X-Git-Url: http://gitweb.michael.orlitzky.com/?a=blobdiff_plain;f=src%2FMisc.hs;h=4b285e4cc3b0cff1f8344aa09c905ed6b0c3fe99;hb=40a354da29b99d773fc18c4c4ad0d136a93d7264;hp=57dfd433e2ffc4b72cb8daa00f19f94443813404;hpb=d2e1b5009ad0ae3595e874227586617aad068daa;p=spline3.git

diff --git a/src/Misc.hs b/src/Misc.hs
index 57dfd43..4b285e4 100644
--- a/src/Misc.hs
+++ b/src/Misc.hs
@@ -1,3 +1,4 @@
+{-# LANGUAGE BangPatterns #-}
 -- | The Misc module contains helper functions that seem out of place
 --   anywhere else.
 module Misc
@@ -7,7 +8,7 @@ import qualified Data.Vector as V (Vector, elem, empty, filter)
 import Test.Framework (Test, testGroup)
 import Test.Framework.Providers.HUnit (testCase)
 import Test.Framework.Providers.QuickCheck2 (testProperty)
-import Test.HUnit
+import Test.HUnit (Assertion, assertEqual)
 import Test.QuickCheck
 
 
@@ -24,11 +25,12 @@ import Test.QuickCheck
 --   24
 --
 factorial :: Int -> Int
-factorial n
-    | n <= 1 = 1
-    | n > 20 = error "integer overflow in factorial function"
-    | otherwise = product [1..n]
-
+factorial !n
+    | n > 20    = error "integer overflow in factorial function"
+    | otherwise = go 1 n
+    where go !acc !i
+                | i <= 1    = acc
+                | otherwise = go (acc * i) (i - 1)
 
 -- | Takes a three-dimensional list, and flattens it into a
 --   one-dimensional one.