[Sean Chittenden]:
>> > 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:

The question is what "10".prev should be. String#succ is not injective
and thus does not have an inverse.

I don't think it is surjective either. There is no x such that

	x.succ == "a"

right? So what should "a".prev be?

// Niklas