From bdfc171dec14f4330a93e65c094452b20b448e91 Mon Sep 17 00:00:00 2001
From: xing <fthvgb1>
Date: Sat, 24 Sep 2022 22:55:39 +0800
Subject: [PATCH] =?UTF-8?q?=E5=AE=8C=E5=96=84range?=
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---
 helper/func.go      | 19 +++++++++++++++++--
 helper/func_test.go | 33 +++++++++++++++++++++++++++++++++
 2 files changed, 50 insertions(+), 2 deletions(-)

diff --git a/helper/func.go b/helper/func.go
index 043a196..2d36e0d 100644
--- a/helper/func.go
+++ b/helper/func.go
@@ -30,10 +30,17 @@ func StructColumn[T any, M any](arr []M, field string) (r []T) {
 }
 
 func RangeSlice[T ~int | ~uint | ~int64 | ~int8 | ~int16 | ~int32 | ~uint64](start, end, step T) []T {
-	r := make([]T, 0, int((end-start+1)/step+1))
-	for i := start; i <= end; {
+	l := int((end-start+1)/step + 1)
+	if l < 0 {
+		l = 0 - l
+	}
+	r := make([]T, 0, l)
+	for i := start; ; {
 		r = append(r, i)
 		i = i + step
+		if (step > 0 && i > end) || (step < 0 && i < end) {
+			break
+		}
 	}
 	return r
 }
@@ -199,3 +206,11 @@ func SliceReduce[T, R any](arr []T, fn func(T, R) R, r R) R {
 	}
 	return r
 }
+
+func SliceReverse[T any](arr []T) []T {
+	var r []T
+	for i := len(arr); i > 0; i-- {
+		r = append(r, arr[i-1])
+	}
+	return r
+}
diff --git a/helper/func_test.go b/helper/func_test.go
index c5f66a1..36694e1 100644
--- a/helper/func_test.go
+++ b/helper/func_test.go
@@ -112,6 +112,15 @@ func TestRangeSlice(t *testing.T) {
 			},
 			want: []int{1, 4, 7, 10},
 		},
+		{
+			name: "t4",
+			args: args{
+				start: 0,
+				end:   -5,
+				step:  -1,
+			},
+			want: []int{0, -1, -2, -3, -4, -5},
+		},
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
@@ -411,3 +420,27 @@ func TestSliceMap(t *testing.T) {
 		})
 	}
 }
+
+func TestSliceReverse(t *testing.T) {
+	type args struct {
+		arr []int
+	}
+	tests := []struct {
+		name string
+		args args
+		want []int
+	}{
+		{
+			name: "t1",
+			args: args{arr: RangeSlice(1, 10, 1)},
+			want: RangeSlice(10, 1, -1),
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := SliceReverse(tt.args.arr); !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("SliceReverse() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}