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jnapejnape
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Merge branch 'functor-unification' into recursion-schemes
2 parents 51646db + e88df4a commit d95e2e5

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11 files changed

+269
-4
lines changed

11 files changed

+269
-4
lines changed

‎src/main/java/com/jnape/palatable/lambda/adt/hmap/TypeSafeKey.java

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*
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* @param <T> The type of the value that this key maps to inside an HMap
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*/
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@SuppressWarnings("unused")
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public interface TypeSafeKey<T> {
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/**

‎src/main/java/com/jnape/palatable/lambda/functions/builtin/fn2/Cons.java

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package com.jnape.palatable.lambda.functions.builtin.fn2;
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import com.jnape.palatable.lambda.functions.Fn1;
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import com.jnape.palatable.lambda.functions.Fn2;
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import com.jnape.palatable.lambda.iterators.ConsingIterator;
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/**
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* Prepend an element to an <code>Iterable</code>.
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*
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* @param <A> the Iterable element type
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*/
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public final class Cons<A> implements Fn2<A, Iterable<A>, Iterable<A>> {
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private static final Cons INSTANCE = new Cons();
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private Cons() {
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}
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@Override
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public Iterable<A> apply(A a, Iterable<A> as) {
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return () -> new ConsingIterator<>(a, as);
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}
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@SuppressWarnings("unchecked")
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public static <A> Cons<A> cons() {
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return (Cons<A>) INSTANCE;
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}
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public static <A> Fn1<Iterable<A>, Iterable<A>> cons(A a) {
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return Cons.<A>cons().apply(a);
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}
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public static <A> Iterable<A> cons(A a, Iterable<A> as) {
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return cons(a).apply(as);
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}
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}

‎src/main/java/com/jnape/palatable/lambda/iterators/ConsingIterator.java

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package com.jnape.palatable.lambda.iterators;
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import java.util.Iterator;
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import java.util.NoSuchElementException;
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import java.util.function.Supplier;
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public final class ConsingIterator<A> implements Iterator<A> {
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private final A head;
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private final Supplier<Iterator<A>> asSupplier;
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private Iterator<A> asIterator;
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private boolean iteratedHead;
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public ConsingIterator(A head, Iterable<A> as) {
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this.head = head;
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this.asSupplier = as::iterator;
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iteratedHead = false;
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}
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@Override
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public boolean hasNext() {
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if (!iteratedHead)
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return true;
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if (asIterator == null)
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asIterator = asSupplier.get();
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return asIterator.hasNext();
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}
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@Override
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public A next() {
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if (!hasNext())
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throw new NoSuchElementException();
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if (!iteratedHead) {
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iteratedHead = true;
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return head;
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}
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while (asIterator instanceof ConsingIterator && ((ConsingIterator) asIterator).iteratedHead) {
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ConsingIterator<A> cons = (ConsingIterator<A>) asIterator;
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if (cons.iteratedHead && cons.asIterator != null)
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asIterator = cons.asIterator;
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}
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return asIterator.next();
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}
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}

‎src/main/java/com/jnape/palatable/lambda/lens/functions/Over.java

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@@ -25,6 +25,8 @@
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*/
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public final class Over<S, T, A, B> implements Fn3<Lens<S, T, A, B>, Function<? super A, ? extends B>, S, T> {
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private static final Over INSTANCE = new Over();
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private Over() {
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}
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@@ -35,8 +37,9 @@ public T apply(Lens<S, T, A, B> lens, Function<? super A, ? extends B> fn, S s)
3537
.runIdentity();
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}
3739

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@SuppressWarnings("unchecked")
3841
public static <S, T, A, B> Over<S, T, A, B> over() {
39-
return new Over<>();
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return (Over<S, T, A, B>) INSTANCE;
4043
}
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public static <S, T, A, B> Fn2<Function<? super A, ? extends B>, S, T> over(

