test: add example for stream package

stream/stream.go

@@ -1,9 +1,8 @@
 // Copyright 2023 dudaodong@gmail.com. All rights resulterved.
 // Use of this source code is governed by MIT license
 
-// Package stream implements a sequence of elements supporting sequential and parallel aggregate operations.
-// this package is an experiment to explore if stream in go can work as the way java does. it's complete, but not
-// powerful like other libs
+// Package stream implements a sequence of elements supporting sequential and operations.
+// this package is an experiment to explore if stream in go can work as the way java does. it's function is very limited.
 package stream
 
 import (
@@ -53,12 +52,13 @@ type stream[T any] struct {
 }
 
 // Of creates a stream stream whose elements are the specified values.
+// Play: https://go.dev/play/p/jI6_iZZuVFE
 func Of[T any](elems ...T) stream[T] {
 	return FromSlice(elems)
 }
 
 // Generate stream where each element is generated by the provided generater function
-// generater function: func() func() (item T, ok bool) {}
+// Play: https://go.dev/play/p/rkOWL1yA3j9
 func Generate[T any](generator func() func() (item T, ok bool)) stream[T] {
 	source := make([]T, 0)
 
@@ -75,11 +75,13 @@ func Generate[T any](generator func() func() (item T, ok bool)) stream[T] {
 }
 
 // FromSlice creates stream from slice.
+// Play: https://go.dev/play/p/wywTO0XZtI4
 func FromSlice[T any](source []T) stream[T] {
 	return stream[T]{source: source}
 }
 
 // FromChannel creates stream from channel.
+// Play: https://go.dev/play/p/9TZYugGMhXZ
 func FromChannel[T any](source <-chan T) stream[T] {
 	s := make([]T, 0)
 
@@ -91,6 +93,7 @@ func FromChannel[T any](source <-chan T) stream[T] {
 }
 
 // FromRange creates a number stream from start to end. both start and end are included. [start, end]
+// Play: https://go.dev/play/p/9Ex1-zcg-B-
 func FromRange[T constraints.Integer | constraints.Float](start, end, step T) stream[T] {
 	if end < start {
 		panic("stream.FromRange: param start should be before param end")
@@ -109,6 +112,7 @@ func FromRange[T constraints.Integer | constraints.Float](start, end, step T) st
 }
 
 // Concat creates a lazily concatenated stream whose elements are all the elements of the first stream followed by all the elements of the second stream.
+// Play: https://go.dev/play/p/HM4OlYk_OUC
 func Concat[T any](a, b stream[T]) stream[T] {
 	source := make([]T, 0)
 
@@ -119,6 +123,7 @@ func Concat[T any](a, b stream[T]) stream[T] {
 }
 
 // Distinct returns a stream that removes the duplicated items.
+// Play: https://go.dev/play/p/eGkOSrm64cB
 func (s stream[T]) Distinct() stream[T] {
 	source := make([]T, 0)
 
@@ -147,6 +152,7 @@ func hashKey(data any) string {
 }
 
 // Filter returns a stream consisting of the elements of this stream that match the given predicate.
+// Play: https://go.dev/play/p/MFlSANo-buc
 func (s stream[T]) Filter(predicate func(item T) bool) stream[T] {
 	source := make([]T, 0)
 
@@ -160,6 +166,7 @@ func (s stream[T]) Filter(predicate func(item T) bool) stream[T] {
 }
 
 // Map returns a stream consisting of the elements of this stream that apply the given function to elements of stream.
+// Play: https://go.dev/play/p/OtNQUImdYko
 func (s stream[T]) Map(mapper func(item T) T) stream[T] {
 	source := make([]T, s.Count())
 
@@ -171,6 +178,7 @@ func (s stream[T]) Map(mapper func(item T) T) stream[T] {
 }
 
 // Peek returns a stream consisting of the elements of this stream, additionally performing the provided action on each element as elements are consumed from the resulting stream.
+// Play: https://go.dev/play/p/u1VNzHs6cb2
 func (s stream[T]) Peek(consumer func(item T)) stream[T] {
 	for _, v := range s.source {
 		consumer(v)
@@ -181,6 +189,7 @@ func (s stream[T]) Peek(consumer func(item T)) stream[T] {
 
