/*
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 org.openrdf.model.Value;
import org.openrdf.query.algebra.evaluation.ValueExprEvaluationException;
import org.openrdf.query.algebra.evaluation.util.QueryEvaluationUtil;
import com.bigdata.bop.BOp;
import com.bigdata.bop.IBindingSet;
import com.bigdata.bop.IValueExpression;
import com.bigdata.rdf.error.SparqlTypeErrorException;
import com.bigdata.rdf.internal.IV;
import com.bigdata.rdf.internal.impl.literal.XSDBooleanIV;
import com.bigdata.rdf.sparql.ast.FilterNode;
/**
* Calculates the "effective boolean value" of an IValueExpression. See the
* SPARQL spec for details.
*/
public class EBVBOp extends XSDBooleanIVValueExpression
implements INeedsMaterialization {
/**
*
*/
private static final long serialVersionUID = -5701967329003122236L;
@SuppressWarnings("rawtypes")
public EBVBOp(final IValueExpression<? extends IV> x) {
this(new BOp[] { x }, BOp.NOANNS);
}
/**
* Required shallow copy constructor.
*/
public EBVBOp(final BOp[] args, final Map<String, Object> anns) {
super(args, anns);
if (args.length != 1 || args[0] == null)
throw new IllegalArgumentException();
}
/**
* Constructor required for {@link com.bigdata.bop.BOpUtility#deepCopy(FilterNode)}.
*/
public EBVBOp(final EBVBOp op) {
super(op);
}
/**
* 11.2.2 Effective Boolean Value (EBV)
*
* Effective boolean value is used to calculate the arguments to the logical
* functions logical-and, logical-or, and fn:not, as well as evaluate the
* result of a FILTER expression.
*
* The XQuery Effective Boolean Value rules rely on the definition of
* XPath's fn:boolean. The following rules reflect the rules for fn:boolean
* applied to the argument types present in SPARQL Queries:
*
* The EBV of any literal whose type is xsd:boolean or numeric is false if
* the lexical form is not valid for that datatype (e.g.
* "abc"^^xsd:integer).
*
* If the argument is a typed literal with a datatype of xsd:boolean, the
* EBV is the value of that argument.
*
* If the argument is a plain literal or a typed literal with a datatype of
* xsd:string, the EBV is false if the operand value has zero length;
* otherwise the EBV is true.
*
* If the argument is a numeric type or a typed literal with a datatype
* derived from a numeric type, the EBV is false if the operand value is NaN
* or is numerically equal to zero; otherwise the EBV is true.
*
* All other arguments, including unbound arguments, produce a type error.
*
* An EBV of true is represented as a typed literal with a datatype of
* xsd:boolean and a lexical value of "true"; an EBV of false is represented
* as a typed literal with a datatype of xsd:boolean and a lexical value of
* "false".
*/
@Override
@SuppressWarnings("rawtypes")
public boolean accept(final IBindingSet bs) {
final IV iv = getAndCheckBound(0, bs);
if (iv instanceof XSDBooleanIV) {
return ((XSDBooleanIV) iv).booleanValue();
}
final Value val = super.asValue(iv);
try {
return QueryEvaluationUtil.getEffectiveBooleanValue(val);
} catch (ValueExprEvaluationException ex) {
throw new SparqlTypeErrorException();
}
}
/**
* The {@link EBVBOp} only needs materialization if its internal value
* expression does not evaluate to an {@link XSDBooleanIV}.
*/
@Override
public Requirement getRequirement() {
return INeedsMaterialization.Requirement.SOMETIMES;
}
}