X-Git-Url: http://gitweb.michael.orlitzky.com/?a=blobdiff_plain;f=src%2FMisc.hs;h=b9322ef0c2d49b23f26350af2e32eb04b403b2d5;hb=3228e541540bf785d95bbdbfe4a44c486182e45e;hp=b1cb1affcce0a53463c5f9ae400c5da27fabd157;hpb=3f7331f579118687cd73b977ce6aa7d401f88a09;p=spline3.git

diff --git a/src/Misc.hs b/src/Misc.hs
index b1cb1af..b9322ef 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
@@ -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.
@@ -58,6 +60,9 @@ transpose_xz m =
 
 -- | Takes a list, and returns True if its elements are pairwise
 --   equal. Returns False otherwise.
+--
+--   Only used in tests.
+--
 all_equal :: (Eq a) => [a] -> Bool
 all_equal xs =
     all (== first_element) other_elements
@@ -80,6 +85,8 @@ all_equal xs =
 --   >>> disjoint xs ys
 --   False
 --
+--   Only used in tests.
+--
 disjoint :: (Eq a) => V.Vector a -> V.Vector a -> Bool
 disjoint xs ys =
   intersect xs ys == V.empty