Initial Commit

haskell/current

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+leap

haskell/leap/README.md

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+# Leap
+
+Write a program that will take a year and report if it is a leap year.
+
+The tricky thing here is that a leap year occurs:
+
+```plain
+on every year that is evenly divisible by 4
+  except every year that is evenly divisible by 100
+    unless the year is also evenly divisible by 400
+```
+
+For example, 1997 is not a leap year, but 1996 is.  1900 is not a leap
+year, but 2000 is.
+
+If your language provides a method in the standard library that does
+this look-up, pretend it doesn't exist and implement it yourself.
+
+## Notes
+
+For a delightful, four minute explanation of the whole leap year
+phenomenon, go watch [this youtube video][video].
+
+[video]: http://www.youtube.com/watch?v=xX96xng7sAE
+
+Check out [Exercism
+Help](http://help.exercism.io/getting-started-with-haskell.html) for
+instructions to get started writing Haskell.
+
+## Running Tests
+
+Use `runhaskell` (included in the Haskell Platform) to compile and run your
+Haskell code.
+
+    $ runhaskell -Wall bob_test.hs
+
+## Source
+
+JavaRanch Cattle Drive, exercise 3 [view source](http://www.javaranch.com/leap.jsp)

haskell/leap/leap_test.hs

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+import Test.HUnit (Assertion, (@=?), runTestTT, Test(..), Counts(..))
+import System.Exit (ExitCode(..), exitWith)
+import LeapYear (isLeapYear)
+
+exitProperly :: IO Counts -> IO ()
+exitProperly m = do
+  counts <- m
+  exitWith $ if failures counts /= 0 || errors counts /= 0 then ExitFailure 1 else ExitSuccess
+
+testCase :: String -> Assertion -> Test
+testCase label assertion = TestLabel label (TestCase assertion)
+
+main :: IO ()
+main = exitProperly $ runTestTT $ TestList
+       [ TestList isLeapYearTests ]
+
+isLeapYearTests :: [Test]
+isLeapYearTests =
+  [ testCase "vanilla leap year" $
+    True @=? isLeapYear 1996
+  , testCase "any old year" $
+    False @=? isLeapYear 1997
+  , testCase "century" $
+    False @=? isLeapYear 1900
+  , testCase "exceptional century" $
+    True @=? isLeapYear 2400
+  ]