lo

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 Go to latest Published: Jun 19, 2022 License: MIT Imports: 7 Imported by: 0

README

lo

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✨ samber/lo is a Lodash-style Go library based on Go 1.18+ Generics.

This project started as an experiment with the new generics implementation. It may look like Lodash in some aspects. I used to code with the fantastic "go-funk" package, but "go-funk" uses reflection and therefore is not typesafe.

As expected, benchmarks demonstrate that generics will be much faster than implementations based on the "reflect" package. Benchmarks also show similar performance gains compared to pure for loops. See below.

In the future, 5 to 10 helpers will overlap with those coming into the Go standard library (under package names slices and maps). I feel this library is legitimate and offers many more valuable abstractions.

See also:

  • samber/do: A dependency injection toolkit based on Go 1.18+ Generics
  • samber/mo: Monads based on Go 1.18+ Generics (Option, Result, Either...)

Why this name?

I wanted a short name, similar to "Lodash" and no Go package currently uses this name.

🚀 Install

go get github.com/samber/lo@v1

This library is v1 and follows SemVer strictly.

No breaking changes will be made to exported APIs before v2.0.0.

💡 Usage

You can import lo using:

import (
    "github.com/samber/lo"
    lop "github.com/samber/lo/parallel"
)

Then use one of the helpers below:

names := lo.Uniq[string]([]string{"Samuel", "Marc", "Samuel"})
// []string{"Samuel", "Marc"}

Most of the time, the compiler will be able to infer the type so that you can call: lo.Uniq([]string{...}).

🤠 Spec

GoDoc: https://godoc.org/github.com/samber/lo

Supported helpers for slices:

  • Filter
  • Map
  • FilterMap
  • FlatMap
  • Reduce
  • ForEach
  • Times
  • Uniq
  • UniqBy
  • GroupBy
  • Chunk
  • PartitionBy
  • Flatten
  • Shuffle
  • Reverse
  • Fill
  • Repeat
  • KeyBy
  • Drop
  • DropRight
  • DropWhile
  • DropRightWhile
  • Reject
  • Count
  • CountBy

Supported helpers for maps:

  • Keys
  • Values
  • PickBy
  • PickByKeys
  • PickByValues
  • OmitBy
  • OmitByKeys
  • OmitByValues
  • Entries
  • FromEntries
  • Invert
  • Assign (merge of maps)
  • MapKeys
  • MapValues

Supported math helpers:

  • Range / RangeFrom / RangeWithSteps
  • Clamp
  • SumBy

Supported helpers for strings:

  • Substring
  • RuneLength

Supported helpers for tuples:

  • T2 -> T9
  • Unpack2 -> Unpack9
  • Zip2 -> Zip9
  • Unzip2 -> Unzip9

Supported intersection helpers:

  • Contains
  • ContainsBy
  • Every
  • EveryBy
  • Some
  • SomeBy
  • None
  • NoneBy
  • Intersect
  • Difference
  • Union

Supported search helpers:

  • IndexOf
  • LastIndexOf
  • Find
  • FindIndexOf
  • FindLastIndexOf
  • Min
  • MinBy
  • Max
  • MaxBy
  • Last
  • Nth
  • Sample
  • Samples

Conditional helpers:

  • Ternary (1 line if/else statement)
  • If / ElseIf / Else
  • Switch / Case / Default

Type manipulation helpers:

  • ToPtr
  • ToSlicePtr
  • ToAnySlice
  • FromAnySlice
  • Empty
  • Coalesce

Concurrency helpers:

  • Attempt
  • AttemptWithDelay
  • Debounce
  • Async

Error handling:

  • Must
  • Try
  • TryCatch
  • TryWithErrorValue
  • TryCatchWithErrorValue

Constraints:

  • Clonable
Map

Manipulates a slice of one type and transforms it into a slice of another type:

import "github.com/samber/lo"

lo.Map[int64, string]([]int64{1, 2, 3, 4}, func(x int64, _ int) string {
    return strconv.FormatInt(x, 10)
})
// []string{"1", "2", "3", "4"}

Parallel processing: like lo.Map(), but the mapper function is called in a goroutine. Results are returned in the same order.

import lop "github.com/samber/lo/parallel"

lop.Map[int64, string]([]int64{1, 2, 3, 4}, func(x int64, _ int) string {
    return strconv.FormatInt(x, 10)
})
// []string{"1", "2", "3", "4"}

You also can control the conurrency limit by optional ParallelOption to limit the maximum number of concurrent iteratee goroutines running at the same time.

lop.Map(list, iteratee, lop.WithConcurrency(20)) // up to 20 concurrent goroutines running at the same time
FlatMap

Manipulates a slice and transforms and flattens it to a slice of another type.

lo.FlatMap[int, string]([]int{0, 1, 2}, func(x int, _ int) []string {
	return []string{
		strconv.FormatInt(x, 10),
		strconv.FormatInt(x, 10),
	}
})
// []string{"0", "0", "1", "1", "2", "2"}
FilterMap

Returns a slice which obtained after both filtering and mapping using the given callback function.

The callback function should return two values: the result of the mapping operation and whether the result element should be included or not.

matching := lo.FilterMap[string, string]([]string{"cpu", "gpu", "mouse", "keyboard"}, func(x string, _ int) (string, bool) {
    if strings.HasSuffix(x, "pu") {
        return "xpu", true
    }
    return "", false
})
// []string{"xpu", "xpu"}
Filter

Iterates over a collection and returns an array of all the elements the predicate function returns true for.

even := lo.Filter[int]([]int{1, 2, 3, 4}, func(x int, _ int) bool {
    return x%2 == 0
})
// []int{2, 4}
Contains

Returns true if an element is present in a collection.

present := lo.Contains[int]([]int{0, 1, 2, 3, 4, 5}, 5)
// true
ContainsBy

Returns true if the predicate function returns true.

present := lo.ContainsBy[int]([]int{0, 1, 2, 3, 4, 5}, func(x int) bool {
    return x == 3
})
// true
Reduce

Reduces a collection to a single value. The value is calculated by accumulating the result of running each element in the collection through an accumulator function. Each successive invocation is supplied with the return value returned by the previous call.

sum := lo.Reduce[int, int]([]int{1, 2, 3, 4}, func(agg int, item int, _ int) int {
    return agg + item
}, 0)
// 10
ForEach

Iterates over elements of a collection and invokes the function over each element.

import "github.com/samber/lo"

lo.ForEach[string]([]string{"hello", "world"}, func(x string, _ int) {
    println(x)
})
// prints "hello\nworld\n"

Parallel processing: like lo.ForEach(), but the callback is called as a goroutine.

import lop "github.com/samber/lo/parallel"

lop.ForEach[string]([]string{"hello", "world"}, func(x string, _ int) {
    println(x)
})
// prints "hello\nworld\n" or "world\nhello\n"

You also can control the conurrency limit by optional ParallelOption to limit the maximum number of concurrent iteratee goroutines running at the same time.

lop.ForEach(list, iteratee, lop.WithConcurrency(20)) // up to 20 concurrent goroutines running at the same time
Times

Times invokes the iteratee n times, returning an array of the results of each invocation. The iteratee is invoked with index as argument.

import "github.com/samber/lo"

lo.Times[string](3, func(i int) string {
    return strconv.FormatInt(int64(i), 10)
})
// []string{"0", "1", "2"}

Parallel processing: like lo.Times(), but callback is called in goroutine.

import lop "github.com/samber/lo/parallel"

lop.Times[string](3, func(i int) string {
    return strconv.FormatInt(int64(i), 10)
})
// []string{"0", "1", "2"}

You also can control the conurrency limit by optional ParallelOption to limit the maximum number of concurrent iteratee goroutines running at the same time.

lop.Times(60, iteratee, lop.WithConcurrency(20)) // up to 20 concurrent goroutines running at the same time
Uniq

Returns a duplicate-free version of an array, in which only the first occurrence of each element is kept. The order of result values is determined by the order they occur in the array.

uniqValues := lo.Uniq[int]([]int{1, 2, 2, 1})
// []int{1, 2}
UniqBy

Returns a duplicate-free version of an array, in which only the first occurrence of each element is kept. The order of result values is determined by the order they occur in the array. It accepts iteratee which is invoked for each element in array to generate the criterion by which uniqueness is computed.

uniqValues := lo.UniqBy[int, int]([]int{0, 1, 2, 3, 4, 5}, func(i int) int {
    return i%3
})
// []int{0, 1, 2}
GroupBy

Returns an object composed of keys generated from the results of running each element of collection through iteratee.

