6.9.2 FD Selection Constraint

The selection constraint exists in a version where the sequence contains only FD variables. It is exported on feature fd of module Select:

X={Select.fd [X1 ... Xn] I}

Here is how the information about X can be improved by this constraint. Since X must ultimately be identified with one Xi, its domain is at most the union of their domains (it cannot take other values than they can). More precisely, its domain is at most the union of the domains of the Xis at positions that are still in the domain of I (i.e. that may still be selected). In other words, if $I\in D$ , and $X_i\in D_i$ , then

$X\in\bigcup\limits_{i\in D}D_i$