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Merge pull request #15 from kemitix/combinators

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Combinators
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Paul Campbell 2017-12-13 06:30:12 +00:00 committed by GitHub
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78
src/main/java/net/kemitix/mon/combinator/After.java Normal file
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/**
* 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 combinator.
*
* <p>Original from http://boundsofjava.com/newsletter/003-introducing-combinators-part1</p>
*
* @param <T> the argument type
* @param <R> the result type
*
* @author Federico Peralta Schaffner (fps@boundsofjava.com)
*/
@FunctionalInterface
public interface After<T, R> extends
Function<Function<T, R>,
Function<
BiConsumer<T, R>,
Function<T, R>>> {
/**
* 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 <T> the argument type
* @param <R> 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 <T, R> Function<T, R> decorate(
final Function<T, R> function,
final BiConsumer<T, R> after
) {
return After.<T, R>create().apply(function)
.apply(after);
}
/**
* Create an After curried function.
*
* @param <T> the argument type
* @param <R> the result type
*
* @return a curried function that will pass the argument and the result of the function to the supplied bi-consumer
*/
static <T, R> After<T, R> create() {
return function -> after -> argument -> {
final R result = function.apply(argument);
after.accept(argument, result);
return result;
};
}
}

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src/main/java/net/kemitix/mon/combinator/Around.java Normal file
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/**
* 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.concurrent.atomic.AtomicReference;
import java.util.function.BiConsumer;
import java.util.function.Function;
/**
* Around pattern combinator.
*
* <p>Original from http://boundsofjava.com/newsletter/003-introducing-combinators-part1</p>
*
* @param <T> the argument type
* @param <R> the result type
*
* @author Federico Peralta Schaffner (fps@boundsofjava.com)
*/
@FunctionalInterface
public interface Around<T, R> extends
Function<
Function<T, R>,
Function<
BiConsumer<Around.Executable<R>, T>,
Function<T, R>>> {
/**
* Decorates a function with an BiConsumer that will be supplier with an executable to perform the function, and the
* argument that will be applied when executed.
*
* @param function the function to apply the argument to and return the result value of
* @param around the bi-consumer that will supplied with the executable and the argument
* @param <T> the argument type
* @param <R> the result type
*
* @return a partially applied Function that will take an argument, and the result of applying it to function
*/
static <T, R> Function<T, R> decorate(
final Function<T, R> function,
final BiConsumer<Executable<R>, T> around
) {
return Around.<T, R>create().apply(function)
.apply(around);
}
/**
* Create an Around curried function.
*
* @param <T> the argument type
* @param <R> the result type
*
* @return a curried function that will execute the around function, passing an executable and the invocations
* argument. The around function must {@code execute()} the executable and may capture the result.
*/
static <T, R> Around<T, R> create() {
return function -> around -> argument -> {
final AtomicReference<R> result = new AtomicReference<>();
final Executable<R> callback = () -> {
result.set(function.apply(argument));
return result.get();
};
around.accept(callback, argument);
return result.get();
};
}
/**
* The executable that will be supplied to the around function to trigger the surrounded function.
*
* @param <R> the return type of the function
*/
@FunctionalInterface
interface Executable<R> {
/**
* Executes the function.
*
* @return the result of applying the function
*/
R execute();
}
}

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src/main/java/net/kemitix/mon/combinator/Before.java Normal file
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/**
* 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.Consumer;
import java.util.function.Function;
/**
* Before pattern combinator.
*
* <p>Original from http://boundsofjava.com/newsletter/003-introducing-combinators-part1</p>
*
* @param <T> the argument type
* @param <R> the result type
*
* @author Federico Peralta Schaffner (fps@boundsofjava.com)
*/
@FunctionalInterface
public interface Before<T, R> extends
Function<
Consumer<T>,
Function<
Function<T, R>,
Function<T, R>>> {
/**
* Decorates a function with a Consumer that will be supplied with the argument before applying it to the function.
*
* @param before the consumer that will receive the argument before the function
* @param function the function to apply the argument to and return the result value of
* @param <T> the argument type
* @param <R> 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 <T, R> Function<T, R> decorate(
final Consumer<T> before,
final Function<T, R> function
) {
return Before.<T, R>create().apply(before)
.apply(function);
}
/**
* Create a Before curried function.
*
* @param <T> the argument type
* @param <R> the result type
*
* @return a curried function that will pass the argument to before applying the supplied function
*/
static <T, R> Before<T, R> create() {
return before -> function -> argument -> {
before.accept(argument);
return function.apply(argument);
};
}
}

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src/main/java/net/kemitix/mon/combinator/package-info.java Normal file
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/**
* 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;

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src/test/java/net/kemitix/mon/combinator/AfterTest.java Normal file
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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<String> events = new ArrayList<>();
final Function<Integer, Integer> squareDecorated =
After.decorate(
argument -> function(argument, events),
(argument, result) -> after(argument, result, 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<String> events
) {
events.add(String.format("after %d -> %d", argument, result));
}
private static Integer function(
final Integer argument,
final List<String> events
) {
events.add("function");
return argument * argument;
}
}

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src/test/java/net/kemitix/mon/combinator/AroundTest.java Normal file
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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 AroundTest {
@Test
public void canCreateAnAroundCombinator() {
//given
final List<String> events = new ArrayList<>();
final Function<Integer, Integer> squareDecorated =
Around.decorate(
argument -> function(argument, events),
(executable, argument) -> around(executable, argument, events)
);
//when
final Integer result = squareDecorated.apply(2);
//then
assertThat(result).isEqualTo(4);
assertThat(events).containsExactly("around before 2", "function", "around after 4");
}
private void around(
final Around.Executable<Integer> executable,
final Integer argument,
final List<String> events
) {
events.add("around before " + argument);
final Integer result = executable.execute();
events.add("around after " + result);
}
private static Integer function(
final Integer argument,
final List<String> events
) {
events.add("function");
return argument * argument;
}
}

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src/test/java/net/kemitix/mon/combinator/BeforeTest.java Normal file
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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 BeforeTest {
@Test
public void canCreateBeforeCombinator() {
//given
final List<String> events = new ArrayList<>();
final Function<Integer, Integer> squareDecorated =
Before.decorate(
argument -> before(argument, events),
argument -> function(argument, events)
);
//when
final Integer result = squareDecorated.apply(2);
//then
assertThat(result).isEqualTo(4);
assertThat(events).containsExactly("before 2", "function");
}
private static void before(
final Integer argument,
final List<String> events
) {
events.add("before " + argument);
}
private static Integer function(
final Integer argument,
final List<String> events
) {
events.add("function");
return argument * argument;
}
}