Compendium of functions, data structures, monadic wrappers and more which, hopefully, will be included as a standard library of the language
Package slices provides utilities to work with slices
Table of contents
- Cut
- Delete
- DeleteOrder
- Extract
- ExtractIdx
- Find
- FindIdx
- Insert
- InsertVector
- Peek
- Pop
- PopFront
- PushFront
- Shift
- Unshift
Cut removes a sector from slice given lower and upper bounds. Bounds are represented as indices of the slice. E.g: Cut([1, 2, 3, 4], 1, 2) -> [1, 4] Cut([4], 0, 0) -> [] Cut will returned the original slice without the cut subslice.
Code
func Cut[T any](arr []T, from, to int) []T {
if len(arr) < 1 {
return arr
}
if from < 0 {
from = 0
}
if from >= len(arr) {
from = len(arr) - 1
}
if to < 0 {
to = 0
}
if to >= len(arr) {
to = len(arr) - 1
}
if len(arr) == 1 {
return arr[:0]
}
if from > to {
return append(arr[:from], arr[from+to+1:]...)
}
return append(arr[:from], arr[to+1:]...)
}Delete removes the element in idx position, without preserving array order. In case idx
is out of bounds, noop.
Code
func Delete[T any](arr []T, idx int) []T {
le := len(arr) - 1
if le < 0 || idx > le || idx < 0 {
return arr
}
var t T
arr[idx] = arr[le]
arr[le] = t
arr = arr[:le]
return arr
}DeleteOrder removes the element in idx position, preserving array order. In case idx
is out of bounds, noop.
Code
func DeleteOrder[T any](arr []T, idx int) []T {
le := len(arr) - 1
if le < 0 || idx > le || idx < 0 {
return arr
}
var t T
if le > 0 {
copy(arr[idx:], arr[idx+1:])
}
arr[le] = t
arr = arr[:le]
return arr
}Extract gets and deletes the element than matches predicate. Returned values are the modified slice, the item or zero value if not found, and whether item was found
Code
func Extract[T any](arr []T, predicate func(t T) bool) ([]T, T, bool) {
res, idx := FindIdx(arr, predicate)
if idx < 0 {
return arr, res, false
}
arr = Delete(arr, idx)
return arr, res, true
}ExtractIdx gets and deletes the element at the given position. Returned values are the modified slice, the item or zero value if not found, and whether item was found
Code
func ExtractIdx[T any](arr []T, idx int) (res []T, item T, ok bool) {
if idx >= len(arr) || idx < 0 {
return
}
ok = true
item = arr[idx]
res = Delete(arr, idx)
return
}Find returns the first element that matches predicate
Code
func Find[T any](arr []T, predicate func(t T) bool) (res T, ok bool) {
var idx int
res, idx = FindIdx(arr, predicate)
ok = idx > -1
return
}FindIdx returns the first element that matches predicate as well as the position on the slice.
Code
func FindIdx[T any](arr []T, predicate func(t T) bool) (res T, idx int) {
idx = IndexOf(arr, predicate)
if idx < 0 {
return
}
res = arr[idx]
return
}Insert places the given item at the position idx for the given slice
Code
func Insert[T any](arr []T, item T, idx int) []T {
if arr == nil {
return []T{item}
}
if idx < 0 || idx > len(arr) {
return arr
}
return append(arr[:idx], append([]T{item}, arr[idx:]...)...)
}InsertVector places the given vector at the position idx for the given slice, moving
existing elements to the right.
Code
func InsertVector[T any](arr, items []T, idx int) (res []T) {
if arr == nil {
res = items[:]
return
}
if items == nil || len(items) == 0 {
res = arr
return
}
if idx < 0 || idx > len(arr) {
return arr
}
return append(arr[:idx], append(items, arr[idx:]...)...)
}Peek returns the item corresponding to idx
Code
func Peek[T any](arr []T, idx int) (item T, ok bool) {
if len(arr) < 1 || idx >= len(arr) {
return
}
item = arr[idx]
ok = true
return
}Pop deletes and returns the last item from the slice, starting from the end.
