CLP - missing variable binding

#1

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?

?- 2X+Y #= 5 , 2Y +X #= 7 , [Y,X] ins -1000000…sup.
X = 1,
Y = 3.

?- 2X+Y #= 5 , 2Y +X #= 7 , [Y,X] ins inf…100000.
X = 1,
Y = 3.

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

I would appreciate any comment or pointer to further reading.

Thanks,

Stefan

#2

The FD in CLPFD means “finite domain” and inf…sup is not finite, so it returns the relation instead.

#3

Sorry, but -1000000…sup is also not finite, but yields a solution, i.e. can be solved. Why that?

#4

Iam,

-1000000…sup has a finite beginning, which alows the engine to have a starting point.