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.gitignore vendored
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@ -60,7 +60,3 @@ Temporary Items
docs/public
.trivycache/
.vscode/launch.json
.claude
AGENTS.md
bench*txt
ACTION_PLAN.md

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@ -1,25 +0,0 @@
---
title: "DropWhile"
date: 2025-01-16T00:00:00-00:00
---
`DropWhile` drops elements from the beginning of the slice while the predicate returns true. It returns the remaining elements starting from the first element where the predicate returns false.
```go
package main
import (
"fmt"
u "github.com/rjNemo/underscore"
)
func main() {
nums := []int{1, 2, 3, 4, 5, 6, 7, 8, 9}
lessThan5 := func(n int) bool { return n < 5 }
fmt.Println(u.DropWhile(nums, lessThan5)) // [5, 6, 7, 8, 9]
words := []string{"apple", "banana", "cherry", "date"}
shortWords := func(s string) bool { return len(s) < 6 }
fmt.Println(u.DropWhile(words, shortWords)) // ["banana", "cherry", "date"]
}
```

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@ -1,31 +0,0 @@
---
title: "First"
date: 2025-01-16T00:00:00-00:00
---
`First` returns the first element of the slice. Returns an error if the slice is empty.
```go
package main
import (
"fmt"
u "github.com/rjNemo/underscore"
)
func main() {
nums := []int{1, 2, 3, 4, 5}
first, err := u.First(nums)
if err != nil {
panic(err)
}
fmt.Println(first) // 1
// Handle empty slice
empty := []int{}
_, err = u.First(empty)
if err != nil {
fmt.Println("Error:", err) // Error: underscore: empty slice
}
}
```

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@ -1,23 +0,0 @@
---
title: "FirstN"
date: 2025-01-16T00:00:00-00:00
---
`FirstN` returns the first n elements of the slice. If n is greater than the slice length, returns the entire slice. If n is less than or equal to 0, returns an empty slice.
```go
package main
import (
"fmt"
u "github.com/rjNemo/underscore"
)
func main() {
nums := []int{1, 2, 3, 4, 5, 6, 7, 8, 9}
fmt.Println(u.FirstN(nums, 3)) // [1, 2, 3]
fmt.Println(u.FirstN(nums, 0)) // []
fmt.Println(u.FirstN(nums, 10)) // [1, 2, 3, 4, 5, 6, 7, 8, 9]
fmt.Println(u.FirstN(nums, -5)) // []
}
```

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@ -1,39 +0,0 @@
---
title: "FoldRight"
date: 2025-01-16T00:00:00-00:00
---
`FoldRight` is like Reduce but processes elements from right to left. Also known as foldr in Haskell. Important for non-associative operations where the order of evaluation matters.
```go
package main
import (
"fmt"
u "github.com/rjNemo/underscore"
)
func main() {
// Subtraction is non-associative
nums := []int{1, 2, 3}
// FoldRight: 1 - (2 - (3 - 0)) = 1 - (2 - 3) = 1 - (-1) = 2
result := u.FoldRight(nums, 0, func(n, acc int) int { return n - acc })
fmt.Println(result) // 2
// Compare with Reduce (left fold): (0 - 1) - 2 - 3 = -6
leftResult := u.Reduce(nums, func(n, acc int) int { return acc - n }, 0)
fmt.Println(leftResult) // -6
// Building a list in order
buildList := u.FoldRight(nums, []int{}, func(n int, acc []int) []int {
return append([]int{n}, acc...)
})
fmt.Println(buildList) // [1, 2, 3]
// String concatenation
words := []string{"a", "b", "c"}
concat := u.FoldRight(words, "", func(s, acc string) string { return s + acc })
fmt.Println(concat) // "abc"
}
```

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@ -1,32 +0,0 @@
---
title: "Init"
date: 2025-01-16T00:00:00-00:00
---
`Init` returns all elements except the last one, and the last element separately. Returns an empty slice and zero value if the input slice is empty. Useful for destructuring lists from the right.
```go
package main
import (
"fmt"
u "github.com/rjNemo/underscore"
)
func main() {
nums := []int{1, 2, 3, 4, 5}
init, last := u.Init(nums)
fmt.Println(init) // [1, 2, 3, 4]
fmt.Println(last) // 5
// Single element
single, val := u.Init([]int{42})
fmt.Println(single) // []
fmt.Println(val) // 42
// Empty slice
empty, zero := u.Init([]int{})
fmt.Println(empty) // []
fmt.Println(zero) // 0
}
```

