I’m using: SWI-Prolog version 8.0.2-1

Why do I get no bindings for X and Y in the third query, although I get bindings in the first two queries?

?- 2*X+Y #= 5 , 2*Y +X #= 7 , [Y,X] ins -1000000…sup.

X = 1,

Y = 3.

?- 2*X+Y #= 5 , 2*Y +X #= 7 , [Y,X] ins inf…100000.

X = 1,

Y = 3.

?- 2*X+Y #= 5 , 2*Y +X #= 7 , [Y,X] ins inf…sup.

X+2*Y#=7,
2*X+Y#=5.

I would appreciate any comment or pointer to further reading.

Thanks,

Stefan