X-Git-Url: http://gitweb.michael.orlitzky.com/?a=blobdiff_plain;f=src%2FMisc.hs;h=d0eb7286559ecd0b5098fd67afd38bcbb0179e1c;hb=b494ff845304fe1f255130539e271e6bfc2a5d3e;hp=34c682e31a7609e590898311885ea397fed1f6c4;hpb=26f0a2204a0bdb41b1d6aa5430544c404b77e638;p=spline3.git

diff --git a/src/Misc.hs b/src/Misc.hs
index 34c682e..d0eb728 100644
--- a/src/Misc.hs
+++ b/src/Misc.hs
@@ -1,8 +1,16 @@
+{-# LANGUAGE BangPatterns #-}
 -- | The Misc module contains helper functions that seem out of place
 --   anywhere else.
 module Misc
 where
 
+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 (Assertion, assertEqual)
+import Test.QuickCheck
+
 
 -- | The standard factorial function. See
 --   <http://www.willamette.edu/~fruehr/haskell/evolution.html> for
@@ -17,11 +25,12 @@ where
 --   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.
@@ -35,11 +44,78 @@ flatten :: [[[a]]] -> [a]
 flatten xs = concat $ concat xs
 
 
+-- | Switch the x and z dimensions of a three-dimensional list.
+transpose_xz :: [[[a]]] -> [[[a]]]
+transpose_xz [] = []
+transpose_xz [[]] = [[]]
+transpose_xz [[[]]] = [[[]]]
+transpose_xz m =
+    [[[ m !! x !! y !! z | x <- [0..xsize]]
+                      | y <- [0..ysize]]
+                      | z <- [0..zsize]]
+    where
+      zsize = (length m) - 1
+      ysize = length (head m) - 1
+      xsize = length (head $ head m) - 1
+
 -- | 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
     where
       first_element  = head xs
       other_elements = tail xs
+
+
+-- | Returns 'True' if the vectors xs and ys are disjoint, 'False'
+--   otherwise.
+--
+--   Examples:
+--
+--   >>> let xs = Data.Vector.fromList [1,2,3]
+--   >>> let ys = Data.Vector.fromList [4,5,6]
+--   >>> disjoint xs ys
+--   True
+--
+--   >>> let ys = Data.Vector.fromList [3,4,5]
+--   >>> 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
+  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 =
+    n <= 20 ==> factorial n >= n
+
+
+test_flatten1 :: Assertion
+test_flatten1 =
+    assertEqual "flatten actually works" expected_list actual_list
+    where
+      target = [[[1::Int]], [[2, 3]]]
+      expected_list = [1, 2, 3]
+      actual_list = flatten target
+
+
+misc_tests :: Test.Framework.Test
+misc_tests =
+    testGroup "Misc Tests" [
+      testCase "flatten (1)" test_flatten1 ]
+
+
+misc_properties :: Test.Framework.Test
+misc_properties =
+    testGroup "Misc Properties" [
+      testProperty "factorial greater" prop_factorial_greater ]