 // Skip returns a stream consisting of the remaining elements of this stream after discarding the first n elements of the stream.
 // If this stream contains fewer than n elements then an empty stream will be returned.
+// Play: https://go.dev/play/p/fNdHbqjahum
 func (s stream[T]) Skip(n int) stream[T] {
 	if n <= 0 {
 		return s
@@ -201,6 +210,7 @@ func (s stream[T]) Skip(n int) stream[T] {
 }
 
 // Limit returns a stream consisting of the elements of this stream, truncated to be no longer than maxSize in length.
+// Play: https://go.dev/play/p/qsO4aniDcGf
 func (s stream[T]) Limit(maxSize int) stream[T] {
 	if s.source == nil {
 		return s
@@ -220,6 +230,7 @@ func (s stream[T]) Limit(maxSize int) stream[T] {
 }
 
 // AllMatch returns whether all elements of this stream match the provided predicate.
+// Play: https://go.dev/play/p/V5TBpVRs-Cx
 func (s stream[T]) AllMatch(predicate func(item T) bool) bool {
 	for _, v := range s.source {
 		if !predicate(v) {
@@ -231,6 +242,7 @@ func (s stream[T]) AllMatch(predicate func(item T) bool) bool {
 }
 
 // AnyMatch returns whether any elements of this stream match the provided predicate.
+// Play: https://go.dev/play/p/PTCnWn4OxSn
 func (s stream[T]) AnyMatch(predicate func(item T) bool) bool {
 	for _, v := range s.source {
 		if predicate(v) {
@@ -242,11 +254,13 @@ func (s stream[T]) AnyMatch(predicate func(item T) bool) bool {
 }
 
 // NoneMatch returns whether no elements of this stream match the provided predicate.
+// Play: https://go.dev/play/p/iWS64pL1oo3
 func (s stream[T]) NoneMatch(predicate func(item T) bool) bool {
 	return !s.AnyMatch(predicate)
 }
 
 // ForEach performs an action for each element of this stream.
+// Play: https://go.dev/play/p/Dsm0fPqcidk
 func (s stream[T]) ForEach(action func(item T)) {
 	for _, v := range s.source {
 		action(v)
@@ -254,20 +268,23 @@ func (s stream[T]) ForEach(action func(item T)) {
 }
 
 // Reduce performs a reduction on the elements of this stream, using an associative accumulation function, and returns an Optional describing the reduced value, if any.
-func (s stream[T]) Reduce(init T, accumulator func(a, b T) T) T {
+// Play: https://go.dev/play/p/g-xkHiuIpTi
+func (s stream[T]) Reduce(initial T, accumulator func(a, b T) T) T {
 	for _, v := range s.source {
-		init = accumulator(init, v)
+		initial = accumulator(initial, v)
 	}
 
-	return init
+	return initial
 }
 
 // Count returns the count of elements in the stream.
+// Play: https://go.dev/play/p/r3koY6y_Xo-
 func (s stream[T]) Count() int {
 	return len(s.source)
 }
 
 // FindFirst returns the first element of this stream and true, or zero value and false if the stream is empty.
+// Play: https://go.dev/play/p/9xEf0-6C1e3
 func (s stream[T]) FindFirst() (T, bool) {
 	var result T
 
@@ -279,6 +296,7 @@ func (s stream[T]) FindFirst() (T, bool) {
 }
 
 // Reverse returns a stream whose elements are reverse order of given stream.
+// Play: https://go.dev/play/p/A8_zkJnLHm4
 func (s stream[T]) Reverse() stream[T] {
 	l := len(s.source)
 	source := make([]T, l)
@@ -290,6 +308,7 @@ func (s stream[T]) Reverse() stream[T] {
 }
 
