Add CollectionProviderInterface::lazy()

Author: emonkak

src/Enumerable.php

@@ -860,14 +860,15 @@ public function isEmpty()
         return Iterators::isEmpty($xs);
     }
 
-    private function newCollection($source)
+    protected function newCollection($source)
     {
         return new Collection($source, $this->getProvider());
     }
 
-    private function newLazyCollection(callable $factory)
+    protected function newLazyCollection(callable $factory)
     {
-        return new Collection(Iterators::createLazy($factory), $this->getProvider());
+        $provider = $this->getProvider();
+        return new Collection($provider->lazy($factory), $provider);
     }
 
     private function resolveComparer($comparer)

src/Provider/ArrayProvider.php

@@ -374,4 +374,12 @@ public function iterate($initial, callable $f)
     {
         throw new \OverflowException("Can't handle infinite stream.");
     }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function lazy(callable $factory)
+    {
+        return $factory();
+    }
 }

src/Provider/CollectionProviderInterface.php

@@ -178,4 +178,10 @@ public function renum($xs);
      * @return array|\Iterator
      */
     public function iterate($initial, callable $f);
+
+    /**
+     * @param callable $factory
+     * @return array|\Iterator
+     */
+    public function lazy(callable $factory);
 }

src/Provider/GeneratorProvider.php

@@ -451,4 +451,12 @@ public function iterate($initial, callable $f)
             }
         });
     }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function lazy(callable $factory)
+    {
+        return Iterators::createLazy($factory);
+    }
 }

src/Provider/IteratorProvider.php

@@ -287,4 +287,12 @@ public function iterate($initial, callable $f)
     {
         return new IterateIterator($initial, $f);
     }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function lazy(callable $factory)
+    {
+        return Iterators::createLazy($factory);
+    }
 }