feat: add IsSorted

random/random.go

@@ -13,10 +13,10 @@ import (
 )
 
 const (
-	NUMERAL       = "0123456789"
-	LOWER_LETTERS = "abcdefghijklmnopqrstuvwxyz"
-	UPPER_LETTERS = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
-	LETTERS       = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"
+	Numeral       = "0123456789"
+	LowwerLetters = "abcdefghijklmnopqrstuvwxyz"
+	UpperLetters  = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
+	Letters       = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"
 )
 
 // RandInt generate random int between min and max, maybe min,  not be max.
@@ -51,31 +51,31 @@ func RandBytes(length int) []byte {
 // RandString generate random string of specified length.
 // Play: https://go.dev/play/p/W2xvRUXA7Mi
 func RandString(length int) string {
-	return random(LETTERS, length)
+	return random(Letters, length)
 }
 
 // RandUpper generate a random upper case string.
 // Play: https://go.dev/play/p/29QfOh0DVuh
 func RandUpper(length int) string {
-	return random(UPPER_LETTERS, length)
+	return random(UpperLetters, length)
 }
 
 // RandLower generate a random lower case string.
 // Play: https://go.dev/play/p/XJtZ471cmtI
 func RandLower(length int) string {
-	return random(LOWER_LETTERS, length)
+	return random(LowwerLetters, length)
 }
 
 // RandNumeral generate a random numeral string of specified length.
 // Play: https://go.dev/play/p/g4JWVpHsJcf
 func RandNumeral(length int) string {
-	return random(NUMERAL, length)
+	return random(Numeral, length)
 }
 
 // RandNumeralOrLetter generate a random numeral or letter string.
 // Play: https://go.dev/play/p/19CEQvpx2jD
 func RandNumeralOrLetter(length int) string {
-	return random(NUMERAL+LETTERS, length)
+	return random(Numeral+Letters, length)
 }
 
 // random generate a random string based on given string range.

slice/slice.go

@@ -6,7 +6,6 @@ package slice
 
 import (
 	"fmt"
-	"math"
 	"math/rand"
 	"reflect"
 	"sort"
@@ -559,24 +558,72 @@ func DeleteAt[T any](slice []T, start int, end ...int) []T {
 	return slice
 }
 
-// Drop creates a slice with `n` elements dropped from the beginning when n > 0, or `n` elements dropped from the ending when n < 0.
+// Drop drop n elements from the start of a slice.
 // Play: https://go.dev/play/p/pJ-d6MUWcvK
 func Drop[T any](slice []T, n int) []T {
 	size := len(slice)
 
-	if size == 0 || n == 0 {
-		return slice
-	}
-
-	if math.Abs(float64(n)) >= float64(size) {
+	if size <= n {
 		return []T{}
 	}
 
-	if n < 0 {
-		return slice[0 : size+n]
+	if n <= 0 {
+		return slice
 	}
 
-	return slice[n:size]
+	result := make([]T, 0, size-n)
+
+	return append(result, slice[n:]...)
+}
+
+// DropRight drop n elements from the end of a slice.
+// Play: todo
+func DropRight[T any](slice []T, n int) []T {
+	size := len(slice)
+
+	if size <= n {
+		return []T{}
+	}
+
+	if n <= 0 {
+		return slice
+	}
+
+	result := make([]T, 0, size-n)
+
+	return append(result, slice[:size-n]...)
+}
+
+// DropWhile drop n elements from the start of a slice while predicate function returns true.
+// Play: todo
+func DropWhile[T any](slice []T, predicate func(item T) bool) []T {
+	i := 0
+
+	for ; i < len(slice); i++ {
+		if !predicate(slice[i]) {
+			break
+		}
+	}
+
+	result := make([]T, 0, len(slice)-i)
+
+	return append(result, slice[i:]...)
+}
+
+// DropRightWhile drop n elements from the end of a slice while predicate function returns true.
+// Play: todo
+func DropRightWhile[T any](slice []T, predicate func(item T) bool) []T {
+	i := len(slice) - 1
+
+	for ; i >= 0; i-- {
+		if !predicate(slice[i]) {
+			break
+		}
+	}
+
+	result := make([]T, 0, i+1)
+
+	return append(result, slice[:i+1]...)
 }
 
 // InsertAt insert the value or other slice into slice at index.
@@ -783,6 +830,36 @@ func Shuffle[T any](slice []T) []T {
 	return slice
 }
 
