Change type signatures of Data.List.NonEmpty.intersect and Data.List.NonEmpty.intersectBy to return a List instead of a NonEmptyList

CHANGELOG.md

@@ -6,6 +6,8 @@ Notable changes to this project are documented in this file. The format is based
 
 Breaking changes:
 
+- Changed type signatures of `Data.List.NonEmpty.intersect` and `Data.List.NonEmpty.intersectBy` to return a `List` instead of a `NonEmptyList` (#217)
+
 New features:
 
 Bugfixes:

src/Data/List/NonEmpty.purs

@@ -284,11 +284,11 @@ union = wrappedOperation2 "union" L.union
 unionBy :: forall a. (a -> a -> Boolean) -> NonEmptyList a -> NonEmptyList a -> NonEmptyList a
 unionBy = wrappedOperation2 "unionBy" <<< L.unionBy
 
-intersect :: forall a. Eq a => NonEmptyList a -> NonEmptyList a -> NonEmptyList a
-intersect = wrappedOperation2 "intersect" L.intersect
+intersect :: forall a. Eq a => NonEmptyList a -> NonEmptyList a -> L.List a
+intersect = intersectBy eq
 
-intersectBy :: forall a. (a -> a -> Boolean) -> NonEmptyList a -> NonEmptyList a -> NonEmptyList a
-intersectBy = wrappedOperation2 "intersectBy" <<< L.intersectBy
+intersectBy :: forall a. (a -> a -> Boolean) -> NonEmptyList a -> NonEmptyList a -> L.List a
+intersectBy eq xs ys = L.intersectBy eq (toList xs) (toList ys)
 
 zipWith :: forall a b c. (a -> b -> c) -> NonEmptyList a -> NonEmptyList b -> NonEmptyList c
 zipWith f (NonEmptyList (x :| xs)) (NonEmptyList (y :| ys)) =

test/Test/Data/List/NonEmpty.purs

@@ -203,10 +203,13 @@ testNonEmptyList = do
   assert $ NEL.unionBy (\_ y -> y < 5) (nel 1 [2, 3]) (nel 2 [3, 4, 5, 6]) == nel 1 [2, 3, 5, 6]
 
   log "intersect should return the intersection of two lists"
-  assert $ NEL.intersect (nel 1 [2, 3, 4, 3, 2, 1]) (nel 1 [1, 2, 3]) == nel 1 [2, 3, 3, 2, 1]
+  assert $ NEL.intersect (nel 1 [2, 3, 4, 3, 2, 1]) (nel 1 [1, 2, 3]) == L.fromFoldable [1, 2, 3, 3, 2, 1]
+
+  log "intersect should return empty list when lists do not intersect"
+  assert $ NEL.intersect (nel 1 [2, 3, 4, 3, 2, 1]) (nel 5 [6, 7, 8]) == L.Nil
 
   log "intersectBy should return the intersection of two lists using the specified equivalence relation"
-  assert $ NEL.intersectBy (\x y -> (x * 2) == y) (nel 1 [2, 3]) (nel 2 [6]) == nel 1 [3]
+  assert $ NEL.intersectBy (\x y -> (x * 2) == y) (nel 1 [2, 3]) (nel 2 [6]) == L.fromFoldable [1, 3]
 
   log "zipWith should use the specified function to zip two lists together"
   assert $ NEL.zipWith (\x y -> nel (show x) [y]) (nel 1 [2, 3]) (nel "a" ["b", "c"]) == nel (nel "1" ["a"]) [nel "2" ["b"], nel "3" ["c"]]