1 files changed, 26 insertions, 0 deletions
diff --git a/src/main/java/org/zwobble/mammoth/internal/util/Iterables.java b/src/main/java/org/zwobble/mammoth/internal/util/Iterables.java
index cb2ac36..7297894 100644
--- a/src/main/java/org/zwobble/mammoth/internal/util/Iterables.java
+++ b/src/main/java/org/zwobble/mammoth/internal/util/Iterables.java
@@ -2,6 +2,7 @@ package org.zwobble.mammoth.internal.util;
 
 import java.util.Iterator;
 import java.util.Optional;
+import java.util.function.BiFunction;
 import java.util.function.Function;
 import java.util.function.Predicate;
 import java.util.stream.Stream;
@@ -26,6 +27,15 @@ public class Iterables {
         };
     }
 
+    public static <T, R> Iterable<R> lazyMap(Iterable<T> iterable, BiFunction<Integer, T, R> function) {
+        return new Iterable<R>() {
+            @Override
+            public Iterator<R> iterator() {
+                return map(iterable.iterator(), function);
+            }
+        };
+    }
+
     public static <T> Optional<T> getFirst(Iterable<? extends T> iterable) {
         Iterator<? extends T> iterator = iterable.iterator();
         if (iterator.hasNext()) {
@@ -105,6 +115,22 @@ public class Iterables {
         };
     }
 
+    private static <T, R> Iterator<R> map(Iterator<T> iterator, BiFunction<Integer, T, R> function) {
+        return new Iterator<R>() {
+            private int nextIndex = 0;
+
+            @Override
+            public boolean hasNext() {
+                return iterator.hasNext();
+            }
+
+            @Override
+            public R next() {
+                return function.apply(nextIndex++, iterator.next());
+            }
+        };
+    }
+
     public static <T> boolean any(Iterable<T> iterable, Predicate<T> predicate) {
         return stream(iterable).anyMatch(predicate);
     }