+// IsAscending checks if a slice is ascending order.
+// Play: todo
+func IsAscending[T constraints.Ordered](slice []T) bool {
+	for i := 1; i < len(slice); i++ {
+		if slice[i-1] > slice[i] {
+			return false
+		}
+	}
+
+	return true
+}
+
+// IsDescending checks if a slice is descending order.
+// Play: todo
+func IsDescending[T constraints.Ordered](slice []T) bool {
+	for i := 1; i < len(slice); i++ {
+		if slice[i-1] < slice[i] {
+			return false
+		}
+	}
+
+	return true
+}
+
+// IsSorted checks if a slice is sorted(ascending or descending).
+// Play: todo
+func IsSorted[T constraints.Ordered](slice []T) bool {
+	return IsAscending(slice) || IsDescending(slice)
+}
+
 // Sort sorts a slice of any ordered type(number or string), use quick sort algrithm.
 // default sort order is ascending (asc), if want descending order, set param `sortOrder` to `desc`.
 // Play: https://go.dev/play/p/V9AVjzf_4Fk

slice/slice_example_test.go

@@ -482,10 +482,74 @@ func ExampleDrop() {
 	// Output:
 	// [a b c]
 	// [b c]
-	// [a b]
+	// [a b c]
 	// []
 }
 
+func ExampleDropRight() {
+	result1 := DropRight([]string{"a", "b", "c"}, 0)
+	result2 := DropRight([]string{"a", "b", "c"}, 1)
+	result3 := DropRight([]string{"a", "b", "c"}, -1)
+	result4 := DropRight([]string{"a", "b", "c"}, 4)
+
+	fmt.Println(result1)
+	fmt.Println(result2)
+	fmt.Println(result3)
+	fmt.Println(result4)
+
+	// Output:
+	// [a b c]
+	// [a b]
+	// [a b c]
+	// []
+}
+
+func ExampleDropWhile() {
+	numbers := []int{1, 2, 3, 4, 5}
+
+	result1 := DropWhile(numbers, func(n int) bool {
+		return n != 2
+	})
+	result2 := DropWhile(numbers, func(n int) bool {
+		return true
+	})
+	result3 := DropWhile(numbers, func(n int) bool {
+		return n == 0
+	})
+
+	fmt.Println(result1)
+	fmt.Println(result2)
+	fmt.Println(result3)
+
+	// Output:
+	// [2 3 4 5]
+	// []
+	// [1 2 3 4 5]
+}
+
+func ExampleDropRightWhile() {
+	numbers := []int{1, 2, 3, 4, 5}
+
+	result1 := DropRightWhile(numbers, func(n int) bool {
+		return n != 2
+	})
+	result2 := DropRightWhile(numbers, func(n int) bool {
+		return true
+	})
+	result3 := DropRightWhile(numbers, func(n int) bool {
+		return n == 0
+	})
+
+	fmt.Println(result1)
+	fmt.Println(result2)
+	fmt.Println(result3)
+
+	// Output:
+	// [1 2]
+	// []
+	// [1 2 3 4 5]
+}
+
 func ExampleInsertAt() {
 	result1 := InsertAt([]string{"a", "b", "c"}, 0, "1")
 	result2 := InsertAt([]string{"a", "b", "c"}, 1, "1")
@@ -621,6 +685,54 @@ func ExampleReverse() {
 	// [d c b a]
 }
 
+func ExampleIsAscending() {
+
+	result1 := IsAscending([]int{1, 2, 3, 4, 5})
+	result2 := IsAscending([]int{5, 4, 3, 2, 1})
+	result3 := IsAscending([]int{2, 1, 3, 4, 5})
+
+	fmt.Println(result1)
+	fmt.Println(result2)
+	fmt.Println(result3)
+
+	// Output:
+	// true
+	// false
+	// false
+}
+
+func ExampleIsDescending() {
+
+	result1 := IsDescending([]int{5, 4, 3, 2, 1})
+	result2 := IsDescending([]int{1, 2, 3, 4, 5})
+	result3 := IsDescending([]int{2, 1, 3, 4, 5})
+
+	fmt.Println(result1)
+	fmt.Println(result2)
+	fmt.Println(result3)
+
+	// Output:
+	// true
+	// false
+	// false
+}
+
+func ExampleIsSorted() {
+
+	result1 := IsSorted([]int{1, 2, 3, 4, 5})
+	result2 := IsSorted([]int{5, 4, 3, 2, 1})
+	result3 := IsSorted([]int{2, 1, 3, 4, 5})
+
+	fmt.Println(result1)
+	fmt.Println(result2)
+	fmt.Println(result3)
+
+	// Output:
+	// true
+	// true
+	// false
+}
+
 func ExampleSort() {
 	nums := []int{1, 4, 3, 2, 5}
 

