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From: Joseph Wright <joseph.wright@MORNINGSTAR2.CO.UK>
Subject: Tools for processing numbers
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Hello all,

I've been giving some thought to examining how to re-write siunitx in
expl3.  I've made some progress on the options side (hence keys3), but
I'm now thinking a little about the number analysis part.

I wonder if it might be useful to create a lower-level tool package for
processing numbers.  I was thinking that the following might be useful:
- Something like \ifinteger, \ifnumber, etc. as in biblatex
- Ability to parse numbers as in siunitx
- More structured returning of parsed value

The last point is relevant as siunitx uses a number of hacks to get the
appropriate data out.  I think it might be better to provide something like:

<sign><pre-decimal><post-decimal><sign-exp><pre-decimal-exp><post-decimal-exp>

or

<sign><mantissa><sign><exponent>

in a structured return format (errors to be thought about).  Does
something like this sound useful as a more generalised package?
-- 
Joseph Wright