The index of Uxi comes out before the bang, and you're using the index to pack things into the coll, so consequently, you're packing the previous value. If you use an int on the index, and clock it out with the random, you will get what you expect..

Thanks - couldn't see for looking! I've been using an abstraction for years that had that little bug in it, and never noticed until yesterday; I feel cleaner now! Cheers Roger