Merge branch 'ka/slice-last-n'

slice.go

@@ -742,3 +742,31 @@ func SliceShuffleCopy[T any](in []T) []T {
 
  return res
 }
+
+// SliceLastN return up to last n elements from input slice in original order.
+func SliceLastN[T any](in []T, n int) []T {
+ if n < 0 {
+ panic("n should be greater than 0")
+ }
+
+ inLen := len(in)
+
+ if inLen == 0 || n == 0 {
+ return make([]T, 0)
+ }
+
+ if inLen == n {
+ res := make([]T, n)
+ copy(res, in)
+
+ return res
+ }
+
+ n = Min(inLen, n)
+ res := make([]T, n)
+ for i := n - 1; i >= 0; i-- {
+ res[i] = in[inLen-n+i]
+ }
+
+ return res
+}

slice_test.go

@@ -1816,3 +1816,49 @@ func TestSliceShuffleCopy(t *testing.T) {
  })
  }
 }
+
+func TestSliceLastN(t *testing.T) {
+ table := []struct {
+ in []int
+ n int
+ exp []int
+ }{
+ {
+ in: nil,
+ n: 10,
+ exp: []int{},
+ },
+ {
+ in: nil,
+ n: 0,
+ exp: []int{},
+ },
+ {
+ in: []int{10},
+ n: 0,
+ exp: []int{},
+ },
+ {
+ in: []int{10},
+ n: 1,
+ exp: []int{10},
+ },
+ {
+ in: []int{10},
+ n: 6,
+ exp: []int{10},
+ },
+ {
+ in: []int{10, 20, 30, 40, 50},
+ n: 2,
+ exp: []int{40, 50},
+ },
+ }
+
+ for _, row := range table {
+ t.Run("", func(t *testing.T) {
+ res := just.SliceLastN(row.in, row.n)
+ require.Equal(t, row.exp, res)
+ })
+ }
+}