internal Binary( RegOp op, RegExTree l, RegExTree r ) : base( op ) { lKid = l; rKid = r; }
internal Leaf( RegOp op ) : base( op ) { }
internal int maxRep; // max repetitions for finiteRep. internal Unary( RegOp op, RegExTree l ) : base( op ) { kid = l; }
internal RegExTree( RegOp op ) { this.op = op; }