slice/slice_test.go

@@ -377,7 +377,7 @@ func TestDeleteAt(t *testing.T) {
 }
 
 func TestDrop(t *testing.T) {
-	assert := internal.NewAssert(t, "TestInterfaceSlice")
+	assert := internal.NewAssert(t, "TestDrop")
 
 	assert.Equal([]int{}, Drop([]int{}, 0))
 	assert.Equal([]int{}, Drop([]int{}, 1))
@@ -388,9 +388,64 @@ func TestDrop(t *testing.T) {
 	assert.Equal([]int{}, Drop([]int{1, 2, 3, 4, 5}, 5))
 	assert.Equal([]int{}, Drop([]int{1, 2, 3, 4, 5}, 6))
 
-	assert.Equal([]int{1, 2, 3, 4}, Drop([]int{1, 2, 3, 4, 5}, -1))
-	assert.Equal([]int{}, Drop([]int{1, 2, 3, 4, 5}, -6))
-	assert.Equal([]int{}, Drop([]int{1, 2, 3, 4, 5}, -6))
+	assert.Equal([]int{1, 2, 3, 4, 5}, Drop([]int{1, 2, 3, 4, 5}, -1))
+}
+
+func TestDropRight(t *testing.T) {
+	assert := internal.NewAssert(t, "TestDropRight")
+
+	assert.Equal([]int{}, DropRight([]int{}, 0))
+	assert.Equal([]int{}, DropRight([]int{}, 1))
+	assert.Equal([]int{}, DropRight([]int{}, -1))
+
+	assert.Equal([]int{1, 2, 3, 4, 5}, DropRight([]int{1, 2, 3, 4, 5}, 0))
+	assert.Equal([]int{1, 2, 3, 4}, DropRight([]int{1, 2, 3, 4, 5}, 1))
+	assert.Equal([]int{}, DropRight([]int{1, 2, 3, 4, 5}, 5))
+	assert.Equal([]int{}, DropRight([]int{1, 2, 3, 4, 5}, 6))
+
+	assert.Equal([]int{1, 2, 3, 4, 5}, DropRight([]int{1, 2, 3, 4, 5}, -1))
+}
+
+func TestDropWhile(t *testing.T) {
+	assert := internal.NewAssert(t, "TestDropWhile")
+
+	numbers := []int{1, 2, 3, 4, 5}
+
+	r1 := DropWhile(numbers, func(n int) bool {
+		return n != 2
+	})
+	assert.Equal([]int{2, 3, 4, 5}, r1)
+
+	r2 := DropWhile(numbers, func(n int) bool {
+		return true
+	})
+	assert.Equal([]int{}, r2)
+
+	r3 := DropWhile(numbers, func(n int) bool {
+		return n == 0
+	})
+	assert.Equal([]int{1, 2, 3, 4, 5}, r3)
+}
+
+func TestDropRightWhile(t *testing.T) {
+	assert := internal.NewAssert(t, "TestDropRightWhile")
+
+	numbers := []int{1, 2, 3, 4, 5}
+
+	r1 := DropRightWhile(numbers, func(n int) bool {
+		return n != 2
+	})
+	assert.Equal([]int{1, 2}, r1)
+
+	r2 := DropRightWhile(numbers, func(n int) bool {
+		return true
+	})
+	assert.Equal([]int{}, r2)
+
+	r3 := DropRightWhile(numbers, func(n int) bool {
+		return n == 0
+	})
+	assert.Equal([]int{1, 2, 3, 4, 5}, r3)
 }
 
 func TestInsertAt(t *testing.T) {
@@ -548,6 +603,30 @@ func TestDifferenceBy(t *testing.T) {
 	assert.Equal([]int{1, 2}, DifferenceBy(s1, s2, addOne))
 }
 
