On Oct 4, 4:32 pm, Duncan Booth <[EMAIL PROTECTED]> wrote: > Duncan Booth <[EMAIL PROTECTED]> wrote: > > the invariant that you are looking for is that for all non-negative a, b: > > x[a:b:1] reversed is x[-len(x)+b-1:-len(x)+a-1:-1] > > I should of course have said "all a, b in the range 0 <= a <= len(x) and 0 > <= b <= len(x)".
Thanks, again! I figured it out from Fred's and your initial posts. IM(ns)HO, this is non-intuitive. I would expect that the reverse of x[i,j,k] would be x[j,i,-k]; eg; x[0:len(x):1] would be x[len(x):0:-1]. This representation is little more than syntactic sugar for x[y for y in range(i,j,k)], with a -1 adjustment to i and j if k is < 0 (due to the way range operates) and with appropriate boundary checking on i and j. The default values for i and j would become (0,len(x)), flopped for k < 0. There may be a good (or not-so-good) reason this representation wouldn't have worked or would have caused problems. Or maybe it is just personal preference. -- http://mail.python.org/mailman/listinfo/python-list