Code
func Pop[T any](arr []T) (res []T, item T, ok bool) {
if len(arr) < 1 {
return
}
var t T
le := len(arr) - 1
res = arr[:le]
item = arr[le]
ok = true
arr[le] = t
return
}PopFront retrieves and deletes the element at the head of the slice
Code
func PopFront[T any](arr []T) (res []T, item T, ok bool) {
if len(arr) < 1 {
res = arr
return
}
item, res = arr[0], arr[1:]
return
}PushFront inserts the item at the head of the slice
Code
func PushFront[T any](arr []T, item T) []T {
return append([]T{item}, arr...)
}Shift inserts the item at the head of the slice
Code
func Shift[T any](arr []T) ([]T, T, bool) {
return PopFront(arr)
}Unshift inserts the item at the head of the slice
Code
func Unshift[T any](arr []T, item T) []T {
return PushFront(arr, item)
}Package maps provides utilities to work with maps
Table of contents
Equals returns whether 2 maps are equals in values
Code
func Equals[K comparable, V any](m1, m2 map[K]V, eq func(V, V) bool) bool {
if len(m1) != len(m2) {
return false
}
if m1 == nil && m2 != nil {
return false
}
if m1 != nil && m2 == nil {
return false
}
for k1, v1 := range m1 {
v2, ok := m2[k1]
if !ok {
return false
}
if !eq(v1, v2) {
return false
}
}
return true
}Filter discards those entries from the map that do not match predicate.
Code
func Filter[K comparable, V any](
m map[K]V,
p func(K, V) bool,
) map[K]V {
if m == nil {
return nil
}
res := make(map[K]V, len(m))
for k, v := range m {
if p(k, v) {
res[k] = v
}
}
return res
}FilterInPlace deletes those entries from the map that do not match predicate.
Code
func FilterInPlace[K comparable, V any](
m map[K]V,
p func(K, V) bool,
) map[K]V {
if m == nil {
return nil
}
for k, v := range m {
if !p(k, v) {
delete(m, k)
}
}
return m
}FilterMap both filters and maps a map. The predicate function should return a fp.Option monad: fp.Some to indicate the entry should be kept. fp.None to indicate the entry should be discarded
Code
func FilterMap[K1 comparable, V1 any, K2 comparable, V2 any](
m map[K1]V1,
p func(K1, V1) fp.Option[tuples.Tuple2[K2, V2]],
) map[K2]V2 {
if m == nil {
return nil
}
res := make(map[K2]V2, len(m))
for k1, v1 := range m {
tpl := p(k1, v1)
if tpl.IsSome() {
v := tpl.UnwrapUnsafe()
res[v.V1] = v.V2
}
}
return res
}FilterMapTuple both filters and maps the given map by receiving a predicate which returns mapped values, and a boolean to indicate whether that entry should be kept.
Code
func FilterMapTuple[K1 comparable, V1 any, K2 comparable, V2 any](
m map[K1]V1,
p func(K1, V1) (K2, V2, bool),
) map[K2]V2 {
if m == nil {
return nil
}
res := make(map[K2]V2, len(m))
for k1, v1 := range m {
if k2, v2, ok := p(k1, v1); ok {
res[k2] = v2
}
}
return res
}Fold compacts the given map into a single type by taking into account the initial value
Code
func Fold[K comparable, V any, R any](
m map[K]V,
p func(R, K, V) R,
initial R,
) R {
if m == nil {
return initial
}
r := initial
for k, v := range m {
r = p(r, k, v)
}
return r
}Map transforms a map into another one, with same or different types
Code
func Map[K1 comparable, V1 any, K2 comparable, V2 any](
m map[K1]V1,
p func(K1, V1) (K2, V2),
) map[K2]V2 {
if m == nil {
return nil
}
res := make(map[K2]V2, len(m))
for k1, v1 := range m {
k2, v2 := p(k1, v1)
res[k2] = v2
}
return res
}Reduce compacts the given map into a single type
Code
func Reduce[K comparable, V any, R any](
m map[K]V,
p func(R, K, V) R,
) R {
var r R
if m == nil {
return r
}
for k, v := range m {
r = p(r, k, v)
}
return r
}Slice converts a map into a slice
Code
func Slice[K comparable, V, R any](
m map[K]V,
p func(K, V) R,
) slices.Slice[R] {
res := make([]R, len(m))
i := 0
for k, v := range m {
res[i] = p(k, v)
i++
}
return res
}Table of contents
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