/*
* Copyright (C) 2015 Open Whisper Systems
*
* 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, either version 3 of the License, or
* (at your option) any later version.
*
* 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, see <http://www.gnu.org/licenses/>.
*/
package org.anhonesteffort.flock.util.guava;
/**
* Determines an output value based on an input value.
*
* <p>See the Guava User Guide article on <a href=
* "http://code.google.com/p/guava-libraries/wiki/FunctionalExplained">the use of {@code
* Function}</a>.
*
* @author Kevin Bourrillion
* @since 2.0 (imported from Google Collections Library)
*/
public interface Function<F, T> {
/**
* Returns the result of applying this function to {@code input}. This method is <i>generally
* expected</i>, but not absolutely required, to have the following properties:
*
* <ul>
* <li>Its execution does not cause any observable side effects.
* <li>The computation is <i>consistent with equals</i>; that is, {@link Objects#equal
* Objects.equal}{@code (a, b)} implies that {@code Objects.equal(function.apply(a),
* function.apply(b))}.
* </ul>
*
* @throws NullPointerException if {@code input} is null and this function does not accept null
* arguments
*/
T apply(F input);
/**
* Indicates whether another object is equal to this function.
*
* <p>Most implementations will have no reason to override the behavior of {@link Object#equals}.
* However, an implementation may also choose to return {@code true} whenever {@code object} is a
* {@link org.anhonesteffort.flock.util.guava.Function} that it considers <i>interchangeable</i> with this one. "Interchangeable"
* <i>typically</i> means that {@code Objects.equal(this.apply(f), that.apply(f))} is true for all
* {@code f} of type {@code F}. Note that a {@code false} result from this method does not imply
* that the functions are known <i>not</i> to be interchangeable.
*/
@Override
boolean equals(Object object);
}