Mapped list with index

.gitignore

@@ -4,3 +4,6 @@ build/
 .project
 .settings/
 .idea/
+gradle/
+gradlew
+gradle.bat

reactfx/build.gradle

@@ -9,7 +9,7 @@ group = 'org.reactfx'
 
 dependencies {
     // Test dependencies
-    testImplementation group: 'junit', name: 'junit', version: '4.12'
+    testImplementation group: 'org.junit.jupiter', name: 'junit-jupiter-api', version: '5.13.4'
     testImplementation group: 'org.hamcrest', name: 'hamcrest-library', version: '1.3'
     testImplementation group: 'org.junit.contrib', name: 'junit-theories', version: '4.12'
     testImplementation group: 'com.pholser', name: 'junit-quickcheck-core', version: '0.4'

reactfx/src/main/java/org/reactfx/collection/LiveList.java

@@ -3,6 +3,7 @@
 import java.util.Collections;
 import java.util.List;
 import java.util.NoSuchElementException;
+import java.util.function.BiFunction;
 import java.util.function.BinaryOperator;
 import java.util.function.Consumer;
 import java.util.function.Function;
@@ -21,6 +22,7 @@
 import org.reactfx.collection.LiveList.QuasiModificationObserver;
 import org.reactfx.util.AccumulatorSize;
 import org.reactfx.util.Experimental;
+import org.reactfx.util.Tuple2;
 import org.reactfx.util.WrapperBase;
 import org.reactfx.value.Val;
 
@@ -179,6 +181,10 @@ default <F> LiveList<F> map(Function<? super E, ? extends F> f) {
         return map(this, f);
     }
 
+    default <F> LiveList<F> map(BiFunction<Integer, ? super E, ? extends F> f) {
+        return map(this, f);
+    }
+
     default <F> LiveList<F> mapDynamic(
             ObservableValue<? extends Function<? super E, ? extends F>> f) {
         return mapDynamic(this, f);
@@ -291,12 +297,25 @@ static Val<Integer> sizeOf(ObservableList<?> list) {
         return Val.create(() -> list.size(), list);
     }
 
+    /**
+     * If you wish to use the index of the element in your mapping function, check {@link #map(ObservableList, BiFunction)}.
+     * @param f a mapping function taking the element from source as input and producing a result
+     */
     static <E, F> LiveList<F> map(
             ObservableList<? extends E> list,
             Function<? super E, ? extends F> f) {
         return new MappedList<>(list, f);
     }
 
+    /**
+     * @param f a mapping function taking the index and the element from source as input and producing a result
+     */
+    static <E, F> LiveList<F> map(
+            ObservableList<? extends E> list,
+            BiFunction<Integer, ? super E, ? extends F> f) {
+        return new MappedList<>(list, f);
+    }
+
     static <E, F> LiveList<F> mapDynamic(
             ObservableList<? extends E> list,
             ObservableValue<? extends Function<? super E, ? extends F>> f) {

reactfx/src/main/java/org/reactfx/collection/MappedList.java

@@ -1,6 +1,7 @@
 package org.reactfx.collection;
 
 import java.util.List;
+import java.util.function.BiFunction;
 import java.util.function.Function;
 
 import javafx.beans.value.ObservableValue;
@@ -13,18 +14,24 @@
 class MappedList<E, F> extends LiveListBase<F>
 implements UnmodifiableByDefaultLiveList<F> {
     private final ObservableList<? extends E> source;
-    private final Function<? super E, ? extends F> mapper;
+    private final BiFunction<Integer, ? super E, ? extends F> mapper;
 
     public MappedList(
             ObservableList<? extends E> source,
             Function<? super E, ? extends F> mapper) {
+        this(source, (index, elem) -> mapper.apply(elem));
+    }
+
+    public MappedList(
+            ObservableList<? extends E> source,
+            BiFunction<Integer, ? super E, ? extends F> mapper) {
         this.source = source;
         this.mapper = mapper;
     }
 
     @Override
     public F get(int index) {
-        return mapper.apply(source.get(index));
+        return mapper.apply(index, source.get(index));
     }
 
     @Override
@@ -44,6 +51,12 @@ private void sourceChanged(QuasiListChange<? extends E> change) {
     static <E, F> QuasiListChange<F> mappedChangeView(
             QuasiListChange<? extends E> change,
             Function<? super E, ? extends F> mapper) {
+        return mappedChangeView(change, (index, elem) -> mapper.apply(elem));
+    }
+
+    static <E, F> QuasiListChange<F> mappedChangeView(
+            QuasiListChange<? extends E> change,
+            BiFunction<Integer, ? super E, ? extends F> mapper) {
         return new QuasiListChange<F>() {
 
             @Override
@@ -63,7 +76,7 @@ public int getAddedSize() {
 
                     @Override
                     public List<? extends F> getRemoved() {
-                        return Lists.mappedView(mod.getRemoved(), mapper);
+                        return Lists.mappedView(mod.getRemoved(), (index, elem) -> mapper.apply(mod.getFrom(), elem));
                     }
                 });
             }

reactfx/src/main/java/org/reactfx/util/Lists.java

@@ -10,6 +10,7 @@
 import java.util.List;
 import java.util.ListIterator;
 import java.util.Objects;
+import java.util.function.BiFunction;
 import java.util.function.Function;
 
 public final class Lists {
@@ -188,6 +189,23 @@ public int size() {
         };
     }
 
+    public static <E, F> List<F> mappedView(
+            List<? extends E> source,
+            BiFunction<Integer, ? super E, ? extends F> f) {
+        return new AbstractList<F>() {
+
+            @Override
+            public F get(int index) {
+                return f.apply(index, source.get(index));
+            }
+
+            @Override
+            public int size() {
+                return source.size();
+            }
+        };
+    }
+
     @SafeVarargs
     public static <E> List<E> concatView(List<? extends E>... lists) {
         return concatView(Arrays.asList(lists));