> >> I'm not sure how much useful it is.  And I'm (little bit) afraid of it
> >> might cause request for String#prev, which is way difficult to define.
> > 
> > IMO the *only* way to define String#prev is such that
> > aString.prev.succ == aString.succ.prev == aString.
> 
> This is not enough to uniquely define String#prev. 
> 
> 	"09".succ == "9".succ

Ehh... bad number/string to use as an example:

irb(main):001:0> "08".succ == "8".succ
false
irb(main):002:0> "08".succ
"09"
irb(main):003:0> "8".succ
"9"

-sc

-- 
Sean Chittenden