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Defines the pattern for taking item from collection of JSONArray by index (#842)
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‎README.md

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@@ -83,18 +83,20 @@ Functions
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Functions can be invoked at the tail end of a path - the input to a function is the output of the path expression.
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The function output is dictated by the function itself.
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| Function | Description | Output type |
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| :------------------------ | :------------------------------------------------------------------ |:----------- |
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| min() | Provides the min value of an array of numbers | Double |
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| max() | Provides the max value of an array of numbers | Double |
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| avg() | Provides the average value of an array of numbers | Double |
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| stddev() | Provides the standard deviation value of an array of numbers | Double |
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| length() | Provides the length of an array | Integer |
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| sum() | Provides the sum value of an array of numbers | Double |
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| keys() | Provides the property keys (An alternative for terminal tilde `~`) | `Set<E>` |
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| concat(X) | Provides a concatinated version of the path output with a new item | like input |
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| append(X) | add an item to the json path output array | like input |
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| Function | Description | Output type |
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|:----------|:-------------------------------------------------------------------------------------|:---------------------|
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| min() | Provides the min value of an array of numbers | Double |
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| max() | Provides the max value of an array of numbers | Double |
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| avg() | Provides the average value of an array of numbers | Double |
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| stddev() | Provides the standard deviation value of an array of numbers | Double |
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| length() | Provides the length of an array | Integer |
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| sum() | Provides the sum value of an array of numbers | Double |
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| keys() | Provides the property keys (An alternative for terminal tilde `~`) | `Set<E>` |
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| concat(X) | Provides a concatinated version of the path output with a new item | like input |
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| append(X) | add an item to the json path output array | like input |
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| first() | Provides the first item of an array | Depends on the array |
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| last() | Provides the last item of an array | Depends on the array |
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| index(X) | Provides the item of an array of index: X, if the X is negative, take from backwards | Depends on the array |
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Filter Operators
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-----------------
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‎json-path/src/main/java/com/jayway/jsonpath/internal/function/PathFunctionFactory.java

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@@ -8,6 +8,9 @@
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import com.jayway.jsonpath.internal.function.numeric.Min;
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import com.jayway.jsonpath.internal.function.numeric.StandardDeviation;
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import com.jayway.jsonpath.internal.function.numeric.Sum;
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import com.jayway.jsonpath.internal.function.sequence.First;
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import com.jayway.jsonpath.internal.function.sequence.Index;
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import com.jayway.jsonpath.internal.function.sequence.Last;
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import com.jayway.jsonpath.internal.function.text.Concatenate;
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import com.jayway.jsonpath.internal.function.text.Length;
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@@ -46,6 +49,11 @@ public class PathFunctionFactory {
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map.put("size", Length.class);
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map.put("append", Append.class);
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map.put("keys", KeySetFunction.class);
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// Sequential Functions
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map.put("first", First.class);
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map.put("last", Last.class);
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map.put("index", Index.class);
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FUNCTIONS = Collections.unmodifiableMap(map);

‎json-path/src/main/java/com/jayway/jsonpath/internal/function/sequence/AbstractSequenceAggregation.java

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package com.jayway.jsonpath.internal.function.sequence;
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import com.jayway.jsonpath.JsonPathException;
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import com.jayway.jsonpath.internal.EvaluationContext;
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import com.jayway.jsonpath.internal.PathRef;
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import com.jayway.jsonpath.internal.function.Parameter;
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import com.jayway.jsonpath.internal.function.PathFunction;
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import java.util.ArrayList;
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import java.util.List;
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/**
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* Defines the pattern for taking item from collection of JSONArray by index
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*
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* Created by git9527 on 6/11/22.
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*/
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public abstract class AbstractSequenceAggregation implements PathFunction {
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protected abstract int targetIndex(EvaluationContext ctx, List<Parameter> parameters);
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@Override
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public Object invoke(String currentPath, PathRef parent, Object model, EvaluationContext ctx, List<Parameter> parameters) {
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if(ctx.configuration().jsonProvider().isArray(model)){
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Iterable<?> objects = ctx.configuration().jsonProvider().toIterable(model);
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List<Object> objectList = new ArrayList<>();
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objects.forEach(objectList::add);
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int targetIndex = this.targetIndex(ctx, parameters);
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if (targetIndex >= 0) {
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return objectList.get(targetIndex);
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} else {
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int realIndex = objectList.size() + targetIndex;
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if (realIndex > 0) {
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return objectList.get(realIndex);
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} else {
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throw new JsonPathException("Target index:" + targetIndex + " larger than object count:" + objectList.size());
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}
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}
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}
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throw new JsonPathException("Aggregation function attempted to calculate value using empty array");
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}
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protected int getIndexFromParameters(EvaluationContext ctx, List<Parameter> parameters) {
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List<Number> numbers = Parameter.toList(Number.class, ctx, parameters);
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return numbers.get(0).intValue();
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}
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}

