shuffle

4 years ago · 33383583ac
parent af3c747de5
commit 33383583ac
1 changed files with 12 additions and 0 deletions
--- a/cl-rng.lisp
+++ b/cl-rng.lisp
@ -26,3 +26,15 @@

 (export 'weighted)

+(defun shuffle! (sequence &key (provider *default-randomness-provider*))
+  (if (listp sequence)
+      (loop for i from (1- (length sequence)) above 0 do
+	   (rotatef (nth i sequence)
+		    (nth (funcall provider :limit i :transform #'floor) sequence)))
+      (loop for i from (1- (length sequence)) above 0 do
+	   (rotatef (aref sequence i)
+		    (aref sequence (funcall provider :limit i :transform #'floor)))))
+  sequence)
+
+(export 'shuffle!)
+