Has anyone ever needed to "shuffle" an NArray? I can certainly convert
it to an array and do the sort_by {rand} idiom, and then convert it
back. I currently:

na.size.times do
  p1,p2 = rand(na.size),rand(na.size)
  na[p1],na[p2] = na[p2],na[p1]
end

which works, but I wondering if anyone knew a better way.
Thanks
pth