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Message-ID:  <50470957.9040100@morningstar2.co.uk>
Date:         Wed, 5 Sep 2012 09:12:07 +0100
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Sender: Mailing list for the LaTeX3 project <LATEX-L@listserv.uni-heidelberg.de>
From: Joseph Wright <joseph.wright@MORNINGSTAR2.CO.UK>
Subject: Deprecated function: \tl_tail:w
To: LATEX-L@listserv.uni-heidelberg.de
Precedence: list
Status: R

Hello all,

The \tl_tail:w function is deprecated and will be removed from expl3
after 2012-12-31.

The background here is  that as implemented in the current release,
\tl_tail:n will strip the braces in output such as

  \tl_tail:n { a { b } }

but not

  \tl_tail:n { a { b } { c } }

An upcoming CTAN release will fix the behaviour of \tl_tail:n such that
braces will never be removed (the 'tail' will be 'what is left after
\tl_head:n has acted'). However, this cannot be fixed in \tl_tail:w, and
so we are removing it as documented.

The recommended replacement is

  \use_none:n <tokens to have head removed>

with either inside a \tl_if_blank:nF test or the use of an empty group

  \use_none:nn  <tokens to have head removed> { }

Also note that \tl_tail:n will prevent expansion of the result inside a
x-type expansion

  \tl_set:Nx { \tl_tail:n { <tokens> } }

and expands correctly inside an f-type expansion


  \tl_set:Nf { \tl_tail:n { <tokens> } }

and so the functionality of \tl_tail:w is very rarely required.
--
Joseph Wright