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slice_std.go
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slice_std.go
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package g
// Map is a map operator, like js/java's map.
func Map[F any, T any](values []F, f func(F, int) T) []T {
result := make([]T, 0, len(values))
for i, v := range values {
result = append(result, f(v, i))
}
return result
}
// Reduce is a reduce operator, like js's reduce.
func Reduce[F any, T any](values []F, f func(T, F, int) T) T {
var result T
for i, v := range values {
result = f(result, v, i)
}
return result
}
// Partition is a partition operator, like java's partition.
func Partition[T any](values []T, size int) [][]T {
partitions := (len(values) + size - 1) / size
result := make([][]T, partitions)
for i := 0; i < partitions; i++ {
end := (i + 1) * size
if end > len(values) {
end = len(values)
}
result[i] = values[i*size : end]
}
return result
}
// GroupBy is a group by operator, like guava's group by.
func GroupBy[T any, K comparable](values []T, f func(T, int) K) map[K][]T {
result := make(map[K][]T)
for i, v := range values {
key := f(v, i)
result[key] = append(result[key], v)
}
return result
}
// Contains check v is contained by values.
func Contains[T comparable](values []T, v T) bool {
for _, vv := range values {
if vv == v {
return true
}
}
return false
}
// Uniq remove duplicated elements from values
func Uniq[T comparable](values []T) []T {
result := make([]T, 0, len(values))
for _, v := range values {
if !Contains(result, v) {
result = append(result, v)
}
}
return result
}
// UniqBy remove duplicated elements from values, based on given func.
func UniqBy[V any, T comparable](values []V, f func(V) T) []V {
result := make([]V, 0, len(values))
for _, v := range values {
idx := 0
for _, vv := range result {
if f(v) == f(vv) {
break
}
idx++
}
if idx == len(result) {
result = append(result, v)
}
}
return result
}
// IndexOf find the index of v in values, return -1 if element not found.
func IndexOf[T comparable](values []T, v T) int {
for i, vv := range values {
if vv == v {
return i
}
}
return -1
}
// LastIndexOf find the last index of v in values, return -1 if element not found.
func LastIndexOf[T comparable](values []T, v T) int {
for i := len(values) - 1; i >= 0; i-- {
if values[i] == v {
return i
}
}
return -1
}
// IndexOfBy find the index of v in values, return -1 if element not found.
func IndexOfBy[T comparable](values []T, f func(T, int) bool) int {
for i, v := range values {
if f(v, i) {
return i
}
}
return -1
}
// LastIndexOfBy find the last index of v in values, return -1 if element not found.
func LastIndexOfBy[T comparable](values []T, f func(T, int) bool) int {
for i := len(values) - 1; i >= 0; i-- {
if f(values[i], i) {
return i
}
}
return -1
}
// Filter is a filter operator, like java's filter.
func Filter[T any](values []T, f func(T, int) bool) []T {
result := make([]T, 0, len(values))
for i, v := range values {
if f(v, i) {
result = append(result, v)
}
}
return result
}
// Flat2 flatten 2-dimensional array to 1-dimensional array.
func Flat2[T any](values [][]T) []T {
result := make([]T, 0, len(values))
for _, v := range values {
result = append(result, v...)
}
return result
}
// Flat3 flatten 3-dimensional array to 1-dimensional array.
func Flat3[T any](values [][][]T) []T {
result := make([]T, 0, len(values))
for _, v := range values {
result = append(result, Flat2(v)...)
}
return result
}
// Slice2Map transfer slice to a map base on given func.
func Slice2Map[K comparable, V any](values []V, f func(V, int) K) map[K]V {
result := make(map[K]V)
for i, v := range values {
result[f(v, i)] = v
}
return result
}
// Reverse reverse the order of elements in values.
func Reverse[T any](values []T) []T {
for i, j := 0, len(values)-1; i < j; i, j = i+1, j-1 {
values[i], values[j] = values[j], values[i]
}
return values
}
// AssertSlice assert interface list to target type, panic if elements of values are not T.
func AssertSlice[T any](values []any) []T {
result := make([]T, len(values))
for i, v := range values {
result[i] = v.(T)
}
return result
}
// AnySlice convert []T to []interface{}/[]any.
func AnySlice[T any](values []T) []any {
result := make([]any, len(values))
for i, v := range values {
result[i] = v
}
return result
}
// CopySlice copy slice.
func CopySlice[T any](values []T) []T {
result := make([]T, len(values))
copy(result, values)
return result
}
func Repeat[T any](v T, n int) []T {
result := make([]T, n)
for i := 0; i < n; i++ {
result[i] = v
}
return result
}