feat: update iterator package

iterator/iterator.go

@@ -0,0 +1,174 @@
+// 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 pacakge 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 "github.com/duke-git/lancet/v2/lancetconstraints"
+
+// Iterator supports iterating over a sequence of values of type `E`.
+type Iterator[T any] interface {
+	// Next checks if there is a next value in the iteration or not
+	HasNext() bool
+	// Next returns the next value in the iteration if there is one,
+	// and reports whether the returned value is valid.
+	// Once Next returns ok==false, the iteration is over,
+	// and all subsequent calls will return ok==false.
+	Next() (item T, ok bool)
+}
+
+// StopIterator is an  interface for stopping Iterator.
+type StopIterator[T any] interface {
+	Iterator[T]
+
+	// Stop indicates that the iterator will no longer be used.
+	// After a call to Stop, future calls to Next may panic.
+	// Stop may be called multiple times;
+	// all calls after the first will have no effect.
+	Stop()
+}
+
+// DeleteIter is an Iter that implements a Delete method.
+type DeleteIterator[T any] interface {
+	Iterator[T]
+
+	// Delete deletes the current iterator element;
+	// that is, the one returned by the last call to Next.
+	// Delete should panic if called before Next or after
+	// Next returns false.
+	Delete()
+}
+
+// SetIterator is an Iter that implements a Set method.
+type SetIterator[T any] interface {
+	Iterator[T]
+
+	// Set replaces the current iterator element with v.
+	// Set should panic if called before Next or after
+	// Next returns false.
+	Set(v T)
+}
+
+// PrevIterator is an iterator with a Prev method.
+type PrevIterator[T any] interface {
+	Iterator[T]
+
+	// Prev moves the iterator to the previous position.
+	// After calling Prev, Next will return the value at
+	// that position in the container. For example, after
+	//   it.Next() returning (v, true)
+	//   it.Prev()
+	// another call to it.Next will again return (v, true).
+	// Calling Prev before calling Next may panic.
+	// Calling Prev after Next returns false will move
+	// to the last element, or, if there are no elements,
+	// to the iterator's initial state.
+	Prev()
+}
+
+////////////////////////////////////////////////////////////////////////////////////////////////////
+// Functions that create an Iterator from some other type.                                       //
+////////////////////////////////////////////////////////////////////////////////////////////////////
+
+// FromSlice returns an iterator over a slice of data.
+func FromSlice[T any](slice []T) Iterator[T] {
+	return &sliceIterator[T]{slice: slice, index: -1}
+}
+
+func ToSlice[T any](iter Iterator[T]) []T {
+	result := []T{}
+	for item, ok := iter.Next(); ok; item, ok = iter.Next() {
+		result = append(result, item)
+	}
+	return result
+}
+
+type sliceIterator[T any] struct {
+	slice []T
+	index int
+}
+
+func (iter *sliceIterator[T]) HasNext() bool {
+	return iter.index < len(iter.slice)-1
+}
+
+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
+}
+
+// Prev implements PrevIterator.
+func (iter *sliceIterator[T]) Prev() {
+	if iter.index == -1 {
+		panic("Next function should be called Prev")
+	}
+	if iter.HasNext() {
+		iter.index--
+	} else {
+		iter.index = len(iter.slice) - 1
+	}
+}
+
+// Set implements SetIterator.
+func (iter *sliceIterator[T]) Set(value T) {
+	if iter.index == -1 {
+		panic("Next function should be called Set")
+	}
+	if iter.index >= len(iter.slice) || len(iter.slice) == 0 {
+		panic("No element in current iterator")
+	}
+	iter.slice[iter.index] = value
+}
+
+// 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 FromRange[T lancetconstraints.Number](start, end, step T) Iterator[T] {
+	if end < start {
+		panic("RangeIterator: start should be before end")
+	} else if step <= 0 {
+		panic("RangeIterator: step should be positive")
+	}
+
+	return &rangeIterator[T]{start: start, end: end, step: step}
+}
+
+type rangeIterator[T lancetconstraints.Number] struct {
+	start, end, step T
+}
+
+func (iter *rangeIterator[T]) HasNext() bool {
+	if iter.start >= iter.end {
+		return false
+	}
+	return true
+}
+
+func (iter *rangeIterator[T]) Next() (T, bool) {
+	if iter.start >= iter.end {
+		var zero T
+		return zero, false
+	}
+	num := iter.start
+	iter.start += iter.step
+	return num, true
+}

iterator/iterator_test.go

@@ -0,0 +1,50 @@
+// Copyright 2022 dudaodong@gmail.com. All rights resulterved.
+// Use of this source code is governed by MIT license
+
+// Package iterator implements some feature of C++ STL iterators
+package iterator
+
+import (
+	"testing"
+
+	"github.com/duke-git/lancet/v2/internal"
+)
+
+func TestSliceIterator(t *testing.T) {
+	assert := internal.NewAssert(t, "TestSliceIterator")
+
+	// HashNext
+	t.Run("slice iterator HasNext: ", func(t *testing.T) {
+		iter1 := FromSlice([]int{1, 2, 3, 4})
+		for {
+			item, _ := iter1.Next()
+
+			if item == 4 {
+				assert.Equal(false, iter1.HasNext())
+				break
+			} else {
+				assert.Equal(true, iter1.HasNext())
+			}
+		}
+
+		iter2 := FromSlice([]int{})
+		assert.Equal(false, iter2.HasNext())
+	})
+
+	//Next
+	t.Run("slice iterator Next: ", func(t *testing.T) {
+		iter1 := FromSlice([]int{1, 2, 3, 4})
+		for i := 0; i < 4; i++ {
+			item, ok := iter1.Next()
+			if !ok {
+				break
+			}
+			assert.Equal(i+1, item)
+		}
+
+		iter2 := FromSlice([]int{})
+		_, ok := iter2.Next()
+		assert.Equal(false, ok)
+	})
+
+}

