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 Thank you Luiz Henrique for sending 4.1-work4.
I suspect that my original http transfer got
cut short.

 I was praising Lua yesterday to an ex-student of
mine who is about to take up a job with a Dutch energy
company called Nuon. She will be working in the field
of risk assessment, using weather data. She was telling
me horror stories that she had come across about the
failings of numerical packages that use floating point
arithmetic. I was telling her about alternative data
formats for real numbers (e.g.
which although not always as fast do at least preserve the
rules of arithmetic and so might be considered a far
better bet for applications where accuracy had higher
priority than speed. Such is the dominance of floating
point that few people outside academe seem to realise
that alternatives exist, which may be far better suited
to certain commercial applications.

 It would be interesting to see Lua as a front end
for a system that used GMP and IC-Reals (Imperial College
Exact Real Arithmetic) instead of simply
fixed size integers and floating point reals. To do
this properly would entail merging the memory
allocation and garbage collection routines of all
three parts (Lua, GMP, IC-Reals). I doubt that Lua's
extensibility was originally planned with such
things in mind, but then I also suspect that Lua may
be far easier to adapt to such a project than anything
else. I hope that I am not starting up too many wild
hares by asking what others think of such a thing. 
I have a suspicion that very soon the commercial uses
of exact real arithmetic may be better appreciated,
and it would be nice if Lua were there, out in front.

Gavin Wraith (
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