‎src/main/java/com/jnape/palatable/lambda/lens/functions/Set.java

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@@ -25,6 +25,8 @@
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*/
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public final class Set<S, T, A, B> implements Fn3<Lens<S, T, A, B>, B, S, T> {
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private static final Set INSTANCE = new Set();
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2830
private Set() {
2931
}
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@@ -33,8 +35,9 @@ public T apply(Lens<S, T, A, B> lens, B b, S s) {
3335
return over(lens, constantly(b), s);
3436
}
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@SuppressWarnings("unchecked")
3639
public static <S, T, A, B> Set<S, T, A, B> set() {
37-
return new Set<>();
40+
return INSTANCE;
3841
}
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4043
public static <S, T, A, B> Fn2<B, S, T> set(Lens<S, T, A, B> lens) {

‎src/main/java/com/jnape/palatable/lambda/lens/functions/View.java

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@@ -20,6 +20,8 @@
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*/
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public final class View<S, T, A, B> implements Fn2<Lens<S, T, A, B>, S, A> {
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private static final View INSTANCE = new View();
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2325
private View() {
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}
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@@ -28,8 +30,9 @@ public A apply(Lens<S, T, A, B> lens, S s) {
2830
return lens.<Const<A, ?>, Const<A, T>, Const<A, B>>fix().apply(Const::new, s).runConst();
2931
}
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33+
@SuppressWarnings("unchecked")
3134
public static <S, T, A, B> View<S, T, A, B> view() {
32-
return new View<>();
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return INSTANCE;
3336
}
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3538
public static <S, T, A, B> Fn1<S, A> view(Lens<S, T, A, B> lens) {

‎src/main/java/com/jnape/palatable/lambda/monoid/builtin/Join.java

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package com.jnape.palatable.lambda.monoid.builtin;
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import com.jnape.palatable.lambda.functions.Fn1;
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import com.jnape.palatable.lambda.monoid.Monoid;
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/**
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* A {@link Monoid} instance formed by <code>String</code> that concats two strings together.
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*
9+
* @see Monoid
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*/
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public final class Join implements Monoid<String> {
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private static final Join INSTANCE = new Join();
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private Join() {
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}
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@Override
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public String identity() {
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return "";
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}
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@Override
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public String apply(String x, String y) {
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return x + y;
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}
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public static Join join() {
29+
return INSTANCE;
30+
}
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32+
public static Fn1<String, String> join(String x) {
33+
return join().apply(x);
34+
}
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36+
public static String join(String x, String y) {
37+
return join(x).apply(y);
38+
}
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}

‎src/test/java/com/jnape/palatable/lambda/adt/hmap/TypeSafeKeyTest.java

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package com.jnape.palatable.lambda.adt.hmap;
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import org.junit.Test;
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import static com.jnape.palatable.lambda.adt.hmap.TypeSafeKey.typeSafeKey;
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import static org.junit.Assert.assertFalse;
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8+
public class TypeSafeKeyTest {
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10+
@Test
11+
public void usesReferenceEquality() {
12+
assertFalse(typeSafeKey().equals(typeSafeKey()));
13+
}
14+
}

‎src/test/java/com/jnape/palatable/lambda/functions/builtin/fn2/ConsTest.java

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package com.jnape.palatable.lambda.functions.builtin.fn2;
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import com.jnape.palatable.lambda.functions.Fn1;
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import com.jnape.palatable.traitor.annotations.TestTraits;
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import com.jnape.palatable.traitor.runners.Traits;
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import org.junit.Test;
7+
import org.junit.runner.RunWith;
8+
import testsupport.traits.EmptyIterableSupport;
9+
import testsupport.traits.FiniteIteration;
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import testsupport.traits.ImmutableIteration;
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import testsupport.traits.Laziness;
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import static com.jnape.palatable.lambda.functions.builtin.fn2.Cons.cons;
14+
import static java.util.Arrays.asList;
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import static java.util.Collections.emptyList;
16+
import static org.junit.Assert.assertThat;
17+
import static testsupport.matchers.IterableMatcher.iterates;
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@RunWith(Traits.class)
20+
public class ConsTest {
21+
22+
@TestTraits({Laziness.class, ImmutableIteration.class, FiniteIteration.class, EmptyIterableSupport.class})
23+
public Fn1<Iterable<Object>, Iterable<Object>> createTestSubject() {
24+
return cons(0);
25+
}
26+
27+
@Test
28+
public void consingElementToHeadOfIterable() {
29+
assertThat(cons(0, asList(1, 2, 3)), iterates(0, 1, 2, 3));
30+
}
31+
32+
@Test
33+
public void consingToEmptyIterable() {
34+
assertThat(cons("foo", emptyList()), iterates("foo"));
35+
}
36+
}

