On 23/08/2011, at 4:44 AM, Joseph Wright wrote:

> I have added the scheme broadly as outlined above to l3keys. Feedback
> would be welcome. For example, does 'set_known' convey the appropriate
> idea? Show the variable used for storing the 'return' value be fixes, or
> flexible as in
> 
>  \keys_set_known:nnN { <module> } { <keys> } <return-var>


I slightly prefer having an explicit <return-var>. Not only is the resultant code a little clearer (using, say, \l_fontspec_features_tl instead of \l_keys_leftovers_tl) but also allows some interleaving where you otherwise might have to manually push/pop the value of \l_keys_leftovers_tl.

Cheers,
-- Will