I may have asked this before. If I have, please forgive me for asking
again.
Suppose I have variables X1 ... Xn and Y1 ... Yn, with the constraints
distinct(X1, ..., Xn)
distinct(Y1, ..., Yn)
I now want to add the constraint:
Yi notin {Xj | j != i}, for i = 1 ... n
What would be the most efficient way to do this?
I could, of course, express it as:
Yi != X0
Yi != X1
...
Yi != Xi-1
Yi != Xi+ 1
...
Yi != Xn
The downside of this is that it would introduce a bunch of boolean
variables to keep track of.
Alternatively. I could say:
distinct(X1, .., Xi-1, Yi, Xi+1, ... Xn)
which is overkill, but doesn't add any extra constraints that are not
already covered by the original distinct(X1, ..., Xn) constraint.
Any suggestions as to which is likely to be better? Or is there
another way?
Malcolm
--
"Cleanliness is not next to godliness nowadays,
for cleanliness is made an essential
and godliness is regarded as an offence.
- G.K.Chesterton, On Lying in Bed
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