Question about None

[Terry Reedy]

Paul LaFollette wrote:
> Thank you all for your thoughtful and useful comments.  Since this has
> largely morphed into a discussion of my 3rd question, perhaps it would
> interest you to hear my reason for asking it.
> 
> John is just about spot on. Part of my research involves the
> enumeration and generation of various combinatorial objects using what
> are called "loopless" or "constant time" algorithms.  (This means that
> the time required to move from one object to the next is bounded by a
> constant that is independent of the size of the object.  It is related
> to following idea:  If I generate all of the possible patterns
> expressible with N bits by simply counting in binary, as many as N
> bits may change from one pattern to the next.  On the other hand if I
> use Gray code only one bit changes from each pattern to the next.

But the number of bits you must examine to determine which to change is 
bounded by N and increases with N.