From e71eda7c5e9e96a90892fc2bc481649b671318a6 Mon Sep 17 00:00:00 2001
From: Dimitri Lozeve <dimitri.lozeve@gmail.com>
Date: Wed, 17 Jan 2018 17:13:53 +0000
Subject: [PATCH] Add check for negative number of iterations

---
 src/Lib.hs | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/Lib.hs b/src/Lib.hs
index c52a003..a4d9ae5 100644
--- a/src/Lib.hs
+++ b/src/Lib.hs
@@ -43,6 +43,7 @@ iterateLSystem :: (Eq a, Integral t) => t -> LSystem a -> LSystem a
 iterateLSystem 0 lsystem = lsystem
 iterateLSystem n (LSystem a ax r ang dist rep) =
   iterateLSystem (n-1) $ LSystem a ax' r ang dist rep
+iterateLSystem n lsystem | n < 0 = iterateLSystem (-n) lsystem
   where ax' = concat $ map f ax
         f x = case lookup x r of
                 Just xs -> xs