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@ -1,28 +0,0 @@
---
title: "Intersperse"
date: 2025-01-16T00:00:00-00:00
---
`Intersperse` inserts a separator between each element of the slice. Returns an empty slice if the input is empty. Returns the original element if the input has only one element.
```go
package main
import (
"fmt"
u "github.com/rjNemo/underscore"
)
func main() {
nums := []int{1, 2, 3, 4, 5}
fmt.Println(u.Intersperse(nums, 0)) // [1, 0, 2, 0, 3, 0, 4, 0, 5]
// Useful for formatting
words := []string{"apple", "banana", "cherry"}
fmt.Println(u.Intersperse(words, ",")) // ["apple", ",", "banana", ",", "cherry"]
// Single element - no separator added
single := []int{42}
fmt.Println(u.Intersperse(single, 0)) // [42]
}
```

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@ -3,26 +3,19 @@ title: "Last"
date: 2022-03-21T13:46:24-04:00
---
`Last` returns the last element of the slice. Panics if the slice is empty with a clear error message.
`Last` returns the last element of the slice.
```go
package main
import (
"fmt"
u "github.com/rjNemo/underscore"
"fmt"
u "github.com/rjNemo/underscore"
)
func main() {
nums := []int{1, 9, 2, 8, 3, 7, 4, 6, 5}
fmt.Println(u.Last(nums)) // 5
nums := []int{1, 9, 2, 8, 3, 7, 4, 6, 5}
// Single element
single := []int{42}
fmt.Println(u.Last(single)) // 42
// Empty slice panics with clear message
// empty := []int{}
// u.Last(empty) // panic: underscore.Last: empty slice
fmt.Println(u.Last(nums)) // 5
}
```

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@ -1,51 +0,0 @@
---
title: "ParallelReduce"
date: 2025-01-16T00:00:00-00:00
---
`ParallelReduce` applies a reduction function in parallel using a worker pool. The operation must be associative and commutative for correct results. If workers <= 0, defaults to GOMAXPROCS. On error, the first error is returned and processing is canceled.
**Note:** This is an experimental function. Order of operations is not guaranteed, so use only with associative and commutative operations (like addition, multiplication, min, max).
```go
package main
import (
"context"
"fmt"
"time"
u "github.com/rjNemo/underscore"
)
func main() {
nums := []int{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}
ctx := context.Background()
// Parallel sum (safe - addition is associative and commutative)
result, err := u.ParallelReduce(ctx, nums, 4, func(ctx context.Context, n int, acc int) (int, error) {
// Simulate expensive computation
time.Sleep(10 * time.Millisecond)
return n + acc, nil
}, 0)
if err != nil {
panic(err)
}
fmt.Println(result) // Result will vary due to parallel execution
// With context cancellation
ctx, cancel := context.WithTimeout(context.Background(), 50*time.Millisecond)
defer cancel()
_, err = u.ParallelReduce(ctx, nums, 4, func(ctx context.Context, n int, acc int) (int, error) {
time.Sleep(100 * time.Millisecond)
return n + acc, nil
}, 0)
if err != nil {
fmt.Println("Operation was cancelled:", err)
}
}
```
**Warning:** Do not use ParallelReduce for non-associative operations like subtraction or division, as the results will be unpredictable due to parallel execution order.

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@ -1,43 +0,0 @@
---
title: "Replicate"
date: 2025-01-16T00:00:00-00:00
---
`Replicate` creates a slice containing count copies of value. Returns an empty slice if count is less than or equal to 0. Useful for initialization and testing.
```go
package main
import (
"fmt"
u "github.com/rjNemo/underscore"
)
func main() {
// Basic usage
fmt.Println(u.Replicate(3, "hello"))
// ["hello", "hello", "hello"]
// Numbers
fmt.Println(u.Replicate(5, 0))
// [0, 0, 0, 0, 0]
// Zero count
fmt.Println(u.Replicate(0, 42))
// []
// Negative count
fmt.Println(u.Replicate(-5, "x"))
// []
// Use case: initialize with default values
defaultScores := u.Replicate(10, 100)
fmt.Println(defaultScores)
// [100, 100, 100, 100, 100, 100, 100, 100, 100, 100]
// Use case: creating separators
separator := u.Replicate(40, "-")
fmt.Println(u.Reduce(separator, func(s, acc string) string { return acc + s }, ""))
// ----------------------------------------
}
```

