Hello,
In gnu prolog 1.3.0 no value for X is found for the constraint X*X*X
#= 0 and additionally, gprolog states there is no solution:
| ?- X*X*X #= 0.
no
The problem comes from integer overflow (X*X*X computes the upper bound
as the max of X ** 3, which overflows the integer encoding). Generally
it is recommended to first define the domain of the variable (e.g. using
fd_domain) and then to add constraints. Example:
| ?- fd_domain(X,0,1000), X*X*X #= 0.
X = _#3(0..1000)
Note: in this example X=0 is not detected until labeling, but the
solution is obtained with a labeling:
| ?- fd_domain(X,0,1000), X*X*X#=0, fd_labeling(X).
X = 0 ? ;
no
It is better to use the ** operator (power) for this:
| ?- X**3 #= 0.
X = 0
On the other hand, the (correct) solution X #= 1 is found for X*X*X #= 1:
| ?- X*X*X #= 1.
X = 1
yes
and X #= 2 is found for X*X*X = 8.
GNU Prolog gives no solutions for X*X*X #= 27 (X #= 3), X*X*X #= 64 (X
#= 4), and even states there are none. Is this behaviour intentional?
| ?- fd_domain(X,0,1000), X*X*X#=27, fd_labeling(X).
X = 3
or better
| ?- X**3 #= 27.
X = 3
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