initial commit

cube-scrambler.el

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+(defvar cube-faces "UDLRFB")
+
+(defun cube-scramble (moves)
+  "Generates a list of random scramnles for a 3x3 Rubik's cube and displays it.
+
+MOVES represents the number of moves in the list."
+  (interactive "p")
+  (message (mapconcat 'identity (cube-build-scramble moves) " ")))
+
+(defun cube-build-scramble (moves)
+  "Generates a list of random moves for a 3x3 Rubik's cube
+
+MOVES os the number of moves to generate.  The algorithm will not
+generate a sequence that moves the same face twice in a row."
+  (let (result last-face)
+    (while (> moves 0)
+      (setq last-face (cube-random-face last-face))
+      (push (cube-random-turn last-face) result)
+      (setq moves (1- moves )))
+    result))
+
+(defun cube-random-face (&optional last-face)
+  "Generates a random cube face
+
+If supplied, LAST-FACE will be excluded as a possibility."
+  (let ((faces (cube-filter cube-faces last-face)))
+    (elt faces (random (length faces)))))
+
+(defun cube-random-turn (face)
+  "Generates a random turn directio  for a given face
+
+FACE is a character representing the face to be turned."
+  (let ((suffix (pcase (random 3)
+                  (0 "")
+                  (1 "'")
+                  (2 "2"))))
+    (format "%c%s" face suffix)))
+
+(defun cube-filter (str char)
+  "Filters all instances of a character from a string"
+  (seq-filter (lambda (c) (not (equal c char))) str))