fix: update format

README.md

@@ -32,13 +32,13 @@ English | [简体中文](./README_zh-CN.md)
 
 ### Note:
 
-1. <b>For users who use go1.18 and above, it is recommended to install lancet v2.x.x. Cause v2.x.x rewrite all functions with generics of go1.18.</b>
+1. <b>For users who use go1.18 and above, it is recommended to install lancet v2.x.x. Cause in v2.x.x  all functions was rewriten with generics of go1.18.</b>
 
 ```go
 go get github.com/duke-git/lancet/v2 // will install latest version of v2.x.x
 ```
 
-2. <b>For users who use version below go1.18, you should install v1.x.x. now latest v1 is v1.3.5. </b>
+2. <b>For users who use version below go1.18, you should install v1.x.x. The latest of v1.x.x is v1.3.5. </b>
 
 ```go
 go get github.com/duke-git/lancet@v1.3.5 // below go1.18, install latest version of v1.x.x

README_zh-CN.md

@@ -31,7 +31,7 @@
 
 ### Note:
 
-1. <b>对于使用 go1.18 及以上的用户，建议安装 v2.x.x。 因为 v2.x.x 用 go1.18 的泛型重写了大部分函数。</b>
+1. <b>使用go1.18及以上版本的用户，建议安装v2.x.x。 因为v2.x.x应用go1.18的泛型重写了大部分函数。</b>
 
 ```go
 go get github.com/duke-git/lancet/v2 //安装v2最新版本v2.x.x
@@ -74,7 +74,7 @@ func main() {
 
 ## [lancet API doc](https://uvdream.github.io/lancet-docs/) 感谢[@UvDream](https://github.com/UvDream)整理
 
-### 1. algorithm 算法包实现一些基本算法。eg. sort, search.
+### 1. algorithm包实现一些基本查找和排序算法。
 
 ```go
 import "github.com/duke-git/lancet/v2/algorithm"
@@ -95,7 +95,7 @@ import "github.com/duke-git/lancet/v2/algorithm"
 -   [LinearSearch](https://github.com/duke-git/lancet/blob/main/docs/algorithm_zh-CN.md#LinearSearch)
 -   [LRUCache](https://github.com/duke-git/lancet/blob/main/docs/algorithm_zh-CN.md#LRUCache)
 
-### 2. concurrency 并发包包含一些支持并发编程的功能。例如：goroutine, channel, async 等。
+### 2. concurrency包含一些支持并发编程的功能。例如：goroutine, channel, async 等。
 
 ```go
 import "github.com/duke-git/lancet/v2/concurrency"
@@ -114,7 +114,7 @@ import "github.com/duke-git/lancet/v2/concurrency"
 -   [Take](https://github.com/duke-git/lancet/blob/main/docs/concurrency_zh-CN.md#Take)
 -   [Tee](https://github.com/duke-git/lancet/blob/main/docs/concurrency_zh-CN.md#Tee)
 
-### 3. condition 条件包含一些用于条件判断的函数。eg. And, Or, TernaryOperator...
+### 3. condition包含一些用于条件判断的函数。
 
 ```go
 import "github.com/duke-git/lancet/v2/condition"
@@ -259,7 +259,7 @@ import hashmap "github.com/duke-git/lancet/v2/datastructure/hashmap"
 -   [Heap](https://github.com/duke-git/lancet/blob/main/docs/datastructure/heap.md)
 -   [HashMap](https://github.com/duke-git/lancet/blob/main/docs/datastructure/hashmap.md)
 
-### 8. fileutil 包支持文件基本操作。
+### 8. fileutil 包含文件基本操作。
 
 ```go
 import "github.com/duke-git/lancet/v2/fileutil"
@@ -310,7 +310,7 @@ import "github.com/duke-git/lancet/v2/function"
 -   [Pipeline](https://github.com/duke-git/lancet/blob/main/docs/function_zh-CN.md#Pipeline)
 -   [Watcher](https://github.com/duke-git/lancet/blob/main/docs/function_zh-CN.md#Watcher)
 
-### 11. maputil 包包括一些操作 map 的函数.
+### 11. maputil包括一些操作map的函数.
 
 ```go
 import "github.com/duke-git/lancet/v2/maputil"
@@ -408,7 +408,7 @@ import "github.com/duke-git/lancet/v2/retry"
 -   [RetryDuration](https://github.com/duke-git/lancet/blob/main/docs/retry_zh-CN.md#RetryDuration)
 -   [RetryTimes](https://github.com/duke-git/lancet/blob/main/docs/retry_zh-CN.md#RetryTimes)
 
-### 16. slice 包包含操作切片的方法集合。
+### 16. slice包含操作切片的方法集合。
 
