/* XXL: The eXtensible and fleXible Library for data processing
Copyright (C) 2000-2011 Prof. Dr. Bernhard Seeger
Head of the Database Research Group
Department of Mathematics and Computer Science
University of Marburg
Germany
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 3 of the License, or (at your option) any later version.
This library 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
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with this library; If not, see <http://www.gnu.org/licenses/>.
http://code.google.com/p/xxl/
*/
package xxl.core.predicates;
import java.util.ArrayList;
import java.util.List;
import xxl.core.functions.Function;
/**
* This class provides a decorator predicate that applies a fixed number number
* of mapping functions to the arguments of the underlying predicate. Everytime
* arguments are passed to an <code>invoke</code> method of this class, the
* arguments are seperately mapped using a given mapping functions and
* afterwards passed to the <code>invoke</code> method of the underlying
* predicate.
*
* @param <P> the type of the predicate's parameters.
* @param <R> the type of the underlying predicate's parameters (the return
* type of the mapping functions).
*/
public class MultiFeaturePredicate<P, R> extends AbstractPredicate<P> {
/**
* A reference to the predicate to be decorated. This reference is used to
* perform method calls on the underlying predicate.
*/
protected Predicate<? super R> predicate;
/**
*
* An array of mapping functions that are applied to the arguments of this
* predicate's <code>invoke</code> methods before the <code>invoke</code>
* method of the underlying predicate is called.
*/
protected Function<? super P, ? extends R>[] mappings;
/**
* Creates a new feature predicate that separately applies the specified
* mapping functions to the arguments of it's <code>invoke</code> methods
* before the <code>invoke</code> method of the given predicate is called.
*
* @param predicate the predicate which input arguments should be mapped.
* @param mappings the mapping functions that are applied to the arguments
* of the wrapped predicate.
*/
public MultiFeaturePredicate(Predicate<? super R> predicate, Function<? super P, ? extends R>... mappings) {
this.predicate = predicate;
this.mappings = mappings;
}
/**
* Returns the result of the predicate as a primitive boolean value. The
* mapped arguments of this method are passed to the underlying predicate's
* <code>invoke</code> method.
*
* @param arguments the arguments to the predicate.
* @return the result of the predicate as a primitive boolean value.
*/
@Override
public boolean invoke(List<? extends P> arguments) {
List<R> mappedArguments = new ArrayList<R>(arguments.size());
for (Function<? super P, ? extends R> mapping : mappings)
mappedArguments.add(mapping.invoke(arguments));
return predicate.invoke(mappedArguments);
}
}