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
015package 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 */
025public 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}