| // 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; |
| |
| /** |
| * A lazy function is used to populate a {@link Flow} incrementally. Lazy functions allow calculations to be |
| * deferred. They also support infinitely large Flows, where successive values are computed just as needed. |
| * |
| * @since 5.2.0 |
| */ |
| public interface LazyFunction<T> |
| { |
| /** |
| * Calculates the next value for the function. The return value is tricky: it combines the next value in the |
| * {@link Flow} with a function to compute the value after that as a {@link LazyContinuation}. Alternately, a |
| * LazyFunction can return null to indicate that it has returned all the values it can. |
| * |
| * @return continuation containing next value and next function, or null when no more values can be produced |
| */ |
| LazyContinuation<T> next(); |
| } |