formatting floats (adaptive 16 or 17 decimal precision)

[Jean-Luc-Picard-2021]

Currently GNU Prolog shows me:

/* GNU Prolog 1.5.0 */

?- X is 0.1+0.1+0.1+0.1+0.1+0.1+0.1+0.1.
X = 0.79999999999999993

?- 0.79999999999999993 == 0.7999999999999999.
Yes

?- X is 23/10.
X = 2.2999999999999998

?- 2.2999999999999998 == 2.3.
Yes

An algorithm which would first probe 16 decimal precision, could produce 2.3 and 0.7999999999999999, which looks to me the more common result among Prolog systems,

and is shorter and still valid result. You can try SWI-Prolog:

/* SWI-Prolog 9.3.8 */

?- X is 0.1+0.1+0.1+0.1+0.1+0.1+0.1+0.1.
X = 0.7999999999999999.

?- X is 23/10.
X = 2.3.