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524 lines
14 KiB
Go
524 lines
14 KiB
Go
package lo
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import (
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"math/rand"
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"golang.org/x/exp/constraints"
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)
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// Filter iterates over elements of collection, returning an array of all elements predicate returns truthy for.
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// Play: https://go.dev/play/p/Apjg3WeSi7K
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func Filter[V any](collection []V, predicate func(V, int) bool) []V {
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result := []V{}
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for i, item := range collection {
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if predicate(item, i) {
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result = append(result, item)
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}
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}
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return result
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}
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// Map manipulates a slice and transforms it to a slice of another type.
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// Play: https://go.dev/play/p/OkPcYAhBo0D
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func Map[T any, R any](collection []T, iteratee func(T, int) R) []R {
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result := make([]R, len(collection))
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for i, item := range collection {
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result[i] = iteratee(item, i)
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}
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return result
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}
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// FilterMap returns a slice which obtained after both filtering and mapping using the given callback function.
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// The callback function should return two values:
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// - the result of the mapping operation and
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// - whether the result element should be included or not.
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//
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// Play: https://go.dev/play/p/-AuYXfy7opz
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func FilterMap[T any, R any](collection []T, callback func(T, int) (R, bool)) []R {
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result := []R{}
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for i, item := range collection {
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if r, ok := callback(item, i); ok {
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result = append(result, r)
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}
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}
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return result
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}
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// FlatMap manipulates a slice and transforms and flattens it to a slice of another type.
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// Play: https://go.dev/play/p/YSoYmQTA8-U
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func FlatMap[T any, R any](collection []T, iteratee func(T, int) []R) []R {
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result := []R{}
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for i, item := range collection {
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result = append(result, iteratee(item, i)...)
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}
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return result
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}
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// Reduce reduces collection to a value which is the accumulated result of running each element in collection
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// through accumulator, where each successive invocation is supplied the return value of the previous.
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// Play: https://go.dev/play/p/R4UHXZNaaUG
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func Reduce[T any, R any](collection []T, accumulator func(R, T, int) R, initial R) R {
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for i, item := range collection {
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initial = accumulator(initial, item, i)
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}
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return initial
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}
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// ReduceRight helper is like Reduce except that it iterates over elements of collection from right to left.
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// Play: https://go.dev/play/p/Fq3W70l7wXF
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func ReduceRight[T any, R any](collection []T, accumulator func(R, T, int) R, initial R) R {
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for i := len(collection) - 1; i >= 0; i-- {
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initial = accumulator(initial, collection[i], i)
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}
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return initial
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}
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// ForEach iterates over elements of collection and invokes iteratee for each element.
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// Play: https://go.dev/play/p/oofyiUPRf8t
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func ForEach[T any](collection []T, iteratee func(T, int)) {
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for i, item := range collection {
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iteratee(item, i)
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}
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}
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// Times invokes the iteratee n times, returning an array of the results of each invocation.
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// The iteratee is invoked with index as argument.
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// Play: https://go.dev/play/p/vgQj3Glr6lT
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func Times[T any](count int, iteratee func(int) T) []T {
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result := make([]T, count)
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for i := 0; i < count; i++ {
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result[i] = iteratee(i)
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}
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return result
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}
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// Uniq returns a duplicate-free version of an array, in which only the first occurrence of each element is kept.
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// The order of result values is determined by the order they occur in the array.
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// Play: https://go.dev/play/p/DTzbeXZ6iEN
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func Uniq[T comparable](collection []T) []T {
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result := make([]T, 0, len(collection))
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seen := make(map[T]struct{}, len(collection))
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for _, item := range collection {
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if _, ok := seen[item]; ok {
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continue
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}
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seen[item] = struct{}{}
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result = append(result, item)
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}
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return result
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}
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// UniqBy returns a duplicate-free version of an array, in which only the first occurrence of each element is kept.
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// The order of result values is determined by the order they occur in the array. It accepts `iteratee` which is
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// invoked for each element in array to generate the criterion by which uniqueness is computed.
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// Play: https://go.dev/play/p/g42Z3QSb53u
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func UniqBy[T any, U comparable](collection []T, iteratee func(T) U) []T {
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result := make([]T, 0, len(collection))
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seen := make(map[U]struct{}, len(collection))
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for _, item := range collection {
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key := iteratee(item)
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if _, ok := seen[key]; ok {
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continue
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}
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seen[key] = struct{}{}
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result = append(result, item)
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}
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return result
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}
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// GroupBy returns an object composed of keys generated from the results of running each element of collection through iteratee.
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// Play: https://go.dev/play/p/XnQBd_v6brd
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func GroupBy[T any, U comparable](collection []T, iteratee func(T) U) map[U][]T {
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result := map[U][]T{}
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for _, item := range collection {
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key := iteratee(item)
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result[key] = append(result[key], item)
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}
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return result
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}
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// Chunk returns an array of elements split into groups the length of size. If array can't be split evenly,
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// the final chunk will be the remaining elements.