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@ -1,37 +0,0 @@
---
title: "Scan"
date: 2025-01-16T00:00:00-00:00
---
`Scan` is like Reduce but returns all intermediate accumulator values. Also known as prefix scan or cumulative fold. Useful for tracking running totals, running maximums, or other cumulative operations.
```go
package main
import (
"fmt"
u "github.com/rjNemo/underscore"
)
func main() {
// Running sum
nums := []int{1, 2, 3, 4}
add := func(acc, n int) int { return acc + n }
fmt.Println(u.Scan(nums, 0, add)) // [1, 3, 6, 10]
// Running maximum
values := []int{3, 1, 4, 1, 5, 9, 2}
max := func(acc, n int) int {
if n > acc {
return n
}
return acc
}
fmt.Println(u.Scan(values, 0, max)) // [3, 3, 4, 4, 5, 9, 9]
// String concatenation
words := []string{"hello", "world", "!"}
concat := func(acc, s string) string { return acc + s }
fmt.Println(u.Scan(words, "", concat)) // ["hello", "helloworld", "helloworld!"]
}
```

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@ -1,43 +0,0 @@
---
title: "Sliding"
date: 2025-01-16T00:00:00-00:00
---
`Sliding` creates a sliding window view of the slice with the specified window size. Returns an empty slice if size is less than or equal to 0 or greater than the slice length. Useful for moving averages, n-grams, and pattern matching.
```go
package main
import (
"fmt"
u "github.com/rjNemo/underscore"
)
func main() {
nums := []int{1, 2, 3, 4, 5}
fmt.Println(u.Sliding(nums, 3)) // [[1, 2, 3], [2, 3, 4], [3, 4, 5]]
// Size 2
fmt.Println(u.Sliding(nums, 2)) // [[1, 2], [2, 3], [3, 4], [4, 5]]
// N-grams for text
words := []string{"the", "quick", "brown", "fox"}
bigrams := u.Sliding(words, 2)
fmt.Println(bigrams) // [["the", "quick"], ["quick", "brown"], ["brown", "fox"]]
// Moving average example
data := []int{10, 20, 30, 40, 50}
windows := u.Sliding(data, 3)
for _, window := range windows {
sum := 0
for _, v := range window {
sum += v
}
avg := sum / len(window)
fmt.Printf("Window: %v, Average: %d\n", window, avg)
}
// Window: [10 20 30], Average: 20
// Window: [20 30 40], Average: 30
// Window: [30 40 50], Average: 40
}
```

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@ -1,25 +0,0 @@
---
title: "TakeWhile"
date: 2025-01-16T00:00:00-00:00
---
`TakeWhile` returns elements from the beginning of the slice while the predicate returns true. It stops at the first element where the predicate returns false.
```go
package main
import (
"fmt"
u "github.com/rjNemo/underscore"
)
func main() {
nums := []int{1, 2, 3, 4, 5, 6, 7, 8, 9}
lessThan5 := func(n int) bool { return n < 5 }
fmt.Println(u.TakeWhile(nums, lessThan5)) // [1, 2, 3, 4]
words := []string{"apple", "banana", "cherry", "date"}
shortWords := func(s string) bool { return len(s) < 6 }
fmt.Println(u.TakeWhile(words, shortWords)) // ["apple"]
}
```

