Constrains Member to be a one of the elements in Vars.
Note that this constraint has the same declarative semantics as the standard member/2 predicate, but the order of the arguments are reversed to allow the constraint to be used in constraint expressions.
You may find it more convenient to embed mem(Vars) in a constraint expression.
This constraint is implemented by Gecode's member() constraint.
ConsistencyModule is the optional module specification to give the consistency level for the propagation for this constraint: gfd_gac for domain (generalised arc) consistency.
[eclipse 7]: A :: 1..10, B :: 2..20, mem([A,B], M).
A = A{[1 .. 10]}
B = B{[2 .. 20]}
M = M{[1 .. 20]}
[eclipse 8]: A :: 1..10, B :: 2..20, mem([A,B], M), M #< 5.
A = A{[1 .. 10]}
B = B{[2 .. 20]}
M = M{[1 .. 4]}
[eclipse 9]: A :: 1..10, B :: 2..20, mem([A,B], M), M #< 2.
A = A{[1 .. 10]}
B = B{[2 .. 20]}
M = 1
[eclipse 10]: mem([4,5,5,4,1,5], C).
C = C{[1, 4, 5]}