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?X &=< ?Y

X is before or equal to Y in the domain order
X
variable or domain value
Y
variable or domain value

Description

Constrains X and Y such that X is before Y or the same as Y in the domain order. X and Y must be variables or values of the same domain. If one of them is domain-less, it will be given the same domain as the other.

Modules

This predicate is sensitive to its module context (tool predicate, see @/2).

Examples

    ?- [X,Y] &:: weekday, X &=< Y.
    X = X{[mo, tu, we, th, fr, sa, su]}
    Y = Y{[mo, tu, we, th, fr, sa, su]}
    There is 1 delayed goal.
    Yes (0.00s cpu)

    ?- mo &=< th.
    Yes (0.00s cpu)

    ?- X &=< th.
    X = X{[mo, tu, we, th]}
    Yes (0.00s cpu)

    ?- fr &=< th.
    No (0.00s cpu)

    ?- X &=< Y.
    Arguments have no domains in X &=< Y in module eclipse
    Abort

    ?- X &:: weekday, X &=< red.
    Arguments have different domains (weekday,colour) in X &=< red ...
    Abort

See Also

&=< / 3, &< / 2, &> / 2, &>= / 2, &= / 2, &\= / 2, shift / 3, rotate / 3, domain / 1