‎src/test/java/com/jnape/palatable/lambda/iterators/ConsingIteratorTest.java

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package com.jnape.palatable.lambda.iterators;
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import org.junit.Before;
4+
import org.junit.Test;
5+
6+
import java.util.Collections;
7+
8+
import static com.jnape.palatable.lambda.functions.builtin.fn2.Drop.drop;
9+
import static com.jnape.palatable.lambda.functions.builtin.fn2.Iterate.iterate;
10+
import static com.jnape.palatable.lambda.functions.builtin.fn2.Take.take;
11+
import static com.jnape.palatable.lambda.functions.builtin.fn3.FoldRight.foldRight;
12+
import static java.util.Arrays.asList;
13+
import static org.junit.Assert.assertEquals;
14+
import static org.junit.Assert.assertFalse;
15+
import static org.junit.Assert.assertTrue;
16+
17+
public class ConsingIteratorTest {
18+
19+
private ConsingIterator<Integer> consingIterator;
20+
21+
@Before
22+
public void setUp() {
23+
consingIterator = new ConsingIterator<>(0, asList(1, 2, 3));
24+
}
25+
26+
@Test
27+
public void hasNextIfHeadNotYetIterated() {
28+
assertTrue(consingIterator.hasNext());
29+
}
30+
31+
@Test
32+
public void nextIsHeadIfNotYetIterated() {
33+
assertEquals((Integer) 0, consingIterator.next());
34+
}
35+
36+
@Test
37+
public void hasNextIfMoreElementsAfterHead() {
38+
consingIterator.next();
39+
assertTrue(consingIterator.hasNext());
40+
}
41+
42+
@Test
43+
public void doesNotHaveNextIfNoElementsLeft() {
44+
consingIterator.next();
45+
consingIterator.next();
46+
consingIterator.next();
47+
consingIterator.next();
48+
assertFalse(consingIterator.hasNext());
49+
}
50+
51+
@Test
52+
public void stackSafety() {
53+
Integer stackBlowingNumber = 1000000;
54+
Iterable<Integer> ints = foldRight((x, acc) -> () -> new ConsingIterator<>(x, acc),
55+
(Iterable<Integer>) Collections.<Integer>emptyList(),
56+
take(stackBlowingNumber, iterate(x -> x + 1, 1)));
57+
58+
assertEquals(stackBlowingNumber,
59+
take(1, drop(stackBlowingNumber - 1, ints)).iterator().next());
60+
}
61+
}

‎src/test/java/com/jnape/palatable/lambda/monoid/builtin/JoinTest.java

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package com.jnape.palatable.lambda.monoid.builtin;
2+
3+
import org.junit.Test;
4+
5+
import static com.jnape.palatable.lambda.monoid.builtin.Join.join;
6+
import static org.junit.Assert.assertEquals;
7+
8+
public class JoinTest {
9+
10+
@Test
11+
public void identity() {
12+
assertEquals("", join().identity());
13+
}
14+
15+
@Test
16+
public void monoid() {
17+
assertEquals("ab", join().apply("a", "b"));
18+
assertEquals("a", join().apply("a", ""));
19+
assertEquals("b", join().apply("", "b"));
20+
assertEquals("", join().apply("", ""));
21+
}
22+
}

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