custom-set: Move hints to HINTS.md

exercises/custom-set/HINTS.md

@@ -0,0 +1,26 @@
+## Hints
+
+To complete this exercise, you need to create the data type `CustomSet`,
+with `Eq` and `Show` instances, and implement the following functions:
+
+- `delete`
+- `difference`
+- `empty`
+- `fromList`
+- `insert`
+- `intersection`
+- `isDisjointFrom`
+- `isSubsetOf`
+- `member`
+- `null`
+- `size`
+- `toList`
+- `union`
+
+You will find the type signatures already in place, but it is up to you
+to define the functions.
+
+If you're interested in writing an efficient implementation but don't quite
+know where to start, the best primer I know of is Chris Okasaki's
+"Purely Functional Data Structures", which you can read a version of here:
+https://www.cs.cmu.edu/~rwh/theses/okasaki.pdf

exercises/custom-set/src/CustomSet.hs

@@ -17,9 +17,6 @@ module CustomSet
 
 import Prelude hiding (null)
 
--- The task is to create the data type `CustomSet`, with `Eq`
--- and `Show` instances, and implement the functions below.
-
 delete :: a -> CustomSet a -> CustomSet a
 delete = undefined
 

exercises/custom-set/test/Tests.hs

@@ -21,11 +21,6 @@ import CustomSet
   , union
   )
 
--- If you're interested in writing an efficient implementation but don't quite
--- know where to start, the best primer I know of is Chris Okasaki's
--- "Purely Functional Data Structures", which you can read a version of here:
--- https://www.cs.cmu.edu/~rwh/theses/okasaki.pdf
-
 main :: IO ()
 main = hspecWith defaultConfig {configFastFail = True} specs