On Mon, 27 Apr 2009 20:27:07 -0700, William Clifford wrote: > For some reason I thought I needed this code, but it turns out I don't, > really. > I need something weirder. Anyway, maybe someone else could use this. > > def enrag(start, stop=None, step=1): > '''Yield a range of numbers from inside-out, evens on left.''' [snip code]
Interesting. That's equivalent to a reverse followed by a Monge Shuffle. http://mathworld.wolfram.com/MongesShuffle.html http://en.wikipedia.org/wiki/Shuffling_playing_cards#Mongean_shuffle I wrote a similar function to do this: def monge_shuffle(deck): if len(deck) % 2: # Odd number of items. deck[:] = deck[0::2] + deck[1::2][::-1] else: # Even number of items. deck[:] = deck[1::2] + deck[0::2][::-1] return deck >>> list(enrag(20)) [18, 16, 14, 12, 10, 8, 6, 4, 2, 0, 1, 3, 5, 7, 9, 11, 13, 15, 17, 19] >>> monge_shuffle(range(20)[::-1]) [18, 16, 14, 12, 10, 8, 6, 4, 2, 0, 1, 3, 5, 7, 9, 11, 13, 15, 17, 19] >>> list(enrag(203)) == monge_shuffle(range(203)[::-1]) True I'm curious what your "something weirder" was. -- Steven -- http://mail.python.org/mailman/listinfo/python-list
