X-Git-Url: http://gitweb.michael.orlitzky.com/?a=blobdiff_plain;f=src%2FMisc.hs;h=d0eb7286559ecd0b5098fd67afd38bcbb0179e1c;hb=1bf996325008f79215a607d765adb042026f7444;hp=16b0ead151ad1b29190028db01aa98ef34d6b797;hpb=9849853e69c46b46996e8c775d15661b2aba27a8;p=spline3.git

diff --git a/src/Misc.hs b/src/Misc.hs
index 16b0ead..d0eb728 100644
--- a/src/Misc.hs
+++ b/src/Misc.hs
@@ -1,13 +1,14 @@
+{-# LANGUAGE BangPatterns #-}
 -- | The Misc module contains helper functions that seem out of place
 --   anywhere else.
 module Misc
 where
 
-import Data.List (intersect)
+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 =
+  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
@@ -66,22 +71,29 @@ all_equal xs =
       other_elements = tail xs
 
 
--- | Returns 'True' if the lists xs and ys are disjoint, 'False'
+-- | Returns 'True' if the vectors xs and ys are disjoint, 'False'
 --   otherwise.
 --
 --   Examples:
 --
---   >>> disjoint [1,2,3] [4,5,6]
+--   >>> let xs = Data.Vector.fromList [1,2,3]
+--   >>> let ys = Data.Vector.fromList [4,5,6]
+--   >>> disjoint xs ys
 --   True
 --
---   >>>  disjoint [1,2,3] [3,4,5]
+--   >>> let ys = Data.Vector.fromList [3,4,5]
+--   >>> disjoint xs ys
 --   False
 --
-disjoint :: (Eq a) => [a] -> [a] -> Bool
+--   Only used in tests.
+--
+disjoint :: (Eq a) => V.Vector a -> V.Vector a -> Bool
 disjoint xs ys =
-    intersect xs ys == []
-
-
+  intersect xs ys == V.empty
+  where
+    intersect :: (Eq a) => V.Vector a -> V.Vector a -> V.Vector a
+    intersect ws zs =
+      V.filter (`V.elem` zs) ws
 
 prop_factorial_greater :: Int -> Property
 prop_factorial_greater n =