Is there a way for the solve app to use exact figures?

[cdmackay]

(10-22-2020 04:36 PM)Albert Chan Wrote:  BTW, exact is a bad name. It really meant float2rational (conversion likely *not* exact)

For what it's worth (apologies if this is too off-topic, just ignore), my notes on exact() — largely pinched from Joe Horn; all mistakes are mine — say:

The abc key in CAS for Real input, executes exact()

exact() uses a simple continued-fraction algorithm; not as good as Joe's PDQ algorithm. The accuracy of exact() is controlled by CAS Settings — Epsilon, but has limited range.

Joe says:
The exact() function in CAS has three shortcomings
- it only finds answers which are principal convergents
- it only allows the tolerance (epsilon) to lie between 10^-6 and 10^-14
- it sometimes returns incorrect answers (outside the specified tolerance)

PDQ has none of these shortcomings
It always finds the unique best answer for any target and tolerance.

PDQ: https://www.hpmuseum.org/forum/thread-61.html