From 422022c74d51522980c2084d726f35e563a1d9b4 Mon Sep 17 00:00:00 2001
From: dudaodong <lanliddd.2007@163.com>
Date: Tue, 7 Feb 2023 10:36:07 +0800
Subject: [PATCH] feat: add Range for stream

---
 stream/stream.go      | 25 +++++++++++++++++++++++++
 stream/stream_test.go | 24 ++++++++++++++++++++++++
 2 files changed, 49 insertions(+)

diff --git a/stream/stream.go b/stream/stream.go
index 2ee77b4..9f78627 100644
--- a/stream/stream.go
+++ b/stream/stream.go
@@ -277,6 +277,31 @@ func (s stream[T]) Reverse() stream[T] {
 	return FromSlice(source)
 }
 
+// Range returns a stream whose elements are in the range from start(included) to end(excluded) original stream.
+func (s stream[T]) Range(start, end int) stream[T] {
+	if start < 0 {
+		start = 0
+	}
+	if end < 0 {
+		end = 0
+	}
+	if start >= end {
+		return FromSlice([]T{})
+	}
+
+	source := make([]T, 0)
+
+	if end > len(s.source) {
+		end = len(s.source)
+	}
+
+	for i := start; i < end; i++ {
+		source = append(source, s.source[i])
+	}
+
+	return FromSlice(source)
+}
+
 // ToSlice return the elements in the stream.
 func (s stream[T]) ToSlice() []T {
 	return s.source
diff --git a/stream/stream_test.go b/stream/stream_test.go
index 7226e2b..ac84ea7 100644
--- a/stream/stream_test.go
+++ b/stream/stream_test.go
@@ -268,3 +268,27 @@ func TestStream_Reverse(t *testing.T) {
 
 	assert.Equal([]int{3, 2, 1}, rs.ToSlice())
 }
+
+func TestStream_Range(t *testing.T) {
+	assert := internal.NewAssert(t, "TestStream_Range")
+
+	s := FromSlice([]int{1, 2, 3})
+
+	s1 := s.Range(-1, 0)
+	assert.Equal([]int{}, s1.ToSlice())
+
+	s2 := s.Range(0, -1)
+	assert.Equal([]int{}, s2.ToSlice())
+
+	s3 := s.Range(0, 0)
+	assert.Equal([]int{}, s3.ToSlice())
+
+	s4 := s.Range(1, 1)
+	assert.Equal([]int{}, s4.ToSlice())
+
+	s5 := s.Range(0, 1)
+	assert.Equal([]int{1}, s5.ToSlice())
+
+	s6 := s.Range(0, 4)
+	assert.Equal([]int{1, 2, 3}, s6.ToSlice())
+}