/*
Copyright (C) SYSTAP, LLC DBA Blazegraph 2006-2016. All rights reserved.
Contact:
SYSTAP, LLC DBA Blazegraph
2501 Calvert ST NW #106
Washington, DC 20008
licenses@blazegraph.com
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; version 2 of the License.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
package com.bigdata.rdf.internal.constraints;
import java.util.Map;
import com.bigdata.bop.BOp;
import com.bigdata.bop.IBindingSet;
import com.bigdata.rdf.error.SparqlTypeErrorException;
/**
* This class implements 'AS' in a projection as found in both
* subselects and bind, e.g.
* <pre>
* { SUBSELECT (Foo(?x) AS ?y) ...
* { ...
* }
* }
* </pre>
* or
* <pre>
* BIND (Bar(?x) AS ?y)
* </pre>
* The bind fails if the expression evaluates to some value that is different from
* a pre-existing binding for the target variable.
* If the expr (Foo or Bar above) has an error then the specification is that no binding is done,
* but the unbound value is a success.
*
* The specification for this operation is found as
* <a href="http://www.w3.org/TR/2013/REC-sparql11-query-20130321/#defn_extend">Extend</a>.
*
*/
@SuppressWarnings({ "unchecked", "rawtypes" })
public class ProjectedConstraint extends com.bigdata.bop.constraint.Constraint {
private static final long serialVersionUID = 1L;
public ProjectedConstraint(final BOp[] args, final Map<String, Object> annotations) {
super(args, annotations);
}
public ProjectedConstraint(final ProjectedConstraint op) {
super(op);
}
public ProjectedConstraint(ConditionalBind bind) {
super(new BOp[] { bind }, null);
}
@Override
public boolean accept(IBindingSet bindingSet) {
try {
Object result = ((ConditionalBind) get(0)).get(bindingSet);
return result != null;
} catch (SparqlTypeErrorException stee) {
// Extend(mu, var, expr) = mu if var not in dom(mu) and expr(mu) is an error (from the spec)
return true;
}
}
}