Test and implement set.symmetric_difference

2 files changed, 23 insertions, 0 deletions

diff --git a/src/gleam/set.gleam b/src/gleam/set.gleam
index c04ca92..7fb8a41 100644
--- a/src/gleam/set.gleam
+++ b/src/gleam/set.gleam
@@ -325,3 +325,21 @@ pub fn is_subset(first: Set(member), of second: Set(member)) -> Bool {
 pub fn is_disjoint(first: Set(member), from second: Set(member)) -> Bool {
   intersection(of: first, and: second) == new()
 }
+
+/// Creates a new set that contains members that are present in either set, but
+/// not both.
+///
+/// ```gleam
+/// symmetric_difference(from_list([1, 2, 4]), from_list([3, 4])) |> to_list
+/// // -> [1, 2, 4]
+/// ```
+///
+pub fn symmetric_difference(
+  of first: Set(member),
+  and second: Set(member),
+) -> Set(member) {
+  difference(
+    from: union(of: first, and: second),
+    minus: intersection(of: first, and: second),
+  )
+}
diff --git a/test/gleam/set_test.gleam b/test/gleam/set_test.gleam
index f763c5d..94dd5da 100644
--- a/test/gleam/set_test.gleam
+++ b/test/gleam/set_test.gleam
@@ -129,3 +129,8 @@ pub fn is_disjoint_test() {
   set.is_disjoint(set.from_list([1, 2]), set.from_list([2, 3, 4]))
   |> should.be_false()
 }
+
+pub fn symmetric_difference_test() {
+  set.symmetric_difference(set.from_list([1, 2, 3]), set.from_list([3, 4]))
+  |> should.equal(set.from_list([1, 2, 4]))
+}