itertools: followup to Alex Martelli problem ("number-in-base" ``oneliner'') and Bengt Richter solution

[anton muhin]

Hello, everybody!

Trying to solve the problem in the subj, I found that I miss some 
iterator-related tools. Mostly consequental application of the same 
function to some argument (if I'm not missing something it has a name 
y-combinator).

If we had one, generating the sequence of digits is easy:

iter(y(lambda (q, _): divmod(q, n), (x, 0)).next, (0, 0))

and if we have something like this in itertools

def y(f, x):
   while True:
     yield x
     x = f(x)

it might be one of simplest solutions possible.

I tried to emulate it in the way Bengt wrote his solution:

def y(f, x):
   return (h for t in [itertools.repeat(x)] for h, t in iter(lambda: 
(t.next(), itertools.imap(f, t)), None))

but it, should I say, a little bit too complex

Therefore, a couple of questions:

1) is there easier way to write y with genexps?
2) don't we need y in itertools?

Partially answering the second question: of course, y is too abstract 
and, at least IMHO, doesn't fit Python ideology. However, most of 
itertools IMHO is rather abstract :)

With the best regards,
anton.