 // Range returns a stream whose elements are in the range from start(included) to end(excluded) original stream.
+// Play: https://go.dev/play/p/indZY5V2f4j
 func (s stream[T]) Range(start, end int) stream[T] {
 	if start < 0 {
 		start = 0
@@ -315,6 +334,7 @@ func (s stream[T]) Range(start, end int) stream[T] {
 }
 
 // Sorted returns a stream consisting of the elements of this stream, sorted according to the provided less function.
+// Play: https://go.dev/play/p/XXtng5uonFj
 func (s stream[T]) Sorted(less func(a, b T) bool) stream[T] {
 	source := []T{}
 	source = append(source, s.source...)
@@ -326,6 +346,7 @@ func (s stream[T]) Sorted(less func(a, b T) bool) stream[T] {
 
 // Max returns the maximum element of this stream according to the provided less function.
 // less: a > b
+// Play: https://go.dev/play/p/fm-1KOPtGzn
 func (s stream[T]) Max(less func(a, b T) bool) (T, bool) {
 	var max T
 
@@ -343,6 +364,7 @@ func (s stream[T]) Max(less func(a, b T) bool) (T, bool) {
 
 // Min returns the minimum element of this stream according to the provided less function.
 // less: a < b
+// Play: https://go.dev/play/p/vZfIDgGNRe_0
 func (s stream[T]) Min(less func(a, b T) bool) (T, bool) {
 	var min T
 
@@ -360,6 +382,7 @@ func (s stream[T]) Min(less func(a, b T) bool) (T, bool) {
 }
 
 // ToSlice return the elements in the stream.
+// Play: https://go.dev/play/p/jI6_iZZuVFE
 func (s stream[T]) ToSlice() []T {
 	return s.source
 }

