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Message-ID:  <4993CA61.4030609@morningstar2.co.uk>
Date:         Thu, 12 Feb 2009 07:06:09 +0000
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From: Joseph Wright <joseph.wright@MORNINGSTAR2.CO.UK>
Subject: Re: token_if_expandable
To: LATEX-L@LISTSERV.UNI-HEIDELBERG.DE
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Status: R

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