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@ -1,47 +0,0 @@
---
title: "Tap"
date: 2025-01-16T00:00:00-00:00
---
`Tap` applies a function to each element for side effects (like debugging or logging) and returns the original slice unchanged. Useful for debugging pipelines without breaking the flow.
```go
package main
import (
"fmt"
u "github.com/rjNemo/underscore"
)
func main() {
// Debugging a pipeline
nums := []int{1, 2, 3, 4, 5}
result := u.Tap(
u.Map(
u.Filter(nums, func(n int) bool { return n%2 == 0 }),
func(n int) int { return n * 2 },
),
func(n int) {
fmt.Printf("Debug: %d\n", n) // Prints each value
},
)
fmt.Println(result) // [4, 8]
// Counting elements that pass through
count := 0
filtered := u.Tap(
u.Filter(nums, func(n int) bool { return n > 2 }),
func(n int) { count++ },
)
fmt.Printf("Found %d elements: %v\n", count, filtered)
// Found 3 elements: [3 4 5]
// Logging transformations
data := []string{"hello", "world"}
u.Tap(data, func(s string) {
fmt.Printf("Processing: %s\n", s)
})
}
```

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@ -1,45 +0,0 @@
---
title: "Transpose"
date: 2025-01-16T00:00:00-00:00
---
`Transpose` flips a matrix over its diagonal, swapping rows and columns. Returns an empty slice if the input is empty. Assumes all rows have the same length (uses the length of the first row).
```go
package main
import (
"fmt"
u "github.com/rjNemo/underscore"
)
func main() {
// 2x3 matrix becomes 3x2 matrix
matrix := [][]int{
{1, 2, 3},
{4, 5, 6},
}
transposed := u.Transpose(matrix)
fmt.Println(transposed)
// [[1, 4], [2, 5], [3, 6]]
// Square matrix
square := [][]int{
{1, 2},
{3, 4},
}
fmt.Println(u.Transpose(square))
// [[1, 3], [2, 4]]
// Use case: converting rows to columns for processing
data := [][]string{
{"Name", "Age", "City"},
{"Alice", "30", "NYC"},
{"Bob", "25", "LA"},
}
byColumn := u.Transpose(data)
fmt.Println("Names:", byColumn[0]) // [Name Alice Bob]
fmt.Println("Ages:", byColumn[1]) // [Age 30 25]
fmt.Println("Cities:", byColumn[2]) // [City NYC LA]
}
```

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@ -1,43 +0,0 @@
---
title: "Unzip"
date: 2025-01-16T00:00:00-00:00
---
`Unzip` splits a slice of tuples into two separate slices. The inverse operation of Zip. Useful for separating paired data.
```go
package main
import (
"fmt"
u "github.com/rjNemo/underscore"
)
func main() {
// Basic usage
pairs := []u.Tuple[int, string]{
{Left: 1, Right: "a"},
{Left: 2, Right: "b"},
{Left: 3, Right: "c"},
}
nums, letters := u.Unzip(pairs)
fmt.Println(nums) // [1, 2, 3]
fmt.Println(letters) // ["a", "b", "c"]
// Use case: separating keys and values
keyValuePairs := []u.Tuple[string, int]{
{Left: "apple", Right: 5},
{Left: "banana", Right: 3},
{Left: "cherry", Right: 8},
}
items, counts := u.Unzip(keyValuePairs)
fmt.Println("Items:", items) // Items: [apple banana cherry]
fmt.Println("Counts:", counts) // Counts: [5 3 8]
// Empty slice
emptyNums, emptyStrs := u.Unzip([]u.Tuple[int, string]{})
fmt.Println(emptyNums, emptyStrs) // [] []
}
```

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@ -1,15 +0,0 @@
package underscore
// DropWhile drops elements from the beginning of the slice while the predicate returns true.
// It returns the remaining elements starting from the first element where the predicate returns false.
func DropWhile[T any](values []T, predicate func(T) bool) []T {
for i, v := range values {
if !predicate(v) {
res := make([]T, len(values)-i)
copy(res, values[i:])
return res
}
}
// All elements satisfy predicate, return empty slice
return []T{}
}

