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