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Date:         Tue, 30 Apr 2013 08:42:32 +0100
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From: Joseph Wright <joseph.wright@MORNINGSTAR2.CO.UK>
Subject: Re: Behaviour of \SplitArgument with missing input
To: LATEX-L@LISTSERV.UNI-HEIDELBERG.DE
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Status: R

On 29/04/2013 19:50, scott heard wrote:
> Hello, forgive (and correct) me if I misunderstand how this command should
> be used:
>
>   \DeclareDocumentCommand { \foo }
>     { > { \SplitArgument { 2 } { ; } } m }
>     { \my_command:nnn #1 }
>
> As the output of '\SplitArgument' is some number of brace groups lumped
> together into a '#1', it seems like a test for '-NoValue' would need to be
> moved into '\my_command:nnn', i.e. from the xparse interface, into
> "programmer code".  As `\IfNoValueTF' is an xparse command, that doesn't
> feel correct.  If this is a reasonable interpretation/usage, then my
> personal opinion would be that empty brace groups (or something else)
would
> be preferable to -NoValue-'s.
> scott

That's a separate but related point, and the one I eluded to in my
original e-mail. I've been asked about how one is expected to test for
the '-NoValue-' in the use case outlined, and to provide a code level
interface or (I guess) some guidance on what the team feel is 'correct'
in terms of testing.

I thought it was best to pin down what is the 'correct' behaviour of
\SplitArgument first. However, it is a fair point that this might affect
the desired behaviour. I'd like to see what people feel is needed from
\SplitArgument. (It might turn out we'd prefer to have a different but
code-level testable marker, for example, although that sounds like a lot
of effort.)
-- 
Joseph Wright