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}