feat: add slice.Union

README.md

@@ -469,6 +469,8 @@ Some utilities that are convenient when working with slices.
 - `slice.Filter[A any](as []A, p func(a A) bool) (res []A)`
 - `slice.FilterNot[A any](as []A, p func(a A) bool) (res []A)` - same as `Filter`, but inverses the predicate `p`.
 - `slice.Remove[A comparable](as []A, r []A) (res []A)` - Remove removes any elements in r from as.
+- `slice.Intersection[A comparable](as []A, as2 []A) (res []A)` - Intersection leaves only elements that are both in as and as2.
+- `slice.Union[A comparable](as []A, as2 []A) (res []A)` - Union returns elements that are either in as or in as2.
 - `slice.Partition[A any](as []A, p fun.Predicate[A]) (resT []A, resF []A)` - Partition separates elements in as according to the predicate.
 - `slice.Exists[A any](p fun.Predicate[A]) fun.Predicate[[]A]` - Exists returns a predicate on slices. The predicate is true if there is an element that satisfy the given element-wise predicate. It's false for an empty slice.
 - `slice.Forall[A any](p fun.Predicate[A]) fun.Predicate[[]A]` - Forall returns a predicate on slices. The predicate is true if all elements satisfy the given element-wise predicate. It's true for an empty slice.

slice/slice.go

@@ -286,3 +286,15 @@ func Remove[A comparable](as []A, r []A) (res []A) {
 	sr := ToSet(r)
 	return FilterNot(as, set.Contains(sr))
 }
+
+// Intersection leaves only elements that are both in as and as2.
+func Intersection[A comparable](as []A, as2 []A) (res []A) {
+	sr := ToSet(as2)
+	return Filter(as, set.Contains(sr))
+}
+
+// Union returns elements that are either in as or in as2.
+func Union[A comparable](as []A, as2 []A) (res []A) {
+	sr := ToSet(as)
+	return append(as, FilterNot(as2, set.Contains(sr))...)
+}

slice/slice_test.go

@@ -126,3 +126,17 @@ func TestRemove(t *testing.T) {
 	znats510 := slice.Range(5, 10)
 	assert.ElementsMatch(t, znats510, slice.Remove(znats10, znats5))
 }
+
+func TestIntersection(t *testing.T) {
+	znats10 := slice.Range(0, 10)
+	znats515 := slice.Range(5, 15)
+	znats5 := slice.Range(5, 10)
+	assert.ElementsMatch(t, znats5, slice.Intersection(znats10, znats515))
+}
+
+func TestUnion(t *testing.T) {
+	znats10 := slice.Range(0, 10)
+	znats515 := slice.Range(5, 15)
+	znats15 := slice.Range(0, 15)
+	assert.ElementsMatch(t, znats15, slice.Union(znats10, znats515))
+}