs/site-lisp/elpa/avy-20241101.1357/avy.el
(defun avy--de-bruijn (keys n)
  "De Bruijn sequence for alphabet KEYS and subsequences of length N."
  (let* ((k (length keys))
         (a (make-list (* n k) 0))
         sequence)
    (cl-labels ((db (T p)
                  (if (> T n)
                      (if (eq (% n p) 0)
                          (setq sequence
                                (append sequence
                                        (cl-subseq a 1 (1+ p)))))
                    (setf (nth T a) (nth (- T p) a))
                    (db (1+ T) p)
                    (cl-loop for j from (1+ (nth (- T p) a)) to (1- k) do
                         (setf (nth T a) j)
                         (db (1+ T) T)))))
      (db 1 1)
      (mapcar (lambda (n)
                (nth n keys))
              sequence))))