On Fri, Oct 25, 2013 at 9:59 PM, Joseph Wright
<[log in to unmask]> wrote:

>  - You want to make 'weird' chars (catcode tricks with \lowercase
>    primitive)

A thought:

Conceptually speaking, upper-case and lower-case are concepts that
have to do with letters, and making weird chars is a completely
unrelated feature. The \lowercase trick is what I would call an
implementation detail. With expl3 you have the opportunity to separate
the two concepts in the public interface. Give the weird-char
technique a different name... such as "bijective conversion".