Thanks for your help Hans and the pointer to the extended math library.
Lots more to explore now.
Best Wishes
Keith

On Sat, 16 May 2020, 20:46 Hans Hagen, <j.hagen@xs4all.nl> wrote:

> On 5/16/2020 4:48 PM, Keith McKay wrote:
> > Answering my own problem here.
> >
> > I've just searched through the mailing list archives and it seems that
> > if I add [instance=doublefun] I do not get the Arithmetic Overflow
> > error. Joy!
> fwiw, we have also instance=decimalfun
>
> concerning arithmic:
>
> in metapost we have
>
> scaled  : upto 4K bp
> double  : 64 bit floats
> decimal : configurable accuracy
> complex : dual doubles (only in luametafun)
>
> in lmtx lua we have:
>
> integer  : lua tries to be clever but mixing leads to double
> float    : lua tries to be clever
> decimal  : userdata arbitrary precision (only in lmtx)
> complex  : userdata dual doubles (only in lmtx)
>
> (in lmtx we have an extended math library and these function are also
> available in luametafun)
>
> Hans
>
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>                                            Hans Hagen | PRAGMA ADE
>                Ridderstraat 27 | 8061 GH Hasselt | The Netherlands
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