import lo "github.com/samber/lo"

groups := lo.GroupBy[int, int]([]int{0, 1, 2, 3, 4, 5}, func(i int) int {
    return i%3
})
// map[int][]int{0: []int{0, 3}, 1: []int{1, 4}, 2: []int{2, 5}}

Parallel processing: like lo.GroupBy(), but callback is called in goroutine.

import lop "github.com/samber/lo/parallel"

lop.GroupBy[int, int]([]int{0, 1, 2, 3, 4, 5}, func(i int) int {
    return i%3
})
// map[int][]int{0: []int{0, 3}, 1: []int{1, 4}, 2: []int{2, 5}}

You also can control the conurrency limit by optional ParallelOption to limit the maximum number of concurrent iteratee goroutines running at the same time.

lop.GroupBy(list, iteratee, lop.WithConcurrency(20)) // up to 20 concurrent goroutines running at the same time
Chunk

Returns an array of elements split into groups the length of size. If array can't be split evenly, the final chunk will be the remaining elements.

lo.Chunk[int]([]int{0, 1, 2, 3, 4, 5}, 2)
// [][]int{{0, 1}, {2, 3}, {4, 5}}

lo.Chunk[int]([]int{0, 1, 2, 3, 4, 5, 6}, 2)
// [][]int{{0, 1}, {2, 3}, {4, 5}, {6}}

lo.Chunk[int]([]int{}, 2)
// [][]int{}

lo.Chunk[int]([]int{0}, 2)
// [][]int{{0}}
PartitionBy

Returns an array of elements split into groups. The order of grouped values is determined by the order they occur in collection. The grouping is generated from the results of running each element of collection through iteratee.

import lo "github.com/samber/lo"

partitions := lo.PartitionBy[int, string]([]int{-2, -1, 0, 1, 2, 3, 4, 5}, func(x int) string {
    if x < 0 {
        return "negative"
    } else if x%2 == 0 {
        return "even"
    }
    return "odd"
})
// [][]int{{-2, -1}, {0, 2, 4}, {1, 3, 5}}

Parallel processing: like lo.PartitionBy(), but callback is called in goroutine. Results are returned in the same order.

import lop "github.com/samber/lo/parallel"

partitions := lo.PartitionBy[int, string]([]int{-2, -1, 0, 1, 2, 3, 4, 5}, func(x int) string {
    if x < 0 {
        return "negative"
    } else if x%2 == 0 {
        return "even"
    }
    return "odd"
})
// [][]int{{-2, -1}, {0, 2, 4}, {1, 3, 5}}

You also can control the conurrency limit by optional ParallelOption to limit the maximum number of concurrent iteratee goroutines running at the same time.

lop.PartitionBy(list, iteratee, lop.WithConcurrency(20)) // up to 20 concurrent goroutines running at the same time
Flatten

Returns an array a single level deep.

flat := lo.Flatten[int]([][]int{{0, 1}, {2, 3, 4, 5}})
// []int{0, 1, 2, 3, 4, 5}
Shuffle

Returns an array of shuffled values. Uses the Fisher-Yates shuffle algorithm.

randomOrder := lo.Shuffle[int]([]int{0, 1, 2, 3, 4, 5})
// []int{0, 1, 2, 3, 4, 5}
Reverse

Reverses array so that the first element becomes the last, the second element becomes the second to last, and so on.

reverseOder := lo.Reverse[int]([]int{0, 1, 2, 3, 4, 5})
// []int{5, 4, 3, 2, 1, 0}
Fill

Fills elements of array with initial value.

type foo struct {
	bar string
}

func (f foo) Clone() foo {
	return foo{f.bar}
}

initializedSlice := lo.Fill[foo]([]foo{foo{"a"}, foo{"a"}}, foo{"b"})
// []foo{foo{"b"}, foo{"b"}}
Repeat

Builds a slice with N copies of initial value.

type foo struct {
	bar string
}

func (f foo) Clone() foo {
	return foo{f.bar}
}

slice := lo.Repeat[foo](2, foo{"a"})
// []foo{foo{"a"}, foo{"a"}}
RepeatBy

Builds a slice with values returned by N calls of callback.

slice := lo.RepeatBy[int](0, func (i int) int {
    return math.Pow(i, 2)
})
// []int{}

slice := lo.RepeatBy[int](5, func (i int) int {
    return math.Pow(i, 2)
})
// []int{0, 1, 4, 9, 16}
KeyBy

Transforms a slice or an array of structs to a map based on a pivot callback.

m := lo.KeyBy[int, string]([]string{"a", "aa", "aaa"}, func(str string) int {
    return len(str)
})
// map[int]string{1: "a", 2: "aa", 3: "aaa"}

type Character struct {
	dir  string
	code int
}
characters := []Character{
    {dir: "left", code: 97},
    {dir: "right", code: 100},
}
result := lo.KeyBy[string, Character](characters, func(char Character) string {
    return string(rune(char.code))
})
//map[a:{dir:left code:97} d:{dir:right code:100}]
Drop

Drops n elements from the beginning of a slice or array.

l := lo.Drop[int]([]int{0, 1, 2, 3, 4, 5}, 2)
// []int{2, 3, 4, 5}
DropRight

Drops n elements from the end of a slice or array.

l := lo.DropRight[int]([]int{0, 1, 2, 3, 4, 5}, 2)
// []int{0, 1, 2, 3}
DropWhile

Drop elements from the beginning of a slice or array while the predicate returns true.

l := lo.DropWhile[string]([]string{"a", "aa", "aaa", "aa", "aa"}, func(val string) bool {
	return len(val) <= 2
})
// []string{"aaa", "aa", "aa"}
DropRightWhile

Drop elements from the end of a slice or array while the predicate returns true.

l := lo.DropRightWhile[string]([]string{"a", "aa", "aaa", "aa", "aa"}, func(val string) bool {
	return len(val) <= 2
})
// []string{"a", "aa", "aaa"}
Reject

The opposite of Filter, this method returns the elements of collection that predicate does not return truthy for.

odd := lo.Reject[int]([]int{1, 2, 3, 4}, func(x int, _ int) bool {
    return x%2 == 0
})
// []int{1, 3}
Count

Counts the number of elements in the collection that compare equal to value.

count := lo.Count[int]([]int{1, 5, 1}, 1)
// 2
CountBy

Counts the number of elements in the collection for which predicate is true.

count := lo.CountBy[int]([]int{1, 5, 1}, func(i int) bool {
    return i < 4
})
// 2
Subset

Return part of a slice.

in := []int{0, 1, 2, 3, 4}

sub := lo.Subset(in, 2, 3)
// []int{2, 3, 4}

sub := lo.Subset(in, -4, 3)
// []int{1, 2, 3}

sub := lo.Subset(in, -2, math.MaxUint)
// []int{3, 4}
Replace

Returns a copy of the slice with the first n non-overlapping instances of old replaced by new.

in := []int{0, 1, 0, 1, 2, 3, 0}

slice := lo.Replace(in, 0, 42, 1)
// []int{42, 1, 0, 1, 2, 3, 0}

slice := lo.Replace(in, -1, 42, 1)
// []int{0, 1, 0, 1, 2, 3, 0}

slice := lo.Replace(in, 0, 42, 2)
// []int{42, 1, 42, 1, 2, 3, 0}

slice := lo.Replace(in, 0, 42, -1)
// []int{42, 1, 42, 1, 2, 3, 42}
ReplaceAll

Returns a copy of the slice with all non-overlapping instances of old replaced by new.

in := []int{0, 1, 0, 1, 2, 3, 0}

slice := lo.ReplaceAll(in, 0, 42)
// []int{42, 1, 42, 1, 2, 3, 42}

slice := lo.ReplaceAll(in, -1, 42)
// []int{0, 1, 0, 1, 2, 3, 0}
Keys

Creates an array of the map keys.

keys := lo.Keys[string, int](map[string]int{"foo": 1, "bar": 2})
// []string{"bar", "foo"}
Values

Creates an array of the map values.

values := lo.Values[string, int](map[string]int{"foo": 1, "bar": 2})
// []int{1, 2}
PickBy

Returns same map type filtered by given predicate.

m := lo.PickBy[string, int](map[string]int{"foo": 1, "bar": 2, "baz": 3}, func(key string, value int) bool {
    return value%2 == 1
})
// map[string]int{"foo": 1, "baz": 3}
PickByKeys

Returns same map type filtered by given keys.

m := lo.PickByKeys[string, int](map[string]int{"foo": 1, "bar": 2, "baz": 3}, []string{"foo", "baz"})
// map[string]int{"foo": 1, "baz": 3}
PickByValues

