Add support for the $mapIndexed() and $.forEachIndexed() methods.

pom.xml

@@ -140,6 +140,7 @@
                   <option>-keepattributes Signature,InnerClasses</option>
                   <option>-keep public class com.github.underscore.$ { *; }</option>
                   <option>-keep public class com.github.underscore.*$Chain { *; }</option>
+                  <option>-keep public class com.github.underscore.BiConsumer { *; }</option>
                   <option>-keep public class com.github.underscore.BiFunction { *; }</option>
                   <option>-keep public class com.github.underscore.Consumer { *; }</option>
                   <option>-keep public class com.github.underscore.Function { *; }</option>

src/main/java/com/github/underscore/$.java

@@ -223,6 +223,14 @@ public static <T> void each(final Iterable<T> iterable, final Consumer<? super T
         }
     }
 
+    public static <T> void eachIndexed(final Iterable<T> iterable, final BiConsumer<Integer, ? super T> func) {
+        int index = 0;
+        for (T element : iterable) {
+            func.accept(index, element);
+            index += 1;
+        }
+    }
+
     public void each(final Consumer<? super T> func) {
         each(iterable, func);
     }
@@ -239,10 +247,18 @@ public static <T> void forEach(final Iterable<T> iterable, final Consumer<? supe
         each(iterable, func);
     }
 
+    public static <T> void forEachIndexed(final Iterable<T> iterable, final BiConsumer<Integer, ? super T> func) {
+        eachIndexed(iterable, func);
+    }
+
     public void forEach(final Consumer<? super T> func) {
         each(iterable, func);
     }
 
+    public void forEachIndexed(final BiConsumer<Integer, ? super T> func) {
+        eachIndexed(iterable, func);
+    }
+
     public static <T> void forEachRight(final Iterable<T> iterable, final Consumer<? super T> func) {
         eachRight(iterable, func);
     }
@@ -279,6 +295,20 @@ public static <T, E> Set<T> map(final Set<E> set, final Function<? super E, T> f
         return transformed;
     }
 
+    public static <T, E> List<T> mapIndexed(final List<E> list, final BiFunction<Integer, ? super E, T> func) {
+        final List<T> transformed = newArrayListWithExpectedSize(list.size());
+        int index = 0;
+        for (E element : list) {
+            transformed.add(func.apply(index, element));
+            index += 1;
+        }
+        return transformed;
+    }
+
+    public <F> List<F> mapIndexed(final BiFunction<Integer, ? super T, F> func) {
+        return mapIndexed(newArrayList(iterable), func);
+    }
+
     public static <T, E> List<T> collect(final List<E> list, final Function<? super E, T> func) {
         return map(list, func);
     }

src/main/java/com/github/underscore/BiConsumer.java

@@ -0,0 +1,5 @@
+package com.github.underscore;
+
+public interface BiConsumer<F1, F2> {
+    void accept(F1 arg1, F2 arg2);
+}

src/test/java/com/github/underscore/CollectionsTest.java

@@ -106,6 +106,29 @@ public void accept(final Map.Entry<String, Integer> item) {
         assertEquals("[a=1, b=2, c=3]", resultChain.toString());
     }
 
+/*
+_.forEachIndexed([1, 2, 3], alert);
+=> alerts each number in turn...
+*/
+    @Test
+    @SuppressWarnings("unchecked")
+    public void forEachIndexed() {
+        final List<Integer> result = new ArrayList<Integer>();
+        $.forEachIndexed(asList(1, 2, 3), new BiConsumer<Integer, Integer>() {
+            public void accept(Integer index, Integer item) {
+                result.add(item);
+            }
+        });
+        assertEquals("[1, 2, 3]", result.toString());
+        final List<Integer> resultObj = new ArrayList<Integer>();
+        new $(asList(1, 2, 3)).forEachIndexed(new BiConsumer<Integer, Integer>() {
+            public void accept(Integer index, Integer item) {
+                resultObj.add(item);
+            }
+        });
+        assertEquals("[1, 2, 3]", resultObj.toString());
+    }
+
 /*
 _.forEach([1, 2, 3], alert);
 => alerts each number in turn from right to left...
@@ -220,6 +243,26 @@ public Integer apply(Map.Entry<Integer, String> item) {
         assertEquals("[3, 6, 9]", result.toString());
     }
 
+/*
+_.mapIndexed([1, 2, 3], function(num){ return num * 3; });
+=> [3, 6, 9]
+*/
+    @Test
+    public void mapIndexed() {
+        List<Integer> result = $.mapIndexed(asList(1, 2, 3), new BiFunction<Integer, Integer, Integer>() {
+            public Integer apply(Integer index, Integer item) {
+                return item * 3;
+            }
+        });
+        assertEquals("[3, 6, 9]", result.toString());
+        List<Integer> resultObject = new $<Integer>(asList(1, 2, 3)).mapIndexed(new BiFunction<Integer, Integer, Integer>() {
+            public Integer apply(Integer index, Integer item) {
+                return item * 3;
+            }
+        });
+        assertEquals("[3, 6, 9]", resultObject.toString());
+    }
+
 /*
 _.collect([1, 2, 3], function(num){ return num * 3; });
 => [3, 6, 9]