feat: add CrossJoin function

README.md

@@ -121,6 +121,7 @@ Supported helpers for slices:
 - [IsSorted](#issorted)
 - [IsSortedByKey](#issortedbykey)
 - [Splice](#Splice)
+- [CrossJoin](#CrossJoin)
 
 Supported helpers for maps:
 
@@ -1039,7 +1040,20 @@ result = lo.Splice([]string{"a", "b"}, 42, "1", "2")
 // []string{"a", "b", "1", "2"}
 ```
 
-[[play](https://go.dev/play/p/G5_GhkeSUBA)]
+[[play](https://go.dev/play/p/wiG6XyBBu49)]
+
+### CrossJoin
+
+CrossJoin calculates the cartesian product of two lists. It returns a list of tuples where the first element includes the elements of the first parameter, and the second element contains the elements of the second parameter.
+
+It returns an empty list if either, or both parameters are empty
+
+```go
+result := lo.CrossJoin([]string{"a", "b", "c"}, []int{1, 2, 3})
+// [][2]interface{}{{"a", 1}, {"a", 2}, {"a", 3}, {"b", 1}, {"b", 2}, {"b", 3}, {"c", 1}, {"c", 2}, {"c", 3}
+```
+
+[[play](https://go.dev/play/p/2-DOGciKvAB)]
 
 ### Keys
 

slice.go

@@ -693,3 +693,27 @@ func Splice[T any, Slice ~[]T](collection Slice, i int, elements ...T) Slice {
 
 	return append(append(append(output, collection[:i]...), elements...), collection[i:]...)
 }
+
+// CrossJoin calculates the cartesian product of two lists. It returns a list of
+// tuples where the first element includes the elements of the first parameter, and
+// the second element contains the elements of the second parameter.
+
+// It returns an empty list if either, or both parameters are empty
+
+// Play: https://go.dev/play/p/2-DOGciKvAB
+func CrossJoin[T, U any](listOne []T, listTwo []U) [][2]interface{} {
+
+	if len(listOne) == 0 || len(listTwo) == 0 {
+		return make([][2]interface{}, 0)
+	}
+
+	cartesianProduct := make([][2]interface{}, 0, len(listOne)*len(listTwo))
+
+	for _, a := range listOne {
+		for _, b := range listTwo {
+			cartesianProduct = append(cartesianProduct, [2]interface{}{a, b})
+		}
+	}
+
+	return cartesianProduct
+}

slice_test.go

@@ -1029,3 +1029,34 @@ func TestSplice(t *testing.T) {
 	nonempty := Splice(allStrings, 1, "1", "2")
 	is.IsType(nonempty, allStrings, "type preserved")
 }
+
+func TestCrossJoin(t *testing.T) {
+	t.Parallel()
+	is := assert.New(t)
+
+	listOne := []string{"a", "b", "c"}
+	listTwo := []int{1, 2, 3}
+	emptyList := make([][2]any, 0)
+	mixedList := []any{9.6, 4, "foobar"}
+
+	results := CrossJoin(emptyList, listTwo)
+	is.Equal(emptyList, results)
+
+	results = CrossJoin(listOne, emptyList)
+	is.Equal(emptyList, results)
+
+	results = CrossJoin(emptyList, emptyList)
+	is.Equal(emptyList, results)
+
+	results = CrossJoin([]string{"a"}, listTwo)
+	is.Equal([][2]any{{"a", 1}, {"a", 2}, {"a", 3}}, results)
+
+	results = CrossJoin(listOne, []int{1})
+	is.Equal([][2]any{{"a", 1}, {"b", 1}, {"c", 1}}, results)
+
+	results = CrossJoin(listOne, listTwo)
+	is.Equal([][2]any{{"a", 1}, {"a", 2}, {"a", 3}, {"b", 1}, {"b", 2}, {"b", 3}, {"c", 1}, {"c", 2}, {"c", 3}}, results)
+
+	results = CrossJoin(listOne, mixedList)
+	is.Equal([][2]any{{"a", 9.6}, {"a", 4}, {"a", "foobar"}, {"b", 9.6}, {"b", 4}, {"b", "foobar"}, {"c", 9.6}, {"c", 4}, {"c", "foobar"}}, results)
+}