Precision of `Double's in Hugs

[D. Tweed]

On Sun, 13 Jan 2002, Liyang Hu wrote:

> > From a bit of browsing the code, it appears that setting
> > USE_DOUBLE_PRECISION will increase the precision of both Float
> > and Double types.

Note that I'd recommend getting some clarification about this from either
the current hugs team or Mark Jones (who are probably reading this list),
as I can vaguely recall a couple of times over the last few years where
Mark Jone has said `Hugs should not be used for serious numerical work'
without saying whether this is fixed just by that #define. I could imagine
that there might be several other, deeper assumptions about using float's
for both Float and Double in the source, e.g., if you pass a double to a
Prelude math fn it does get passed in directly to an appropriate one and
not cast to a float before being passed, etc. Hopefully there aren't any
problems like this, but the worst thing would be to end up in the worst of
both worlds where you pay the storage space for doubles and yet don't
_reliably_ get more than float precision.

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