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@ -1,55 +0,0 @@
package underscore_test
import (
"testing"
"github.com/stretchr/testify/assert"
u "github.com/rjNemo/underscore"
)
func TestDropWhile(t *testing.T) {
nums := []int{1, 2, 3, 4, 5, 6, 7, 8, 9}
result := u.DropWhile(nums, func(n int) bool { return n < 5 })
assert.Equal(t, []int{5, 6, 7, 8, 9}, result)
}
func TestDropWhileEmpty(t *testing.T) {
result := u.DropWhile([]int{}, func(n int) bool { return n < 5 })
assert.Equal(t, []int{}, result)
}
func TestDropWhileNoneMatch(t *testing.T) {
nums := []int{5, 6, 7, 8, 9}
result := u.DropWhile(nums, func(n int) bool { return n < 5 })
assert.Equal(t, []int{5, 6, 7, 8, 9}, result)
}
func TestDropWhileAllMatch(t *testing.T) {
nums := []int{1, 2, 3, 4}
result := u.DropWhile(nums, func(n int) bool { return n < 10 })
assert.Equal(t, []int{}, result)
}
func TestDropWhileSingleElement(t *testing.T) {
result := u.DropWhile([]int{5}, func(n int) bool { return n < 10 })
assert.Equal(t, []int{}, result)
}
func TestDropWhileStrings(t *testing.T) {
words := []string{"apple", "banana", "cherry", "date"}
result := u.DropWhile(words, func(s string) bool { return len(s) < 6 })
assert.Equal(t, []string{"banana", "cherry", "date"}, result)
}
func BenchmarkDropWhile(b *testing.B) {
nums := make([]int, 1000)
for i := range nums {
nums[i] = i
}
b.ResetTimer()
for i := 0; i < b.N; i++ {
u.DropWhile(nums, func(n int) bool { return n < 500 })
}
}

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@ -1,33 +0,0 @@
package underscore
import "errors"
// ErrEmptySlice is returned when trying to get the first element of an empty slice
var ErrEmptySlice = errors.New("underscore: empty slice")
// First returns the first element of the slice.
// Returns an error if the slice is empty.
func First[T any](values []T) (T, error) {
var zero T
if len(values) == 0 {
return zero, ErrEmptySlice
}
return values[0], nil
}
// FirstN returns the first n elements of the slice.
// If n is greater than the slice length, returns the entire slice.
// If n is less than or equal to 0, returns an empty slice.
func FirstN[T any](values []T, n int) []T {
if n <= 0 {
return []T{}
}
if n >= len(values) {
res := make([]T, len(values))
copy(res, values)
return res
}
res := make([]T, n)
copy(res, values[:n])
return res
}

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@ -1,97 +0,0 @@
package underscore_test
import (
"errors"
"testing"
"github.com/stretchr/testify/assert"
u "github.com/rjNemo/underscore"
)
func TestFirst(t *testing.T) {
nums := []int{1, 2, 3, 4, 5}
result, err := u.First(nums)
assert.NoError(t, err)
assert.Equal(t, 1, result)
}
func TestFirstEmpty(t *testing.T) {
_, err := u.First([]int{})
assert.Error(t, err)
assert.True(t, errors.Is(err, u.ErrEmptySlice))
}
func TestFirstSingleElement(t *testing.T) {
result, err := u.First([]int{42})
assert.NoError(t, err)
assert.Equal(t, 42, result)
}
func TestFirstStrings(t *testing.T) {
words := []string{"hello", "world"}
result, err := u.First(words)
assert.NoError(t, err)
assert.Equal(t, "hello", result)
}
func TestFirstN(t *testing.T) {
nums := []int{1, 2, 3, 4, 5}
result := u.FirstN(nums, 3)
assert.Equal(t, []int{1, 2, 3}, result)
}
func TestFirstNEmpty(t *testing.T) {
result := u.FirstN([]int{}, 3)
assert.Equal(t, []int{}, result)
}
func TestFirstNZero(t *testing.T) {
nums := []int{1, 2, 3}
result := u.FirstN(nums, 0)
assert.Equal(t, []int{}, result)
}
func TestFirstNNegative(t *testing.T) {
nums := []int{1, 2, 3}
result := u.FirstN(nums, -5)
assert.Equal(t, []int{}, result)
}
func TestFirstNGreaterThanLength(t *testing.T) {
nums := []int{1, 2, 3}
result := u.FirstN(nums, 10)
assert.Equal(t, []int{1, 2, 3}, result)
}
func TestFirstNSingleElement(t *testing.T) {
result := u.FirstN([]int{42}, 1)
assert.Equal(t, []int{42}, result)
}
func TestFirstNAll(t *testing.T) {
nums := []int{1, 2, 3}
result := u.FirstN(nums, 3)
assert.Equal(t, []int{1, 2, 3}, result)
}
func BenchmarkFirst(b *testing.B) {
nums := []int{1, 2, 3, 4, 5}
b.ResetTimer()
for i := 0; i < b.N; i++ {
_, _ = u.First(nums)
}
}
func BenchmarkFirstN(b *testing.B) {
nums := make([]int, 1000)
for i := range nums {
nums[i] = i
}
b.ResetTimer()
for i := 0; i < b.N; i++ {
u.FirstN(nums, 100)
}
}

