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# shift(?X, ?C, ?Y)

Y is C places after X in the domain order
*X*
- variable or domain value
*C*
- variable or integer
*Y*
- variable or domain value

## Description

Constrains X and Y such that Y is C positions after X in the domain
order. C must be an integer or integer variable, and its range is
-(S-1)..S-1 where S is the size of the symbolic domain.
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.
The implementation achieves domain consistency iff C is instantiated
at call time, otherwise only bounds consistency.

### Modules

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

?- [X,Y] &:: weekday, shift(X, 1, Y).
X = X{[mo, tu, we, th, fr, sa]}
Y = Y{[tu, we, th, fr, sa, su]}
There is 1 delayed goal.
Yes (0.00s cpu)
[eclipse 4]: [X,Y]&::weekday, shift(X,C,Y).
X = X{[mo, tu, we, th, fr, sa, su]}
C = C{-6 .. 6}
Y = Y{[mo, tu, we, th, fr, sa, su]}
There are 3 delayed goals.
Yes (0.00s cpu)
?- shift(we, 1, th).
Yes (0.00s cpu)
?- shift(we, 2, fr).
Yes (0.00s cpu)
?- shift(X, -1, th).
X = fr
Yes (0.00s cpu)
?- shift(tu, X, fr).
X = 3
Yes (0.00s cpu)
?- shift(tu,X,Y).
X = X{-1 .. 5}
Y = Y{[mo, tu, we, th, fr, sa, su]}
Delayed goals: ...
?- shift(tu, 1, th).
No (0.00s cpu)
?- shift(X, 1, Y).
Arguments have no domains in shift(X, 1, Y) in module eclipse
Abort
?- X &:: weekday, shift(X, 1, red).
Arguments have different domains (weekday,colour) in shift(X, 1, red) ...
Abort

## See Also

shift / 4, &< / 2, &> / 2, &=< / 2, &>= / 2, &= / 2, &\= / 2, rotate / 3, domain / 1