+func TestIsAscending(t *testing.T) {
+	assert := internal.NewAssert(t, "TestIsAscending")
+
+	assert.Equal(true, IsAscending([]int{1, 2, 3, 4, 5}))
+	assert.Equal(false, IsAscending([]int{5, 4, 3, 2, 1}))
+	assert.Equal(false, IsAscending([]int{2, 1, 3, 4, 5}))
+}
+
+func TestIsDescending(t *testing.T) {
+	assert := internal.NewAssert(t, "TestIsDescending")
+
+	assert.Equal(true, IsDescending([]int{5, 4, 3, 2, 1}))
+	assert.Equal(false, IsDescending([]int{1, 2, 3, 4, 5}))
+	assert.Equal(false, IsDescending([]int{2, 1, 3, 4, 5}))
+}
+
+func TestIsSorted(t *testing.T) {
+	assert := internal.NewAssert(t, "TestIsSorted")
+
+	assert.Equal(true, IsSorted([]int{5, 4, 3, 2, 1}))
+	assert.Equal(true, IsSorted([]int{1, 2, 3, 4, 5}))
+	assert.Equal(false, IsSorted([]int{2, 1, 3, 4, 5}))
+}
+
 func TestSort(t *testing.T) {
 	assert := internal.NewAssert(t, "TestSort")
 

stream/stream.go

@@ -10,6 +10,7 @@ import (
 	"bytes"
 	"encoding/gob"
 
+	"github.com/duke-git/lancet/v2/slice"
 	"golang.org/x/exp/constraints"
 )
 
@@ -23,7 +24,7 @@ import (
 // 	Map(mapper func(item T) T) StreamI[T]
 // 	Peek(consumer func(item T)) StreamI[T]
 
-// 	Sort(less func(a, b T) bool) StreamI[T]
+// 	Sorted(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)
 
@@ -43,7 +44,7 @@ import (
 
 // 	// part of methods custom extension
 // 	Reverse() StreamI[T]
-// 	Range(start, end int64) StreamI[T]
+// 	Range(start, end int) StreamI[T]
 // 	Concat(streams ...StreamI[T]) StreamI[T]
 // }
 
@@ -72,12 +73,12 @@ func Generate[T any](generator func() func() (item T, ok bool)) stream[T] {
 	return FromSlice(source)
 }
 
-// FromSlice create stream from slice.
+// FromSlice creates stream from slice.
 func FromSlice[T any](source []T) stream[T] {
 	return stream[T]{source: source}
 }
 
-// FromChannel create stream from channel.
+// FromChannel creates stream from channel.
 func FromChannel[T any](source <-chan T) stream[T] {
 	s := make([]T, 0)
 
@@ -88,7 +89,7 @@ func FromChannel[T any](source <-chan T) stream[T] {
 	return FromSlice(s)
 }
 
-// FromRange create a number stream from start to end. both start and end are included. [start, end]
+// FromRange creates 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")
@@ -106,6 +107,16 @@ func FromRange[T constraints.Integer | constraints.Float](start, end, step T) st
 	return FromSlice(source)
 }
 
+// Concat creates a lazily concatenated stream whose elements are all the elements of the first stream followed by all the elements of the second stream.
+func Concat[T any](a, b stream[T]) stream[T] {
+	source := make([]T, 0)
+
+	source = append(source, a.source...)
+	source = append(source, b.source...)
+
+	return FromSlice(source)
+}
+
 // Distinct returns a stream that removes the duplicated items.
 func (s stream[T]) Distinct() stream[T] {
 	source := make([]T, 0)
@@ -255,6 +266,98 @@ func (s stream[T]) Count() int {
 	return len(s.source)
 }
 
+// FindFirst returns the first element of this stream and true, or zero value and false if the stream is empty.
+func (s stream[T]) FindFirst() (T, bool) {
+	var result T
+
+	if s.source == nil || len(s.source) == 0 {
+		return result, false
+	}
+
+	return s.source[0], true
+}
+
+// Reverse returns a stream whose elements are reverse order of given stream.
+func (s stream[T]) Reverse() stream[T] {
+	l := len(s.source)
+	source := make([]T, l)
+
+	for i := 0; i < l; i++ {
+		source[i] = s.source[l-1-i]
+	}
+	return FromSlice(source)
+}
+
+// Range returns a stream whose elements are in the range from start(included) to end(excluded) original stream.
+func (s stream[T]) Range(start, end int) stream[T] {
+	if start < 0 {
+		start = 0
+	}
+	if end < 0 {
+		end = 0
+	}
+	if start >= end {
+		return FromSlice([]T{})
+	}
+
+	source := make([]T, 0)
+
+	if end > len(s.source) {
+		end = len(s.source)
+	}
+
+	for i := start; i < end; i++ {
+		source = append(source, s.source[i])
+	}
+
+	return FromSlice(source)
+}
+
+// Sorted returns a stream consisting of the elements of this stream, sorted according to the provided less function.
+func (s stream[T]) Sorted(less func(a, b T) bool) stream[T] {
+	source := []T{}
+	source = append(source, s.source...)
+
+	slice.SortBy(source, less)
+
+	return FromSlice(source)
+}
+
+// Max returns the maximum element of this stream according to the provided less function.
+// less: a > b
+func (s stream[T]) Max(less func(a, b T) bool) (T, bool) {
+	var max T
+
+	if len(s.source) == 0 {
+		return max, false
+	}
+
+	for i, v := range s.source {
+		if less(v, max) || i == 0 {
+			max = v
+		}
+	}
+	return max, true
+}
+
+// Min returns the minimum element of this stream according to the provided less function.
+// less: a < b
+func (s stream[T]) Min(less func(a, b T) bool) (T, bool) {
+	var min T
+
+	if len(s.source) == 0 {
+		return min, false
+	}
+
+	for i, v := range s.source {
+		if less(v, min) || i == 0 {
+			min = v
+		}
+	}
+
+	return min, true
+}
+
 // ToSlice return the elements in the stream.
 func (s stream[T]) ToSlice() []T {
 	return s.source

