From 6bb3b445b4e73ce99649d8dfa3cd3ac00a3a1ae2 Mon Sep 17 00:00:00 2001
From: Justin Lin <caterpillar@openhome.cc>
Date: Mon, 1 Jul 2019 07:46:25 +0800
Subject: [PATCH] refactor

---
 src/sub_str.scad | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/sub_str.scad b/src/sub_str.scad
index 3df9ca87..61cf2413 100644
--- a/src/sub_str.scad
+++ b/src/sub_str.scad
@@ -8,8 +8,9 @@
 *
 **/ 
 
-function sub_str(t, begin, end, result = "") =
-    end == undef ? sub_str(t, begin, len(t)) : (
-        begin == end ? result : sub_str(t, begin + 1, end, str(result, t[begin]))
-    );
+function _sub_str(t, begin, end) = 
+    begin == end ? "" : str(t[begin], sub_str(t, begin + 1, end));
+    
+function sub_str(t, begin, end) = 
+    end == undef ? _sub_str(t, begin, len(t)) : _sub_str(t, begin, end);
     
\ No newline at end of file