content: /**
   * Copyright (C) 2007 The Guava Authors
   *
   * 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 com.fernandocejas.arrow.functions;
  
  import org.jetbrains.annotations.Nullable;
  
  /**
   * Determines an output value based on an input value.
   *
   * <p>The {@link Functions} class provides common functions and related utilites.
   *
   * <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)
   *
   * <p><b>This class contains code derived from <a href="https://github.com/google/guava">Google
   * Guava</a></b>
   */
  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>.
     * Objects.equal}{@code (a, b)} implies that {@code Objects.equal(function.apply(a),
     * function.apply(b))}.
     * </ul>
     *
     * @throws NullPointerException if {@code input} is null
     */
    @Nullable 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 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(@Nullable Object object);
  }
  