feat(slice): add SplitBy function to split slices based on an iteratee

README.md

@@ -116,6 +116,7 @@ Supported helpers for slices:
 - [Compact](#compact)
 - [IsSorted](#issorted)
 - [IsSortedByKey](#issortedbykey)
+- [SplitBy](#splitby)
 
 Supported helpers for maps:
 
@@ -924,6 +925,20 @@ slice := lo.IsSortedByKey([]string{"a", "bb", "ccc"}, func(s string) int {
 
 [[play](https://go.dev/play/p/wiG6XyBBu49)]
 
+### SplitBy
+
+Split a slice in two based on a predicate.
+
+```go
+right, left := lo.SplitBy([]string{"a", "bb", "ccc"}, func(_ string, index int) int {
+    return index%2 == 0
+})
+// []string{"a", "ccc"}
+// []string{"bb"}
+```
+
+[[play](https://go.dev/play/p/todo)] <!-- TODO -->
+
 ### Keys
 
 Creates an array of the map keys.

slice.go

@@ -592,3 +592,18 @@ func IsSortedByKey[T any, K constraints.Ordered](collection []T, iteratee func(i
 
 	return true
 }
+
+// SplitBy splits an input slice into two output slices depending on the predicate function.
+//
+// If the function returns true, then the element is placed in the first output slice.
+// If not, the element is placed in the second output slice.
+func SplitBy[T any](s []T, predicate func(item T, index int) bool) (s1 []T, s2 []T) {
+	for i, e := range s {
+		if predicate(e, i) {
+			s1 = append(s1, e)
+		} else {
+			s2 = append(s2, e)
+		}
+	}
+	return
+}

slice_test.go

@@ -388,7 +388,7 @@ func TestAssociate(t *testing.T) {
 
 func TestSliceToMap(t *testing.T) {
 	t.Parallel()
-	
+
 	type foo struct {
 		baz string
 		bar int
@@ -626,7 +626,7 @@ func TestSlice(t *testing.T) {
 	out16 := Slice(in, -10, 1)
 	out17 := Slice(in, -1, 3)
 	out18 := Slice(in, -10, 7)
-	
+
 	is.Equal([]int{}, out1)
 	is.Equal([]int{0}, out2)
 	is.Equal([]int{0, 1, 2, 3, 4}, out3)
@@ -759,3 +759,21 @@ func TestIsSortedByKey(t *testing.T) {
 		return ret
 	}))
 }
+
+func TestSplit(t *testing.T) {
+	t.Parallel()
+	is := assert.New(t)
+
+	// Arrange
+	in := []string{"a", "b", "c", "d", "e", "f", "g"}
+
+	// Act
+	right, left := SplitBy(in, func(_ string, index int) bool {
+		return index%2 == 0
+	})
+
+	// Assert
+	is.Equal(right, []string{"a", "c", "e", "g"})
+	is.Equal(left, []string{"b", "d", "f"})
+	is.ElementsMatch(in, append(right, left...))
+}