Expr right = null;
RelationDescriptor relation = null;
+ public Set freeVars() {
+ Set lset=left.freeVars();
+ Set rset=right.freeVars();
+ if (lset==null)
+ return rset;
+ if (rset!=null)
+ lset.addAll(rset);
+ return lset;
+ }
+
public TupleOfExpr(Expr left, Expr right, RelationDescriptor relation) {
if ((left == null) || (right == null) || (relation == null)) {
throw new NullPointerException();