This function creates and returns a constraint. When that constraint is posted, it insures that each value of the array vals will be required by exactly one set variable of the array vars.

If the argument vals is not mentioned, the array vals is formed by the union of the values involved in the set variables of vars.

In this context, a constraint will be posted after it has been added to a model and extracted by a solver (for example, an instance of IloSolver documented in the ILOG Solver Reference Manual).