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/*
* Copyright 2003,2004 The Apache Software Foundation.
*
* Licensed 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.commons.functor;
/**
* A functor that takes two arguments and returns an <code>Object</code> value.
* <p>
* Implementors are encouraged but not required to make their functors
* {@link java.io.Serializable Serializable}.
* </p>
* @since 1.0
* @version $Revision$ $Date$
* @author Rodney Waldhoff
*/
public interface BinaryFunction {
/**
* Evaluate this function.
*
* @param left the first element of the ordered pair of arguments
* @param right the second element of the ordered pair of arguments
* @return the result of this function for the given arguments
*/
Object evaluate(Object left, Object right);
/**
* Returns a human readable description of this functor.
* Implementators are strongly encouraged but not
* strictly required to override the default {@link Object}
* implementation of this method.
*
* @return a human readable description of this functor
*/
String toString();
/**
* Returns a hash code for this functor adhering to the
* general {@link Object#hashCode Object.hashCode} contract.
* Implementators are strongly encouraged but not
* strictly required to override the default {@link Object}
* implementation of this method.
*
* @see #equals
* @return a hash code for this functor
*/
int hashCode();
/**
* Indicates whether some other object is &quot;equal to&quot;
* this functor. This method must adhere to
* general {@link Object#equals Object.equals} contract.
* Additionally, this method can return
* <tt>true</tt> <i>only</i> if the specified Object implements
* the same functor interface and is known to produce the same
* results and/or side-effects for the same arguments (if any).
* <p>
* While implementators are strongly encouraged to override
* the default Object implementation of this method,
* note that the default Object implementation
* does in fact adhere to the functor <code>equals</code> contract.
* </p>
* @param that the object to compare this functor to
* @see #hashCode
* @return <code>true</code> iff the given object implements
* this functor interface, and is known to produce the same
* results and/or side-effects for the same arguments
* (if any).
*/
boolean equals(Object that);
}