feat: add Distinct

stream/stream.go

@@ -0,0 +1,108 @@
+// 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 a 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
+
+import (
+	"bytes"
+	"encoding/gob"
+
+	"golang.org/x/exp/constraints"
+)
+
+// A stream should implements methods:
+// type StreamI[T any] interface {
+
+// 	// part methods of Java Stream Specification.
+// 	Distinct() StreamI[T]
+// 	Filter(predicate func(item T) bool) StreamI[T]
+// 	FlatMap(mapper func(item T) StreamI[T]) StreamI[T]
+// 	Map(mapper func(item T) T) StreamI[T]
+// 	Peek(consumer func(item T)) StreamI[T]
+
+// 	Sort(less func(a, b T) bool) StreamI[T]
+// 	Max(less func(a, b T) bool) (T, bool)
+// 	Min(less func(a, b T) bool) (T, bool)
+
+// 	Limit(maxSize int) StreamI[T]
+// 	Skip(n int64) StreamI[T]
+
+// 	AllMatch(predicate func(item T) bool) bool
+// 	AnyMatch(predicate func(item T) bool) bool
+// 	NoneMatch(predicate func(item T) bool) bool
+// 	ForEach(consumer func(item T))
+// 	Reduce(accumulator func(a, b T) T) (T, bool)
+// 	Count() int
+
+// 	FindFirst() (T, bool)
+
+// 	ToSlice() []T
+
+// 	// part of methods custom extension
+// 	Reverse() StreamI[T]
+// 	Range(start, end int64) StreamI[T]
+// 	Concat(streams ...StreamI[T]) StreamI[T]
+// }
+
+type stream[T any] struct {
+	source []T
+}
+
+// FromSlice create stream from slice.
+func FromSlice[T any](source []T) stream[T] {
+	return stream[T]{source: source}
+}
+
+// FromRange create a number stream from start to end. both start and end are included. [start, end]
+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")
+	} else if step <= 0 {
+		panic("stream.FromRange: param step should be positive")
+	}
+
+	l := int((end-start)/step) + 1
+	source := make([]T, l, l)
+
+	for i := 0; i < l; i++ {
+		source[i] = start + (T(i) * step)
+	}
+
+	return stream[T]{source: source}
+}
+
+// Distinct returns a stream that removes the duplicated items.
+func (s stream[T]) Distinct() stream[T] {
+	source := make([]T, 0)
+
+	distinct := map[string]bool{}
+
+	for _, v := range s.source {
+		// todo: performance issue
+		k := hashKey(v)
+		if _, ok := distinct[k]; !ok {
+			distinct[k] = true
+			source = append(source, v)
+		}
+	}
+
+	return FromSlice(source)
+}
+
+func hashKey(data any) string {
+	buffer := bytes.NewBuffer(nil)
+	encoder := gob.NewEncoder(buffer)
+	err := encoder.Encode(data)
+	if err != nil {
+		panic("stream.hashKey: get hashkey failed")
+	}
+	return buffer.String()
+}
+
+// ToSlice return the elements in the stream.
+func (s stream[T]) ToSlice() []T {
+	return s.source
+}

stream/stream_test.go

@@ -0,0 +1,57 @@
+package stream
+
+import (
+	"testing"
+
+	"github.com/duke-git/lancet/v2/internal"
+)
+
+func TestFromSlice(t *testing.T) {
+	assert := internal.NewAssert(t, "TestFromSlice")
+
+	stream := FromSlice([]int{1, 2, 3})
+
+	assert.Equal([]int{1, 2, 3}, stream.ToSlice())
+}
+
+func TestFromRange(t *testing.T) {
+	assert := internal.NewAssert(t, "TestFromRange")
+
+	s1 := FromRange(1, 5, 1)
+	s2 := FromRange(1.1, 5.0, 1.0)
+
+	assert.Equal([]int{1, 2, 3, 4, 5}, s1.ToSlice())
+	assert.Equal([]float64{1.1, 2.1, 3.1, 4.1}, s2.ToSlice())
+}
+
+func TestStream_Distinct(t *testing.T) {
+	assert := internal.NewAssert(t, "TestStream_Distinct")
+
+	nums := FromSlice([]int{1, 2, 2, 3, 3, 3})
+	distinctNums := nums.Distinct()
+
+	assert.Equal([]int{1, 2, 2, 3, 3, 3}, nums.ToSlice())
+	assert.Equal([]int{1, 2, 3}, distinctNums.ToSlice())
+
+	type Person struct {
+		Id   string
+		Name string
+		Age  uint
+	}
+
+	people := []Person{
+		{Id: "001", Name: "Tom", Age: 10},
+		{Id: "001", Name: "Tom", Age: 10},
+		{Id: "002", Name: "Jim", Age: 20},
+		{Id: "003", Name: "Mike", Age: 30},
+	}
+
+	stream := FromSlice(people)
+	distinctStream := stream.Distinct()
+
+	// {[{001 Tom 10} {001 Tom 10} {002 Jim 20} {003 Mike 30}]}
+	t.Log(stream)
+
+	// {[{001 Tom 10} {002 Jim 20} {003 Mike 30}]}
+	t.Log(distinctStream)
+}