Merge pull request #428 from rbasso/binary-search-tree-make-stub-build-tests

binary-search-tree: change stub to be able to run the tests

Author: petertseng

exercises/binary-search-tree/HINTS.md

@@ -12,5 +12,6 @@ with `Eq` and `Show` instances, and implement the functions:
 - `singleton`
 - `toList`
 
-You will find the type signatures already in place, but it is up to you
-to define the functions.
+You will find a dummy data declaration and type signatures already in place,
+but it is up to you to define the functions and create a meaningful data type,
+newtype or type synonym.

exercises/binary-search-tree/src/BST.hs

@@ -10,6 +10,8 @@ module BST
     , toList
     ) where
 
+data BST a = Dummy deriving (Eq, Show)
+
 bstLeft :: BST a -> Maybe (BST a)
 bstLeft = undefined