diff --git a/src/main/java/net/kemitix/mon/combinator/After.java b/src/main/java/net/kemitix/mon/combinator/After.java new file mode 100644 index 0000000..d15d820 --- /dev/null +++ b/src/main/java/net/kemitix/mon/combinator/After.java @@ -0,0 +1,78 @@ +/** + * The MIT License (MIT) + * + * Copyright (c) 2017 Paul Campbell + * + * Permission is hereby granted, free of charge, to any person obtaining a copy of this software + * and associated documentation files (the "Software"), to deal in the Software without restriction, + * including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, + * and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, + * subject to the following conditions: + * + * The above copyright notice and this permission notice shall be included in all copies + * or substantial portions of the Software. + * + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, + * INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE + * AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, + * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, + * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. + */ + +package net.kemitix.mon.combinator; + +import java.util.function.BiConsumer; +import java.util.function.Function; + +/** + * After pattern comninator. + * + *

Original from http://boundsofjava.com/newsletter/003-introducing-combinators-part1

+ * + * @param the argument type + * @param the result type + * + * @author Federico Peralta Schaffner (fps@boundsofjava.com) + */ +@FunctionalInterface +public interface After extends + Function, + Function< + BiConsumer, + Function>> { + + /** + * Decorates a function with a Consumer that will be supplier with the argument before applying it to the function. + * + * @param function the function to apply the argument to and return the result value of + * @param after the bi-consumer that will receive the argument and the result of the function + * @param the argument type + * @param the result type + * + * @return a partially applied Function that will take an argument and return the result of applying it to the + * function parameter + */ + static Function decorate( + final Function function, + final BiConsumer after + ) { + return After.create().apply(function) + .apply(after); + } + + /** + * Create an After curried function. + * + * @param the argument type + * @param the result type + * + * @return a curried function that will pass the argument and the result of the function to the supplied bi-consumer + */ + static After create() { + return function -> after -> argument -> { + final R result = function.apply(argument); + after.accept(argument, result); + return result; + }; + } +} diff --git a/src/test/java/net/kemitix/mon/combinator/AfterTest.java b/src/test/java/net/kemitix/mon/combinator/AfterTest.java new file mode 100644 index 0000000..cf82ccd --- /dev/null +++ b/src/test/java/net/kemitix/mon/combinator/AfterTest.java @@ -0,0 +1,42 @@ +package net.kemitix.mon.combinator; + +import org.junit.Test; + +import java.util.ArrayList; +import java.util.List; +import java.util.function.Function; + +import static org.assertj.core.api.Assertions.assertThat; + +public class AfterTest { + + @Test + public void canCreateAfterCombinator() { + //given + final List events = new ArrayList<>(); + final Function squareDecorated = + After.decorate(i -> function(i, events), (v, r) -> after(v, r, events)); + + //when + final Integer result = squareDecorated.apply(2); + //then + assertThat(result).isEqualTo(4); + assertThat(events).containsExactly("function", "after 2 -> 4"); + } + + private static void after( + final Integer argument, + final Integer result, + final List events + ) { + events.add("after " + argument + " -> " + result); + } + + private static Integer function( + final Integer argument, + final List events + ) { + events.add("function"); + return argument * argument; + } +}