iterator/operation.go

@@ -0,0 +1,61 @@
+// 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 pacakge 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
+
+// Map creates a new iterator which applies a function to all items of input iterator.
+func Map[T any, U any](iter Iterator[T], iteratee func(item T) U) Iterator[U] {
+	return &mapIterator[T, U]{
+		iter:     iter,
+		iteratee: iteratee,
+	}
+}
+
+type mapIterator[T any, U any] struct {
+	iter     Iterator[T]
+	iteratee func(T) U
+}
+
+func (mr *mapIterator[T, U]) HasNext() bool {
+	return mr.iter.HasNext()
+}
+
+func (mr *mapIterator[T, U]) Next() (U, bool) {
+	var zero U
+	item, ok := mr.iter.Next()
+	if !ok {
+		return zero, false
+	}
+	return mr.iteratee(item), true
+}
+
+// Filter creates a new iterator that returns only the items that pass specified predicate function.
+func Filter[T any](iter Iterator[T], predicateFunc func(item T) bool) Iterator[T] {
+	return &filterIterator[T]{iter: iter, predicateFunc: predicateFunc}
+}
+
+type filterIterator[T any] struct {
+	iter          Iterator[T]
+	predicateFunc func(T) bool
+}
+
+func (fr *filterIterator[T]) Next() (T, bool) {
+	for item, ok := fr.iter.Next(); ok; item, ok = fr.iter.Next() {
+		if fr.predicateFunc(item) {
+			return item, true
+		}
+	}
+	var zero T
+	return zero, false
+}
+
+func (fr *filterIterator[T]) HasNext() bool {
+	return fr.iter.HasNext()
+}

slice/slice.go

@@ -170,33 +170,29 @@ func EqualWith[T, U any](slice1 []T, slice2 []U, comparator func(T, U) bool) boo
 
 // Every return true if all of the values in the slice pass the predicate function.
 func Every[T any](slice []T, predicate func(index int, item T) bool) bool {
-	var currentLength int
-
 	for i, v := range slice {
-		if predicate(i, v) {
-			currentLength++
+		if !predicate(i, v) {
+			return false
 		}
 	}
 
-	return currentLength == len(slice)
+	return true
 }
 
 // None return true if all the values in the slice mismatch the criteria
 func None[T any](slice []T, predicate func(index int, item T) bool) bool {
-
-	var currentLength int
+	l := 0
 	for i, v := range slice {
 		if !predicate(i, v) {
-			currentLength++
+			l++
 		}
 	}
 
-	return currentLength == len(slice)
+	return l == len(slice)
 }
 
 // Some return true if any of the values in the list pass the predicate function.
 func Some[T any](slice []T, predicate func(index int, item T) bool) bool {
-
 	for i, v := range slice {
 		if predicate(i, v) {
 			return true
@@ -421,6 +417,15 @@ func ReplaceAll[T comparable](slice []T, old T, new T) []T {
 	return Replace(slice, old, new, -1)
 }
 
+// Repeat creates a slice with length n whose elements are param `item`.
+func Repeat[T any](item T, n int) []T {
+	result := make([]T, n)
+	for i := range result {
+		result[i] = item
+	}
+	return result
+}
+
 // InterfaceSlice convert param to slice of interface.
 func InterfaceSlice(slice any) []any {
 	sv := sliceValue(slice)
@@ -618,6 +623,17 @@ func UnionBy[T any, V comparable](predicate func(item T) V, slices ...[]T) []T {
 	return result
 }
 
+// Merge all given slices into one slice
+func Merge[T any](slices ...[]T) []T {
+	result := make([]T, 0)
+
+	for _, item := range slices {
+		result = append(result, item...)
+	}
+
+	return result
+}
+
 // Intersection creates a slice of unique values that included by all slices.
 func Intersection[T comparable](slices ...[]T) []T {
 	if len(slices) == 0 {

slice/slice_test.go

@@ -446,6 +446,18 @@ func TestUnionBy(t *testing.T) {
 	assert.Equal(result, []int{0, 2, 4, 10})
 }
 
+func TestMerge(t *testing.T) {
+	assert := internal.NewAssert(t, "TestMerge")
+
+	s1 := []int{1, 2, 3, 4}
+	s2 := []int{2, 3, 4, 5}
+	s3 := []int{4, 5, 6}
+
+	assert.Equal([]int{1, 2, 3, 4, 2, 3, 4, 5, 4, 5, 6}, Merge(s1, s2, s3))
+	assert.Equal([]int{1, 2, 3, 4, 2, 3, 4, 5}, Merge(s1, s2))
+	assert.Equal([]int{2, 3, 4, 5, 4, 5, 6}, Merge(s2, s3))
+}
+
 func TestIntersection(t *testing.T) {
 	s1 := []int{1, 2, 2, 3}
 	s2 := []int{1, 2, 3, 4}
@@ -672,3 +684,11 @@ func TestKeyBy(t *testing.T) {
 
 	assert.Equal(result, map[int]string{1: "a", 2: "ab", 3: "abc"})
 }
+
+func TestRepeat(t *testing.T) {
+	assert := internal.NewAssert(t, "TestRepeat")
+
+	result := Repeat("a", 6)
+
+	assert.Equal(result, []string{"a", "a", "a", "a", "a", "a"})
+}