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@ -1,14 +0,0 @@
package underscore
// FoldRight is like Reduce but processes elements from right to left.
// Also known as foldr in Haskell.
//
// Example: FoldRight([]int{1,2,3}, 0, func(n, acc int) int { return n - acc })
//
// → 1 - (2 - (3 - 0)) = 1 - (2 - 3) = 1 - (-1) = 2
func FoldRight[T, P any](values []T, acc P, fn func(T, P) P) P {
for i := len(values) - 1; i >= 0; i-- {
acc = fn(values[i], acc)
}
return acc
}

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@ -1,80 +0,0 @@
package underscore_test
import (
"testing"
"github.com/stretchr/testify/assert"
u "github.com/rjNemo/underscore"
)
func TestFoldRight(t *testing.T) {
nums := []int{1, 2, 3, 4}
result := u.FoldRight(nums, 0, func(n, acc int) int { return n + acc })
assert.Equal(t, 10, result)
}
func TestFoldRightEmpty(t *testing.T) {
result := u.FoldRight([]int{}, 42, func(n, acc int) int { return n + acc })
assert.Equal(t, 42, result)
}
func TestFoldRightSingleElement(t *testing.T) {
result := u.FoldRight([]int{5}, 0, func(n, acc int) int { return n + acc })
assert.Equal(t, 5, result)
}
func TestFoldRightSubtraction(t *testing.T) {
// FoldRight: 1 - (2 - (3 - 0)) = 1 - (2 - 3) = 1 - (-1) = 2
nums := []int{1, 2, 3}
result := u.FoldRight(nums, 0, func(n, acc int) int { return n - acc })
assert.Equal(t, 2, result)
}
func TestFoldRightDivision(t *testing.T) {
// FoldRight with float: 2.0 / (4.0 / (8.0 / 1.0)) = 2.0 / (4.0 / 8.0) = 2.0 / 0.5 = 4.0
nums := []float64{2.0, 4.0, 8.0}
result := u.FoldRight(nums, 1.0, func(n, acc float64) float64 { return n / acc })
assert.Equal(t, 4.0, result)
}
func TestFoldRightStrings(t *testing.T) {
words := []string{"a", "b", "c"}
result := u.FoldRight(words, "", func(s, acc string) string { return s + acc })
assert.Equal(t, "abc", result)
}
func TestFoldRightVsReduce(t *testing.T) {
nums := []int{1, 2, 3}
// Reduce (left fold): (0 - 1) - 2 - 3 = -6
reduceResult := u.Reduce(nums, func(n, acc int) int { return acc - n }, 0)
assert.Equal(t, -6, reduceResult)
// FoldRight: 1 - (2 - (3 - 0)) = 1 - (2 - 3) = 1 - (-1) = 2
foldRightResult := u.FoldRight(nums, 0, func(n, acc int) int { return n - acc })
assert.Equal(t, 2, foldRightResult)
// They should be different for non-associative operations
assert.NotEqual(t, reduceResult, foldRightResult)
}
func TestFoldRightBuildList(t *testing.T) {
nums := []int{1, 2, 3}
result := u.FoldRight(nums, []int{}, func(n int, acc []int) []int {
return append([]int{n}, acc...)
})
assert.Equal(t, []int{1, 2, 3}, result)
}
func BenchmarkFoldRight(b *testing.B) {
nums := make([]int, 1000)
for i := range nums {
nums[i] = i
}
b.ResetTimer()
for i := 0; i < b.N; i++ {
u.FoldRight(nums, 0, func(n, acc int) int { return n + acc })
}
}

18
init.go
View file

@ -1,18 +0,0 @@
package underscore
// Init returns all elements except the last one, and the last element separately.
// Returns an empty slice and zero value if the input slice is empty.
// Also known as "uncons from the right" or "snoc" inverse.
func Init[T any](values []T) ([]T, T) {
var last T
if len(values) == 0 {
return []T{}, last
}
if len(values) == 1 {
return []T{}, values[0]
}
res := make([]T, len(values)-1)
copy(res, values[:len(values)-1])
return res, values[len(values)-1]
}

