/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.jena.graph.compose;
import org.apache.jena.graph.* ;
import org.apache.jena.util.iterator.* ;
/**
Class representing the dynamic set difference L - R of two graphs. This is updatable;
the updates are written through to one or other of the base graphs.
*/
public class Difference extends Dyadic implements Graph
{
/**
Initialise a graph representing the difference L - R.
*/
public Difference( Graph L, Graph R )
{ super( L, R ); }
/**
Add a triple to the difference: add it to the left operand, and remove it from the
right operand.
*/
@Override public void performAdd( Triple t )
{
L.add( t );
R.delete( t );
}
/**
Remove a triple from the difference: remove it from the left operand. [It could
be added to the right operand instead, but somehow that feels less satisfactory.]
*/
@Override public void performDelete( Triple t )
{ L.delete( t ); }
@Override public ExtendedIterator<Triple> _graphBaseFind( Triple t )
{ return L.find( t ). filterDrop ( ifIn( R ) ); }
}