stream/stream_example_test.go

@@ -0,0 +1,375 @@
+package stream
+
+import (
+	"fmt"
+)
+
+func ExampleOf() {
+	s := Of(1, 2, 3)
+
+	data := s.ToSlice()
+
+	fmt.Println(data)
+
+	// Output:
+	// [1 2 3]
+}
+
+func ExampleFromSlice() {
+	s := FromSlice([]int{1, 2, 3})
+
+	data := s.ToSlice()
+
+	fmt.Println(data)
+
+	// Output:
+	// [1 2 3]
+}
+
+func ExampleFromChannel() {
+	ch := make(chan int)
+	go func() {
+		for i := 1; i < 4; i++ {
+			ch <- i
+		}
+		close(ch)
+	}()
+
+	s := FromChannel(ch)
+
+	data := s.ToSlice()
+
+	fmt.Println(data)
+
+	// Output:
+	// [1 2 3]
+}
+
+func ExampleFromRange() {
+	s := FromRange(1, 5, 1)
+
+	data := s.ToSlice()
+	fmt.Println(data)
+
+	// Output:
+	// [1 2 3 4 5]
+}
+
+func ExampleGenerate() {
+	n := 0
+	max := 4
+
+	generator := func() func() (int, bool) {
+		return func() (int, bool) {
+			n++
+			return n, n < max
+		}
+	}
+
+	s := Generate(generator)
+
+	data := s.ToSlice()
+
+	fmt.Println(data)
+
+	// Output:
+	// [1 2 3]
+}
+
+func ExampleConcat() {
+	s1 := FromSlice([]int{1, 2, 3})
+	s2 := FromSlice([]int{4, 5, 6})
+
+	s := Concat(s1, s2)
+
+	data := s.ToSlice()
+
+	fmt.Println(data)
+
+	// Output:
+	// [1 2 3 4 5 6]
+}
+
+func ExampleStream_Distinct() {
+	originalStream := FromSlice([]int{1, 2, 2, 3, 3, 3})
+	distinctStream := originalStream.Distinct()
+
+	data1 := originalStream.ToSlice()
+	data2 := distinctStream.ToSlice()
+
+	fmt.Println(data1)
+	fmt.Println(data2)
+
+	// Output:
+	// [1 2 2 3 3 3]
+	// [1 2 3]
+}
+
+func ExampleStream_Filter() {
+	original := FromSlice([]int{1, 2, 3, 4, 5})
+
+	isEven := func(n int) bool {
+		return n%2 == 0
+	}
+
+	even := original.Filter(isEven)
+
+	fmt.Println(even.ToSlice())
+
+	// Output:
+	// [2 4]
+}
+
+func ExampleStream_Map() {
+	original := FromSlice([]int{1, 2, 3})
+
+	addOne := func(n int) int {
+		return n + 1
+	}
+
+	increament := original.Map(addOne)
+
+	fmt.Println(increament.ToSlice())
+
+	// Output:
+	// [2 3 4]
+}
+
+func ExampleStream_Peek() {
+	original := FromSlice([]int{1, 2, 3})
+
+	data := []string{}
+	peekStream := original.Peek(func(n int) {
+		data = append(data, fmt.Sprint("value", n))
+	})
+
+	fmt.Println(original.ToSlice())
+	fmt.Println(peekStream.ToSlice())
+	fmt.Println(data)
+
+	// Output:
+	// [1 2 3]
+	// [1 2 3]
+	// [value1 value2 value3]
+}
+
+func ExampleStream_Skip() {
+	original := FromSlice([]int{1, 2, 3, 4})
+
+	s1 := original.Skip(-1)
+	s2 := original.Skip(0)
+	s3 := original.Skip(1)
+	s4 := original.Skip(5)
+
+	fmt.Println(s1.ToSlice())
+	fmt.Println(s2.ToSlice())
+	fmt.Println(s3.ToSlice())
+	fmt.Println(s4.ToSlice())
+
+	// Output:
+	// [1 2 3 4]
+	// [1 2 3 4]
+	// [2 3 4]
+	// []
+}
+
+func ExampleStream_Limit() {
+	original := FromSlice([]int{1, 2, 3, 4})
+
+	s1 := original.Limit(-1)
+	s2 := original.Limit(0)
+	s3 := original.Limit(1)
+	s4 := original.Limit(5)
+
+	fmt.Println(s1.ToSlice())
+	fmt.Println(s2.ToSlice())
+	fmt.Println(s3.ToSlice())
+	fmt.Println(s4.ToSlice())
+
+	// Output:
+	// []
+	// []
+	// [1]
+	// [1 2 3 4]
+}
+
+func ExampleStream_AllMatch() {
+	original := FromSlice([]int{1, 2, 3})
+
+	result1 := original.AllMatch(func(item int) bool {
+		return item > 0
+	})
+
+	result2 := original.AllMatch(func(item int) bool {
+		return item > 1
+	})
+
+	fmt.Println(result1)
+	fmt.Println(result2)
+
+	// Output:
+	// true
+	// false
+}
+
+func ExampleStream_AnyMatch() {
+	original := FromSlice([]int{1, 2, 3})
+
+	result1 := original.AnyMatch(func(item int) bool {
+		return item > 1
+	})
+
+	result2 := original.AnyMatch(func(item int) bool {
+		return item > 3
+	})
+
+	fmt.Println(result1)
+	fmt.Println(result2)
+
+	// Output:
+	// true
+	// false
+}
+
+func ExampleStream_NoneMatch() {
+	original := FromSlice([]int{1, 2, 3})
+
+	result1 := original.NoneMatch(func(item int) bool {
+		return item > 3
+	})
+
+	result2 := original.NoneMatch(func(item int) bool {
+		return item > 1
+	})
+
+	fmt.Println(result1)
+	fmt.Println(result2)
+
+	// Output:
+	// true
+	// false
+}
+
+func ExampleStream_ForEach() {
+	original := FromSlice([]int{1, 2, 3})
+
+	result := 0
+	original.ForEach(func(item int) {
+		result += item
+	})
+
+	fmt.Println(result)
+
+	// Output:
+	// 6
+}
+
+func ExampleStream_Reduce() {
+	original := FromSlice([]int{1, 2, 3})
+
+	result := 0
+
+	original.ForEach(func(item int) {
+		result += item
+	})
+
+	fmt.Println(result)
+
+	// Output:
+	// 6
+}
+
+func ExampleStream_FindFirst() {
+	original := FromSlice([]int{1, 2, 3})
+
+	result, ok := original.FindFirst()
+
+	fmt.Println(result)
+	fmt.Println(ok)
+
+	// Output:
+	// 1
+	// true
+}
+
+func ExampleStream_Reverse() {
+	original := FromSlice([]int{1, 2, 3})
+
+	reverse := original.Reverse()
+
+	fmt.Println(reverse.ToSlice())
+
+	// Output:
+	// [3 2 1]
+}
+
+func ExampleStream_Range() {
+	original := FromSlice([]int{1, 2, 3})
+
+	s1 := original.Range(0, 0)
+	s2 := original.Range(0, 1)
+	s3 := original.Range(0, 3)
+	s4 := original.Range(1, 2)
+
+	fmt.Println(s1.ToSlice())
+	fmt.Println(s2.ToSlice())
+	fmt.Println(s3.ToSlice())
+	fmt.Println(s4.ToSlice())
+
+	// Output:
+	// []
+	// [1]
+	// [1 2 3]
+	// [2]
+}
+
+func ExampleStream_Sorted() {
+	original := FromSlice([]int{4, 2, 1, 3})
+
+	sorted := original.Sorted(func(a, b int) bool { return a < b })
+
+	fmt.Println(original.ToSlice())
+	fmt.Println(sorted.ToSlice())
+
+	// Output:
+	// [4 2 1 3]
+	// [1 2 3 4]
+}
+
+func ExampleStream_Max() {
+	original := FromSlice([]int{4, 2, 1, 3})
+
+	max, ok := original.Max(func(a, b int) bool { return a > b })
+
+	fmt.Println(max)
+	fmt.Println(ok)
+
+	// Output:
+	// 4
+	// true
+}
+
+func ExampleStream_Min() {
+	original := FromSlice([]int{4, 2, 1, 3})
+
+	min, ok := original.Min(func(a, b int) bool { return a < b })
+
+	fmt.Println(min)
+	fmt.Println(ok)
+
+	// Output:
+	// 1
+	// true
+}
+
+func ExampleStream_Count() {
+	s1 := FromSlice([]int{1, 2, 3})
+	s2 := FromSlice([]int{})
+
+	fmt.Println(s1.Count())
+	fmt.Println(s2.Count())
+
+	// Output:
+	// 3
+	// 0
+}

