From 222df4d65e4a8ba02c5452f0301fee92425e875e Mon Sep 17 00:00:00 2001
From: Taylor Fausak <taylor@fausak.me>
Date: Sun, 6 Apr 2014 16:48:08 -0500
Subject: [PATCH] Make roughness independent of tile value

---
 library/Hs2048/AI.hs        | 6 +++---
 test-suite/Hs2048/AISpec.hs | 2 +-
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/library/Hs2048/AI.hs b/library/Hs2048/AI.hs
index 215cda2..940fb20 100644
--- a/library/Hs2048/AI.hs
+++ b/library/Hs2048/AI.hs
@@ -72,14 +72,14 @@ quality b = sum
     each other. Smooth boards are generally better.
 
     >>> roughness [[Just 2, Just 4]]
-    2
+    1
     >>> roughness [[Just 2, Just 2]]
     0
 
     Blank tiles are ignored for the purposes of calculating roughness.
 
     >>> roughness [[Just 2, Nothing, Just 4]]
-    2
+    1
 -}
 roughness :: B.Board -> Int
 roughness b = boardRoughness b + boardRoughness (B.rotate b)
@@ -96,6 +96,6 @@ duplicates :: B.Board -> [[Int]]
 duplicates = group . sort . (=<<) catMaybes
 
 vectorRoughness :: V.Vector -> Int
-vectorRoughness v = sum (fmap abs (zipWith subtract ts (tail ts)))
+vectorRoughness v = length (filter id (zipWith (/=) ts (tail ts)))
   where
     ts = catMaybes v
diff --git a/test-suite/Hs2048/AISpec.hs b/test-suite/Hs2048/AISpec.hs
index cf2a8a6..c119760 100644
--- a/test-suite/Hs2048/AISpec.hs
+++ b/test-suite/Hs2048/AISpec.hs
@@ -34,4 +34,4 @@ spec = do
             roughness [] `shouldBe` 0
 
         it "calculates the roughness of a board" $ do
-            roughness b `shouldBe` 5734
+            roughness b `shouldBe` 16