01: /*
02: * Copyright Aduna (http://www.aduna-software.com/) (c) 1997-2006.
03: *
04: * Licensed under the Aduna BSD-style license.
05: */
06: package org.openrdf.query.algebra;
07:
08: import java.util.Collections;
09: import java.util.Set;
10:
11: /**
12: * A tuple expression that contains exactly one solution with zero bindings.
13: */
14: public class SingletonSet extends QueryModelNodeBase implements
15: TupleExpr {
16:
17: public Set<String> getBindingNames() {
18: return Collections.emptySet();
19: }
20:
21: public <X extends Exception> void visit(QueryModelVisitor<X> visitor)
22: throws X {
23: visitor.meet(this );
24: }
25:
26: @Override
27: public SingletonSet clone() {
28: return (SingletonSet) super.clone();
29: }
30: }
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