fix(stream): reverse and number stream methods

number_stream.go

@@ -0,0 +1,67 @@
+package streams
+
+import (
+	"sync/atomic"
+
+	"golang.org/x/exp/constraints"
+)
+
+type NumberStream[T constraints.Integer | constraints.Float] struct {
+	Stream[T]
+}
+
+func ToNumberStream[T constraints.Integer | constraints.Float](s *Stream[T]) *NumberStream[T] {
+	return &NumberStream[T]{
+		Stream: Stream[T]{
+			data: s.data,
+			run:  s.run,
+			ran:  atomic.Bool{},
+		},
+	}
+}
+func (s *NumberStream[T]) Sum() (result T) {
+	s.Run()
+	for t := range s.data {
+		result += t
+	}
+	return result
+}
+func (s *NumberStream[T]) Average() (result float64) {
+	s.Run()
+	var count int
+	for t := range s.data {
+		result += float64(t)
+		count++
+	}
+	if count == 0 {
+		return 0
+	}
+	return result / float64(count)
+}
+func (s *NumberStream[T]) Max() (result *T) {
+	s.Run()
+	for t := range s.data {
+		if result == nil || t > *result {
+			result = &t
+		}
+	}
+	return result
+}
+
+func (s *NumberStream[T]) Min() (result *T) {
+	s.Run()
+	for t := range s.data {
+		if result == nil || t < *result {
+			result = &t
+		}
+	}
+	return result
+}
+
+func (s *NumberStream[T]) Count() (result int64) {
+	s.Run()
+	for range s.data {
+		result++
+	}
+	return result
+}

number_stream_test.go

@@ -0,0 +1,50 @@
+package streams
+
+import "testing"
+
+func TestNumberStream_Average(t *testing.T) {
+	s := New(1, 2, 3, 4, 5)
+	ns := ToNumberStream(s)
+	if ns.Average() != 3 {
+		t.Fail()
+	}
+}
+func TestNumberStream_AverageEmpty(t *testing.T) {
+	s := New([]int{}...)
+	ns := ToNumberStream(s)
+	if ns.Average() != 0 {
+		t.Fail()
+	}
+}
+
+func TestNumberStream_Count(t *testing.T) {
+	s := New(1, 2, 3, 4, 5)
+	ns := ToNumberStream(s)
+	if ns.Count() != 5 {
+		t.Fail()
+	}
+}
+
+func TestNumberStream_Max(t *testing.T) {
+	s := New(1, 2, 3, 4, 5)
+	ns := ToNumberStream(s)
+	if *ns.Max() != 5 {
+		t.Fail()
+	}
+}
+
+func TestNumberStream_Min(t *testing.T) {
+	s := New(1, 2, 3, 4, 5)
+	ns := ToNumberStream(s)
+	if *ns.Min() != 1 {
+		t.Fail()
+	}
+}
+
+func TestNumberStream_Sum(t *testing.T) {
+	s := New(1, 2, 3, 4, 5)
+	ns := ToNumberStream(s)
+	if ns.Sum() != 15 {
+		t.Fail()
+	}
+}

stream_methods.go

@@ -2,8 +2,6 @@ package streams
 
 import (
 	"sync/atomic"
-
-	"golang.org/x/exp/constraints"
 )
 
 func (s *Stream[T]) Filter(filter FilterFun[T]) *Stream[T] {
@@ -286,23 +284,20 @@ func (s *Stream[T]) Count() (cnt int64) {
 	return
 }
 
-type NumberStream[T constraints.Integer | constraints.Float] struct {
-	Stream[T]
-}
-
-func ToNumberStream[T constraints.Integer | constraints.Float](s *Stream[T]) *NumberStream[T] {
-	return &NumberStream[T]{
-		Stream: Stream[T]{
-			data: s.data,
-			run:  s.run,
-			ran:  atomic.Bool{},
+func (s *Stream[T]) Reverse() *Stream[T] {
+	ch := make(chan T)
+	return &Stream[T]{
+		data: ch,
+		run: func() {
+			s.Run()
+			defer close(ch)
+			var data []T
+			for t := range s.data {
+				data = append(data, t)
+			}
+			for i := len(data) - 1; i >= 0; i-- {
+				ch <- data[i]
+			}
 		},
 	}
 }
-func (s *NumberStream[T]) Sum() (result T) {
-	s.Run()
-	for t := range s.data {
-		result += t
-	}
-	return result
-}

stream_methods_test.go

@@ -259,3 +259,8 @@ func TestMSortedDesc(t *testing.T) {
 		{"abc", 2},
 	}))
 }
+
+func TestMethodReverse(t *testing.T) {
+	collected := New([]int{1, 2, 3, 4, 5}...).Reverse().Collect()
+	assert.Equal(t, []int{5, 4, 3, 2, 1}, collected)
+}