This function returns a resource constraint predicate whose operator(const IlcResourceConstraint& rc) returns IlcTrue if and only if rc can be ranked first among the non-ranked resource constraints. In particular, it returns IlcFalse if rc is already ranked or if rc represents a virtual source or sink node (empty handle). This predicate is implemented using IlcResourceConstraint::isPossibleFirst.

This functions exists with either an IloEnv or an IloSolver as argument.