On 08/08/2009, at 10:46 PM, Joseph Wright wrote:

> Looking at some code related to building "latex3.ltx" (as an
> experiment), I notice that \ExplSyntax(On/Off) are not \protected. The
> plan is that all *user* functions should be robust, but how do people
> see this with design functions (not only the case in hand, but  
> anything
> else using mixed upper- and lower-case)?


Considering that the things that \ExplSyntaxXYZ do are not expandable,  
I think it would be correct to define them \protected.

Speaking generally, however, I'm not sure how much expansion we should  
be restricting. Lars in particular, recently, has been advocating  
keeping things expandable (and LuaTeX should broaden the applicability  
of what can be done there) but at this stage I've got nothing much to  
say :)

Will