tapestry-func/src/main/java/org/apache/tapestry5/func/LazyZip.java

// Copyright 2010 The Apache Software Foundation
//
// 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 org.apache.tapestry5.func;

class LazyZip<A, B> implements LazyFunction<Tuple<A, B>>
{
    private final Flow<A> aFlow;

    private final Flow<B> bFlow;

    public LazyZip(Flow<A> aFlow, Flow<B> bFlow)
    {
        this.aFlow = aFlow;
        this.bFlow = bFlow;
    }

    @Override
    public LazyContinuation<Tuple<A, B>> next()
    {
        if (aFlow.isEmpty() || bFlow.isEmpty())
            return null;

        LazyZipValue<A, B> nextValue = new LazyZipValue<A, B>(aFlow, bFlow);

        return new LazyContinuation<Tuple<A, B>>(nextValue, new LazyZip<A, B>(aFlow.rest(), bFlow.rest()));
    }
}