From 738b4042c0b29cc7519ca2ba183118cdc6ad5be3 Mon Sep 17 00:00:00 2001
From: rbasso <rbasso@sharpgeeks.net>
Date: Wed, 19 Oct 2016 22:11:18 +0900
Subject: [PATCH] word-count: Generalize test suite.

- Generalize the test suite to accept multiple signatures.
- Change the test suite to be case insensitive.
- Add `HINTS.md` explaining that the test suite is flexible.
- Add two example solutions: one very simple; the other with a custom type.
- Add the simplest type signature to the stub solution.
- Remove unneeded dependencies from `package.yaml`.
- Remove old example solution.
---
 exercises/word-count/HINTS.md                 | 21 +++++++++++++
 .../examples/success-newtype/WordCount.hs     | 31 +++++++++++++++++++
 .../examples/success-newtype/package.yaml     | 21 +++++++++++++
 .../examples/success-simple/WordCount.hs      | 13 ++++++++
 .../examples/success-simple/package.yaml      | 20 ++++++++++++
 exercises/word-count/package.yaml             |  2 --
 exercises/word-count/src/Example.hs           |  8 -----
 exercises/word-count/src/WordCount.hs         |  3 +-
 exercises/word-count/test/Tests.hs            | 21 +++++++++----
 9 files changed, 123 insertions(+), 17 deletions(-)
 create mode 100644 exercises/word-count/HINTS.md
 create mode 100644 exercises/word-count/examples/success-newtype/WordCount.hs
 create mode 100644 exercises/word-count/examples/success-newtype/package.yaml
 create mode 100644 exercises/word-count/examples/success-simple/WordCount.hs
 create mode 100644 exercises/word-count/examples/success-simple/package.yaml
 delete mode 100644 exercises/word-count/src/Example.hs

diff --git a/exercises/word-count/HINTS.md b/exercises/word-count/HINTS.md
new file mode 100644
index 000000000..cd5e0bc86
--- /dev/null
+++ b/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.
diff --git a/exercises/word-count/examples/success-newtype/WordCount.hs b/exercises/word-count/examples/success-newtype/WordCount.hs
new file mode 100644
index 000000000..6640269cc
--- /dev/null
+++ b/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
diff --git a/exercises/word-count/examples/success-newtype/package.yaml b/exercises/word-count/examples/success-newtype/package.yaml
new file mode 100644
index 000000000..34b9adf46
--- /dev/null
+++ b/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
diff --git a/exercises/word-count/examples/success-simple/WordCount.hs b/exercises/word-count/examples/success-simple/WordCount.hs
new file mode 100644
index 000000000..9c79b8d25
--- /dev/null
+++ b/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)
diff --git a/exercises/word-count/examples/success-simple/package.yaml b/exercises/word-count/examples/success-simple/package.yaml
new file mode 100644
index 000000000..bac8ecd0b
--- /dev/null
+++ b/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
diff --git a/exercises/word-count/package.yaml b/exercises/word-count/package.yaml
index 57a9dbf85..f14977c1f 100644
--- a/exercises/word-count/package.yaml
+++ b/exercises/word-count/package.yaml
@@ -2,7 +2,6 @@ name: word-count
 
 dependencies:
   - base
-  - containers
 
 library:
   exposed-modules: WordCount
@@ -10,7 +9,6 @@ library:
   dependencies:
   # - foo       # List here the packages you
   # - bar       # want to use in your solution.
-    - split
 
 tests:
   test:
diff --git a/exercises/word-count/src/Example.hs b/exercises/word-count/src/Example.hs
deleted file mode 100644
index 89a80b1d9..000000000
--- a/exercises/word-count/src/Example.hs
+++ /dev/null
@@ -1,8 +0,0 @@
-module WordCount (wordCount) where
-import Data.Char (toLower, isAlphaNum)
-import Data.Map.Strict (Map, fromListWith)
-import Data.List.Split (wordsBy)
-
-wordCount :: String -> Map String Int
-wordCount = fromListWith (+) . map pair . wordsBy (not . isAlphaNum)
-  where pair word = (map toLower word, 1)
\ No newline at end of file
diff --git a/exercises/word-count/src/WordCount.hs b/exercises/word-count/src/WordCount.hs
index af6109af7..07db8f29d 100644
--- a/exercises/word-count/src/WordCount.hs
+++ b/exercises/word-count/src/WordCount.hs
@@ -1,3 +1,4 @@
 module WordCount (wordCount) where
 
-wordCount = undefined
+wordCount :: String -> [(String, Int)]
+wordCount xs = undefined
diff --git a/exercises/word-count/test/Tests.hs b/exercises/word-count/test/Tests.hs
index 0561cd2b2..862a7b886 100644
--- a/exercises/word-count/test/Tests.hs
+++ b/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.