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Matcher that allows the user to specify a partial ordering (a relative
order) between items in an iterable. The iterable may contain gaps inbetween two matching items. Gaps may appear at the beginning, end or in between. A user may specify may gaps in the sequence. e.g. Given an iterable 1, 2, 3, 4, 5, 6, 7 if the user were to specify containsInRelativeOrder(2, 4, 6) this would match successfully. This commit is the direct incorporation of a patch provided by Kevin Pauli. See also https://groups.google.com/forum/?fromgroups#!topic/hamcrest-dev/FsLlyRcGPzs
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‎hamcrest-library/src/main/java/org/hamcrest/collection/IsIterableContainingInRelativeOrder.java

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package org.hamcrest.collection;
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import java.util.ArrayList;
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import java.util.List;
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import org.hamcrest.Description;
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import org.hamcrest.Factory;
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import org.hamcrest.Matcher;
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import org.hamcrest.TypeSafeDiagnosingMatcher;
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import static java.util.Arrays.asList;
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import static org.hamcrest.core.IsEqual.equalTo;
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public class IsIterableContainingInRelativeOrder<E> extends TypeSafeDiagnosingMatcher<Iterable<? extends E>> {
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private final List<Matcher<? super E>> matchers;
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public IsIterableContainingInRelativeOrder(List<Matcher<? super E>> matchers) {
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this.matchers = matchers;
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}
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@Override
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protected boolean matchesSafely(Iterable<? extends E> iterable, Description mismatchDescription) {
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MatchSeriesInRelativeOrder<E> matchSeriesInRelativeOrder = new MatchSeriesInRelativeOrder<E>(matchers, mismatchDescription);
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matchSeriesInRelativeOrder.processItems(iterable);
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return matchSeriesInRelativeOrder.isFinished();
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}
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public void describeTo(Description description) {
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description.appendText("iterable containing ").appendList("[", ", ", "]", matchers).appendText(" in relative order");
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}
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private static class MatchSeriesInRelativeOrder<F> {
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public final List<Matcher<? super F>> matchers;
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private final Description mismatchDescription;
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private int nextMatchIx = 0;
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private F lastMatchedItem = null;
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public MatchSeriesInRelativeOrder(List<Matcher<? super F>> matchers, Description mismatchDescription) {
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this.mismatchDescription = mismatchDescription;
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if (matchers.isEmpty()) {
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throw new IllegalArgumentException("Should specify at least one expected element");
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}
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this.matchers = matchers;
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}
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public void processItems(Iterable<? extends F> iterable) {
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for (F item : iterable) {
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if (nextMatchIx < matchers.size()) {
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Matcher<? super F> matcher = matchers.get(nextMatchIx);
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if (matcher.matches(item)) {
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lastMatchedItem = item;
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nextMatchIx++;
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}
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}
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}
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}
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public boolean isFinished() {
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if (nextMatchIx < matchers.size()) {
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mismatchDescription.appendDescriptionOf(matchers.get(nextMatchIx)).appendText(" was not found");
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if (lastMatchedItem != null) {
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mismatchDescription.appendText(" after ").appendValue(lastMatchedItem);
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}
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return false;
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}
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return true;
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}
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}
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/**
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* Creates a matcher for {@link Iterable}s that matches when a single pass over the
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* examined {@link Iterable} yields a series of items, that contains items logically equal to the
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* corresponding item in the specified items, in the same relative order
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* <p/>
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* For example:
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* <pre>assertThat(Arrays.asList("a", "b", "c", "d", "e"), containsInRelativeOrder("b", "d"))</pre>
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*
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* @param items
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* the items that must be contained within items provided by an examined {@link Iterable} in the same relative order
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*/
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@Factory
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public static <E> Matcher<Iterable<? extends E>> containsInRelativeOrder(E... items) {
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List<Matcher<? super E>> matchers = new ArrayList<Matcher<? super E>>();
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for (E item : items) {
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matchers.add(equalTo(item));
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}
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return containsInRelativeOrder(matchers);
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}
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/**
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* Creates a matcher for {@link Iterable}s that matches when a single pass over the
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* examined {@link Iterable} yields a series of items, that each satisfying the corresponding
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* matcher in the specified matchers, in the same relative order.
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* <p/>
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* For example:
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* <pre>assertThat(Arrays.asList("a", "b", "c", "d", "e"), containsInRelativeOrder(equalTo("b"), equalTo("d")))</pre>
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*
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* @param itemMatchers
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* the matchers that must be satisfied by the items provided by an examined {@link Iterable} in the same relative order
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*/
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@Factory
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public static <E> Matcher<Iterable<? extends E>> containsInRelativeOrder(Matcher<? super E>... itemMatchers) {
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return containsInRelativeOrder(asList(itemMatchers));
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}
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/**
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* Creates a matcher for {@link Iterable}s that matches when a single pass over the
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* examined {@link Iterable} yields a series of items, that contains items satisfying the corresponding
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* matcher in the specified list of matchers, in the same relative order.
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* <p/>
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* For example:
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* <pre>assertThat(Arrays.asList("a", "b", "c", "d", "e"), contains(Arrays.asList(equalTo("b"), equalTo("d"))))</pre>
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*
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* @param itemMatchers
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* a list of matchers, each of which must be satisfied by the items provided by
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* an examined {@link Iterable} in the same relative order
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*/
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@Factory
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public static <E> Matcher<Iterable<? extends E>> containsInRelativeOrder(List<Matcher<? super E>> itemMatchers) {
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return new IsIterableContainingInRelativeOrder<E>(itemMatchers);
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}
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}

