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Date:         Fri, 13 Aug 2010 13:23:31 +0100
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From: Joseph Wright <joseph.wright@MORNINGSTAR2.CO.UK>
Subject: l3fp: A floating point unit for expl3
To: LATEX-L@listserv.uni-heidelberg.de
Precedence: list
Status: R

Hello all,

A while ago I posted a message concerning my initial commit to the SVN 
of a module for LaTeX3 for mathematics with real numbers. After a bit of 
work (and some reading) I've decided that it is better to go with a 
floating point approach rather than the initial fixed point arithmetic. 
I've just committed the base arithmetic part of the module to the SVN.

The aim is to support two general areas, typesetting requirements and 
processing scientific data. For the arithmetic operations, I've 
therefore gone for an output precision of +-1 in the last (10th) place, 
and an input range up to 9.999999999e99. As this is all being done in 
TeX I hope that the balance makes sense to people.

The next thing to look at adding is trigonometric functions, as these 
are needed for typesetting arbitrary rotations. I'm also hoping to 
include exponents/logarithms when time allows. Obviously, I'd be happy 
to hear about other functions that might be useful or indeed better 
implementations for the ones that are provided.

The basic functions that I've added should hopefully work properly. I'm 
also hopeful that now I've had time to 'polish' things a bit these 
should be broadly stable. Please do try them out and report back any 
issues. I'll certainly be doing this in siunitx, where I'm planning to 
use the fpu to support some additional features.

An obvious approach to floating point work is to use LuaTeX, which can 
do these things natively. Currently, expl3 works across all of the 
modern engines, and so a LuaTeX-only solution isn't really applicable. 
However, I will be looking at using Lua when available. In the fpu 
context that will mean keeping the documented functions (\fp_add:Nn, 
etc.) but swapping out the internals to use the much faster native 
arithmetic Lua provides. I'll look at this area after the fpu covers 
trig and log functions.
-- 
Joseph Wright