On Apr 28, 12:19�am, William Clifford <mr.william.cliff...@gmail.com> wrote: > On Apr 27, 9:22�pm, Steven D'Aprano > > > > > > <ste...@remove.this.cybersource.com.au> wrote: > > 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.htmlhttp://en.wikipedia.or... > > > 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. > > Thanks for the links! Funny, while I worked on this I didn't think of > looking up card shuffling to see if there might be an algorithms for > it. I didn't think enrag (or her sister garne) would be unique, but I > didn't expect they could be useful either. Cool! > > I weirder I needed was to generate an Ulam spiral sequence like this: > > [4, 3, 2, > �5, 0, 1, > �7, 8, 9] > > I found a couple of ways, one of which I'm a somewhat happier with.
What's your solution (I got a couple, also). > > -- > William Clifford- Hide quoted text - > > - Show quoted text - -- http://mail.python.org/mailman/listinfo/python-list
