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feat: return nil for slice operations that received nil #409

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feat: return nil for slice operations that received nil #409

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80 changes: 80 additions & 0 deletions slice.go
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Expand Up @@ -9,6 +9,10 @@ import (
// Filter iterates over elements of collection, returning an array of all elements predicate returns truthy for.
// Play: https://go.dev/play/p/Apjg3WeSi7K
func Filter[V any](collection []V, predicate func(item V, index int) bool) []V {
if collection == nil {
return nil
}

result := make([]V, 0, len(collection))

for i, item := range collection {
Expand All @@ -23,6 +27,10 @@ func Filter[V any](collection []V, predicate func(item V, index int) bool) []V {
// Map manipulates a slice and transforms it to a slice of another type.
// Play: https://go.dev/play/p/OkPcYAhBo0D
func Map[T any, R any](collection []T, iteratee func(item T, index int) R) []R {
if collection == nil {
return nil
}

result := make([]R, len(collection))

for i, item := range collection {
Expand All @@ -39,6 +47,10 @@ func Map[T any, R any](collection []T, iteratee func(item T, index int) R) []R {
//
// Play: https://go.dev/play/p/-AuYXfy7opz
func FilterMap[T any, R any](collection []T, callback func(item T, index int) (R, bool)) []R {
if collection == nil {
return nil
}

result := []R{}

for i, item := range collection {
Expand All @@ -55,6 +67,10 @@ func FilterMap[T any, R any](collection []T, callback func(item T, index int) (R
// no value is added to the final slice.
// Play: https://go.dev/play/p/YSoYmQTA8-U
func FlatMap[T any, R any](collection []T, iteratee func(item T, index int) []R) []R {
if collection == nil {
return nil
}

result := make([]R, 0, len(collection))

for i, item := range collection {
Expand Down Expand Up @@ -110,6 +126,10 @@ func Times[T any](count int, iteratee func(index int) T) []T {
// The order of result values is determined by the order they occur in the array.
// Play: https://go.dev/play/p/DTzbeXZ6iEN
func Uniq[T comparable](collection []T) []T {
if collection == nil {
return nil
}

result := make([]T, 0, len(collection))
seen := make(map[T]struct{}, len(collection))

Expand All @@ -130,6 +150,10 @@ func Uniq[T comparable](collection []T) []T {
// invoked for each element in array to generate the criterion by which uniqueness is computed.
// Play: https://go.dev/play/p/g42Z3QSb53u
func UniqBy[T any, U comparable](collection []T, iteratee func(item T) U) []T {
if collection == nil {
return nil
}

result := make([]T, 0, len(collection))
seen := make(map[U]struct{}, len(collection))

Expand Down Expand Up @@ -169,6 +193,10 @@ func Chunk[T any](collection []T, size int) [][]T {
panic("Second parameter must be greater than 0")
}

if collection == nil {
return nil
}

chunksNum := len(collection) / size
if len(collection)%size != 0 {
chunksNum += 1
Expand All @@ -192,6 +220,10 @@ func Chunk[T any](collection []T, size int) [][]T {
// of running each element of collection through iteratee.
// Play: https://go.dev/play/p/NfQ_nGjkgXW
func PartitionBy[T any, K comparable](collection []T, iteratee func(item T) K) [][]T {
if collection == nil {
return nil
}

result := [][]T{}
seen := map[K]int{}

Expand All @@ -218,6 +250,10 @@ func PartitionBy[T any, K comparable](collection []T, iteratee func(item T) K) [
// Flatten returns an array a single level deep.
// Play: https://go.dev/play/p/rbp9ORaMpjw
func Flatten[T any](collection [][]T) []T {
if collection == nil {
return nil
}

totalLen := 0
for i := range collection {
totalLen += len(collection[i])
Expand Down Expand Up @@ -282,6 +318,10 @@ func Shuffle[T any](collection []T) []T {
// Reverse reverses array so that the first element becomes the last, the second element becomes the second to last, and so on.
// Play: https://go.dev/play/p/fhUMLvZ7vS6
func Reverse[T any](collection []T) []T {
if collection == nil {
return nil
}