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// Play: https://go.dev/play/p/EeKl0AuTehH
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func Chunk[T any](collection []T, size int) [][]T {
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if size <= 0 {
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panic("Second parameter must be greater than 0")
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}
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chunksNum := len(collection) / size
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if len(collection)%size != 0 {
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chunksNum += 1
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}
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result := make([][]T, 0, chunksNum)
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for i := 0; i < chunksNum; i++ {
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last := (i + 1) * size
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if last > len(collection) {
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last = len(collection)
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}
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result = append(result, collection[i*size:last])
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}
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return result
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}
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// PartitionBy returns an array of elements split into groups. The order of grouped values is
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// determined by the order they occur in collection. The grouping is generated from the results
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// of running each element of collection through iteratee.
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// Play: https://go.dev/play/p/NfQ_nGjkgXW
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func PartitionBy[T any, K comparable](collection []T, iteratee func(x T) K) [][]T {
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result := [][]T{}
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seen := map[K]int{}
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for _, item := range collection {
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key := iteratee(item)
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resultIndex, ok := seen[key]
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if !ok {
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resultIndex = len(result)
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seen[key] = resultIndex
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result = append(result, []T{})
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}
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result[resultIndex] = append(result[resultIndex], item)
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}
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return result
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// unordered:
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// groups := GroupBy[T, K](collection, iteratee)
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// return Values[K, []T](groups)
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}
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// Flatten returns an array a single level deep.
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// Play: https://go.dev/play/p/rbp9ORaMpjw
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func Flatten[T any](collection [][]T) []T {
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totalLen := 0
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for i := range collection {
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totalLen += len(collection[i])
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}
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result := make([]T, 0, totalLen)
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for i := range collection {
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result = append(result, collection[i]...)
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}
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return result
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}
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// Shuffle returns an array of shuffled values. Uses the Fisher-Yates shuffle algorithm.
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// Play: https://go.dev/play/p/Qp73bnTDnc7
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func Shuffle[T any](collection []T) []T {
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rand.Shuffle(len(collection), func(i, j int) {
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collection[i], collection[j] = collection[j], collection[i]
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})
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return collection
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}
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// Reverse reverses array so that the first element becomes the last, the second element becomes the second to last, and so on.
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// Play: https://go.dev/play/p/fhUMLvZ7vS6
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func Reverse[T any](collection []T) []T {
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length := len(collection)
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half := length / 2
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for i := 0; i < half; i = i + 1 {
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j := length - 1 - i
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collection[i], collection[j] = collection[j], collection[i]
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}
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return collection
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}
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// Fill fills elements of array with `initial` value.
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// Play: https://go.dev/play/p/VwR34GzqEub
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func Fill[T Clonable[T]](collection []T, initial T) []T {
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result := make([]T, 0, len(collection))
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for range collection {
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result = append(result, initial.Clone())
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}
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return result
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}
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// Repeat builds a slice with N copies of initial value.
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// Play: https://go.dev/play/p/g3uHXbmc3b6
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func Repeat[T Clonable[T]](count int, initial T) []T {
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result := make([]T, 0, count)
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for i := 0; i < count; i++ {
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result = append(result, initial.Clone())
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}
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return result
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}
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// RepeatBy builds a slice with values returned by N calls of callback.
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// Play: https://go.dev/play/p/ozZLCtX_hNU
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func RepeatBy[T any](count int, predicate func(int) T) []T {
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result := make([]T, 0, count)
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for i := 0; i < count; i++ {
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result = append(result, predicate(i))
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}
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return result
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}
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// KeyBy transforms a slice or an array of structs to a map based on a pivot callback.
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// Play: https://go.dev/play/p/mdaClUAT-zZ
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func KeyBy[K comparable, V any](collection []V, iteratee func(V) K) map[K]V {
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result := make(map[K]V, len(collection))
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for _, v := range collection {
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k := iteratee(v)
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result[k] = v
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}
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return result
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}
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// Associate returns a map containing key-value pairs provided by transform function applied to elements of the given slice.
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// If any of two pairs would have the same key the last one gets added to the map.
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// The order of keys in returned map is not specified and is not guaranteed to be the same from the original array.
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// Play: https://go.dev/play/p/WHa2CfMO3Lr
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func Associate[T any, K comparable, V any](collection []T, transform func(T) (K, V)) map[K]V {
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result := make(map[K]V)
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for _, t := range collection {
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k, v := transform(t)
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result[k] = v
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}
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return result
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}
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// SliceToMap returns a map containing key-value pairs provided by transform function applied to elements of the given slice.
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// If any of two pairs would have the same key the last one gets added to the map.
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// The order of keys in returned map is not specified and is not guaranteed to be the same from the original array.
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// Alias of Associate().
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// Play: https://go.dev/play/p/WHa2CfMO3Lr
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func SliceToMap[T any, K comparable, V any](collection []T, transform func(T) (K, V)) map[K]V {
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return Associate(collection, transform)
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}
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// Drop drops n elements from the beginning of a slice or array.
