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https://github.com/youthlin/stream
Go Stream, like Java 8 Stream.
https://github.com/youthlin/stream
filter flatmap foreach functional functional-programming go-stream map reduce
Last synced: about 2 months ago
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Go Stream, like Java 8 Stream.
- Host: GitHub
- URL: https://github.com/youthlin/stream
- Owner: youthlin
- License: mit
- Created: 2020-11-12T03:52:50.000Z (about 4 years ago)
- Default Branch: main
- Last Pushed: 2024-02-08T10:00:38.000Z (10 months ago)
- Last Synced: 2024-07-31T20:52:54.806Z (4 months ago)
- Topics: filter, flatmap, foreach, functional, functional-programming, go-stream, map, reduce
- Language: Go
- Homepage:
- Size: 29.3 KB
- Stars: 88
- Watchers: 3
- Forks: 11
- Open Issues: 1
-
Metadata Files:
- Readme: README.md
- License: LICENSE
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README
# Go Stream
[](https://pkg.go.dev/github.com/youthlin/stream)
[](https://goreportcard.com/report/github.com/youthlin/stream)
[](https://travis-ci.org/youthlin/stream)
[](https://codecov.io/gh/youthlin/stream)
Go Stream, like Java 8 Stream.
Blog Post: https://youthlin.com/?p=1755
## How to get
```shell script
go get github.com/youthlin/stream
```
国内镜像: https://gitee.com/youthlin/stream
在 `go.mod` 中引入模块路径 `github.com/youthlin/stream` 及版本后，
再添加 replace 即可：
```go
// go.mod
require github.com/youthlin/stream latest
replace github.com/youthlin/stream latest => gitee.com/youthlin/stream latest
```
## Play online
https://play.golang.org/p/nPQJYqA3-Jr
```go
package main
import (
"fmt"
"github.com/youthlin/stream"
"github.com/youthlin/stream/types"
)
func main() {
m := stream.IntRange(0, 10).
Filter(func(e types.T) bool {
return e.(int)%2 == 0
}).
Map(func(e types.T) types.R {
return e.(int) * 2
}).
ReduceWith(map[int]string{}, func(acc types.R, e types.T) types.R {
m := acc.(map[int]string)
m[e.(int)] = fmt.Sprintf("<%d>", e)
return m
})
fmt.Println(m)
// Output:
// map[0:<0> 4:<4> 8:<8> 12:<12> 16:<16>]
}
```
## Examples
```go
type Stream interface {
// stateless operate 无状态操作
Filter(types.Predicate) Stream // 过滤
Map(types.Function) Stream // 转换
FlatMap(func(t types.T) Stream) Stream // 打平
Peek(types.Consumer) Stream // peek 每个元素
// stateful operate 有状态操作
Distinct(types.IntFunction) Stream // 去重
Sorted(types.Comparator) Stream // 排序
Limit(int64) Stream // 限制个数
Skip(int64) Stream // 跳过个数
// terminal operate 终止操作
// 遍历
ForEach(types.Consumer)
// return []T 转为切片
ToSlice() []types.T
// return []X which X is the type of some
ToElementSlice(some types.T) types.R
// return []X which X is same as the `typ` representation
ToSliceOf(typ reflect.Type) types.R
// 测试是否所有元素满足条件
AllMatch(types.Predicate) bool
// 测试是否没有元素满足条件
NoneMatch(types.Predicate) bool
// 测试是否有任意元素满足条件
AnyMatch(types.Predicate) bool
// Reduce return optional.Empty if no element. calculate result by (T, T) -> T from first element
Reduce(accumulator types.BinaryOperator) optional.Optional
// type of initValue is same as element. (T, T) -> T
ReduceFrom(initValue types.T, accumulator types.BinaryOperator) types.T
// type of initValue is different from element. (R, T) -> R
ReduceWith(initValue types.R, accumulator func(types.R, types.T) types.R) types.R
FindFirst() optional.Optional
// 返回元素个数
Count() int64
}
func ExampleOf() {
fmt.Println(stream.Of().Count())
fmt.Println(stream.Of(1).Count())
fmt.Println(stream.Of("a", "b").Count())
var s = []int{1, 2, 3, 4}
stream.Of(stream.Slice(s)...).ForEach(func(t types.T) {
fmt.Printf("%d,", t)
})
// Output:
// 0
// 1
// 2
// 1,2,3,4,
}
func ExampleOfSlice() {
var intArr = []int{1, 2, 3, 4}
stream.OfSlice(intArr).ForEach(func(e types.T) {
fmt.Printf("%d,", e)
})
var nilArr []int
stream.OfSlice(nilArr).ForEach(func(e types.T) {
fmt.Printf("should not print")
})
var strArr = []string{"a", "b"}
stream.OfSlice(strArr).
Map(func(e types.T) types.R {
return fmt.Sprintf("<%s>", e)
}).
ForEach(func(e types.T) {
fmt.Printf("%s,", e)
})
// Output:
// 1,2,3,4,,,
}
func ExampleOfMap() {
var m1 = map[int]string{
3: "c",
2: "b",
1: "a",
}
s := stream.OfMap(m1).
Map(func(e types.T) types.R {
p := e.(types.Pair)
p.First, p.Second = p.Second, p.First
return p
}).
Sorted(func(left types.T, right types.T) int {
p1 := left.(types.Pair)
p2 := right.(types.Pair)
return p1.Second.(int) - p2.Second.(int)
}).
ToSlice()
fmt.Println(s)
stream.OfMap(nil).ForEach(func(e types.T) {
fmt.Println("not print")
})
// Output:
// [{a 1} {b 2} {c 3}]
}
func ExampleStream_Filter() {
stream.Of(0, 1, 2, 3, 4, 5, 6, 7, 8, 9).
Filter(func(e types.T) bool {
return e.(int)%3 == 0
}).
ForEach(func(e types.T) {
fmt.Println(e)
})
// Output:
// 0
// 3
// 6
// 9
}
func ExampleStream_Map() {
stream.IntRange(0, 5).
Map(func(t types.T) types.R {
return fmt.Sprintf("<%d>", t.(int))
}).
ForEach(func(t types.T) {
fmt.Printf("%v", t)
})
// Output:
// <0><1><2><3><4>
}
func ExampleStream_FlatMap() {
stream.Of([]int{0, 2, 4, 6, 8}, []int{1, 3, 5, 7, 9}).
FlatMap(func(t types.T) stream.Stream {
return stream.Of(stream.Slice(t)...)
}).
ForEach(func(t types.T) {
fmt.Printf("%d", t)
})
// Output:
// 0246813579
}
func ExampleStream_Sorted() {
stream.IntRange(1, 10).
Sorted(types.ReverseOrder(types.IntComparator)).
ForEach(func(t types.T) {
fmt.Printf("%d,", t)
})
// Output:
// 9,8,7,6,5,4,3,2,1,
}
func TestToMap(t *testing.T) {
m := stream.IntRange(0, 10).ReduceWith(make(map[int]int), func(acc types.R, t types.T) types.R {
acc.(map[int]int)[t.(int)] = t.(int) * 10
return acc
})
t.Log(m)
// Output:
// map[0:0 1:10 2:20 3:30 4:40 5:50 6:60 7:70 8:80 9:90]
}
```
## Change Log
- v0.0.3 2020-12-08 add factory method: OfInts, OfInt64s, OfFloat32s, OfFloat64s, OfStrings;
add Stream method: ReduceBy
- v0.0.2 2020-12-07 add factory method: OfSlice, OfMap
- v0.0.1 2020-11-12 first version
## Todo
- [ ] add Benchmark test
- [ ] support parallel stream