 ```go
 import "github.com/duke-git/lancet/v2/slice"
@@ -496,7 +496,7 @@ import "github.com/duke-git/lancet/v2/strutil"
 -   [Wrap](https://github.com/duke-git/lancet/blob/main/docs/strutil_zh-CN.md#Wrap)
 -   [Unwrap](https://github.com/duke-git/lancet/blob/main/docs/strutil_zh-CN.md#Unwrap)
 
-### 18. system 包含 os, runtime, shell command 相关函数。
+### 18. system包含os, runtime, shell command的相关函数。
 
 ```go
 import "github.com/duke-git/lancet/v2/system"

iterator/iterator.go

@@ -11,6 +11,8 @@
 package iterator
 
 import (
+	"context"
+
 	"golang.org/x/exp/constraints"
 )
 
@@ -102,21 +104,15 @@ func (iter *sliceIterator[T]) HasNext() bool {
 
 func (iter *sliceIterator[T]) Next() (T, bool) {
 	iter.index++
+
 	ok := iter.index >= 0 && iter.index < len(iter.slice)
+
 	var item T
 	if ok {
 		item = iter.slice[iter.index]
 	}
-	return item, ok
 
-	// if len(iter.slice) == 0 {
-	// 	var zero T
-	// 	return zero, false
-	// }
-	// iter.index++
-	// item := iter.slice[0]
-	// iter.slice = iter.slice[1:]
-	// return item, true
+	return item, ok
 }
 
 // Prev implements PrevIterator.
@@ -171,3 +167,41 @@ func (iter *rangeIterator[T]) Next() (T, bool) {
 	iter.start += iter.step
 	return num, true
 }
+
+// FromRange creates a iterator which returns the numeric range between start inclusive and end
+// exclusive by the step size. start should be less than end, step shoud be positive.
+func FromChannel[T any](channel <-chan T) Iterator[T] {
+	return &channelIterator[T]{channel: channel}
+}
+
+type channelIterator[T any] struct {
+	channel <-chan T
+}
+
+func (iter *channelIterator[T]) Next() (T, bool) {
+	item, ok := <-iter.channel
+	return item, ok
+}
+
+func (iter *channelIterator[T]) HasNext() bool {
+	return len(iter.channel) == 0
+}
+
+// ToChannel create a new goroutine to pull items from the channel iterator to the returned channel.
+func ToChannel[T any](ctx context.Context, iter Iterator[T], buffer int) <-chan T {
+	result := make(chan T, buffer)
+
+	go func() {
+		defer close(result)
+
+		for item, ok := iter.Next(); ok; item, ok = iter.Next() {
+			select {
+			case result <- item:
+			case <-ctx.Done():
+				return
+			}
+		}
+	}()
+
+	return result
+}

iterator/iterator_test.go

@@ -5,6 +5,7 @@
 package iterator
 
 import (
+	"context"
 	"testing"
 
 	"github.com/duke-git/lancet/v2/internal"
@@ -47,4 +48,56 @@ func TestSliceIterator(t *testing.T) {
 		assert.Equal(false, ok)
 	})
 
+	t.Run("slice iterator ToSlice: ", func(t *testing.T) {
+		iter := FromSlice([]int{1, 2, 3, 4})
+		item, _ := iter.Next()
+		assert.Equal(1, item)
+
+		data := ToSlice(iter)
+		assert.Equal([]int{2, 3, 4}, data)
+	})
+
+}
+
+func TestRangeIterator(t *testing.T) {
+	assert := internal.NewAssert(t, "TestRangeIterator")
+
+	t.Run("range iterator: ", func(t *testing.T) {
+		iter := FromRange(1, 4, 1)
+
+		item, ok := iter.Next()
+		assert.Equal(1, item)
+		assert.Equal(true, ok)
+
+		item, ok = iter.Next()
+		assert.Equal(2, item)
+		assert.Equal(true, ok)
+
+		item, ok = iter.Next()
+		assert.Equal(3, item)
+		assert.Equal(true, ok)
+
+		_, ok = iter.Next()
+		assert.Equal(false, ok)
+		assert.Equal(false, iter.HasNext())
+	})
+
+}
+
+func TestChannelIterator(t *testing.T) {
+	assert := internal.NewAssert(t, "TestRangeIterator")
+
+	iter := FromSlice([]int{1, 2, 3, 4})
+
+	ctx, cancel := context.WithCancel(context.Background())
+	iter = FromChannel(ToChannel(ctx, iter, 0))
+	item, ok := iter.Next()
+	assert.Equal(1, item)
+	assert.Equal(true, ok)
+	assert.Equal(true, iter.HasNext())
+
+	cancel()
+
+	_, ok = iter.Next()
+	assert.Equal(false, ok)
 }

iterator/operation.go

@@ -59,3 +59,81 @@ func (fr *filterIterator[T]) Next() (T, bool) {
 func (fr *filterIterator[T]) HasNext() bool {
 	return fr.iter.HasNext()
 }
+
