>>>>> "P" == Paul Brannan <pbrannan / atdesk.com> writes:

P> Perhaps posting this is not wise, but here is an implementation, with
P> some examples.  Maybe this will make the problem more concrete, or maybe
P> it is a Pandora's box.  Read it at your own risk.

 Well, this is not really the reverse of the algorithm for #succ. You can
 see it for example with "9%".

 With your algorithm the result is "9$", but for ruby "8%".succ is "9%"
 (i.e. it search first if it exist alpha-numeric character in the string
 and if found it make the increment on these characters.)


Guy Decoux