Adds string termination

Author: pitchart

src/Reducer/Termination/ToString.php

@@ -0,0 +1,34 @@
+<?php
+
+namespace Pitchart\Transformer\Reducer\Termination;
+
+use Pitchart\Transformer\Termination;
+
+class ToString implements Termination
+{
+    /**
+     * @var string
+     */
+    private $glue;
+
+    public function __construct($glue = '')
+    {
+        $this->glue = $glue;
+    }
+
+    public function init()
+    {
+        return '';
+    }
+
+    public function step($result, $current)
+    {
+        return $result.$this->glue.$current;
+    }
+
+    public function complete($result)
+    {
+        return $result;
+    }
+
+}

src/Transducer/transducers.php

@@ -269,6 +269,14 @@ function to_single()
     return new Reducer\Termination\SingleResult();
 }
 
+/**
+ * @return Reducer\Termination\ToString
+ */
+function to_string($glue = '')
+{
+    return new Reducer\Termination\ToString($glue);
+}
+
 /**
  * @return Reducer\Termination\ToArray
  */

src/Transformer.php

@@ -271,15 +271,25 @@ public function groupBy(callable $callback)
     }
 
     /**
-     * @return mixed
+     * @param string $glue
+     *
+     * @return string
+     */
+    public function toString($glue = '')
+    {
+        return $this->terminate(t\to_string($glue));
+    }
+
+    /**
+     * @return array
      */
     public function toArray()
     {
         return $this->terminate(t\to_array());
     }
 
     /**
-     * @return mixed
+     * @return \Iterator
      */
     public function toIterator()
     {

tests/TransformerTest.php

@@ -43,6 +43,13 @@ public function test_can_transduce_into_iterator()
         self::assertEquals([1, 2, 3, 4, 5, 6], $values);
     }
 
+    public function test_can_transduce_into_string()
+    {
+        $result = (new Transformer(range(1, 6)))->toString('');
+
+        self::assertEquals('123456', $result);
+    }
+
     public function test_can_map_items_of_iterable()
     {
         $mapped = (new Transformer(range(1,6)))