kind=defined
names=shuffle!
visibility=public

--- shuffle!        -> self

配列を破壊的にシャッフルします。

例:

   a = [ 1, 2, 3 ]           #=> [1, 2, 3]
   a.shuffle!                #=> [2, 3, 1]
   a                         #=> [2, 3, 1]