+// Join creates an iterator that join all elements of iters[0], then all elements of iters[1] and so on.
+func Join[T any](iters ...Iterator[T]) Iterator[T] {
+	return &joinIterator[T]{
+		iters: iters,
+	}
+}
+
+type joinIterator[T any] struct {
+	iters []Iterator[T]
+}
+
+func (iter *joinIterator[T]) Next() (T, bool) {
+	for len(iter.iters) > 0 {
+		item, ok := iter.iters[0].Next()
+		if ok {
+			return item, true
+		}
+		iter.iters = iter.iters[1:]
+	}
+	var zero T
+	return zero, false
+}
+
+func (iter *joinIterator[T]) HasNext() bool {
+	if len(iter.iters) == 0 {
+		return false
+	}
+	if len(iter.iters) == 1 {
+		return iter.iters[0].HasNext()
+	}
+
+	result := iter.iters[0].HasNext()
+
+	for i := 1; i < len(iter.iters); i++ {
+		it := iter.iters[i]
+		hasNext := it.HasNext()
+		result = result || hasNext
+	}
+
+	return result
+}
+
+// Reduce reduces iter to a single value using the reduction function reducer
+func Reduce[T any, U any](iter Iterator[T], initial U, reducer func(U, T) U) U {
+	acc := initial
+
+	for item, ok := iter.Next(); ok; item, ok = iter.Next() {
+		acc = reducer(acc, item)
+	}
+
+	return acc
+}
+
+func Take[T any](it Iterator[T], num int) Iterator[T] {
+	return &takeIterator[T]{it: it, num: num}
+}
+
+type takeIterator[T any] struct {
+	it  Iterator[T]
+	num int
+}
+
+func (iter *takeIterator[T]) Next() (T, bool) {
+	if iter.num <= 0 {
+		var zero T
+		return zero, false
+	}
+	item, ok := iter.it.Next()
+	if ok {
+		iter.num--
+	}
+	return item, ok
+}
+
+func (iter *takeIterator[T]) HasNext() bool {
+	return iter.num > 0
+}

iterator/operation_test.go

@@ -0,0 +1,73 @@
+// Copyright 2022 dudaodong@gmail.com. All rights resulterved.
+// Use of this source code is governed by MIT license
+
+// Package iterator provides a way to iterate over values stored in containers.
+// note:
+// 1. Full feature iterator is complicated, this package is just a experiment to explore how iterators could work in Go.
+// 2. The functionality of this package is very simple and limited, may not meet the actual dev needs.
+// 3. It is currently under development, unstable, and will not be completed for some time in the future.
+// So, based on above factors, you may not use it in production. but, anyone is welcome to improve it.
+// Hope that Go can support iterator in future. see https://github.com/golang/go/discussions/54245 and https://github.com/golang/go/discussions/56413
+package iterator
+
+import (
+	"testing"
+
+	"github.com/duke-git/lancet/v2/internal"
+)
+
+func TestMapIterator(t *testing.T) {
+	assert := internal.NewAssert(t, "TestMapIterator")
+
+	iter := FromSlice([]int{1, 2, 3, 4})
+
+	iter = Map(iter, func(n int) int { return n / 2 })
+
+	result := ToSlice(iter)
+	assert.Equal([]int{0, 1, 1, 2}, result)
+}
+
+func TestFilterIterator(t *testing.T) {
+	assert := internal.NewAssert(t, "TestFilterIterator")
+
+	iter := FromSlice([]int{1, 2, 3, 4})
+
+	iter = Filter(iter, func(n int) bool { return n < 3 })
+
+	result := ToSlice(iter)
+	assert.Equal([]int{1, 2}, result)
+}
+
+func TestJoinIterator(t *testing.T) {
+	assert := internal.NewAssert(t, "TestJoinIterator")
+
+	iter1 := FromSlice([]int{1, 2})
+	iter2 := FromSlice([]int{3, 4})
+
+	iter := Join(iter1, iter2)
+
+	item, ok := iter.Next()
+	assert.Equal(1, item)
+	assert.Equal(true, ok)
+
+	assert.Equal([]int{2, 3, 4}, ToSlice(iter))
+}
+
+func TestReduce(t *testing.T) {
+	assert := internal.NewAssert(t, "TestReduce")
+
+	iter := FromSlice([]int{1, 2, 3, 4})
+	sum := Reduce(iter, 0, func(a, b int) int { return a + b })
+	assert.Equal(10, sum)
+}
+
+func TestTakeIterator(t *testing.T) {
+	assert := internal.NewAssert(t, "TestTakeIterator")
+
+	iter := FromSlice([]int{1, 2, 3, 4, 5})
+
+	iter = Take(iter, 3)
+
+	result := ToSlice(iter)
+	assert.Equal([]int{1, 2, 3}, result)
+}