length := len(collection)
half := length / 2

Expand All @@ -296,6 +336,10 @@ func Reverse[T any](collection []T) []T {
// Fill fills elements of array with `initial` value.
// Play: https://go.dev/play/p/VwR34GzqEub
func Fill[T Clonable[T]](collection []T, initial T) []T {
if collection == nil {
return nil
}

result := make([]T, 0, len(collection))

for range collection {
Expand Down Expand Up @@ -369,6 +413,10 @@ func SliceToMap[T any, K comparable, V any](collection []T, transform func(item
// Drop drops n elements from the beginning of a slice or array.
// Play: https://go.dev/play/p/JswS7vXRJP2
func Drop[T any](collection []T, n int) []T {
if collection == nil {
return nil
}

if len(collection) <= n {
return make([]T, 0)
}
Expand All @@ -381,6 +429,10 @@ func Drop[T any](collection []T, n int) []T {
// DropRight drops n elements from the end of a slice or array.
// Play: https://go.dev/play/p/GG0nXkSJJa3
func DropRight[T any](collection []T, n int) []T {
if collection == nil {
return nil
}

if len(collection) <= n {
return []T{}
}
Expand All @@ -392,6 +444,10 @@ func DropRight[T any](collection []T, n int) []T {
// DropWhile drops elements from the beginning of a slice or array while the predicate returns true.
// Play: https://go.dev/play/p/7gBPYw2IK16
func DropWhile[T any](collection []T, predicate func(item T) bool) []T {
if collection == nil {
return nil
}

i := 0
for ; i < len(collection); i++ {
if !predicate(collection[i]) {
Expand All @@ -406,6 +462,10 @@ func DropWhile[T any](collection []T, predicate func(item T) bool) []T {
// DropRightWhile drops elements from the end of a slice or array while the predicate returns true.
// Play: https://go.dev/play/p/3-n71oEC0Hz
func DropRightWhile[T any](collection []T, predicate func(item T) bool) []T {
if collection == nil {
return nil
}

i := len(collection) - 1
for ; i >= 0; i-- {
if !predicate(collection[i]) {
Expand All @@ -420,6 +480,10 @@ func DropRightWhile[T any](collection []T, predicate func(item T) bool) []T {
// Reject is the opposite of Filter, this method returns the elements of collection that predicate does not return truthy for.
// Play: https://go.dev/play/p/YkLMODy1WEL
func Reject[V any](collection []V, predicate func(item V, index int) bool) []V {
if collection == nil {
return nil
}

result := []V{}

for i, item := range collection {
Expand Down Expand Up @@ -483,6 +547,10 @@ func CountValuesBy[T any, U comparable](collection []T, mapper func(item T) U) m
// Subset returns a copy of a slice from `offset` up to `length` elements. Like `slice[start:start+length]`, but does not panic on overflow.
// Play: https://go.dev/play/p/tOQu1GhFcog
func Subset[T any](collection []T, offset int, length uint) []T {
if collection == nil {
return nil
}

size := len(collection)

if offset < 0 {
Expand All @@ -506,6 +574,10 @@ func Subset[T any](collection []T, offset int, length uint) []T {
// Slice returns a copy of a slice from `start` up to, but not including `end`. Like `slice[start:end]`, but does not panic on overflow.
// Play: https://go.dev/play/p/8XWYhfMMA1h
func Slice[T any](collection []T, start int, end int) []T {
if collection == nil {
return nil
}

size := len(collection)

if start >= end {
Expand All @@ -532,6 +604,10 @@ func Slice[T any](collection []T, start int, end int) []T {
// Replace returns a copy of the slice with the first n non-overlapping instances of old replaced by new.
// Play: https://go.dev/play/p/XfPzmf9gql6
func Replace[T comparable](collection []T, old T, new T, n int) []T {
if collection == nil {
return nil
}

result := make([]T, len(collection))
copy(result, collection)

Expand All @@ -554,6 +630,10 @@ func ReplaceAll[T comparable](collection []T, old T, new T) []T {
// Compact returns a slice of all non-zero elements.
// Play: https://go.dev/play/p/tXiy-iK6PAc
func Compact[T comparable](collection []T) []T {
if collection == nil {
return nil
}

var zero T

result := make([]T, 0, len(collection))
Expand Down