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// Play: https://go.dev/play/p/JswS7vXRJP2
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func Drop[T any](collection []T, n int) []T {
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if len(collection) <= n {
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return make([]T, 0)
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}
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result := make([]T, 0, len(collection)-n)
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return append(result, collection[n:]...)
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}
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// DropRight drops n elements from the end of a slice or array.
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// Play: https://go.dev/play/p/GG0nXkSJJa3
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func DropRight[T any](collection []T, n int) []T {
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if len(collection) <= n {
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return []T{}
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}
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result := make([]T, 0, len(collection)-n)
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return append(result, collection[:len(collection)-n]...)
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}
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// DropWhile drops elements from the beginning of a slice or array while the predicate returns true.
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// Play: https://go.dev/play/p/7gBPYw2IK16
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func DropWhile[T any](collection []T, predicate func(T) bool) []T {
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i := 0
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for ; i < len(collection); i++ {
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if !predicate(collection[i]) {
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break
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}
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}
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result := make([]T, 0, len(collection)-i)
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return append(result, collection[i:]...)
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}
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// DropRightWhile drops elements from the end of a slice or array while the predicate returns true.
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// Play: https://go.dev/play/p/3-n71oEC0Hz
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func DropRightWhile[T any](collection []T, predicate func(T) bool) []T {
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i := len(collection) - 1
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for ; i >= 0; i-- {
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if !predicate(collection[i]) {
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break
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}
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}
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result := make([]T, 0, i+1)
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return append(result, collection[:i+1]...)
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}
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// Reject is the opposite of Filter, this method returns the elements of collection that predicate does not return truthy for.
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// Play: https://go.dev/play/p/YkLMODy1WEL
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func Reject[V any](collection []V, predicate func(V, int) bool) []V {
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result := []V{}
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for i, item := range collection {
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if !predicate(item, i) {
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result = append(result, item)
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}
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}
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return result
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}
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// Count counts the number of elements in the collection that compare equal to value.
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// Play: https://go.dev/play/p/Y3FlK54yveC
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func Count[T comparable](collection []T, value T) (count int) {
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for _, item := range collection {
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if item == value {
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count++
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}
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}
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return count
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}
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// CountBy counts the number of elements in the collection for which predicate is true.
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// Play: https://go.dev/play/p/ByQbNYQQi4X
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func CountBy[T any](collection []T, predicate func(T) bool) (count int) {
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for _, item := range collection {
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if predicate(item) {
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count++
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}
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}
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return count
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}
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// Subset returns a copy of a slice from `offset` up to `length` elements. Like `slice[start:start+length]`, but does not panic on overflow.
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// Play: https://go.dev/play/p/tOQu1GhFcog
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func Subset[T any](collection []T, offset int, length uint) []T {
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size := len(collection)
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if offset < 0 {
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offset = size + offset
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if offset < 0 {
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offset = 0
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}
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}
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if offset > size {
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return []T{}
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}
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if length > uint(size)-uint(offset) {
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length = uint(size - offset)
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}
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return collection[offset : offset+int(length)]
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}
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// 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.
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// Play: https://go.dev/play/p/8XWYhfMMA1h
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func Slice[T any](collection []T, start int, end int) []T {
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size := len(collection)
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if start >= end {
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return []T{}
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}
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if start > size {
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start = size
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}
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if end > size {
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end = size
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}
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return collection[start:end]
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}
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// Replace returns a copy of the slice with the first n non-overlapping instances of old replaced by new.
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// Play: https://go.dev/play/p/XfPzmf9gql6
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func Replace[T comparable](collection []T, old T, new T, n int) []T {
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result := make([]T, len(collection))
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copy(result, collection)
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for i := range result {
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if result[i] == old && n != 0 {
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result[i] = new
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n--
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}
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}
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return result
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}
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// ReplaceAll returns a copy of the slice with all non-overlapping instances of old replaced by new.
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// Play: https://go.dev/play/p/a9xZFUHfYcV
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func ReplaceAll[T comparable](collection []T, old T, new T) []T {
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return Replace(collection, old, new, -1)
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}
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// Compact returns a slice of all non-zero elements.
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// Play: https://go.dev/play/p/tXiy-iK6PAc
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func Compact[T comparable](collection []T) []T {
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var zero T
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result := []T{}
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for _, item := range collection {
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if item != zero {
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result = append(result, item)
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}
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}
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return result
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}
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// IsSorted checks if a slice is sorted.
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// Play: https://go.dev/play/p/mc3qR-t4mcx
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func IsSorted[T constraints.Ordered](collection []T) bool {
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for i := 1; i < len(collection); i++ {
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if collection[i-1] > collection[i] {
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return false
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}
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}
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return true
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}
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// IsSortedByKey checks if a slice is sorted by iteratee.
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// Play: https://go.dev/play/p/wiG6XyBBu49
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func IsSortedByKey[T any, K constraints.Ordered](collection []T, iteratee func(T) K) bool {
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size := len(collection)
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for i := 0; i < size-1; i++ {
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if iteratee(collection[i]) > iteratee(collection[i+1]) {
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return false
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}
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}
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return true
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}
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