1 files changed, 47 insertions, 0 deletions
diff --git a/src/main/java/org/zwobble/couscous/util/ExtraIterables.java b/src/main/java/org/zwobble/couscous/util/ExtraIterables.java
index 1fd9fca..cd9b3df 100644
--- a/src/main/java/org/zwobble/couscous/util/ExtraIterables.java
+++ b/src/main/java/org/zwobble/couscous/util/ExtraIterables.java
@@ -1,7 +1,14 @@
 package org.zwobble.couscous.util;
 
+import com.google.common.collect.Iterables;
+
 import java.util.Iterator;
 import java.util.function.BiFunction;
+import java.util.function.Function;
+import java.util.stream.Stream;
+import java.util.stream.StreamSupport;
+
+import static org.zwobble.couscous.util.ExtraLists.list;
 
 public class ExtraIterables {
     private ExtraIterables() {}
@@ -69,4 +76,44 @@ public class ExtraIterables {
             }
         };
     }
+
+    public static <T> Iterable<T> lazyCons(T head, Iterable<T> tails) {
+        return Iterables.concat(list(head), tails);
+    }
+
+    public static <T, R> Iterable<R> lazyMap(Iterable<T> iterable, Function<T, R> function) {
+        return new Iterable<R>() {
+            @Override
+            public Iterator<R> iterator() {
+                return map(iterable.iterator(), function);
+            }
+        };
+    }
+
+    private static <T, R> Iterator<R> map(Iterator<T> iterator, Function<T, R> function) {
+        return new Iterator<R>() {
+            @Override
+            public boolean hasNext() {
+                return iterator.hasNext();
+            }
+
+            @Override
+            public R next() {
+                return function.apply(iterator.next());
+            }
+        };
+    }
+
+    public static <T, R> Iterable<R> lazyFlatMap(Iterable<T> iterable, Function<T, Iterable<R>> function) {
+        return new Iterable<R>() {
+            @Override
+            public Iterator<R> iterator() {
+                return stream(iterable).flatMap(element -> stream(function.apply(element))).iterator();
+            }
+        };
+    }
+
+    public static <T> Stream<T> stream(Iterable<T> iterable) {
+        return StreamSupport.stream(iterable.spliterator(), false);
+    }
 }