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Message-ID:  <54533878.5030100@morningstar2.co.uk>
Date:         Fri, 31 Oct 2014 07:21:28 +0000
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From: Joseph Wright <joseph.wright@MORNINGSTAR2.CO.UK>
Subject: Re: group level and document commands
To: LATEX-L@LISTSERV.UNI-HEIDELBERG.DE
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Status: R

On 31/10/2014 05:44, aparsloe wrote:
> A section of code that worked for me in July only partly works now. One
> issue that I've noticed is that
> 
> \group_begin:
> ...
> \DeclareDocumentCommand \test ...
> ...
> \group_end:
> 
> will not in fact create a document command \test -- I get an "Undefined
> control sequence" message when I try to use it in the wider document.
> The declaration must be outside the group commands -- at least that is
> what my experiments tell me. (But \test is recognised within the group
> commands.) Is that correct? And is it new? -- I don't recall meeting
> this issue back in July.
> 
> The xparse documentation doesn't seem to mention this issue and perhaps
> should. I can understand the documenters assuming that a document-wide
> command would only be defined at the highest level, but in my context
> (working with instant preview in LyX) it was quite natural to define it
> within the \group_begin:, \group_end: commands of another funtion. I've
> changed that now which has resolved at least some of the problem.
> 
> Andrew

xparse has never created global commands: they are local to TeX groups.
This has not changed recently, so I am not sure why you've not noticed
it before.

The question of dealing with context-dependent commands is still an open
one, but at the moment having \DeclareDocumentCommand respect grouping
seems to be the most sensible approach.
--
Joseph Wright