Update Pairs.php

More functional way

Author: Roman Gemini

src/Pairs.php

@@ -30,15 +30,13 @@ function toString($list)
         return $list;
     }
 
-    $arr = [];
-    $iter = function ($items) use (&$arr, &$iter) {
-        if ($items != null) {
-            $arr[] = toString(car($items));
-            $iter(cdr($items));
+    $iter = function ($items, array $acc) use (&$iter) {
+        if ($items == null) {
+            return $acc;
         }
-
+        return $iter(cdr($items), array_merge($acc, toString(car($items))));
     };
-    $iter($list);
+    $arr = $iter($list, []);
 
     return "(" . implode(", ", $arr) . ")";
 }