Returns same map type filtered by given values.

m := lo.PickByValues[string, int](map[string]int{"foo": 1, "bar": 2, "baz": 3}, []int{1, 3})
// map[string]int{"foo": 1, "baz": 3}
OmitBy

Returns same map type filtered by given predicate.

m := lo.OmitBy[string, int](map[string]int{"foo": 1, "bar": 2, "baz": 3}, func(key string, value int) bool {
    return value%2 == 1
})
// map[string]int{"bar": 2}
OmitByKeys

Returns same map type filtered by given keys.

m := lo.OmitByKeys[string, int](map[string]int{"foo": 1, "bar": 2, "baz": 3}, []string{"foo", "baz"})
// map[string]int{"bar": 2}
OmitByValues

Returns same map type filtered by given values.

m := lo.OmitByValues[string, int](map[string]int{"foo": 1, "bar": 2, "baz": 3}, []int{1, 3})
// map[string]int{"bar": 2}
Entries

Transforms a map into array of key/value pairs.

entries := lo.Entries[string, int](map[string]int{"foo": 1, "bar": 2})
// []lo.Entry[string, int]{
//     {
//         Key: "foo",
//         Value: 1,
//     },
//     {
//         Key: "bar",
//         Value: 2,
//     },
// }
FromEntries

Transforms an array of key/value pairs into a map.

m := lo.FromEntries[string, int]([]lo.Entry[string, int]{
    {
        Key: "foo",
        Value: 1,
    },
    {
        Key: "bar",
        Value: 2,
    },
})
// map[string]int{"foo": 1, "bar": 2}
Invert

Creates a map composed of the inverted keys and values. If map contains duplicate values, subsequent values overwrite property assignments of previous values.

m1 := lo.Invert[string, int]([map[string]int{"a": 1, "b": 2})
// map[int]string{1: "a", 2: "b"}

m2 := lo.Invert[string, int]([map[string]int{"a": 1, "b": 2, "c": 1})
// map[int]string{1: "c", 2: "b"}
Assign

Merges multiple maps from left to right.

mergedMaps := lo.Assign[string, int](
    map[string]int{"a": 1, "b": 2},
    map[string]int{"b": 3, "c": 4},
)
// map[string]int{"a": 1, "b": 3, "c": 4}
MapKeys

Manipulates a map keys and transforms it to a map of another type.

m2 := lo.MapKeys[int, int, string](map[int]int{1: 1, 2: 2, 3: 3, 4: 4}, func(_ int, v int) string {
    return strconv.FormatInt(int64(v), 10)
})
// map[string]int{"1": 1, "2": 2, "3": 3, "4": 4}
MapValues

Manipulates a map values and transforms it to a map of another type.

m1 := map[int]int64{1: 1, 2: 2, 3: 3}

m2 := lo.MapValues[int, int64, string](m1, func(x int64, _ int) string {
	return strconv.FormatInt(x, 10)
})
// map[int]string{1: "1", 2: "2", 3: "3"}
Range / RangeFrom / RangeWithSteps

Creates an array of numbers (positive and/or negative) progressing from start up to, but not including end.

result := Range(4)
// [0, 1, 2, 3]

result := Range(-4);
// [0, -1, -2, -3]

result := RangeFrom(1, 5);
// [1, 2, 3, 4]

result := RangeFrom[float64](1.0, 5);
// [1.0, 2.0, 3.0, 4.0]

result := RangeWithSteps(0, 20, 5);
// [0, 5, 10, 15]

result := RangeWithSteps[float32](-1.0, -4.0, -1.0);
// [-1.0, -2.0, -3.0]

result := RangeWithSteps(1, 4, -1);
// []

result := Range(0);
// []
Clamp

Clamps number within the inclusive lower and upper bounds.

r1 := lo.Clamp(0, -10, 10)
// 0

r2 := lo.Clamp(-42, -10, 10)
// -10

r3 := lo.Clamp(42, -10, 10)
// 10
SumBy

Summarizes the values in a collection using the given return value from the iteration function. If collection is empty 0 is returned.

strings := []string{"foo", "bar"}
sum := lo.SumBy(strings, func(item string) int {
    return len(item)
})
// 6
Substring

Return part of a string.

sub := lo.Substring("hello", 2, 3)
// "llo"

sub := lo.Substring("hello", -4, 3)
// "ell"

sub := lo.Substring("hello", -2, math.MaxUint)
// "lo"
RuneLength

An alias to utf8.RuneCountInString which returns the number of runes in string.

sub := lo.RuneLength("hellô")
// 5

sub := len("hellô")
// 6
T2 -> T9

Creates a tuple from a list of values.

tuple1 := lo.T2[string, int]("x", 1)
// Tuple2[string, int]{A: "x", B: 1}

func example() (string, int) { return "y", 2 }
tuple2 := lo.T2[string, int](example())
// Tuple2[string, int]{A: "y", B: 2}
Unpack2 -> Unpack9

Returns values contained in tuple.

r1, r2 := lo.Unpack2[string, int](lo.Tuple2[string, int]{"a", 1})
// "a", 1
Zip2 -> Zip9

Zip creates a slice of grouped elements, the first of which contains the first elements of the given arrays, the second of which contains the second elements of the given arrays, and so on.

When collections have different size, the Tuple attributes are filled with zero value.

tuples := lo.Zip2[string, int]([]string{"a", "b"}, []int{1, 2})
// []Tuple2[string, int]{{A: "a", B: 1}, {A: "b", B: 2}}
Unzip2 -> Unzip9

Unzip accepts an array of grouped elements and creates an array regrouping the elements to their pre-zip configuration.

a, b := lo.Unzip2[string, int]([]Tuple2[string, int]{{A: "a", B: 1}, {A: "b", B: 2}})
// []string{"a", "b"}
// []int{1, 2}
Every

Returns true if all elements of a subset are contained into a collection or if the subset is empty.

ok := lo.Every[int]([]int{0, 1, 2, 3, 4, 5}, []int{0, 2})
// true

ok := lo.Every[int]([]int{0, 1, 2, 3, 4, 5}, []int{0, 6})
// false
EveryBy

Returns true if the predicate returns true for all of the elements in the collection or if the collection is empty.

b := EveryBy[int]([]int{1, 2, 3, 4}, func(x int) bool {
    return x < 5
})
// true
Some

Returns true if at least 1 element of a subset is contained into a collection. If the subset is empty Some returns false.

ok := lo.Some[int]([]int{0, 1, 2, 3, 4, 5}, []int{0, 2})
// true

ok := lo.Some[int]([]int{0, 1, 2, 3, 4, 5}, []int{-1, 6})
// false
SomeBy

Returns true if the predicate returns true for any of the elements in the collection. If the collection is empty SomeBy returns false.

b := SomeBy[int]([]int{1, 2, 3, 4}, func(x int) bool {
    return x < 3
})
// true
None

Returns true if no element of a subset are contained into a collection or if the subset is empty.

b := None[int]([]int{0, 1, 2, 3, 4, 5}, []int{0, 2})
// false
b := None[int]([]int{0, 1, 2, 3, 4, 5}, []int{-1, 6})
// true
NoneBy

Returns true if the predicate returns true for none of the elements in the collection or if the collection is empty.

b := NoneBy[int]([]int{1, 2, 3, 4}, func(x int) bool {
    return x < 0
})
// true
Intersect

Returns the intersection between two collections.

result1 := lo.Intersect[int]([]int{0, 1, 2, 3, 4, 5}, []int{0, 2})
// []int{0, 2}

result2 := lo.Intersect[int]([]int{0, 1, 2, 3, 4, 5}, []int{0, 6}
// []int{0}

result3 := lo.Intersect[int]([]int{0, 1, 2, 3, 4, 5}, []int{-1, 6})
// []int{}
Difference

Returns the difference between two collections.

  • The first value is the collection of element absent of list2.
  • The second value is the collection of element absent of list1.
left, right := lo.Difference[int]([]int{0, 1, 2, 3, 4, 5}, []int{0, 2, 6})
// []int{1, 3, 4, 5}, []int{6}

left, right := lo.Difference[int]([]int{0, 1, 2, 3, 4, 5}, []int{0, 1, 2, 3, 4, 5})
// []int{}, []int{}
Union

Returns all distinct elements from both collections. Result will not change the order of elements relatively.

union := lo.Union[int]([]int{0, 1, 2, 3, 4, 5}, []int{0, 2, 10})
// []int{0, 1, 2, 3, 4, 5, 10}
IndexOf

Returns the index at which the first occurrence of a value is found in an array or return -1 if the value cannot be found.

found := lo.IndexOf[int]([]int{0, 1, 2, 1, 2, 3}, 2)
// 2

notFound := lo.IndexOf[int]([]int{0, 1, 2, 1, 2, 3}, 6)
// -1
LastIndex

Returns the index at which the last occurrence of a value is found in an array or return -1 if the value cannot be found.

found := lo.LastIndexOf[int]([]int{0, 1, 2, 1, 2, 3}, 2)
// 4

notFound := lo.LastIndexOf[int]([]int{0, 1, 2, 1, 2, 3}, 6)
// -1
Find

Search an element in a slice based on a predicate. It returns element and true if element was found.

str, ok := lo.Find[string]([]string{"a", "b", "c", "d"}, func(i string) bool {
    return i == "b"
})
// "b", true

str, ok := lo.Find[string]([]string{"foobar"}, func(i string) bool {
    return i == "b"
})
// "", false
FindIndexOf

FindIndexOf searches an element in a slice based on a predicate and returns the index and true. It returns -1 and false if the element is not found.

str, index, ok := lo.FindIndexOf[string]([]string{"a", "b", "a", "b"}, func(i string) bool {
    return i == "b"
})
// "b", 1, true

str, index, ok := lo.FindIndexOf[string]([]string{"foobar"}, func(i string) bool {
    return i == "b"
})
// "", -1, false
FindLastIndexOf

FindLastIndexOf searches an element in a slice based on a predicate and returns the index and true. It returns -1 and false if the element is not found.

str, index, ok := lo.FindLastIndexOf[string]([]string{"a", "b", "a", "b"}, func(i string) bool {
    return i == "b"
})
// "b", 4, true

str, index, ok := lo.FindLastIndexOf[string]([]string{"foobar"}, func(i string) bool {
    return i == "b"
})
// "", -1, false
Min

Search the minimum value of a collection.

min := lo.Min[int]([]int{1, 2, 3})
// 1

min := lo.Min[int]([]int{})
// 0
MinBy

Search the minimum value of a collection using the given comparison function. If several values of the collection are equal to the smallest value, returns the first such value.

min := lo.MinBy[string]([]string{"s1", "string2", "s3"}, func(item string, min string) bool {
    return len(item) < len(min)
})
// "s1"

min := lo.MinBy[string]([]string{}, func(item string, min string) bool {
    return len(item) < len(min)
})
// ""
Max

Search the maximum value of a collection.

max := lo.Max[int]([]int{1, 2, 3})
// 3

max := lo.Max[int]([]int{})
// 0
MaxBy

Search the maximum value of a collection using the given comparison function. If several values of the collection are equal to the greatest value, returns the first such value.

max := lo.MaxBy[string]([]string{"string1", "s2", "string3"}, func(item string, max string) bool {
    return len(item) > len(max)
})
// "string1"

max := lo.MaxBy[string]([]string{}, func(item string, max string) bool {
    return len(item) > len(max)
})
// ""
Last

Returns the last element of a collection or error if empty.

last, err := lo.Last[int]([]int{1, 2, 3})
// 3
Nth

Returns the element at index nth of collection. If nth is negative, the nth element from the end is returned. An error is returned when nth is out of slice bounds.

nth, err := lo.Nth[int]([]int{0, 1, 2, 3}, 2)
// 2

nth, err := lo.Nth[int]([]int{0, 1, 2, 3}, -2)
// 2
Sample

Returns a random item from collection.

lo.Sample[string]([]string{"a", "b", "c"})
// a random string from []string{"a", "b", "c"}

lo.Sample[string]([]string{})
// ""
Samples

Returns N random unique items from collection.

lo.Samples[string]([]string{"a", "b", "c"}, 3)
// []string{"a", "b", "c"} in random order
Ternary

A 1 line if/else statement.

result := lo.Ternary[string](true, "a", "b")
// "a"

result := lo.Ternary[string](false, "a", "b")
// "b"
If / ElseIf / Else
result := lo.If[int](true, 1).
    ElseIf(false, 2).
    Else(3)
// 1

result := lo.If[int](false, 1).
    ElseIf(true, 2).
    Else(3)
// 2

result := lo.If[int](false, 1).
    ElseIf(false, 2).
    Else(3)
// 3

Using callbacks:

result := lo.IfF[int](true, func () int {
        return 1
    }).
    ElseIfF(false, func () int {
        return 2
    }).
    ElseF(func () int {
        return 3
    })
// 1

Mixed:

result := lo.IfF[int](true, func () int {
        return 1
    }).
    Else(42)
// 1
Switch / Case / Default
result := lo.Switch[int, string](1).
    Case(1, "1").
    Case(2, "2").
    Default("3")
// "1"

result := lo.Switch[int, string](2).
    Case(1, "1").
    Case(2, "2").
    Default("3")
// "2"

result := lo.Switch[int, string](42).
    Case(1, "1").
    Case(2, "2").
    Default("3")
// "3"

Using callbacks:

result := lo.Switch[int, string](1).
    CaseF(1, func() string {
        return "1"
    }).
    CaseF(2, func() string {
        return "2"
    }).
    DefaultF(func() string {
        return "3"
    })
// "1"

Mixed:

result := lo.Switch[int, string](1).
    CaseF(1, func() string {
        return "1"
    }).
    Default("42")
// "1"
ToPtr

Returns a pointer copy of value.

ptr := lo.ToPtr[string]("hello world")
// *string{"hello world"}
ToSlicePtr

Returns a slice of pointer copy of value.

ptr := lo.ToSlicePtr[string]([]string{"hello", "world"})
// []*string{"hello", "world"}
ToAnySlice

Returns a slice with all elements mapped to any type.

elements := lo.ToAnySlice[int]([]int{1, 5, 1})
// []any{1, 5, 1}
FromAnySlice

Returns an any slice with all elements mapped to a type. Returns false in case of type conversion failure.

elements, ok := lo.FromAnySlice[string]([]any{"foobar", 42})
// []string{}, false

elements, ok := lo.FromAnySlice[string]([]any{"foobar", "42"})
// []string{"foobar", "42"}, true
Empty

Returns an empty value.

lo.Empty[int]()
// 0
lo.Empty[string]()
// ""
lo.Empty[bool]()
// false
Coalesce

Returns the first non-empty arguments. Arguments must be comparable.

result, ok := lo.Coalesce(0, 1, 2, 3)
// 1 true

result, ok := lo.Coalesce("")
// "" false

var nilStr *string
str := "foobar"
result, ok := lo.Coalesce[*string](nil, nilStr, &str)
// &"foobar" true
Attempt

Invokes a function N times until it returns valid output. Returning either the caught error or nil. When first argument is less than 1, the function runs until a sucessfull response is returned.

iter, err := lo.Attempt(42, func(i int) error {
    if i == 5 {
        return nil
    }

    return fmt.Errorf("failed")
})
// 6
// nil

iter, err := lo.Attempt(2, func(i int) error {
    if i == 5 {
        return nil
    }

    return fmt.Errorf("failed")
})
// 2
// error "failed"

iter, err := lo.Attempt(0, func(i int) error {
    if i < 42 {
        return fmt.Errorf("failed")
    }

    return nil
})
// 43
// nil

For more advanced retry strategies (delay, exponential backoff...), please take a look on cenkalti/backoff.

AttemptWithDelay

Invokes a function N times until it returns valid output, with a pause betwwen each call. Returning either the caught error or nil.

When first argument is less than 1, the function runs until a sucessfull response is returned.

iter, duration, err := lo.AttemptWithDelay(5, 2*time.Second, func(i int, duration time.Duration) error {
    if i == 2 {
        return nil
    }

    return fmt.Errorf("failed")
})
// 3
// ~ 4 seconds
// nil

For more advanced retry strategies (delay, exponential backoff...), please take a look on cenkalti/backoff.

Debounce

NewDebounce creates a debounced instance that delays invoking functions given until after wait milliseconds have elapsed, until cancel is called.

f := func() {
    println("Called once after 100ms when debounce stopped invoking!")
}

debounce, cancel := lo.NewDebounce(100 * time.Millisecond, f)
for j := 0; j < 10; j++ {
    debounce()
}

time.Sleep(1 * time.Second)
cancel()
Synchronize

Wraps the underlying callback in a mutex. It receives an optional mutex.

s := lo.Synchronize()

for i := 0; i < 10; i++ {
    go s.Do(func () {
        println("will be called sequentially")
    })
}

It is equivalent to:

mu := sync.Mutex{}

func foobar() {
    mu.Lock()
    defer mu.Unlock()

    // ...
}
Async

Executes a function in a goroutine and returns the result in a channel.

ch := lo.Async(func() error { time.Sleep(10 * time.Second); return nil })
// chan error (nil)
Async{0->6}

Executes a function in a goroutine and returns the result in a channel. For function with multiple return values, the results will be returned as a tuple inside the channel. For function without return, struct{} will be returned in the channel.

ch := lo.Async0(func() { time.Sleep(10 * time.Second) })
// chan struct{}

ch := lo.Async1(func() int {
  time.Sleep(10 * time.Second);
  return 42
})
// chan int (42)

ch := lo.Async2(func() (int, string) {
  time.Sleep(10 * time.Second);
  return 42, "Hello"
})
// chan lo.Tuple2[int, string] ({42, "Hello"})
Must

Wraps a function call to panics if second argument is error or false, returns the value otherwise.

val := lo.Must(time.Parse("2006-01-02", "2022-01-15"))
// 2022-01-15

val := lo.Must(time.Parse("2006-01-02", "bad-value"))
// panics
Must{0->6}

Must* has the same behavior than Must, but returns multiple values.

func example0() (error)
func example1() (int, error)
func example2() (int, string, error)
func example3() (int, string, time.Date, error)
func example4() (int, string, time.Date, bool, error)
func example5() (int, string, time.Date, bool, float64, error)
func example6() (int, string, time.Date, bool, float64, byte, error)

lo.Must0(example0())
val1 := lo.Must1(example1())    // alias to Must
val1, val2 := lo.Must2(example2())
val1, val2, val3 := lo.Must3(example3())
val1, val2, val3, val4 := lo.Must4(example4())
val1, val2, val3, val4, val5 := lo.Must5(example5())
val1, val2, val3, val4, val5, val6 := lo.Must6(example6())

You can wrap functions like func (...) (..., ok bool).

// math.Signbit(float64) bool
lo.Must0(math.Signbit(v))

// bytes.Cut([]byte,[]byte) ([]byte, []byte, bool)
before, after := lo.Must2(bytes.Cut(s, sep))

Try

Calls the function and return false in case of error and on panic.

ok := lo.Try(func() error {
    panic("error")
    return nil
})
// false

ok := lo.Try(func() error {
    return nil
})
// true

ok := lo.Try(func() error {
    return fmt.Errorf("error")
})
// false

Try{0->6}

The same behavior than Try, but callback returns 2 variables.

ok := lo.Try2(func() (string, error) {
    panic("error")
    return "", nil
})
// false

TryWithErrorValue

The same behavior than Try, but also returns value passed to panic.

err, ok := lo.TryWithErrorValue(func() error {
    panic("error")
    return nil
})
// "error", false

TryCatch

The same behavior than Try, but calls the catch function in case of error.

caught := false

ok := lo.TryCatch(func() error {
    panic("error")
    return nil
}, func() {
    caught = true
})
// false
// caught == true

TryCatchWithErrorValue

The same behavior than TryWithErrorValue, but calls the catch function in case of error.

caught := false

ok := lo.TryCatchWithErrorValue(func() error {
    panic("error")
    return nil
}, func(val any) {
    caught = val == "error"
})
// false
// caught == true

🛩 Benchmark

We executed a simple benchmark with the a dead-simple lo.Map loop:

See the full implementation here.

_ = lo.Map[int64](arr, func(x int64, i int) string {
    return strconv.FormatInt(x, 10)
})

Result:

Here is a comparison between lo.Map, lop.Map, go-funk library and a simple Go for loop.

$ go test -benchmem -bench ./...
goos: linux
goarch: amd64
pkg: github.com/samber/lo
cpu: Intel(R) Core(TM) i5-7267U CPU @ 3.10GHz
cpu: Intel(R) Core(TM) i7 CPU         920  @ 2.67GHz
BenchmarkMap/lo.Map-8         	       8	 132728237 ns/op	39998945 B/op	 1000002 allocs/op
BenchmarkMap/lop.Map-8        	       2	 503947830 ns/op	119999956 B/op	 3000007 allocs/op
BenchmarkMap/reflect-8        	       2	 826400560 ns/op	170326512 B/op	 4000042 allocs/op
BenchmarkMap/for-8            	       9	 126252954 ns/op	39998674 B/op	 1000001 allocs/op
PASS
ok  	github.com/samber/lo	6.657s
  • lo.Map is way faster (x7) than go-funk, a relection-based Map implementation.
  • lo.Map have the same allocation profile than for.
  • lo.Map is 4% slower than for.
  • lop.Map is slower than lo.Map because it implies more memory allocation and locks. lop.Map will be usefull for long-running callbacks, such as i/o bound processing.
  • for beats other implementations for memory and CPU.

🤝 Contributing

Don't hesitate ;)

Install go 1.18
make go1.18beta1

If your OS currently not default to Go 1.18, replace BIN=go by BIN=go1.18beta1 in the Makefile.

With Docker
docker-compose run --rm dev
Without Docker
# Install some dev dependencies
make tools

# Run tests
make test
# or
make watch-test

👤 Authors

  • Samuel Berthe

💫 Show your support

Give a ⭐️ if this project helped you!

support us

📝 License

Copyright © 2022 Samuel Berthe.

This project is MIT licensed.

Documentation

Index

Constants

This section is empty.

Variables

This section is empty.

Functions

func Assign 

func Assign[K comparable, V any](maps ...map[K]V) map[K]V

Assign merges multiple maps from left to right.

func Async 

func Async[A any](f func() A) chan A

Async executes a function in a goroutine and returns the result in a channel.

func Async0 

func Async0(f func()) chan struct{}

Async0 executes a function in a goroutine and returns a channel set once the function finishes.

func Async1 

func Async1[A any](f func() A) chan A

Async1 is an alias to Async.

func Async2 

func Async2[A any, B any](f func() (A, B)) chan Tuple2[A, B]

Async2 has the same behavior as Async, but returns the 2 results as a tuple inside the channel.

func Async3 

func Async3[A any, B any, C any](f func() (A, B, C)) chan Tuple3[A, B, C]

Async3 has the same behavior as Async, but returns the 3 results as a tuple inside the channel.

func Async4 

func Async4[A any, B any, C any, D any](f func() (A, B, C, D)) chan Tuple4[A, B, C, D]

Async4 has the same behavior as Async, but returns the 4 results as a tuple inside the channel.

func Async5 

func Async5[A any, B any, C any, D any, E any](f func() (A, B, C, D, E)) chan Tuple5[A, B, C, D, E]

Async5 has the same behavior as Async, but returns the 5 results as a tuple inside the channel.

func Async6 

func Async6[A any, B any, C any, D any, E any, F any](f func() (A, B, C, D, E, F)) chan Tuple6[A, B, C, D, E, F]

Async6 has the same behavior as Async, but returns the 6 results as a tuple inside the channel.

func Attempt 

func Attempt(maxIteration int, f func(int) error) (int, error)

Attempt invokes a function N times until it returns valid output. Returning either the caught error or nil. When first argument is less than `1`, the function runs until a successful response is returned.

func AttemptWithDelay 

func AttemptWithDelay(maxIteration int, delay time.Duration, f func(int, time.Duration) error) (int, time.Duration, error)

AttemptWithDelay invokes a function N times until it returns valid output, with a pause betwwen each call. Returning either the caught error or nil. When first argument is less than `1`, the function runs until a sucessfull response is returned.

func Chunk 

func Chunk[T any](collection []T, size int) [][]T

Chunk returns an array of elements split into groups the length of size. If array can't be split evenly, the final chunk will be the remaining elements.

func Clamp 

func Clamp[T constraints.Ordered](value T, min T, max T) T

Clamp clamps number within the inclusive lower and upper bounds.

func Coalesce 

func Coalesce[T comparable](v ...T) (result T, ok bool)

Coalesce returns the first non-empty arguments. Arguments must be comparable.

func Contains 

func Contains[T comparable](collection []T, element T) bool

Contains returns true if an element is present in a collection.

func ContainsBy 

func ContainsBy[T any](collection []T, predicate func(T) bool) bool

ContainsBy returns true if predicate function return true.

func Count 

func Count[T comparable](collection []T, value T) (count int)

Count counts the number of elements in the collection that compare equal to value.

func CountBy 

func CountBy[T any](collection []T, predicate func(T) bool) (count int)

CountBy counts the number of elements in the collection for which predicate is true.

func Difference 

func Difference[T comparable](list1 []T, list2 []T) ([]T, []T)

Difference returns the difference between two collections. The first value is the collection of element absent of list2. The second value is the collection of element absent of list1.

func Drop 

func Drop[T any](collection []T, n int) []T

Drop drops n elements from the beginning of a slice or array.

func DropRight 

func DropRight[T any](collection []T, n int) []T

DropRight drops n elements from the end of a slice or array.

func DropRightWhile 

func DropRightWhile[T any](collection []T, predicate func(T) bool) []T

DropRightWhile drops elements from the end of a slice or array while the predicate returns true.

func DropWhile 

func DropWhile[T any](collection []T, predicate func(T) bool) []T

DropWhile drops elements from the beginning of a slice or array while the predicate returns true.

func Empty 

func Empty[T any]() T

Empty returns an empty value.

func Every 

func Every[T comparable](collection []T, subset []T) bool

Every returns true if all elements of a subset are contained into a collection or if the subset is empty.

func EveryBy 

func EveryBy[V any](collection []V, predicate func(V) bool) bool

EveryBy returns true if the predicate returns true for all of the elements in the collection or if the collection is empty.

func Fill 

func Fill[T Clonable[T]](collection []T, initial T) []T

Fill fills elements of array with `initial` value.

func Filter 

func Filter[V any](collection []V, predicate func(V, int) bool) []V

Filter iterates over elements of collection, returning an array of all elements predicate returns truthy for.

func FilterMap 

func FilterMap[T any, R any](collection []T, callback func(T, int) (R, bool)) []R

FilterMap returns a slice which obtained after both filtering and mapping using the given callback function. The callback function should return two values:

  • the result of the mapping operation and
  • whether the result element should be included or not.

func Find 

func Find[T any](collection []T, predicate func(T) bool) (T, bool)

Find search an element in a slice based on a predicate. It returns element and true if element was found.

func FindIndexOf 

func FindIndexOf[T any](collection []T, predicate func(T) bool) (T, int, bool)

FindIndexOf searches an element in a slice based on a predicate and returns the index and true. It returns -1 and false if the element is not found.

func FindLastIndexOf 

func FindLastIndexOf[T any](collection []T, predicate func(T) bool) (T, int, bool)

FindLastIndexOf searches last element in a slice based on a predicate and returns the index and true. It returns -1 and false if the element is not found.

func FindOrElse 

func FindOrElse[T any](collection []T, fallback T, predicate func(T) bool) T

FindOrElse search an element in a slice based on a predicate. It returns the element if found or a given fallback value otherwise.

func FlatMap 

func FlatMap[T any, R any](collection []T, iteratee func(T, int) []R) []R

FlatMap manipulates a slice and transforms and flattens it to a slice of another type.

func Flatten 

func Flatten[T any](collection [][]T) []T

Flatten returns an array a single level deep.

func ForEach 

func ForEach[T any](collection []T, iteratee func(T, int))

ForEach iterates over elements of collection and invokes iteratee for each element.

func FromAnySlice 

func FromAnySlice[T any](in []any) (out []T, ok bool)

FromAnySlice returns an `any` slice with all elements mapped to a type. Returns false in case of type conversion failure.

func FromEntries 

func FromEntries[K comparable, V any](entries []Entry[K, V]) map[K]V

FromEntries transforms an array of key/value pairs into a map.

func GroupBy 

func GroupBy[T any, U comparable](collection []T, iteratee func(T) U) map[U][]T

GroupBy returns an object composed of keys generated from the results of running each element of collection through iteratee.

func If 

func If[T any](condition bool, result T) *ifElse[T]

If.

func IfF 

func IfF[T any](condition bool, resultF func() T) *ifElse[T]

IfF.

func IndexOf 

func IndexOf[T comparable](collection []T, element T) int

IndexOf returns the index at which the first occurrence of a value is found in an array or return -1 if the value cannot be found.

func Intersect 

func Intersect[T comparable](list1 []T, list2 []T) []T

Intersect returns the intersection between two collections.

func Invert 

func Invert[K comparable, V comparable](in map[K]V) map[V]K

Invert creates a map composed of the inverted keys and values. If map contains duplicate values, subsequent values overwrite property assignments of previous values.

func KeyBy 

func KeyBy[K comparable, V any](collection []V, iteratee func(V) K) map[K]V

KeyBy transforms a slice or an array of structs to a map based on a pivot callback.

func Keys 

func Keys[K comparable, V any](in map[K]V) []K

Keys creates an array of the map keys.

func Last 

func Last[T any](collection []T) (T, error)

Last returns the last element of a collection or error if empty.

func LastIndexOf 

func LastIndexOf[T comparable](collection []T, element T) int

LastIndexOf returns the index at which the last occurrence of a value is found in an array or return -1 if the value cannot be found.

func Map 

func Map[T any, R any](collection []T, iteratee func(T, int) R) []R

Map manipulates a slice and transforms it to a slice of another type.

func MapKeys 

func MapKeys[K comparable, V any, R comparable](in map[K]V, iteratee func(V, K) R) map[R]V

MapKeys manipulates a map keys and transforms it to a map of another type.

func MapValues 

func MapValues[K comparable, V any, R any](in map[K]V, iteratee func(V, K) R) map[K]R

MapValues manipulates a map values and transforms it to a map of another type.

func Max 

func Max[T constraints.Ordered](collection []T) T

Max searches the maximum value of a collection.

func MaxBy 

func MaxBy[T any](collection []T, comparison func(T, T) bool) T

MaxBy search the maximum value of a collection using the given comparison function. If several values of the collection are equal to the greatest value, returns the first such value.

func Min 

func Min[T constraints.Ordered](collection []T) T

Min search the minimum value of a collection.

func MinBy 

func MinBy[T any](collection []T, comparison func(T, T) bool) T

MinBy search the minimum value of a collection using the given comparison function. If several values of the collection are equal to the smallest value, returns the first such value.

func Must 

func Must[T any](val T, err any) T

Must is a helper that wraps a call to a function returning a value and an error and panics if err is error or false.

func Must0 

func Must0(err any)

Must0 has the same behavior than Must, but callback returns no variable.

func Must1 

func Must1[T any](val T, err any) T

Must1 is an alias to Must

func Must2 

func Must2[T1 any, T2 any](val1 T1, val2 T2, err any) (T1, T2)

Must2 has the same behavior than Must, but callback returns 2 variables.

func Must3 

func Must3[T1 any, T2 any, T3 any](val1 T1, val2 T2, val3 T3, err any) (T1, T2, T3)

Must3 has the same behavior than Must, but callback returns 3 variables.

func Must4 

func Must4[T1 any, T2 any, T3 any, T4 any](val1 T1, val2 T2, val3 T3, val4 T4, err any) (T1, T2, T3, T4)

Must4 has the same behavior than Must, but callback returns 4 variables.

func Must5 

func Must5[T1 any, T2 any, T3 any, T4 any, T5 any](val1 T1, val2 T2, val3 T3, val4 T4, val5 T5, err any) (T1, T2, T3, T4, T5)

Must5 has the same behavior than Must, but callback returns 5 variables.

func Must6 

func Must6[T1 any, T2 any, T3 any, T4 any, T5 any, T6 any](val1 T1, val2 T2, val3 T3, val4 T4, val5 T5, val6 T6, err any) (T1, T2, T3, T4, T5, T6)

Must6 has the same behavior than Must, but callback returns 6 variables.

func NewDebounce 

func NewDebounce(duration time.Duration, f ...func()) (func(), func())

NewDebounce creates a debounced instance that delays invoking functions given until after wait milliseconds have elapsed.

func None 

func None[V comparable](collection []V, subset []V) bool

None returns true if no element of a subset are contained into a collection or if the subset is empty.

func NoneBy 

func NoneBy[V any](collection []V, predicate func(V) bool) bool

NoneBy returns true if the predicate returns true for none of the elements in the collection or if the collection is empty.

func Nth 

func Nth[T any](collection []T, nth int) (T, error)

Nth returns the element at index `nth` of collection. If `nth` is negative, the nth element from the end is returned. An error is returned when nth is out of slice bounds.

func OmitBy 

func OmitBy[K comparable, V any](in map[K]V, predicate func(K, V) bool) map[K]V

PickBy returns same map type filtered by given predicate.

func OmitByKeys 

func OmitByKeys[K comparable, V any](in map[K]V, keys []K) map[K]V

OmitByKeys returns same map type filtered by given keys.

func OmitByValues 

func OmitByValues[K comparable, V comparable](in map[K]V, values []V) map[K]V

OmitByValues returns same map type filtered by given values.

func PartitionBy 

func PartitionBy[T any, K comparable](collection []T, iteratee func(x T) K) [][]T

PartitionBy returns an array of elements split into groups. The order of grouped values is determined by the order they occur in collection. The grouping is generated from the results of running each element of collection through iteratee.

func PickBy 

func PickBy[K comparable, V any](in map[K]V, predicate func(K, V) bool) map[K]V

PickBy returns same map type filtered by given predicate.

func PickByKeys 

func PickByKeys[K comparable, V any](in map[K]V, keys []K) map[K]V

PickByKeys returns same map type filtered by given keys.

func PickByValues 

func PickByValues[K comparable, V comparable](in map[K]V, values []V) map[K]V

PickByValues returns same map type filtered by given values.

func Range 

func Range(elementNum int) []int

Range creates an array of numbers (positive and/or negative) with given length.

func RangeFrom 

func RangeFrom[T constraints.Integer | constraints.Float](start T, elementNum int) []T

RangeFrom creates an array of numbers from start with specified length.

func RangeWithSteps 

func RangeWithSteps[T constraints.Integer | constraints.Float](start, end, step T) []T

RangeWithSteps creates an array of numbers (positive and/or negative) progressing from start up to, but not including end. step set to zero will return empty array.

func Reduce 

func Reduce[T any, R any](collection []T, accumulator func(R, T, int) R, initial R) R

Reduce reduces collection to a value which is the accumulated result of running each element in collection through accumulator, where each successive invocation is supplied the return value of the previous.

func Reject 

func Reject[V any](collection []V, predicate func(V, int) bool) []V

Reject is the opposite of Filter, this method returns the elements of collection that predicate does not return truthy for.

func Repeat 

func Repeat[T Clonable[T]](count int, initial T) []T

Repeat builds a slice with N copies of initial value.

func RepeatBy 

func RepeatBy[T any](count int, predicate func(int) T) []T

RepeatBy builds a slice with values returned by N calls of callback.

func Replace 

func Replace[T comparable](collection []T, old T, new T, n int) []T

Replace returns a copy of the slice with the first n non-overlapping instances of old replaced by new.

func ReplaceAll 

func ReplaceAll[T comparable](collection []T, old T, new T) []T

ReplaceAll returns a copy of the slice with all non-overlapping instances of old replaced by new.

func Reverse 

func Reverse[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.

func RuneLength 

func RuneLength(str string) int

RuneLength is an alias to utf8.RuneCountInString which returns the number of runes in string.

func Sample 

func Sample[T any](collection []T) T

Sample returns a random item from collection.

func Samples 

func Samples[T any](collection []T, count int) []T

Samples returns N random unique items from collection.

func Shuffle 

func Shuffle[T any](collection []T) []T

Shuffle returns an array of shuffled values. Uses the Fisher-Yates shuffle algorithm.

func Some 

func Some[T comparable](collection []T, subset []T) bool

Some returns true if at least 1 element of a subset is contained into a collection. If the subset is empty Some returns false.

func SomeBy 

func SomeBy[V any](collection []V, predicate func(V) bool) bool

SomeBy returns true if the predicate returns true for any of the elements in the collection. If the collection is empty SomeBy returns false.

func Subset 

func Subset[T any](collection []T, offset int, length uint) []T

Subset return part of a slice.

func Substring 

func Substring[T ~string](str T, offset int, length uint) T

Substring return part of a string.

func SumBy 

func SumBy[T any, R constraints.Float | constraints.Integer](collection []T, iteratee func(T) R) R

Summarizes the values in a collection.

func Switch 

func Switch[T comparable, R any](predicate T) *switchCase[T, R]

Switch is a pure functional switch/case/default statement.

func Synchronize 

func Synchronize(opt ...sync.Locker) *synchronize

Synchronize wraps the underlying callback in a mutex. It receives an optional mutex.

func Ternary 

func Ternary[T any](condition bool, ifOutput T, elseOutput T) T

Ternary is a 1 line if/else statement.

func Times 

func Times[T any](count int, iteratee func(int) T) []T

Times invokes the iteratee n times, returning an array of the results of each invocation. The iteratee is invoked with index as argument.

func ToAnySlice 

func ToAnySlice[T any](collection []T) []any

ToAnySlice returns a slice with all elements mapped to `any` type

func ToPtr 

func ToPtr[T any](x T) *T

ToPtr returns a pointer copy of value.

func ToSlicePtr 

func ToSlicePtr[T any](collection []T) []*T

ToSlicePtr returns a slice of pointer copy of value.

func Try 

func Try(callback func() error) (ok bool)

Try calls the function and return false in case of error.

func Try0 

func Try0(callback func()) bool

Try0 has the same behavior than Try, but callback returns no variable.

func Try1 

func Try1[T any](callback func() error) bool

Try1 is an alias to Try.

func Try2 

func Try2[T any](callback func() (T, error)) bool

Try2 has the same behavior than Try, but callback returns 2 variables.

func Try3 

func Try3[T, R any](callback func() (T, R, error)) bool

Try3 has the same behavior than Try, but callback returns 3 variables.

func Try4 

func Try4[T, R, S any](callback func() (T, R, S, error)) bool

Try4 has the same behavior than Try, but callback returns 4 variables.

func Try5 

func Try5[T, R, S, Q any](callback func() (T, R, S, Q, error)) bool

Try5 has the same behavior than Try, but callback returns 5 variables.

func Try6 

func Try6[T, R, S, Q, U any](callback func() (T, R, S, Q, U, error)) bool

Try6 has the same behavior than Try, but callback returns 6 variables.

func TryCatch 

func TryCatch(callback func() error, catch func())

TryCatch has the same behavior than Try, but calls the catch function in case of error.

func TryCatchWithErrorValue 

func TryCatchWithErrorValue(callback func() error, catch func(any))

TryCatchWithErrorValue has the same behavior than TryWithErrorValue, but calls the catch function in case of error.

func TryWithErrorValue 

func TryWithErrorValue(callback func() error) (errorValue any, ok bool)

TryWithErrorValue has the same behavior than Try, but also returns value passed to panic.

func Union 

func Union[T comparable](list1 []T, list2 []T) []T

Union returns all distinct elements from both collections. result returns will not change the order of elements relatively.

func Uniq 

func Uniq[T comparable](collection []T) []T

Uniq returns a duplicate-free version of an array, in which only the first occurrence of each element is kept. The order of result values is determined by the order they occur in the array.

func UniqBy 

func UniqBy[T any, U comparable](collection []T, iteratee func(T) U) []T

UniqBy returns a duplicate-free version of an array, in which only the first occurrence of each element is kept. The order of result values is determined by the order they occur in the array. It accepts `iteratee` which is invoked for each element in array to generate the criterion by which uniqueness is computed.

func Unpack2 

func Unpack2[A any, B any](tuple Tuple2[A, B]) (A, B)

Unpack2 returns values contained in tuple.

func Unpack3 

func Unpack3[A any, B any, C any](tuple Tuple3[A, B, C]) (A, B, C)

Unpack3 returns values contained in tuple.

func Unpack4 

func Unpack4[A any, B any, C any, D any](tuple Tuple4[A, B, C, D]) (A, B, C, D)

Unpack4 returns values contained in tuple.

func Unpack5 

func Unpack5[A any, B any, C any, D any, E any](tuple Tuple5[A, B, C, D, E]) (A, B, C, D, E)

Unpack5 returns values contained in tuple.

func Unpack6 

func Unpack6[A any, B any, C any, D any, E any, F any](tuple Tuple6[A, B, C, D, E, F]) (A, B, C, D, E, F)

Unpack6 returns values contained in tuple.

func Unpack7 

func Unpack7[A any, B any, C any, D any, E any, F any, G any](tuple Tuple7[A, B, C, D, E, F, G]) (A, B, C, D, E, F, G)

Unpack7 returns values contained in tuple.

func Unpack8 

func Unpack8[A any, B any, C any, D any, E any, F any, G any, H any](tuple Tuple8[A, B, C, D, E, F, G, H]) (A, B, C, D, E, F, G, H)

Unpack8 returns values contained in tuple.

func Unpack9 

func Unpack9[A any, B any, C any, D any, E any, F any, G any, H any, I any](tuple Tuple9[A, B, C, D, E, F, G, H, I]) (A, B, C, D, E, F, G, H, I)

Unpack9 returns values contained in tuple.

func Unzip2 

func Unzip2[A any, B any](tuples []Tuple2[A, B]) ([]A, []B)

Unzip2 accepts an array of grouped elements and creates an array regrouping the elements to their pre-zip configuration.

func Unzip3 

func Unzip3[A any, B any, C any](tuples []Tuple3[A, B, C]) ([]A, []B, []C)

Unzip3 accepts an array of grouped elements and creates an array regrouping the elements to their pre-zip configuration.

func Unzip4 

func Unzip4[A any, B any, C any, D any](tuples []Tuple4[A, B, C, D]) ([]A, []B, []C, []D)

Unzip4 accepts an array of grouped elements and creates an array regrouping the elements to their pre-zip configuration.

func Unzip5 

func Unzip5[A any, B any, C any, D any, E any](tuples []Tuple5[A, B, C, D, E]) ([]A, []B, []C, []D, []E)

Unzip5 accepts an array of grouped elements and creates an array regrouping the elements to their pre-zip configuration.

func Unzip6 

func Unzip6[A any, B any, C any, D any, E any, F any](tuples []Tuple6[A, B, C, D, E, F]) ([]A, []B, []C, []D, []E, []F)

Unzip6 accepts an array of grouped elements and creates an array regrouping the elements to their pre-zip configuration.

func Unzip7 

func Unzip7[A any, B any, C any, D any, E any, F any, G any](tuples []Tuple7[A, B, C, D, E, F, G]) ([]A, []B, []C, []D, []E, []F, []G)

Unzip7 accepts an array of grouped elements and creates an array regrouping the elements to their pre-zip configuration.

func Unzip8 

func Unzip8[A any, B any, C any, D any, E any, F any, G any, H any](tuples []Tuple8[A, B, C, D, E, F, G, H]) ([]A, []B, []C, []D, []E, []F, []G, []H)

Unzip8 accepts an array of grouped elements and creates an array regrouping the elements to their pre-zip configuration.

func Unzip9 

func Unzip9[A any, B any, C any, D any, E any, F any, G any, H any, I any](tuples []Tuple9[A, B, C, D, E, F, G, H, I]) ([]A, []B, []C, []D, []E, []F, []G, []H, []I)

Unzip9 accepts an array of grouped elements and creates an array regrouping the elements to their pre-zip configuration.

func Values 

func Values[K comparable, V any](in map[K]V) []V

Values creates an array of the map values.

Types

type Clonable 

type Clonable[T any] interface {
	Clone() T
}

Clonable defines a constraint of types having Clone() T method.

type Entry 

type Entry[K comparable, V any] struct {
	Key   K
	Value V
}

Entry defines a key/value pairs.

func Entries 

func Entries[K comparable, V any](in map[K]V) []Entry[K, V]

Entries transforms a map into array of key/value pairs.

type Tuple2 

type Tuple2[A any, B any] struct {
	A A
	B B
}

Tuple2 is a group of 2 elements (pair).

func T2 

func T2[A any, B any](a A, b B) Tuple2[A, B]

T2 creates a tuple from a list of values.

func Zip2 

func Zip2[A any, B any](a []A, b []B) []Tuple2[A, B]

Zip2 creates a slice of grouped elements, the first of which contains the first elements of the given arrays, the second of which contains the second elements of the given arrays, and so on. When collections have different size, the Tuple attributes are filled with zero value.

type Tuple3 

type Tuple3[A any, B any, C any] struct {
	A A
	B B
	C C
}

Tuple3 is a group of 3 elements.

func T3 

func T3[A any, B any, C any](a A, b B, c C) Tuple3[A, B, C]

T3 creates a tuple from a list of values.

func Zip3 

func Zip3[A any, B any, C any](a []A, b []B, c []C) []Tuple3[A, B, C]

Zip3 creates a slice of grouped elements, the first of which contains the first elements of the given arrays, the second of which contains the second elements of the given arrays, and so on. When collections have different size, the Tuple attributes are filled with zero value.

type Tuple4 

type Tuple4[A any, B any, C any, D any] struct {
	A A
	B B
	C C
	D D
}

Tuple4 is a group of 4 elements.

func T4 

func T4[A any, B any, C any, D any](a A, b B, c C, d D) Tuple4[A, B, C, D]

T4 creates a tuple from a list of values.

func Zip4 

func Zip4[A any, B any, C any, D any](a []A, b []B, c []C, d []D) []Tuple4[A, B, C, D]

Zip4 creates a slice of grouped elements, the first of which contains the first elements of the given arrays, the second of which contains the second elements of the given arrays, and so on. When collections have different size, the Tuple attributes are filled with zero value.

type Tuple5 

type Tuple5[A any, B any, C any, D any, E any] struct {
	A A
	B B
	C C
	D D
	E E
}

Tuple5 is a group of 5 elements.

func T5 

func T5[A any, B any, C any, D any, E any](a A, b B, c C, d D, e E) Tuple5[A, B, C, D, E]

T5 creates a tuple from a list of values.

func Zip5 

func Zip5[A any, B any, C any, D any, E any](a []A, b []B, c []C, d []D, e []E) []Tuple5[A, B, C, D, E]

Zip5 creates a slice of grouped elements, the first of which contains the first elements of the given arrays, the second of which contains the second elements of the given arrays, and so on. When collections have different size, the Tuple attributes are filled with zero value.

type Tuple6 

type Tuple6[A any, B any, C any, D any, E any, F any] struct {
	A A
	B B
	C C
	D D
	E E
	F F
}

Tuple6 is a group of 6 elements.

func T6 

func T6[A any, B any, C any, D any, E any, F any](a A, b B, c C, d D, e E, f F) Tuple6[A, B, C, D, E, F]

T6 creates a tuple from a list of values.

func Zip6 

func Zip6[A any, B any, C any, D any, E any, F any](a []A, b []B, c []C, d []D, e []E, f []F) []Tuple6[A, B, C, D, E, F]

Zip6 creates a slice of grouped elements, the first of which contains the first elements of the given arrays, the second of which contains the second elements of the given arrays, and so on. When collections have different size, the Tuple attributes are filled with zero value.

type Tuple7 

type Tuple7[A any, B any, C any, D any, E any, F any, G any] struct {
	A A
	B B
	C C
	D D
	E E
	F F
	G G
}

Tuple7 is a group of 7 elements.

func T7 

func T7[A any, B any, C any, D any, E any, F any, G any](a A, b B, c C, d D, e E, f F, g G) Tuple7[A, B, C, D, E, F, G]

T7 creates a tuple from a list of values.

func Zip7 

func Zip7[A any, B any, C any, D any, E any, F any, G any](a []A, b []B, c []C, d []D, e []E, f []F, g []G) []Tuple7[A, B, C, D, E, F, G]

Zip7 creates a slice of grouped elements, the first of which contains the first elements of the given arrays, the second of which contains the second elements of the given arrays, and so on. When collections have different size, the Tuple attributes are filled with zero value.

type Tuple8 

type Tuple8[A any, B any, C any, D any, E any, F any, G any, H any] struct {
	A A
	B B
	C C
	D D
	E E
	F F
	G G
	H H
}

Tuple8 is a group of 8 elements.

func T8 

func T8[A any, B any, C any, D any, E any, F any, G any, H any](a A, b B, c C, d D, e E, f F, g G, h H) Tuple8[A, B, C, D, E, F, G, H]

T8 creates a tuple from a list of values.

func Zip8 

func Zip8[A any, B any, C any, D any, E any, F any, G any, H any](a []A, b []B, c []C, d []D, e []E, f []F, g []G, h []H) []Tuple8[A, B, C, D, E, F, G, H]

Zip8 creates a slice of grouped elements, the first of which contains the first elements of the given arrays, the second of which contains the second elements of the given arrays, and so on. When collections have different size, the Tuple attributes are filled with zero value.

type Tuple9 

type Tuple9[A any, B any, C any, D any, E any, F any, G any, H any, I any] struct {
	A A
	B B
	C C
	D D
	E E
	F F
	G G
	H H
	I I
}

Tuple9 is a group of 9 elements.

func T9 

func T9[A any, B any, C any, D any, E any, F any, G any, H any, I any](a A, b B, c C, d D, e E, f F, g G, h H, i I) Tuple9[A, B, C, D, E, F, G, H, I]

T8 creates a tuple from a list of values.

func Zip9 

func Zip9[A any, B any, C any, D any, E any, F any, G any, H any, I any](a []A, b []B, c []C, d []D, e []E, f []F, g []G, h []H, i []I) []Tuple9[A, B, C, D, E, F, G, H, I]

Zip9 creates a slice of grouped elements, the first of which contains the first elements of the given arrays, the second of which contains the second elements of the given arrays, and so on. When collections have different size, the Tuple attributes are filled with zero value.

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