‎hamcrest-library/src/test/java/org/hamcrest/collection/IsIterableContainingInRelativeOrderTest.java

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package org.hamcrest.collection;
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import java.util.ArrayList;
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import java.util.List;
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import org.hamcrest.AbstractMatcherTest;
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import org.hamcrest.FeatureMatcher;
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import org.hamcrest.Matcher;
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import static java.util.Arrays.asList;
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import static org.hamcrest.collection.IsIterableContainingInRelativeOrder.containsInRelativeOrder;
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import static org.hamcrest.core.IsEqual.equalTo;
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@SuppressWarnings("unchecked")
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public class IsIterableContainingInRelativeOrderTest extends AbstractMatcherTest {
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// temporary hack until the Java type system works
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private final Matcher<Iterable<? extends WithValue>> contains123 = containsInRelativeOrder(value(1), value(2), value(3));
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@Override
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protected Matcher<?> createMatcher() {
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return containsInRelativeOrder(1, 2);
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}
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public void testMatchingSingleItemIterable() throws Exception {
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assertMatches("Single item iterable", containsInRelativeOrder(1), asList(1));
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}
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public void testMatchingMultipleItemIterable() throws Exception {
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assertMatches("Multiple item iterable", containsInRelativeOrder(1, 2, 3), asList(1, 2, 3));
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}
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public void testMatchesWithMoreElementsThanExpectedAtBeginning() throws Exception {
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assertMatches("More elements at beginning", containsInRelativeOrder(2, 3, 4), asList(1, 2, 3, 4));
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}
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public void testMatchesWithMoreElementsThanExpectedAtEnd() throws Exception {
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assertMatches("More elements at end", containsInRelativeOrder(1, 2, 3), asList(1, 2, 3, 4));
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}
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public void testMatchesWithMoreElementsThanExpectedInBetween() throws Exception {
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assertMatches("More elements in between", containsInRelativeOrder(1, 3), asList(1, 2, 3));
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}
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public void testDoesNotMatchWithFewerElementsThanExpected() throws Exception {
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List<WithValue> valueList = asList(make(1), make(2));
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assertMismatchDescription("value with <3> was not found after <WithValue 2>", contains123, valueList);
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}
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public void testDoesNotMatchIfSingleItemNotFound() throws Exception {
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assertMismatchDescription("value with <4> was not found", containsInRelativeOrder(value(4)), asList(make(3)));
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}
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public void testDoesNotMatchIfOneOfMultipleItemsNotFound() throws Exception {
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assertMismatchDescription("value with <3> was not found after <WithValue 2>", contains123, asList(make(1), make(2), make(4)));
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}
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public void testDoesNotMatchEmptyIterable() throws Exception {
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assertMismatchDescription("value with <4> was not found", containsInRelativeOrder(value(4)), new ArrayList<WithValue>());
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}
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public void testHasAReadableDescription() {
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assertDescription("iterable containing [<1>, <2>] in relative order", containsInRelativeOrder(1, 2));
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}
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public static class WithValue {
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private final int value;
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public WithValue(int value) { this.value = value; }
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public int getValue() { return value; }
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@Override public String toString() { return "WithValue " + value; }
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}
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public static WithValue make(int value) {
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return new WithValue(value);
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}
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public static Matcher<WithValue> value(int value) {
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return new FeatureMatcher<WithValue, Integer>(equalTo(value), "value with", "value") {
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@Override protected Integer featureValueOf(WithValue actual) { return actual.getValue(); }
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};
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}
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}

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