stream/stream_test.go

@@ -247,3 +247,92 @@ func TestStream_Reduce(t *testing.T) {
 
 	assert.Equal(6, result)
 }
+
+func TestStream_FindFirst(t *testing.T) {
+	assert := internal.NewAssert(t, "TestStream_FindFirst")
+
+	stream := FromSlice([]int{1, 2, 3})
+
+	result, ok := stream.FindFirst()
+
+	assert.Equal(1, result)
+	assert.Equal(true, ok)
+}
+
+func TestStream_Reverse(t *testing.T) {
+	assert := internal.NewAssert(t, "TestStream_Reverse")
+
+	s := FromSlice([]int{1, 2, 3})
+
+	rs := s.Reverse()
+
+	assert.Equal([]int{3, 2, 1}, rs.ToSlice())
+}
+
+func TestStream_Range(t *testing.T) {
+	assert := internal.NewAssert(t, "TestStream_Range")
+
+	s := FromSlice([]int{1, 2, 3})
+
+	s1 := s.Range(-1, 0)
+	assert.Equal([]int{}, s1.ToSlice())
+
+	s2 := s.Range(0, -1)
+	assert.Equal([]int{}, s2.ToSlice())
+
+	s3 := s.Range(0, 0)
+	assert.Equal([]int{}, s3.ToSlice())
+
+	s4 := s.Range(1, 1)
+	assert.Equal([]int{}, s4.ToSlice())
+
+	s5 := s.Range(0, 1)
+	assert.Equal([]int{1}, s5.ToSlice())
+
+	s6 := s.Range(0, 4)
+	assert.Equal([]int{1, 2, 3}, s6.ToSlice())
+}
+
+func TestStream_Concat(t *testing.T) {
+	assert := internal.NewAssert(t, "TestStream_Concat")
+
+	s1 := FromSlice([]int{1, 2, 3})
+	s2 := FromSlice([]int{4, 5, 6})
+
+	s := Concat(s1, s2)
+
+	assert.Equal([]int{1, 2, 3, 4, 5, 6}, s.ToSlice())
+}
+
+func TestStream_Sorted(t *testing.T) {
+	assert := internal.NewAssert(t, "TestStream_Sorted")
+
+	s := FromSlice([]int{4, 2, 1, 3})
+
+	s1 := s.Sorted(func(a, b int) bool { return a < b })
+
+	assert.Equal([]int{4, 2, 1, 3}, s.ToSlice())
+	assert.Equal([]int{1, 2, 3, 4}, s1.ToSlice())
+}
+
+func TestStream_Max(t *testing.T) {
+	assert := internal.NewAssert(t, "TestStream_Max")
+
+	s := FromSlice([]int{4, 2, 1, 3})
+
+	max, ok := s.Max(func(a, b int) bool { return a > b })
+
+	assert.Equal(4, max)
+	assert.Equal(true, ok)
+}
+
+func TestStream_Min(t *testing.T) {
+	assert := internal.NewAssert(t, "TestStream_Min")
+
+	s := FromSlice([]int{4, 2, 1, 3})
+
+	max, ok := s.Max(func(a, b int) bool { return a < b })
+
+	assert.Equal(1, max)
+	assert.Equal(true, ok)
+}

validator/validator.go

@@ -281,6 +281,10 @@ func IsZeroValue(value any) bool {
 	}
 
 	rv := reflect.ValueOf(value)
+	if rv.Kind() == reflect.Ptr {
+		rv = rv.Elem()
+	}
+
 	if !rv.IsValid() {
 		return true
 	}