word-count: Generalize test suite.

exercises/word-count/HINTS.md

@@ -0,0 +1,21 @@
+## Hints
+
+To complete this exercise you need to implement the function `wordCount`,
+that takes a *text* and returns how many times each *word* appears.
+
+If it is your first time solving this exercise, it is recommended that you
+stick to the provided signature:
+
+```haskell
+wordCount :: String -> [(String, Int)]
+```
+
+Later, it may be a good idea to revisit this problem and play with other data
+types and libraries:
+
+- `Text`, from package *text*.
+- `Map`, from package *containers*.
+- `MultiSet`, from package *multiset*
+
+The test suite was intentionally designed to accept almost any type signature
+that makes sense, so you are encouraged to find the one you think is the best.

exercises/word-count/examples/success-newtype/WordCount.hs

@@ -0,0 +1,31 @@
+{-# LANGUAGE TypeFamilies #-}
+
+module WordCount (wordCount) where
+
+import Prelude hiding (null)
+import Data.Char      (isAlphaNum)
+import Data.Text      (Text, null, split, toLower)
+import Data.MultiSet  (MultiSet, Occur, fromList, fromOccurList, toOccurList)
+
+import qualified GHC.Exts (IsList(..))
+
+wordCount :: Text -> Bag Text
+wordCount = Bag
+          . fromList
+          . map toLower
+          . wordsBy (not . isAlphaNum)
+
+-- The `text` package misses this function that
+-- exists in package `split`, but works on lists.
+wordsBy :: (Char -> Bool) -> Text -> [Text]
+wordsBy p = filter (not . null) . split p
+
+-- MultiSet is not an instance of `IsList`, so we create
+-- a newtype to wrap it, avoiding an orphan instance.
+newtype Bag a = Bag { toMultiSet :: MultiSet a }
+
+instance (Ord a) => GHC.Exts.IsList (Bag a)
+  where
+    type Item (Bag a) = (a, Occur)
+    fromList = Bag . fromOccurList
+    toList   = toOccurList . toMultiSet

exercises/word-count/examples/success-newtype/package.yaml

@@ -0,0 +1,21 @@
+name: word-count
+
+dependencies:
+  - base
+
+library:
+  exposed-modules: WordCount
+  source-dirs: src
+  dependencies:
+  # - foo       # List here the packages you
+  # - bar       # want to use in your solution.
+    - multiset
+    - text
+
+tests:
+  test:
+    main: Tests.hs
+    source-dirs: test
+    dependencies:
+      - word-count
+      - hspec

exercises/word-count/examples/success-simple/WordCount.hs

@@ -0,0 +1,13 @@
+module WordCount (wordCount) where
+
+import Control.Arrow   ((&&&))
+import Data.Char       (toLower, isAlphaNum)
+import Data.List       (group, sort)
+import Data.List.Split (wordsBy)
+
+wordCount :: String -> [(String, Int)]
+wordCount = map (head &&& length)
+          . group
+          . sort
+          . map (map toLower)
+          . wordsBy (not . isAlphaNum)

exercises/word-count/examples/success-simple/package.yaml

@@ -0,0 +1,20 @@
+name: word-count
+
+dependencies:
+  - base
+
+library:
+  exposed-modules: WordCount
+  source-dirs: src
+  dependencies:
+  # - foo       # List here the packages you
+  # - bar       # want to use in your solution.
+    - split
+
+tests:
+  test:
+    main: Tests.hs
+    source-dirs: test
+    dependencies:
+      - word-count
+      - hspec

exercises/word-count/package.yaml

@@ -2,15 +2,13 @@ name: word-count
 
 dependencies:
   - base
-  - containers
 
 library:
   exposed-modules: WordCount
   source-dirs: src
   dependencies:
   # - foo       # List here the packages you
   # - bar       # want to use in your solution.
-    - split
 
 tests:
   test:

exercises/word-count/src/WordCount.hs

@@ -1,3 +1,4 @@
 module WordCount (wordCount) where
 
-wordCount = undefined
+wordCount :: String -> [(String, Int)]
+wordCount xs = undefined

exercises/word-count/test/Tests.hs

@@ -1,9 +1,11 @@
 {-# OPTIONS_GHC -fno-warn-type-defaults #-}
 {-# LANGUAGE RecordWildCards #-}
 
+import Data.Bifunctor    (bimap)
+import Data.Char         (toLower)
 import Data.Foldable     (for_)
-import Data.Map          (fromList)
-import Test.Hspec        (Spec, describe, it, shouldBe)
+import GHC.Exts          (fromList, toList)
+import Test.Hspec        (Spec, describe, it, shouldMatchList)
 import Test.Hspec.Runner (configFastFail, defaultConfig, hspecWith)
 
 import WordCount (wordCount)
@@ -15,11 +17,18 @@ specs :: Spec
 specs = describe "word-count" $
           describe "wordCount" $ for_ cases test
   where
-
-    test Case{..} = it description $ returnedMap `shouldBe` expectedMap
+    -- Here we used `fromIntegral`, `fromList` and `toList` to generalize
+    -- the tests, accepting any function that receives a string-like argumment
+    -- and returns a type that can be converted to [(String, Integer)].
+    -- Also, the words are lower-cased before comparison and the output's
+    -- order is ignored.
+    test Case{..} = it description $ expression `shouldMatchList` expected
       where
-        returnedMap = wordCount input
-        expectedMap = fromIntegral <$> fromList expected
+        expression = map (bimap (map toLower . toList) fromIntegral)
+                   . toList
+                   . wordCount
+                   . fromList
+                   $ input
 
 -- Test cases adapted from `exercism/x-common/word-count.json` on 2016-07-26.