From 28eae4262ae7c31d77f09a10020ec6a0005a207d Mon Sep 17 00:00:00 2001
From: James Crayne <jim.crayne@gmail.com>
Date: Wed, 30 May 2018 01:54:16 +0000
Subject: off by 1 bug

---
 src/Data/Word64RangeMap.hs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

(limited to 'src')

diff --git a/src/Data/Word64RangeMap.hs b/src/Data/Word64RangeMap.hs
index 36428233..0b25f56d 100644
--- a/src/Data/Word64RangeMap.hs
+++ b/src/Data/Word64RangeMap.hs
@@ -96,7 +96,7 @@ lookupArray i r = do
     ra <- readRefArray r
     (zr,nr) <- getBounds ra -- bounds of mutable range array
     let (dr,mr) = (nr+1 - zr) `divMod` 2
-    lookupArrayHelper i r (zr+dr+mr) zr nr
+    lookupArrayHelper i r (zr+dr+mr-1) zr nr
 
 lookupArrayHelper :: RangeArray ra m b ref => Index -> RangeMap ra b ref
                                        -> OuterIndex{- current position  -}
-- 
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