References: <55DBB7F6.1070307@clear.net.nz>
            <55DABA1D.3050706@morningstar2.co.uk>
            <55DCFDF7.7080305@clear.net.nz>
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.9; rv:38.0)
            Gecko/20100101 Thunderbird/38.2.0
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 8bit
Message-ID:  <55DEC161.4050901@morningstar2.co.uk>
Date:         Thu, 27 Aug 2015 08:50:57 +0100
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: Joseph Wright <joseph.wright@MORNINGSTAR2.CO.UK>
Subject: Re: Catcode changes
To: LATEX-L@LISTSERV.UNI-HEIDELBERG.DE
In-Reply-To:  <55DCFDF7.7080305@clear.net.nz>
Precedence: list
Envelope-To: <rainer.schoepf@GMX.NET>
Status: R

On 26/08/2015 00:44, aparsloe wrote:
> (2) Using \fp_to_scientific:n on the result of an l3fp calculation
> produces, say, 6.023e23. I want to write this as 6.023 \times 10^{23},
> but the "e" of 6.023e23 doesn't have its "usual" catcode so
> \tl_replace_once:Nnn doesn't find the "e". (I presume "e" has catcode
> "other" -- I haven't checked.) Hence I rescan 6.023e23 with an empty
> setup and then use \tl_replace_once:Nnn (which now does find the "e").

Your question has prompted us to take another look at
\fp_to_scientific:n/\fp_to_tl:n. The catcode of "e" is clearly not
expected here: I'm going to adjust to produce a 'letter'. We are
wondering about the wider use case for \fp_to_scientific:n: as it stands
the code doesn't *always* produce a number of the for

  [-]<digits>.<digits>e[-]<digits>

so it can't be parsed without some testing. That's little different to
\fp_to_tl:n, which in many ways might be more generally useful. Can you
fill us in on your use?

Joseph

P.S. Something seems to be up with your system/e-mail date settings: all
of your mail is from the future!