    001    // Copyright 2010 The Apache Software Foundation
    002    //
    003    // Licensed under the Apache License, Version 2.0 (the "License");
    004    // you may not use this file except in compliance with the License.
    005    // You may obtain a copy of the License at
    006    //
    007    // http://www.apache.org/licenses/LICENSE-2.0
    008    //
    009    // Unless required by applicable law or agreed to in writing, software
    010    // distributed under the License is distributed on an "AS IS" BASIS,
    011    // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    012    // See the License for the specific language governing permissions and
    013    // limitations under the License.
    014
    015    package org.apache.tapestry5.func;
    016
    017    /**
    018     * A reducer takes an accumulator value and a single value from a collection and computes a new
    019     * accumulator value.
    020     * <A> type of accumulator
    021     * <T> type of collection value
    022     *
    023     * @since 5.2.0
    024     */
    025    public interface Reducer<A, T>
    026    {
    027        /**
    028         * Run a computation using the current value of the accumulator and an element (from a Flow),
    029         * and return the new accumulator.
    030         */
    031        A reduce(A accumulator, T element);
    032    }