Bitwise OR?

[Tim N. van der Leeuw]

I wonder what causes one version to be faster for positive, and the
other faster for negative numbers? I can see that the pos-version
doesn't make as many iterations as the neg version, but it doesn't pad
the length of the result to the requested number of digits and
potentially produces more digits.

I also wonder if it wouldn't be faster to put the numbers into a list
and join the list into a string -- did you test with that?

Cheers,

--Tim