On 03/01/2011 15:16, Will Robertson wrote:
> Not for xparse, no. We have steered away from offering features that will work sometimes but not always (with the exception of the expandable optional argument parsing, which is in a bit of a funny spot -- I lean toward suggesting it should be moved to another package).

On the expandable stuff, there are a lot of 'health warnings', and I 
think somewhere I said that this particular feature might not survive 
long-term.

(Totally agree on the general gist: anything which needs 'special 
consideration' at the argument level is beyond what xparse can do.)
-- 
Joseph Wright