Le 30/04/2013 16:06, Joseph Wright a écrit : > Providing optional values is another question: we can tackle that a bit > later (I hope). > > On where '-NoValue-' 'lives', the current approach is that it's an > xparse-only concept as it's provided by xparse and so not available if > you use > > \RequirePackage{expl3} > > you can't use it. I don't see that as a problem; the need currently only arises for users of xparse anyway. Why cannot xparse provide both \IfNoValueTF and a public \xparse_if_no_value:n(TF) ? > An alternative view is that it's a more general marker which can then be > defined at the token list level, with a test > > \tl_if_no_value:n(TF) > > [or similar: have to watch clash with \quark_if_no_value:n(TF)]. This > test would then be a code level equivalent of \IfNoValue(TF). It seems to me that the idea of a missing value only arises in cases where the input is not controlled (note that the low-level l3keys took another approach), as in user input via the LaTeX user interface; if some other packaqe one day needs to develop the same concept (say for file parsing) it would not be too late to add a function to the core kernel and make \xparse_if_no_value:n(TF) synonyms. Cheers, Julien "_FrnchFrgg_" Rivaud