Re: How undefined is undefined behaviour?

[tehtmi <tehtmi@...>]

This point can surely be opposed, but I take the following perspective. 
Suppose we call "next" a few times, then add a new index, then call 
"next" again. Nothing formally connects the latter "next" call to the 
former. It is not an error to call "next" with whatever index (we do not 
need to start a "traversal" at the beginning nor proceed in any 
particular order); it just returns the next index like the manual says. 
The undefined behavior is only undefined based on an abstracted 
perspective ("traversal") which cannot be known by the language 
implementation, so the language implementation must not behave badly 
(nor even throw an error).

The statement in the manual is just a friendly reminder that the order 
of indices might change.