‎json-path/src/main/java/com/jayway/jsonpath/internal/function/sequence/First.java

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package com.jayway.jsonpath.internal.function.sequence;
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import com.jayway.jsonpath.internal.EvaluationContext;
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import com.jayway.jsonpath.internal.function.Parameter;
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import java.util.List;
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/**
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* Take the first item from collection of JSONArray
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*
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* Created by git9527 on 6/11/22.
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*/
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public class First extends AbstractSequenceAggregation {
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@Override
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protected int targetIndex(EvaluationContext ctx, List<Parameter> parameters) {
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return 0;
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}
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}

‎json-path/src/main/java/com/jayway/jsonpath/internal/function/sequence/Index.java

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package com.jayway.jsonpath.internal.function.sequence;
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import com.jayway.jsonpath.internal.EvaluationContext;
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import com.jayway.jsonpath.internal.function.Parameter;
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import java.util.List;
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/**
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* Take the index from first Parameter, then the item from collection of JSONArray by index
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*
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* Created by git9527 on 6/11/22.
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*/
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public class Index extends AbstractSequenceAggregation {
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@Override
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protected int targetIndex(EvaluationContext ctx, List<Parameter> parameters) {
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return getIndexFromParameters(ctx, parameters);
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}
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}

‎json-path/src/main/java/com/jayway/jsonpath/internal/function/sequence/Last.java

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package com.jayway.jsonpath.internal.function.sequence;
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import com.jayway.jsonpath.internal.EvaluationContext;
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import com.jayway.jsonpath.internal.function.Parameter;
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import java.util.List;
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/**
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* Take the first item from collection of JSONArray
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*
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* Created by git9527 on 6/11/22.
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*/
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public class Last extends AbstractSequenceAggregation {
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@Override
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protected int targetIndex(EvaluationContext ctx, List<Parameter> parameters) {
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return -1;
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}
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}

‎json-path/src/main/java/com/jayway/jsonpath/internal/path/PathCompiler.java

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@@ -305,7 +305,7 @@ private List<Parameter> parseFunctionParameters(String funcName) {
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continue;
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}
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if (c == OPEN_BRACE || isDigit(c) || DOUBLE_QUOTE == c) {
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if (c == OPEN_BRACE || isDigit(c) || DOUBLE_QUOTE == c || MINUS == c) {
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type = ParamType.JSON;
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}
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else if (isPathContext(c)) {
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inProperty = true;
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lastSignificantWasComma = false;
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}
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} else if (c == COMMA && !inProperty) {
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} else if (c == COMMA && !inProperty) {
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if (lastSignificantWasComma){
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fail("Found empty property at index "+readPosition);
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}

‎json-path/src/test/java/com/jayway/jsonpath/internal/function/SequentialPathFunctionTest.java

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package com.jayway.jsonpath.internal.function;
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import com.jayway.jsonpath.Configuration;
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import com.jayway.jsonpath.Configurations;
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import org.junit.Test;
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/**
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* Test cases for functions
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*
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* -first
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* -last
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* -index(X)
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*
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* Created by git9527 on 6/11/22.
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*/
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public class SequentialPathFunctionTest extends BaseFunctionTest {
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private Configuration conf = Configurations.JACKSON_CONFIGURATION;
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@Test
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public void testFirstOfNumbers() throws Exception {
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verifyFunction(conf, "$.numbers.first()", NUMBER_SERIES, 1);
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}
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@Test
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public void testLastOfNumbers() throws Exception {
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verifyFunction(conf, "$.numbers.last()", NUMBER_SERIES, 10);
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}
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@Test
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public void testIndexOfNumbers() throws Exception {
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verifyFunction(conf, "$.numbers.index(0)", NUMBER_SERIES, 1);
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verifyFunction(conf, "$.numbers.index(-1)", NUMBER_SERIES, 10);
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verifyFunction(conf, "$.numbers.index(1)", NUMBER_SERIES, 2);
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}
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@Test
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public void testFirstOfText() throws Exception {
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verifyFunction(conf, "$.text.first()", TEXT_SERIES, "a");
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}
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@Test
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public void testLastOfText() throws Exception {
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verifyFunction(conf, "$.text.last()", TEXT_SERIES, "f");
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}
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@Test
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public void testIndexOfText() throws Exception {
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verifyFunction(conf, "$.text.index(0)", TEXT_SERIES, "a");
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verifyFunction(conf, "$.text.index(-1)", TEXT_SERIES, "f");
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verifyFunction(conf, "$.text.index(1)", TEXT_SERIES, "b");
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}
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}

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