✅ haskell: leap

haskell/leap/HELP.md

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+# Help
+
+## Running the tests
+
+To run the test suite, execute the following command:
+
+```bash
+stack test
+```
+
+#### If you get an error message like this...
+
+```
+No .cabal file found in directory
+```
+
+or
+
+```
+RedownloadInvalidResponse Request {
+...
+}
+ "/home/username/.stack/build-plan/lts-xx.yy.yaml" (Response {responseStatus = Status {statusCode = 404, statusMessage = "Not Found"},
+```
+
+You are probably running an old stack version and need
+to upgrade it. Try running:
+
+```bash
+stack upgrade
+```
+
+Or see other options for upgrading at [Stack documentation](https://docs.haskellstack.org/en/stable/install_and_upgrade/#upgrade).
+
+#### Otherwise, if you get an error message like this...
+
+```
+No compiler found, expected minor version match with...
+Try running "stack setup" to install the correct GHC...
+```
+
+Just do as it says and it will download and install
+the correct compiler version:
+
+```bash
+stack setup
+```
+
+
+If you want to play with your solution in GHCi, just run the command:
+
+```bash
+stack ghci
+```
+
+## Submitting your solution
+
+You can submit your solution using the `exercism submit src/LeapYear.hs` command.
+This command will upload your solution to the Exercism website and print the solution page's URL.
+
+It's possible to submit an incomplete solution which allows you to:
+
+- See how others have completed the exercise
+- Request help from a mentor
+
+## Need to get help?
+
+If you'd like help solving the exercise, check the following pages:
+
+- The [Haskell track's documentation](https://exercism.org/docs/tracks/haskell)
+- [Exercism's support channel on gitter](https://gitter.im/exercism/support)
+- The [Frequently Asked Questions](https://exercism.org/docs/using/faqs)
+
+Should those resources not suffice, you could submit your (incomplete) solution to request mentoring.
+
+## Getting Started
+
+Please refer to the [installation](https://exercism.io/tracks/haskell/installation)
+and [learning](https://exercism.io/tracks/haskell/learning) help pages.
+
+## Feedback, Issues, Pull Requests
+
+The [exercism/haskell](https://github.com/exercism/haskell) repository on
+GitHub is the home for all of the Haskell exercises.
+
+If you have feedback about an exercise, or want to help implementing a new
+one, head over there and create an issue.  We'll do our best to help you!
+{{ with .Spec.Credits }}

haskell/leap/README.md

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+# Leap
+
+Welcome to Leap on Exercism's Haskell Track.
+If you need help running the tests or submitting your code, check out `HELP.md`.
+
+## Instructions
+
+Given a year, report if it is a leap year.
+
+The tricky thing here is that a leap year in the Gregorian calendar occurs:
+
+```text
+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.
+
+## Notes
+
+Though our exercise adopts some very simple rules, there is more to
+learn!
+
+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
+
+To complete this exercise you need to implement the function `isLeapYear`
+that takes a year and determines whether it is a leap year.
+
+## Source
+
+### Created by
+
+- @etrepum
+
+### Contributed to by
+
+- @iHiD
+- @karen-pal
+- @kytrinyx
+- @navossoc
+- @paulrex
+- @petertseng
+- @ppartarr
+- @rbasso
+- @sshine
+- @tejasbubane
+- @tofische
+
+### Based on
+
+JavaRanch Cattle Drive, exercise 3 - http://www.javaranch.com/leap.jsp

haskell/leap/examples/error-nosig/package.yaml

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+name: leap
+
+dependencies:
+  - base
+
+library:
+  exposed-modules: LeapYear
+  source-dirs: src
+
+tests:
+  test:
+    main: Tests.hs
+    source-dirs: test
+    dependencies:
+      - leap
+      - hspec

haskell/leap/examples/error-nosig/src/LeapYear.hs

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+module LeapYear (isLeapYear) where
+
+isLeapYear year = hasFactor 4 && (not (hasFactor 100) || hasFactor 400)
+  where hasFactor n = year `rem` n == 0

haskell/leap/examples/success-standard/package.yaml

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+name: leap
+
+dependencies:
+  - base
+
+library:
+  exposed-modules: LeapYear
+  source-dirs: src
+
+tests:
+  test:
+    main: Tests.hs
+    source-dirs: test
+    dependencies:
+      - leap
+      - hspec

haskell/leap/package.yaml

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+name: leap
+version: 1.6.0.10
+
+dependencies:
+  - base
+
+library:
+  exposed-modules: LeapYear
+  source-dirs: src
+  ghc-options: -Wall
+  # dependencies:
+  # - foo       # List here the packages you
+  # - bar       # want to use in your solution.
+
+tests:
+  test:
+    main: Tests.hs
+    source-dirs: test
+    dependencies:
+      - leap
+      - hspec

haskell/leap/src/LeapYear.hs

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+module LeapYear (isLeapYear) where
+
+isLeapYear :: Integer -> Bool
+isLeapYear year = year `mod` 4 == 0 && ((year `mod` 100 /= 0) || (year `mod` 400 == 0))

haskell/leap/stack.yaml

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+resolver: lts-16.21

haskell/leap/test/Tests.hs

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+{-# OPTIONS_GHC -fno-warn-type-defaults #-}
+{-# LANGUAGE RecordWildCards #-}
+
+import Data.Foldable     (for_)
+import Test.Hspec        (Spec, describe, it, shouldBe)
+import Test.Hspec.Runner (configFastFail, defaultConfig, hspecWith)
+
+import LeapYear (isLeapYear)
+
+main :: IO ()
+main = hspecWith defaultConfig {configFastFail = True} specs
+
+specs :: Spec
+specs = describe "isLeapYear" $ for_ cases test
+  where
+
+    test Case{..} = it explanation assertion
+      where
+        explanation = unwords [show input, "-", description]
+        assertion   = isLeapYear (fromIntegral input) `shouldBe` expected
+
+data Case = Case { description :: String
+                 , input       :: Integer
+                 , expected    :: Bool
+                 }
+
+cases :: [Case]
+cases = [ Case { description = "year not divisible by 4 in common year"
+               , input       = 2015
+               , expected    = False
+               }
+        , Case { description = "year divisible by 2, not divisible by 4 in common year"
+               , input       = 1970
+               , expected    = False
+               }
+        , Case { description = "year divisible by 4, not divisible by 100 in leap year"
+               , input       = 1996
+               , expected    = True
+               }
+        , Case { description = "year divisible by 4 and 5 is still a leap year"
+               , input       = 1960
+               , expected    = True
+               }
+        , Case { description = "year divisible by 100, not divisible by 400 in common year"
+               , input       = 2100
+               , expected    = False
+               }
+        , Case { description = "year divisible by 100 but not by 3 is still not a leap year"
+               , input       = 1900
+               , expected    = False
+               }
+        , Case { description = "year divisible by 400 in leap year"
+               , input       = 2000
+               , expected    = True
+               }
+        , Case { description = "year divisible by 400 but not by 125 is still a leap year"
+               , input       = 2400
+               , expected    = True
+               }
+        , Case { description = "year divisible by 200, not divisible by 400 in common year"
+               , input       = 1800
+               , expected    = False
+               }
+        ]
+
+-- bd7f470e9ffe40993fc49558a02676ac22827441