Add iter\recurse()

Author: nikic

README.md

@@ -73,6 +73,7 @@ list the function signatures as an overview:
     void     apply(callable $function, iterable $iterable)
     string   join(string $separator, iterable $iterable)
     int      count(iterable $iterable)
+    mixed    recurse(callable $function, $iterable)
     array    toArray(iterable $iterable)
     array    toArrayWithKeys(iterable $iterable)
     bool     isIterable($value)

src/iter.php

@@ -838,6 +838,30 @@ function count($iterable) {
     return $count;
 }
 
+/**
+ * Recursively applies a function, working on entire iterables rather than
+ * individual values.
+ *
+ * The function will be called both on the passed iterable and all iterables it
+ * contains, etc. The call sequence is in post-order (inner before outer).
+ *
+ * Examples:
+ *
+ *     iter\recurse('iter\toArray',
+ *          new ArrayIterator([1, 2, new ArrayIterator([3, 4])]));
+ *     => [1, 2, [3, 4]]
+ *
+ * @param callable $function
+ * @param $iterable
+ * @return mixed
+ */
+function recurse(callable $function, $iterable) {
+    _assertIterable($iterable, 'Second argument');
+    return $function(map(function($value) use($function) {
+        return isIterable($value) ? recurse($function, $value) : $value;
+    }, $iterable));
+}
+
 /**
  * Converts any iterable into an Iterator.
  *

test/iterTest.php

@@ -381,6 +381,21 @@ function() {
         );
     }
 
+    function testRecurse() {
+        $iter = new \ArrayIterator(['a' => 1, 'b' => 2,
+            'c' => new \ArrayIterator(['d' => 3, 'e' => 4])]);
+
+        $this->assertSame(
+            [1, 2, [3, 4]],
+            recurse('iter\toArray', $iter)
+        );
+
+        $this->assertSame(
+            ['a' => 1, 'b' => 2, 'c' => ['d' => 3, 'e' => 4]],
+            recurse('iter\toArrayWithKeys', $iter)
+        );
+    }
+
     private function assertKeysValues(array $keys, array $values, callable $fn) {
         $this->assertSame($keys, toArray(keys($fn())));
         $this->assertSame($values, toArray(values($fn())));