Content-Type: text/plain; charset=us-ascii
Mime-Version: 1.0 (Apple Message framework v1081)
References: <AANLkTinjH5Ppg2QWWBTDBBU9u3Vvdsjnrrr1OvPvWfnA@mail.gmail.com>
            <DA7C7068-6B67-41E9-87F2-21C9E58249A8@gmail.com>
            <AANLkTimhF5fTJJoT3eKHrd=DZE4kOmg60R62pvqxDwDX@mail.gmail.com>
            <4028010D-1144-415D-A984-E3684A7E3EDE@gmail.com>
            <AANLkTi=Wj6whfFRMyr7jkmz+oG1CzO15S=DC2Zf=X_1A@mail.gmail.com>
            <4D5B770A.2000401@morningstar2.co.uk>
            <20110216105124.GA5579@oberdiek.my-fqdn.de>
            <4D5BAE81.4020904@morningstar2.co.uk>
            <AANLkTimE1h6e3W1tPTNP-ebvmMbwuAsct07A5TOqa611@mail.gmail.com>
Content-Transfer-Encoding: 8bit
Message-ID:  <E490BDF7-77A6-4788-842B-12AA97DC98B9@gmail.com>
Date:         Thu, 17 Feb 2011 00:20:23 +1030
Reply-To: Mailing list for the LaTeX3 project
              <LATEX-L@listserv.uni-heidelberg.de>
Sender: Mailing list for the LaTeX3 project <LATEX-L@listserv.uni-heidelberg.de>
From: Will Robertson <wspr81@GMAIL.COM>
Subject: Re: Expandable versions of \uppercase, \MakeUppercase, \lowercase, \MakeLowercase
To: LATEX-L@listserv.uni-heidelberg.de
In-Reply-To:  <AANLkTimE1h6e3W1tPTNP-ebvmMbwuAsct07A5TOqa611@mail.gmail.com>
Precedence: list
Status: R

On 16/02/2011, at 11:58 PM, Bruno Le Floch wrote:

> As I now understand, the key point in all of this is that we can
> detect spaces and braces expandably using delimited arguments, and we
> can then be sure to act on one token at a time.

Ah, I see:

    \long\gdef\UL_brace_check:nw#1#2#{%
      \UL_if_empty:nTF{#2}%
      {\UL_brace_yes:nn{#1}}%
      {\UL_space_check:nw{#1}#2}%
    }

This is clever. Has anyone seen this done before? Are there any downsides?

If it's as good as it seems then it allows all sorts of expandable things, such as optional argument parsing and expandable nested mapping.

Thanks!
-- Will