stream/stream_test.go

@@ -147,13 +147,17 @@ func TestStream_Peek(t *testing.T) {
 func TestStream_Skip(t *testing.T) {
 	assert := internal.NewAssert(t, "TestStream_Peek")
 
-	stream := FromSlice([]int{1, 2, 3, 4, 5, 6})
+	stream := FromSlice([]int{1, 2, 3, 4})
 
 	s1 := stream.Skip(-1)
 	s2 := stream.Skip(0)
+	s3 := stream.Skip(1)
+	s4 := stream.Skip(2)
 
-	assert.Equal([]int{1, 2, 3, 4, 5, 6}, s1.ToSlice())
-	assert.Equal([]int{1, 2, 3, 4, 5, 6}, s2.ToSlice())
+	assert.Equal([]int{1, 2, 3, 4}, s1.ToSlice())
+	assert.Equal([]int{1, 2, 3, 4}, s2.ToSlice())
+	assert.Equal([]int{2, 3, 4}, s3.ToSlice())
+	assert.Equal([]int{3, 4}, s4.ToSlice())
 }
 
 func TestStream_Limit(t *testing.T) {
@@ -248,6 +252,16 @@ func TestStream_Reduce(t *testing.T) {
 	assert.Equal(6, result)
 }
 
+func TestStream_Count(t *testing.T) {
+	assert := internal.NewAssert(t, "TestStream_Count")
+
+	s1 := FromSlice([]int{1, 2, 3})
+	s2 := FromSlice([]int{})
+
+	assert.Equal(3, s1.Count())
+	assert.Equal(0, s2.Count())
+}
+
 func TestStream_FindFirst(t *testing.T) {
 	assert := internal.NewAssert(t, "TestStream_FindFirst")