feat: add Drop func

slice/slice.go

@@ -7,6 +7,7 @@ package slice
 import (
 	"errors"
 	"fmt"
+	"math"
 	"reflect"
 	"sort"
 	"strings"
@@ -332,6 +333,37 @@ func DeleteByIndex(slice interface{}, start int, end ...int) (interface{}, error
 	return v.Interface(), nil
 }
 
+// Drop creates a slice with `n` elements dropped from the beginning when n > 0, or `n` elements dropped from the ending when n < 0
+func Drop(slice interface{}, n int) interface{} {
+	sv := sliceValue(slice)
+
+	if n == 0 {
+		return slice
+	}
+
+	svLen := sv.Len()
+
+	if math.Abs(float64(n)) >= float64(svLen) {
+		return reflect.MakeSlice(sv.Type(), 0, 0).Interface()
+	}
+
+	if n > 0 {
+		res := reflect.MakeSlice(sv.Type(), svLen-n, svLen-n)
+		for i := 0; i < res.Len(); i++ {
+			res.Index(i).Set(sv.Index(i + n))
+		}
+
+		return res.Interface()
+	} else {
+		res := reflect.MakeSlice(sv.Type(), svLen+n, svLen+n)
+		for i := 0; i < res.Len(); i++ {
+			res.Index(i).Set(sv.Index(i))
+		}
+
+		return res.Interface()
+	}
+}
+
 // InsertByIndex insert the element into slice at index.
 // Insert value: s = append(s[:i], append([]T{x}, s[i:]...)...)
 // Insert slice: a = append(a[:i], append(b, a[i:]...)...)

slice/slice_test.go

@@ -326,6 +326,29 @@ func deleteByIndex(t *testing.T, origin, test interface{}, start, end int, expec
 	}
 }
 
+func TestDrop(t *testing.T) {
+	drop(t, []int{}, 0, []int{})
+	drop(t, []int{}, 1, []int{})
+	drop(t, []int{}, -1, []int{})
+
+	drop(t, []int{1, 2, 3, 4, 5}, 0, []int{1, 2, 3, 4, 5})
+	drop(t, []int{1, 2, 3, 4, 5}, 1, []int{2, 3, 4, 5})
+	drop(t, []int{1, 2, 3, 4, 5}, 5, []int{})
+	drop(t, []int{1, 2, 3, 4, 5}, 6, []int{})
+
+	drop(t, []int{1, 2, 3, 4, 5}, -1, []int{1, 2, 3, 4})
+	drop(t, []int{1, 2, 3, 4, 5}, -5, []int{})
+	drop(t, []int{1, 2, 3, 4, 5}, -6, []int{})
+}
+
+func drop(t *testing.T, test interface{}, n int, expected interface{}) {
+	res := Drop(test, n)
+	if !reflect.DeepEqual(res, expected) {
+		internal.LogFailedTestInfo(t, "Drop", test, expected, res)
+		t.FailNow()
+	}
+}
+
 func TestInsertByIndex(t *testing.T) {
 	t1 := []string{"a", "b", "c"}