From 8aba34301b7d81686a70716598b348b554164c29 Mon Sep 17 00:00:00 2001
From: "Yukihiro \"Matz\" Matsumoto" <matz@ruby-lang.org>
Date: Mon, 19 Jan 2015 22:13:34 +0900
Subject: String#[]= should support negative position; close #2707

---
 mrblib/string.rb | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/mrblib/string.rb b/mrblib/string.rb
index 66a668e11..1d9ea9e6a 100644
--- a/mrblib/string.rb
+++ b/mrblib/string.rb
@@ -129,6 +129,9 @@ class String
   # Modify +self+ by replacing the content of +self+
   # at the position +pos+ with +value+.
   def []=(pos, value)
+    if pos < 0
+      pos += self.length
+    end
     b = self[0, pos]
     a = self[pos+1..-1]
     self.replace([b, value, a].join(''))
-- 
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