This gives me a result:
?- {5/(X) = (5/2)}.
X = 2.0 ;
This shows me a constraint, but doesn't let me use X
in any material way:
?- {5/(3-X) = (5/2)}.
{-2.5+5/(3-X)=0.0}.
?- {5/(3-X) = (5/2)}, Z is X.
ERROR: Arguments are not sufficiently instantiated
Of course, if I explicitly give the solution, the constraint goes away and it evaluates as true.
?- {5/(3-X) = (5/2)}, X = 1.
X = 1.
Why, and how can I make it work?
See section A10.3 at https://www.swi-prolog.org/man/clpqr.html
However, clpBNR seems better: