Slice

Package slice implements some functions to manipulate slice.

Source:

https://github.com/duke-git/lancet/blob/main/slice/slice.go

Usage:

import (
    "github.com/duke-git/lancet/v2/slice"
)

Index

AppendIfAbsent
Contain
ContainBy
ContainSubSlice
Chunk
Compact
Concat
Count
CountBy
Difference
DifferenceBy
DifferenceWith
DeleteAt
DeleteRange
Drop
DropRight
DropWhile
DropRightWhile
Equal
EqualWith
Every
Filter
Find^deprecated
FindBy
FindLast^deprecated
FindLastBy
Flatten
FlattenDeep
ForEach
ForEachWithBreak
GroupBy
GroupWith
IntSlice^deprecated
InterfaceSlice^deprecated
Intersection
InsertAt
IndexOf
LastIndexOf
Map
FilterMap
FlatMap
Merge
Reverse
Reduce^deprecated
ReduceBy
ReduceRight
Replace
ReplaceAll
Repeat
Shuffle
IsAscending
IsDescending
IsSorted
IsSortedByKey
Sort
SortBy
SortByField
Some
StringSlice^deprecated
SymmetricDifference
ToSlice
ToSlicePointer
Unique
UniqueBy
Union
UnionBy
UpdateAt
Without
KeyBy
Join
Partition
SetToDefaultIf
Break
RightPadding
LeftPadding

Documentation

AppendIfAbsent

If slice doesn't contain the item, append it to the slice.

Signature:

func AppendIfAbsent[T comparable](slice []T, item T) []T

Example:Run

import (
    "fmt"
    "github.com/duke-git/lancet/v2/slice"
)

func main() {
    result1 := slice.AppendIfAbsent([]string{"a", "b"}, "b")
    result2 := slice.AppendIfAbsent([]string{"a", "b"}, "c")

    fmt.Println(result1)
    fmt.Println(result2)

    // Output:
    // [a b]
    // [a b c]
}

Contain

Check if the target value is in the slice or not.

Signature:

func Contain[T comparable](slice []T, target T) bool

Example:Run

import (
    "fmt"
    "github.com/duke-git/lancet/v2/slice"
)

func main() {
    result1 := slice.Contain([]string{"a", "b", "c"}, "a")
    result2 := slice.Contain([]int{1, 2, 3}, 4)

    fmt.Println(result1)
    fmt.Println(result2)

    // Output:
    // true
    // false
}

ContainBy

returns true if predicate function return true.

Signature:

func ContainBy[T any](slice []T, predicate func(item T) bool) bool

Example:Run

import (
    "fmt"
    "github.com/duke-git/lancet/v2/slice"
)

func main() {
    type foo struct {
        A string
        B int
    }

    array1 := []foo{{A: "1", B: 1}, {A: "2", B: 2}}
    result1 := slice.ContainBy(array1, func(f foo) bool { return f.A == "1" && f.B == 1 })
    result2 := slice.ContainBy(array1, func(f foo) bool { return f.A == "2" && f.B == 1 })

    array2 := []string{"a", "b", "c"}
    result3 := slice.ContainBy(array2, func(t string) bool { return t == "a" })
    result4 := slice.ContainBy(array2, func(t string) bool { return t == "d" })

    fmt.Println(result1)
    fmt.Println(result2)
    fmt.Println(result3)
    fmt.Println(result4)

    // Output:
    // true
    // false
    // true
    // false
}

ContainSubSlice

Check if the slice contain subslice or not.

Signature:

func ContainSubSlice[T comparable](slice, subSlice []T) bool

Example:Run

import (
    "fmt"
    "github.com/duke-git/lancet/v2/slice"
)

func main() {
    result1 := slice.ContainSubSlice([]string{"a", "b", "c"}, []string{"a", "b"})
    result2 := slice.ContainSubSlice([]string{"a", "b", "c"}, []string{"a", "d"})

    fmt.Println(result1)
    fmt.Println(result2)

    // Output:
    // true
    // false
}

Chunk

Creates an slice of elements split into groups the length of `size`.

Signature:

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

Example:Run

import (
    "fmt"
    "github.com/duke-git/lancet/v2/slice"
)

func main() {
    arr := []string{"a", "b", "c", "d", "e"}

    result1 := slice.Chunk(arr, 1)
    result2 := slice.Chunk(arr, 2)
    result3 := slice.Chunk(arr, 3)
    result4 := slice.Chunk(arr, 4)
    result5 := slice.Chunk(arr, 5)

    fmt.Println(result1)
    fmt.Println(result2)
    fmt.Println(result3)
    fmt.Println(result4)
    fmt.Println(result5)

    // Output:
    // [[a] [b] [c] [d] [e]]
    // [[a b] [c d] [e]]
    // [[a b c] [d e]]
    // [[a b c d] [e]]
    // [[a b c d e]]
}

Compact

Creates an slice with all falsey values removed. The values false, nil, 0, and "" are falsey.

Signature:

func Compact[T comparable](slice []T) []T

Example:Run

import (
    "fmt"
    "github.com/duke-git/lancet/v2/slice"
)

func main() {
    result1 := slice.Compact([]int{0})
    result2 := slice.Compact([]int{0, 1, 2, 3})
    result3 := slice.Compact([]string{"", "a", "b", "0"})
    result4 := slice.Compact([]bool{false, true, true})

    fmt.Println(result1)
    fmt.Println(result2)
    fmt.Println(result3)
    fmt.Println(result4)

    // Output:
    // []
    // [1 2 3]
    // [a b 0]
    // [true true]
}

Concat

Creates a new slice concatenating slice with any additional slices.

Signature:

func Concat[T any](slice []T, slices ...[]T) []T

Example:Run

import (
    "fmt"
    "github.com/duke-git/lancet/v2/slice"
)

func main() {
    result1 := slice.Concat([]int{1, 2}, []int{3, 4})
    result2 := slice.Concat([]string{"a", "b"}, []string{"c"}, []string{"d"})

    fmt.Println(result1)
    fmt.Println(result2)

    // Output:
    // [1 2 3 4]
    // [a b c d]
}

Count

Returns the number of occurrences of the given item in the slice.

Signature:

func Count[T comparable](slice []T, item T) int

Example:Run

import (
    "fmt"
    "github.com/duke-git/lancet/v2/slice"
)

func main() {
    nums := []int{1, 2, 3, 3, 4}

    result1 := slice.Count(nums, 1)
    result2 := slice.Count(nums, 3)

    fmt.Println(result1)
    fmt.Println(result2)

    // Output:
    // 1
    // 2
}

CountBy

Iterates over elements of slice with predicate function, returns the number of all matched elements.

Signature:

func CountBy[T any](slice []T, predicate func(index int, item T) bool) int

Example:Run

import (
    "fmt"
    "github.com/duke-git/lancet/v2/slice"
)

func main() {
    nums := []int{1, 2, 3, 4, 5}

    isEven := func(i, num int) bool {
        return num%2 == 0
    }

    result := slice.CountBy(nums, isEven)

    fmt.Println(result)

    // Output:
    // 2
}

Difference

Creates an slice of whose element not included in the other given slice.

Signature:

func Difference[T comparable](slice, comparedSlice []T) []T

Example:Run

import (
    "fmt"
    "github.com/duke-git/lancet/v2/slice"
)

func main() {
    s1 := []int{1, 2, 3, 4, 5}
    s2 := []int{4, 5, 6}

    result := slice.Difference(s1, s2)

    fmt.Println(result)

    // Output:
    // [1 2 3]
}

DifferenceBy

DifferenceBy accepts iteratee func which is invoked for each element of slice and values to generate the criterion by which they're compared.

Signature:

func DifferenceBy[T comparable](slice []T, comparedSlice []T, iteratee func(index int, item T) T) []T

Example:Run

import (
    "fmt"
    "github.com/duke-git/lancet/v2/slice"
)

func main() {
    s1 := []int{1, 2, 3, 4, 5}
    s2 := []int{3, 4, 5}

    addOne := func(i int, v int) int {
        return v + 1
    }

    result := slice.DifferenceBy(s1, s2, addOne)

    fmt.Println(result)

    // Output:
    // [1 2]
}

DifferenceWith

DifferenceWith accepts comparator which is invoked to compare elements of slice to values. The order and references of result values are determined by the first slice.

Signature:

func DifferenceWith[T any](slice []T, comparedSlice []T, comparator func(value, otherValue T) bool) []T

Example:Run

import (
    "fmt"
    "github.com/duke-git/lancet/v2/slice"
)

func main() {
    s1 := []int{1, 2, 3, 4, 5}
    s2 := []int{4, 5, 6, 7, 8}

    isDouble := func(v1, v2 int) bool {
        return v2 == 2*v1
    }

    result := slice.DifferenceWith(s1, s2, isDouble)

    fmt.Println(result)

    // Output:
    // [1 5]
}

DeleteAt

Delete delete the element of slice at index.

Signature:

func DeleteAt[T any](slice []T, index int)

Example:Run

import (
    "fmt"
    "github.com/duke-git/lancet/v2/slice"
)

func main() {
    chars := []string{"a", "b", "c", "d", "e"}

    result1 := slice.DeleteAt(chars, 0)
    result2 := slice.DeleteAt(chars, 4)
    result3 := slice.DeleteAt(chars, 5)
    result4 := slice.DeleteAt(chars, 6)

    fmt.Println(result1)
    fmt.Println(result2)
    fmt.Println(result3)
    fmt.Println(result4)

    // Output:
    // [b c d e]
    // [a b c d]
    // [a b c d]
    // [a b c d]
}

DeleteRange

Delete the element of slice from start index to end index（exclude)

Signature:

func DeleteRange[T any](slice []T, start, end int) []T

Example:Run

import (
    "fmt"
    "github.com/duke-git/lancet/v2/slice"
)

func main() {
    chars := []string{"a", "b", "c", "d", "e"}

    result1 := slice.DeleteRange(chars, 0, 0)
    result2 := slice.DeleteRange(chars, 0, 1)
    result3 := slice.DeleteRange(chars, 0, 3)
    result4 := slice.DeleteRange(chars, 0, 4)
    result5 := slice.DeleteRange(chars, 0, 5)

    fmt.Println(result1)
    fmt.Println(result2)
    fmt.Println(result3)
    fmt.Println(result4)
    fmt.Println(result5)

    // Output:
    // [a b c d e]
    // [b c d e]
    // [d e]
    // [e]
    // []

}

Drop

Drop n elements from the start of a slice.

Signature:

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

Example:Run

import (
    "fmt"
    "github.com/duke-git/lancet/v2/slice"
)

func main() {
    result1 := slice.Drop([]string{"a", "b", "c"}, 0)
    result2 := slice.Drop([]string{"a", "b", "c"}, 1)
    result3 := slice.Drop([]string{"a", "b", "c"}, -1)
    result4 := slice.Drop([]string{"a", "b", "c"}, 4)

    fmt.Println(result1)
    fmt.Println(result2)
    fmt.Println(result3)
    fmt.Println(result4)

    // Output:
    // [a b c]
    // [b c]
    // [a b c]
    // []
}

DropRight

Drop n elements from the end of a slice.

Signature:

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

Example:Run

import (
    "fmt"
    "github.com/duke-git/lancet/v2/slice"
)

func main() {
    result1 := slice.DropRight([]string{"a", "b", "c"}, 0)
    result2 := slice.DropRight([]string{"a", "b", "c"}, 1)
    result3 := slice.DropRight([]string{"a", "b", "c"}, -1)
    result4 := slice.DropRight([]string{"a", "b", "c"}, 4)

    fmt.Println(result1)
    fmt.Println(result2)
    fmt.Println(result3)
    fmt.Println(result4)

    // Output:
    // [a b c]
    // [a b]
    // [a b c]
    // []
}

DropWhile

Drop n elements from the start of a slice while predicate function returns true.

Signature:

func DropWhile[T any](slice []T, predicate func(item T) bool) []T

Example:Run

import (
    "fmt"
    "github.com/duke-git/lancet/v2/slice"
)

func main() {
    result1 := slice.DropWhile(numbers, func(n int) bool {
        return n != 2
    })
    result2 := slice.DropWhile(numbers, func(n int) bool {
        return true
    })
    result3 := slice.DropWhile(numbers, func(n int) bool {
        return n == 0
    })

    fmt.Println(result1)
    fmt.Println(result2)
    fmt.Println(result3)

    // Output:
    // [2 3 4 5]
    // []
    // [1 2 3 4 5]
}

DropRightWhile

Drop n elements from the end of a slice while predicate function returns true.

Signature:

func DropRightWhile[T any](slice []T, predicate func(item T) bool) []T

Example:Run

import (
    "fmt"
    "github.com/duke-git/lancet/v2/slice"
)

func main() {
    numbers := []int{1, 2, 3, 4, 5}

    result1 := slice.DropRightWhile(numbers, func(n int) bool {
        return n != 2
    })
    result2 := slice.DropRightWhile(numbers, func(n int) bool {
        return true
    })
    result3 := slice.DropRightWhile(numbers, func(n int) bool {
        return n == 0
    })

    fmt.Println(result1)
    fmt.Println(result2)
    fmt.Println(result3)

    // Output:
    // [1 2]
    // []
    // [1 2 3 4 5]
}

Equal

Check if two slices are equal: the same length and all elements' order and value are equal.

Signature:

func Equal[T comparable](slice1, slice2 []T) bool

Example:Run

import (
    "fmt"
    "github.com/duke-git/lancet/v2/slice"
)

func main() {
    s1 := []int{1, 2, 3}
    s2 := []int{1, 2, 3}
    s3 := []int{1, 3, 2}

    result1 := slice.Equal(s1, s2)
    result2 := slice.Equal(s1, s3)

    fmt.Println(result1)
    fmt.Println(result2)

    // Output:
    // true
    // false
}

EqualWith

Check if two slices are equal with comparator func.

Signature:

func EqualWith[T, U any](slice1 []T, slice2 []U, comparator func(T, U) bool) bool

Example:Run

import (
    "fmt"
    "github.com/duke-git/lancet/v2/slice"
)

func main() {
    s1 := []int{1, 2, 3}
    s2 := []int{2, 4, 6}

    isDouble := func(a, b int) bool {
        return b == a*2
    }

    result := slice.EqualWith(s1, s2, isDouble)

    fmt.Println(result)

    // Output:
    // true
}

Every

Return true if all of the values in the slice pass the predicate function.

Signature:

func Every[T any](slice []T, predicate func(index int, item T) bool) bool

Example:Run

import (
    "fmt"
    "github.com/duke-git/lancet/v2/slice"
)

func main() {
    nums := []int{1, 2, 3, 5}

    isEven := func(i, num int) bool {
        return num%2 == 0
    }

    result := slice.Every(nums, isEven)

    fmt.Println(result)

    // Output:
    // false
}

Filter

Return all elements which match the function.

Signature:

func Filter[T any](slice []T, predicate func(index int, item T) bool) []T

Example:Run

import (
    "fmt"
    "github.com/duke-git/lancet/v2/slice"
)

func main() {
    nums := []int{1, 2, 3, 4, 5}

    isEven := func(i, num int) bool {
        return num%2 == 0
    }

    result := slice.Filter(nums, isEven)

    fmt.Println(result)

    // Output:
    // [2 4]
}

Find(deprecated: use FindBy)

Iterates over elements of slice, returning the first one that passes a truth test on function.

Signature:

func Find[T any](slice []T, predicate func(index int, item T) bool) (*T, bool)

Example:Run

import (
    "fmt"
    "github.com/duke-git/lancet/v2/slice"
)

func main() {
    nums := []int{1, 2, 3, 4, 5}

    isEven := func(i, num int) bool {
        return num%2 == 0
    }

    result, ok := slice.Find(nums, isEven)

    fmt.Println(*result)
    fmt.Println(ok)

    // Output:
    // 2
    // true
}

FindBy

Iterates over elements of slice, returning the first one that passes a truth test on predicate function.If return T is nil or zero value then no items matched the predicate func. In contrast to Find or FindLast, its return value no longer requires dereferencing.

Signature:

func FindBy[T any](slice []T, predicate func(index int, item T) bool) (v T, ok bool)

Example:Run

import (
    "fmt"
    "github.com/duke-git/lancet/v2/slice"
)

func main() {
    nums := []int{1, 2, 3, 4, 5}

    isEven := func(i, num int) bool {
        return num%2 == 0
    }

    result, ok := slice.FindBy(nums, isEven)

    fmt.Println(result)
    fmt.Println(ok)

    // Output:
    // 2
    // true
}

FindLast(deprecated: use FindLastBy)

iterates over elements of slice from end to begin, returning the last one that passes a truth test on function.

Signature:

func FindLast[T any](slice []T, predicate func(index int, item T) bool) (*T, bool)

Example:Run

import (
    "fmt"
    "github.com/duke-git/lancet/v2/slice"
)

func main() {
    nums := []int{1, 2, 3, 4, 5}

    isEven := func(i, num int) bool {
        return num%2 == 0
    }

    result, ok := slice.FindLast(nums, isEven)

    fmt.Println(*result)
    fmt.Println(ok)

    // Output:
    // 4
    // true
}

FindLastBy

FindLastBy iterates over elements of slice, returning the last one that passes a truth test on predicate function. If return T is nil or zero value then no items matched the predicate func. In contrast to Find or FindLast, its return value no longer requires dereferencing.

Signature:

func FindLastBy[T any](slice []T, predicate func(index int, item T) bool) (v T, ok bool)

Example:Run

import (
    "fmt"
    "github.com/duke-git/lancet/v2/slice"
)

func main() {
    nums := []int{1, 2, 3, 4, 5}

    isEven := func(i, num int) bool {
        return num%2 == 0
    }

    result, ok := slice.FindLastBy(nums, isEven)

    fmt.Println(result)
    fmt.Println(ok)

    // Output:
    // 4
    // true
}

Flatten

Flatten slice with one level.

Signature:

func Flatten(slice any) any

Example:Run

import (
    "fmt"
    "github.com/duke-git/lancet/v2/slice"
)

func main() {
    arrs := [][][]string{{{"a", "b"}}, {{"c", "d"}}}

    result := slice.Flatten(arrs)

    fmt.Println(result)

    // Output:
    // [[a b] [c d]]
}

FlattenDeep

flattens slice recursive.

Signature:

func FlattenDeep(slice any) any

Example:Run

import (
    "fmt"
    "github.com/duke-git/lancet/v2/slice"
)

func main() {
    arrs := [][][]string{{{"a", "b"}}, {{"c", "d"}}}

    result := slice.FlattenDeep(arrs)

    fmt.Println(result)

    // Output:
    // [a b c d]
}

ForEach

Iterates over elements of slice and invokes function for each element.

Signature:

func ForEach[T any](slice []T, iteratee func(index int, item T))

Example:Run

import (
    "fmt"
    "github.com/duke-git/lancet/v2/slice"
)

func main() {
    nums := []int{1, 2, 3}

    var result []int
    addOne := func(_ int, v int) {
        result = append(result, v+1)
    }

    slice.ForEach(nums, addOne)

    fmt.Println(result)

    // Output:
    // [2 3 4]
}

ForEachWithBreak

Iterates over elements of slice and invokes function for each element, when iteratee return false, will break the for each loop.

Signature:

func ForEachWithBreak[T any](slice []T, iteratee func(index int, item T) bool)

Example:Run

import (
    "fmt"
    "github.com/duke-git/lancet/v2/slice"
)

func main() {
    numbers := []int{1, 2, 3, 4, 5}

    var sum int

    slice.ForEachWithBreak(numbers, func(_, n int) bool {
        if n > 3 {
            return false
        }
        sum += n
        return true
    })

    fmt.Println(sum)

    // Output:
    // 6
}

GroupBy

Iterates over elements of the slice, each element will be group by criteria, returns two slices.

Signature:

func GroupBy[T any](slice []T, groupFn func(index int, item T) bool) ([]T, []T)

Example:Run

import (
    "fmt"
    "github.com/duke-git/lancet/v2/slice"
)

func main() {
    nums := []int{1, 2, 3, 4, 5}

    isEven := func(i, num int) bool {
        return num%2 == 0
    }

    even, odd := slice.GroupBy(nums, isEven)

    fmt.Println(even)
    fmt.Println(odd)

    // Output:
    // [2 4]
    // [1 3 5]
}

GroupWith

Return a map composed of keys generated from the results of running each element of slice thru iteratee.

Signature:

func GroupWith[T any, U comparable](slice []T, iteratee func(T) U) map[U][]T

Example:Run

import (
    "fmt"
    "github.com/duke-git/lancet/v2/slice"
)

func main() {
    nums := []float64{6.1, 4.2, 6.3}

    floor := func(num float64) float64 {
        return math.Floor(num)
    }

    result := slice.GroupWith(nums, floor) //map[float64][]float64

    fmt.Println(result)

    // Output:
    // map[4:[4.2] 6:[6.1 6.3]]
}

IntSlice (Deprecated: use generic feature of go1.18+ for replacement)

Convert interface slice to int slice.

Signature:

func IntSlice(slice any) []int

Example:Run

import (
    "fmt"
    "github.com/duke-git/lancet/v2/slice"
)

func main() {
    nums := []interface{}{1, 2, 3}

    result := slice.IntSlice(nums) //[]int{1, 2, 3}
    fmt.Println(result)

    // Output:
    // [1 2 3]
}

InterfaceSlice (Deprecated: use generic feature of go1.18+ for replacement)

Convert value to interface slice.

Signature:

func InterfaceSlice(slice any) []any

Example:Run

import (
    "fmt"
    "github.com/duke-git/lancet/v2/slice"
)

func main() {
    strs := []string{"a", "b", "c"}

    result := slice.InterfaceSlice(strs) //[]interface{}{"a", "b", "c"}
    fmt.Println(result)

    // Output:
    // [a b c]
}

Intersection

Creates a slice of unique values that included by all slices.

Signature:

func Intersection[T comparable](slices ...[]T) []T

Example:Run

import (
    "fmt"
    "github.com/duke-git/lancet/v2/slice"
)

func main() {
    nums1 := []int{1, 2, 3}
    nums2 := []int{2, 3, 4}

    result := slice.Intersection(nums1, nums2)

    fmt.Println(result)

    // Output:
    // [2 3]
}

InsertAt

insert the element into slice at index.

Signature:

func InsertAt[T any](slice []T, index int, value any) []T

Example:Run

import (
    "fmt"
    "github.com/duke-git/lancet/v2/slice"
)

func main() {
    result1 := slice.InsertAt([]string{"a", "b", "c"}, 0, "1")
    result2 := slice.InsertAt([]string{"a", "b", "c"}, 1, "1")
    result3 := slice.InsertAt([]string{"a", "b", "c"}, 2, "1")
    result4 := slice.InsertAt([]string{"a", "b", "c"}, 3, "1")
    result5 := slice.InsertAt([]string{"a", "b", "c"}, 0, []string{"1", "2", "3"})

    fmt.Println(result1)
    fmt.Println(result2)
    fmt.Println(result3)
    fmt.Println(result4)
    fmt.Println(result5)

    // Output:
    // [1 a b c]
    // [a 1 b c]
    // [a b 1 c]
    // [a b c 1]
    // [1 2 3 a b c]
}

IndexOf

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

Signature:

func IndexOf[T comparable](slice []T, item T) int

Example:Run

import (
    "fmt"
    "github.com/duke-git/lancet/v2/slice"
)

func main() {
    strs := []string{"a", "a", "b", "c"}

    result1 := slice.IndexOf(strs, "a")
    result2 := slice.IndexOf(strs, "d")

    fmt.Println(result1)
    fmt.Println(result2)

    // Output:
    // 0
    // -1
}

LastIndexOf

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

Signature:

func LastIndexOf[T comparable](slice []T, item T) int

Example:Run

import (
    "fmt"
    "github.com/duke-git/lancet/v2/slice"
)

func main() {
    strs := []string{"a", "a", "b", "c"}

    result1 := slice.LastIndexOf(strs, "a")
    result2 := slice.LastIndexOf(strs, "d")

    fmt.Println(result1)
    fmt.Println(result2)

    // Output:
    // 1
    // -1
}

Map

Creates an slice of values by running each element in slice thru function.

Signature:

func Map[T any, U any](slice []T, iteratee func(index int, item T) U) []U

Example:Run

import (
    "fmt"
    "github.com/duke-git/lancet/v2/slice"
)

func main() {
    nums := []int{1, 2, 3}

    addOne := func(_ int, v int) int {
        return v + 1
    }

    result := slice.Map(nums, addOne)

    fmt.Println(result)

    // Output:
    // [2 3 4]
}

FilterMap

Returns a slice which apply both filtering and mapping to the given slice. iteratee callback function should returntwo values: 1, mapping result. 2, whether the result element should be included or not.

Signature:

func FilterMap[T any, U any](slice []T, iteratee func(index int, item T) (U, bool)) []U

Example:Run

import (
    "fmt"
    "github.com/duke-git/lancet/v2/slice"
)

func main() {
    nums := []int{1, 2, 3, 4, 5}

    getEvenNumStr := func(i, num int) (string, bool) {
        if num%2 == 0 {
            return strconv.FormatInt(int64(num), 10), true
        }
        return "", false
    }

    result := slice.FilterMap(nums, getEvenNumStr)

    fmt.Printf("%#v", result)

    // Output:
    // []string{"2", "4"}
}

FlatMap

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

Signature:

func FlatMap[T any, U any](slice []T, iteratee func(index int, item T) []U) []U

Example:Run

import (
    "fmt"
    "github.com/duke-git/lancet/v2/slice"
)

func main() {
    nums := []int{1, 2, 3, 4}

    result := slice.FlatMap(nums, func(i int, num int) []string {
        s := "hi-" + strconv.FormatInt(int64(num), 10)
        return []string{s}
    })

    fmt.Printf("%#v", result)

    // Output:
    // []string{"hi-1", "hi-2", "hi-3", "hi-4"}
}

Merge

Merge all given slices into one slice.

Signature:

func Merge[T any](slices ...[]T) []T

Example:Run

import (
    "fmt"
    "github.com/duke-git/lancet/v2/slice"
)

func main() {
    nums1 := []int{1, 2, 3}
    nums2 := []int{3, 4}

    result := slice.Merge(nums1, nums2)

    fmt.Println(result)

    // Output:
    // [1 2 3 3 4]
}

Reverse

Reverse the elements order in slice.

Signature:

func Reverse[T any](slice []T)

Example:Run

import (
    "fmt"
    "github.com/duke-git/lancet/v2/slice"
)

func main() {
    strs := []string{"a", "b", "c", "d"}

    slice.Reverse(strs)

    fmt.Println(strs)

    // Output:
    // [d c b a]
}

Reduce

Reduce slice.(Deprecated: use ReduceBy)

Signature:

func Reduce[T any](slice []T, iteratee func(index int, item1, item2 T) T, initial T) T

Example:Run

import (
    "fmt"
    "github.com/duke-git/lancet/v2/slice"
)

func main() {
    nums := []int{1, 2, 3}

    sum := func(_ int, v1, v2 int) int {
        return v1 + v2
    }

    result := slice.Reduce(nums, sum, 0)

    fmt.Println(result)

    // Output:
    // 6
}

ReduceBy

Produces a value from slice by accumulating the result of each element as passed through the reducer function.

Signature:

func ReduceBy[T any, U any](slice []T, initial U, reducer func(index int, item T, agg U) U) U

Example:Run

import (
    "fmt"
    "github.com/duke-git/lancet/v2/slice"
)

func main() {
    result1 := slice.ReduceBy([]int{1, 2, 3, 4}, 0, func(_ int, item int, agg int) int {
        return agg + item
    })

    result2 := slice.ReduceBy([]int{1, 2, 3, 4}, "", func(_ int, item int, agg string) string {
        return agg + fmt.Sprintf("%v", item)
    })

    fmt.Println(result1)
    fmt.Println(result2)

    // Output:
    // 10
    // 1234
}

ReduceRight

ReduceRight is like ReduceBy, but it iterates over elements of slice from right to left.

Signature:

func ReduceRight[T any, U any](slice []T, initial U, reducer func(index int, item T, agg U) U) U

Example:Run

import (
    "fmt"
    "github.com/duke-git/lancet/v2/slice"
)

func main() {
    result := slice.ReduceRight([]int{1, 2, 3, 4}, "", func(_ int, item int, agg string) string {
        return agg + fmt.Sprintf("%v", item)
    })

    fmt.Println(result)

    // Output:
    // 4321
}

Replace

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

Signature:

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

Example:Run

import (
    "fmt"
    "github.com/duke-git/lancet/v2/slice"
)

func main() {
    strs := []string{"a", "b", "c", "a"}

    result1 := slice.Replace(strs, "a", "x", 0)
    result2 := slice.Replace(strs, "a", "x", 1)
    result3 := slice.Replace(strs, "a", "x", 2)
    result4 := slice.Replace(strs, "a", "x", 3)
    result5 := slice.Replace(strs, "a", "x", -1)

    fmt.Println(result1)
    fmt.Println(result2)
    fmt.Println(result3)
    fmt.Println(result4)
    fmt.Println(result5)

    // Output:
    // [a b c a]
    // [x b c a]
    // [x b c x]
    // [x b c x]
    // [x b c x]
}

ReplaceAll

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

Signature:

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

Example:Run

import (
    "fmt"
    "github.com/duke-git/lancet/v2/slice"
)

func main() {
    result := slice.ReplaceAll([]string{"a", "b", "c", "a"}, "a", "x")

    fmt.Println(result)

    // Output:
    // [x b c x]
}

Repeat

Creates a slice with length n whose elements are passed param item.

Signature:

func Repeat[T any](item T, n int) []T

Example:Run

import (
    "fmt"
    "github.com/duke-git/lancet/v2/slice"
)

func main() {
    result := slice.Repeat("a", 3)

    fmt.Println(result)

    // Output:
    // [a a a]
}

Shuffle

Creates an slice of shuffled values.

Signature:

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

Example:Run

import (
    "fmt"
    "github.com/duke-git/lancet/v2/slice"
)

func main() {
    nums := []int{1, 2, 3, 4, 5}
    result := slice.Shuffle(nums)

    fmt.Println(res)

    // Output:
    // [3 1 5 4 2] (random order)
}

IsAscending

Checks if a slice is ascending order.

Signature:

func IsAscending[T constraints.Ordered](slice []T) bool

Example:Run

import (
    "fmt"
    "github.com/duke-git/lancet/v2/slice"
)

func main() {
    result1 := slice.IsAscending([]int{1, 2, 3, 4, 5})
    result2 := slice.IsAscending([]int{5, 4, 3, 2, 1})
    result3 := slice.IsAscending([]int{2, 1, 3, 4, 5})

    fmt.Println(result1)
    fmt.Println(result2)
    fmt.Println(result3)

    // Output:
    // true
    // false
    // false
}

IsDescending

Checks if a slice is descending order.

Signature:

func IsDescending[T constraints.Ordered](slice []T) bool

Example:Run

import (
    "fmt"
    "github.com/duke-git/lancet/v2/slice"
)

func main() {
    result1 := slice.IsDescending([]int{5, 4, 3, 2, 1})
    result2 := slice.IsDescending([]int{1, 2, 3, 4, 5})
    result3 := slice.IsDescending([]int{2, 1, 3, 4, 5})

    fmt.Println(result1)
    fmt.Println(result2)
    fmt.Println(result3)

    // Output:
    // true
    // false
    // false
}

IsSorted

Checks if a slice is sorted (ascending or descending).

Signature:

func IsSorted[T constraints.Ordered](slice []T) bool

Example:Run

import (
    "fmt"
    "github.com/duke-git/lancet/v2/slice"
)

func main() {
    result1 := slice.IsSorted([]int{5, 4, 3, 2, 1})
    result2 := slice.IsSorted([]int{1, 2, 3, 4, 5})
    result3 := slice.IsSorted([]int{2, 1, 3, 4, 5})

    fmt.Println(result1)
    fmt.Println(result2)
    fmt.Println(result3)

    // Output:
    // true
    // true
    // false
}

IsSortedByKey

Checks if a slice is sorted by iteratee function.

Signature:

func IsSortedByKey[T any, K constraints.Ordered](slice []T, iteratee func(item T) K) bool

Example:Run

import (
    "fmt"
    "github.com/duke-git/lancet/v2/slice"
)

func main() {
    result1 := slice.IsSortedByKey([]string{"a", "ab", "abc"}, func(s string) int {
        return len(s)
    })
    result2 := slice.IsSortedByKey([]string{"abc", "ab", "a"}, func(s string) int {
        return len(s)
    })
    result3 := slice.IsSortedByKey([]string{"abc", "a", "ab"}, func(s string) int {
        return len(s)
    })

    fmt.Println(result1)
    fmt.Println(result2)
    fmt.Println(result3)

    // Output:
    // true
    // true
    // false
}

Sort

Sorts a slice of any ordered type(number or string), use quick sort algrithm. Default sort order is ascending (asc), if want descending order, set param `sortOrder` to `desc`. Ordered type: number(all ints uints floats) or string.

Signature:

func Sort[T constraints.Ordered](slice []T, sortOrder ...string)

Example:Run

import (
    "fmt"
    "github.com/duke-git/lancet/v2/slice"
)

func main() {
    numbers := []int{1, 4, 3, 2, 5}

    slice.Sort(numbers)
    fmt.Println(numbers) // [1 2 3 4 5]

    slice.Sort(numbers, "desc")
    fmt.Println(numbers) // [5 4 3 2 1]

    strings := []string{"a", "d", "c", "b", "e"}

    slice.Sort(strings)
    fmt.Println(strings) //[a b c d e}

    slice.Sort(strings, "desc")
    fmt.Println(strings) //[e d c b a]
}

SortBy

Sorts the slice in ascending order as determined by the less function. This sort is not guaranteed to be stable.

Signature:

func SortBy[T any](slice []T, less func(a, b T) bool)

Example:Run

import (
    "fmt"
    "github.com/duke-git/lancet/v2/slice"
)

func main() {
    numbers := []int{1, 4, 3, 2, 5}

    slice.SortBy(numbers, func(a, b int) bool {
        return a < b
    })
    fmt.Println(numbers) // [1 2 3 4 5]

    type User struct {
        Name string
        Age  uint
    }

    users := []User{
        {Name: "a", Age: 21},
        {Name: "b", Age: 15},
        {Name: "c", Age: 100}}

    slice.SortBy(users, func(a, b User) bool {
        return a.Age < b.Age
    })

    fmt.Printf("sort users by age: %v", users)

    // output
    // [{b 15} {a 21} {c 100}]
}

SortByField

Sort struct slice by field. Slice element should be struct, `field` param type should be int, uint, string, or bool. Default sort type is ascending (asc), if descending order, set `sortType` param to desc.

Signature:

func SortByField(slice any, field string, sortType ...string) error

Example:Run

import (
    "fmt"
    "github.com/duke-git/lancet/v2/slice"
)

func main() {
    type User struct {
        Name string
        Age  uint
    }

    users := []User{
        {Name: "a", Age: 21},
        {Name: "b", Age: 15},
        {Name: "c", Age: 100}}

    err := slice.SortByField(users, "Age", "desc")
    if err != nil {
        return
    }

    fmt.Println(users)

    // Output:
    // [{c 100} {a 21} {b 15}]
}

Some

Return true if any of the values in the list pass the predicate function.

Signature:

func Some[T any](slice []T, predicate func(index int, item T) bool) bool

Example:Run

import (
    "fmt"
    "github.com/duke-git/lancet/v2/slice"
)

func main() {
    nums := []int{1, 2, 3, 5}

    isEven := func(i, num int) bool {
        return num%2 == 0
    }

    result := slice.Some(nums, isEven)

    fmt.Println(result)

    // Output:
    // true
}

StringSlice (Deprecated: use generic feature of go1.18+ for replacement)

Convert interface slice to string slice.

Signature:

func StringSlice(slice any) []string

Example:Run

import (
    "fmt"
    "github.com/duke-git/lancet/v2/slice"
)

func main() {
    strs := []interface{}{"a", "b", "c"}

    result := slice.StringSlice(strs) //[]string{"a", "b", "c"}
    fmt.Println(result)

    // Output:
    // [a b c]
}

SymmetricDifference

Create a slice whose element is in given slices, but not in both slices.

Signature:

func SymmetricDifference[T comparable](slices ...[]T) []T

Example:Run

import (
    "fmt"
    "github.com/duke-git/lancet/v2/slice"
)

func main() {
    nums1 := []int{1, 2, 3}
    nums2 := []int{1, 2, 4}

    result := slice.SymmetricDifference(nums1, nums2)

    fmt.Println(result)

    // Output:
    // [3 4]
}

ToSlice

Creates a slice of give items.

Signature:

func ToSlice[T any](items ...T) []T

Example:Run

import (
    "fmt"
    "github.com/duke-git/lancet/v2/slice"
)

func main() {
    result := slice.ToSlice("a", "b", "c")

    fmt.Println(result)

    // Output:
    // [a b c]
}

ToSlicePointer

Returns a pointer to the slices of a variable parameter transformation

Signature:

func ToSlicePointer[T any](items ...T) []*T

Example:Run

import (
    "fmt"
    "github.com/duke-git/lancet/v2/slice"
)

func main() {
    str1 := "a"
    str2 := "b"

    result := slice.ToSlicePointer(str1, str2)

    expect := []*string{&str1, &str2}

    isEqual := reflect.DeepEqual(result, expect)

    fmt.Println(isEqual)

    // Output:
    // true
}

Unique

Remove duplicate elements in slice.

Signature:

func Unique[T comparable](slice []T) []T

Example:Run

import (
    "fmt"
    "github.com/duke-git/lancet/v2/slice"
)

func main() {
    result := slice.Unique([]string{"a", "a", "b"})
    fmt.Println(result)

    // Output:
    // [a b]
}

UniqueBy

Call iteratee func with every item of slice, then remove duplicated.

Signature:

func UniqueBy[T comparable](slice []T, iteratee func(item T) T) []T

Example:Run

import (
    "fmt"
    "github.com/duke-git/lancet/slice"
)

func main() {
    nums := []int{1, 2, 3, 4, 5, 6}
    result := slice.UniqueBy(nums, func(val int) int {
        return val % 3
    })

    fmt.Println(result)

    // Output:
    // [1 2 0]
}

Union

Creates a slice of unique values, in order, from all given slices. using == for equality comparisons.

Signature:

func Union[T comparable](slices ...[]T) []T

Example:Run

import (
    "fmt"
    "github.com/duke-git/lancet/v2/slice"
)

func main() {
    nums1 := []int{1, 3, 4, 6}
    nums2 := []int{1, 2, 5, 6}

    result := slice.Union(nums1, nums2)

    fmt.Println(result)

    // Output:
    // [1 3 4 6 2 5]
}

UnionBy

UnionBy is like Union, what's more it accepts iteratee which is invoked for each element of each slice.

Signature:

func UnionBy[T any, V comparable](predicate func(item T) V, slices ...[]T) []T

Example:Run

import (
    "fmt"
    "github.com/duke-git/lancet/v2/slice"
)

func main() {
    nums := []int{1, 2, 3, 4}

    divideTwo := func(n int) int {
        return n / 2
    }
    result := slice.UnionBy(divideTwo, nums)

    fmt.Println(result)

    // Output:
    // [1 2 4]
}

UpdateAt

Update the slice element at index. if param index < 0 or index <= len(slice), will return error.

Signature:

func UpdateAt[T any](slice []T, index int, value T) []T

Example:Run

import (
    "fmt"
    "github.com/duke-git/lancet/v2/slice"
)

func main() {
    result1 := slice.UpdateAt([]string{"a", "b", "c"}, -1, "1")
    result2 := slice.UpdateAt([]string{"a", "b", "c"}, 0, "1")
    result3 := slice.UpdateAt([]string{"a", "b", "c"}, 1, "1")
    result4 := slice.UpdateAt([]string{"a", "b", "c"}, 2, "1")
    result5 := slice.UpdateAt([]string{"a", "b", "c"}, 3, "1")

    fmt.Println(result1)
    fmt.Println(result2)
    fmt.Println(result3)
    fmt.Println(result4)
    fmt.Println(result5)

    // Output:
    // [a b c]
    // [1 b c]
    // [a 1 c]
    // [a b 1]
    // [a b c]
}

Without

Creates a slice excluding all given items.

Signature:

func Without[T comparable](slice []T, items ...T) []T

Example:Run

import (
    "fmt"
    "github.com/duke-git/lancet/v2/slice"
)

func main() {
    result := slice.Without([]int{1, 2, 3, 4}, 1, 2)

    fmt.Println(result)

    // Output:
    // [3 4]
}

KeyBy

Converts a slice to a map based on a callback function.

Signature:

func KeyBy[T any, U comparable](slice []T, iteratee func(item T) U) map[U]T

Example:Run

import (
    "fmt"
    "github.com/duke-git/lancet/v2/slice"
)

func main() {
    result := slice.KeyBy([]string{"a", "ab", "abc"}, func(str string) int {
        return len(str)
    })

    fmt.Println(result)

    // Output:
    // map[1:a 2:ab 3:abc]
}

Join

Join the slice item with specify separator.

Signature:

func Join[T any](s []T, separator string) string

Example:Run

import (
    "fmt"
    "github.com/duke-git/lancet/v2/slice"
)

func main() {
    nums := []int{1, 2, 3, 4, 5}

    result1 := slice.Join(nums, ",")
    result2 := slice.Join(nums, "-")

    fmt.Println(result1)
    fmt.Println(result2)

    // Output:
    // 1,2,3,4,5
    // 1-2-3-4-5
}

Partition

Partition all slice elements with the evaluation of the given predicate functions.

Signature:

func Partition[T any](slice []T, predicates ...func(item T) bool) [][]T

Example:Run

import (
    "fmt"
    "github.com/duke-git/lancet/v2/slice"
)

func main() {
    nums := []int{1, 2, 3, 4, 5}

    result1 := slice.Partition(nums)
    result2 := slice.Partition(nums, func(n int) bool { return n%2 == 0 })
    result3 := slice.Partition(nums, func(n int) bool { return n == 1 || n == 2 }, func(n int) bool { return n == 2 || n == 3 || n == 4 })

    fmt.Println(result1)
    fmt.Println(result2)
    fmt.Println(result3)

    // Output:
    // [[1 2 3 4 5]]
    // [[2 4] [1 3 5]]
    // [[1 2] [3 4] [5]]
}

Random

Random get a random item of slice, return idx=-1 when slice is empty.

Signature:

func Random[T any](slice []T) (val T, idx int)

Example:Run

import (
    "fmt"
    "github.com/duke-git/lancet/v2/slice"
)

func main() {
    nums := []int{1, 2, 3, 4, 5}

    val, idx := slice.Random(nums)
    if idx >= 0 && idx < len(nums) && slice.Contain(nums, val) {
        fmt.Println("okk")
    }
    // Output:
    // okk
}

SetToDefaultIf

Sets elements to their default value if they match the given predicate. It retains the positions of the elements in the slice. It returns slice of T and the count of modified slice items

Signature:

func SetToDefaultIf[T any](slice []T, predicate func(T) bool) ([]T, int)

Example:Run

import (
    "fmt"
    "github.com/duke-git/lancet/v2/slice"
)

func main() {
    strs := []string{"a", "b", "a", "c", "d", "a"}
	modifiedStrs, count := slice.SetToDefaultIf(strs, func(s string) bool { return "a" == s })
	
    fmt.Println(modifiedStrs)
	fmt.Println(count)
	
    // Output:
	// [ b  c d ]
	// 3
}

Break

Splits a slice into two based on a predicate function. It starts appending to the second slice after the first element that matches the predicate. All elements after the first match are included in the second slice, regardless of whether they match the predicate or not.

Signature:

func Break[T any](values []T, predicate func(T) bool) ([]T, []T)

Example:Run

import (
    "fmt"
    "github.com/duke-git/lancet/v2/slice"
)

func main() {
    nums := []int{1, 2, 3, 4, 5}
    even := func(n int) bool { return n%2 == 0 }

    resultEven, resultAfterFirstEven := slice.Break(nums, even)
    
    fmt.Println(resultEven)
    fmt.Println(resultAfterFirstEven)
    
    // Output:
    // [1]
    // [2 3 4 5]
}

RightPadding

RightPadding adds padding to the right end of a slice.

Signature:

func RightPadding[T any](slice []T, paddingValue T, paddingLength int) []T

Example:Run

import (
    "fmt"
    "github.com/duke-git/lancet/v2/slice"
)

func main() {
  	nums := []int{1, 2, 3, 4, 5}
	padded := slice.RightPadding(nums, 0, 3)
	fmt.Println(padded)
	// Output:
	// [1 2 3 4 5 0 0 0]
}

LeftPadding

LeftPadding adds padding to the left begin of a slice.

Signature:

func LeftPadding[T any](slice []T, paddingValue T, paddingLength int) []T

Example:Run

import (
    "fmt"
    "github.com/duke-git/lancet/v2/slice"
)

func main() {
  	nums := []int{1, 2, 3, 4, 5}
	padded := slice.LeftPadding(nums, 0, 3)
	fmt.Println(padded)
	// Output:
	// [0 0 0 1 2 3 4 5]
}

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Slice

Source:

Usage:

Index

Documentation

AppendIfAbsent

Contain

ContainBy

ContainSubSlice

Chunk

Compact

Concat

Count

CountBy

Difference

DifferenceBy

DifferenceWith

DeleteAt

DeleteRange

Drop

DropRight

DropWhile

DropRightWhile

Equal

EqualWith

Every

Filter

Find(deprecated: use FindBy)

FindBy

FindLast(deprecated: use FindLastBy)

FindLastBy

Flatten

FlattenDeep

ForEach

ForEachWithBreak

GroupBy

GroupWith

IntSlice (Deprecated: use generic feature of go1.18+ for replacement)

InterfaceSlice (Deprecated: use generic feature of go1.18+ for replacement)

Intersection

InsertAt

IndexOf

LastIndexOf

Map

FilterMap

FlatMap

Merge

Reverse

Reduce

ReduceBy

ReduceRight

Replace

ReplaceAll

Repeat

Shuffle

IsAscending

IsDescending

IsSorted

IsSortedByKey

Sort

SortBy

SortByField

Some

StringSlice (Deprecated: use generic feature of go1.18+ for replacement)

SymmetricDifference

ToSlice

ToSlicePointer

Unique

UniqueBy

Union

UnionBy

UpdateAt

Without

KeyBy