[XeTeX] Whitespace in input

[Philip TAYLOR]

Arthur Reutenauer wrote:
>> "The latter" is what the TeXbok says (P.~39) : "Once a category code
>> has been attached to a character token, the attachment is permanent."
>
>    Yes, because you meant individual tokens (which I understood in
> retrospect).  But in the context of the discussion, you really seemed to
> be saying that you could not change the \catcode's of characters to be
> read, which was the point (not that there is much point left to the
> whole threads any more...)

No no : changing catodes on the fly is standard TeX programming;
what we should not contemplate is changing the /number/ of catcodes
on the fly ...

** Phil.