+{-# LANGUAGE BangPatterns #-}
+
-- | The Misc module contains helper functions that seem out of place
-- anywhere else.
-module Misc
+--
+module Misc (
+ all_equal,
+ disjoint,
+ factorial,
+ flatten,
+ misc_properties,
+ misc_tests,
+ transpose_xz )
where
-import Data.List (intersect)
+import qualified Data.Vector as V ( Vector, elem, empty, filter )
+import Test.Tasty ( TestTree, testGroup )
+import Test.Tasty.HUnit ( Assertion, assertEqual, testCase )
+import Test.Tasty.QuickCheck ( Property, (==>), testProperty )
-- | The standard factorial function. See
-- 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.
-- | 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
+all_equal [] = True -- Vacuously
+all_equal (x:xs) = all (== x) 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 =
+ 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] :: [Int]
+ actual_list = flatten target
+
+
+misc_tests :: TestTree
+misc_tests =
+ testGroup "Misc tests" [
+ testCase "flatten (1)" test_flatten1 ]
+
+
+misc_properties :: TestTree
+misc_properties =
+ testGroup "Misc properties" [
+ testProperty "factorial greater" prop_factorial_greater ]