Will Robertson wrote: > Ideally, I'd like to be able to write \def\foo{bar} and know whether > or not \foo is expandable; until reading about this test I didn't think > such a thing was even possible. > > Any comments? This won't work, will it? A more complex example: \def\foo{\edef\bar{stuff}} is not fully expandable, but if you get the test working should give \c_true. So I think this might not be a good idea. (I assume that this test is supposed to see if something is a macro. I do that in siunitx, but using \meaning and looking for "macro".) Joseph