View file

@ -1,65 +0,0 @@
package underscore_test
import (
"testing"
"github.com/stretchr/testify/assert"
u "github.com/rjNemo/underscore"
)
func TestInit(t *testing.T) {
nums := []int{1, 2, 3, 4, 5}
init, last := u.Init(nums)
assert.Equal(t, []int{1, 2, 3, 4}, init)
assert.Equal(t, 5, last)
}
func TestInitEmpty(t *testing.T) {
init, last := u.Init([]int{})
assert.Equal(t, []int{}, init)
assert.Equal(t, 0, last)
}
func TestInitSingleElement(t *testing.T) {
init, last := u.Init([]int{42})
assert.Equal(t, []int{}, init)
assert.Equal(t, 42, last)
}
func TestInitTwoElements(t *testing.T) {
init, last := u.Init([]int{1, 2})
assert.Equal(t, []int{1}, init)
assert.Equal(t, 2, last)
}
func TestInitStrings(t *testing.T) {
words := []string{"hello", "world", "!"}
init, last := u.Init(words)
assert.Equal(t, []string{"hello", "world"}, init)
assert.Equal(t, "!", last)
}
func TestInitDoesNotMutate(t *testing.T) {
original := []int{1, 2, 3, 4, 5}
init, last := u.Init(original)
// Modify returned slice
init[0] = 999
// Original should be unchanged
assert.Equal(t, 1, original[0])
assert.Equal(t, 5, last)
}
func BenchmarkInit(b *testing.B) {
nums := make([]int, 1000)
for i := range nums {
nums[i] = i
}
b.ResetTimer()
for i := 0; i < b.N; i++ {
u.Init(nums)
}
}

View file

@ -1,23 +0,0 @@
package underscore
// Intersperse inserts a separator between each element of the slice.
// Returns an empty slice if the input is empty.
// Returns the original element if the input has only one element.
//
// Example: Intersperse([]int{1,2,3}, 0) → [1, 0, 2, 0, 3]
func Intersperse[T any](values []T, separator T) []T {
if len(values) == 0 {
return []T{}
}
if len(values) == 1 {
return []T{values[0]}
}
// Result will have len(values) + (len(values)-1) elements
res := make([]T, 0, len(values)*2-1)
res = append(res, values[0])
for i := 1; i < len(values); i++ {
res = append(res, separator, values[i])
}
return res
}

View file

@ -1,60 +0,0 @@
package underscore_test
import (
"testing"
"github.com/stretchr/testify/assert"
u "github.com/rjNemo/underscore"
)
func TestIntersperse(t *testing.T) {
nums := []int{1, 2, 3, 4, 5}
result := u.Intersperse(nums, 0)
assert.Equal(t, []int{1, 0, 2, 0, 3, 0, 4, 0, 5}, result)
}
func TestIntersperseEmpty(t *testing.T) {
result := u.Intersperse([]int{}, 0)
assert.Equal(t, []int{}, result)
}
func TestIntersperseSingleElement(t *testing.T) {
result := u.Intersperse([]int{42}, 0)
assert.Equal(t, []int{42}, result)
}
func TestIntersperseTwoElements(t *testing.T) {
result := u.Intersperse([]int{1, 2}, 0)
assert.Equal(t, []int{1, 0, 2}, result)
}
func TestIntersperseStrings(t *testing.T) {
words := []string{"hello", "world", "!"}
result := u.Intersperse(words, ",")
assert.Equal(t, []string{"hello", ",", "world", ",", "!"}, result)
}
func TestIntersperseComma(t *testing.T) {
words := []string{"apple", "banana", "cherry"}
result := u.Intersperse(words, ",")
assert.Equal(t, []string{"apple", ",", "banana", ",", "cherry"}, result)
}
func TestIntersperseNegativeNumber(t *testing.T) {
nums := []int{1, 2, 3}
result := u.Intersperse(nums, -1)
assert.Equal(t, []int{1, -1, 2, -1, 3}, result)
}
func BenchmarkIntersperse(b *testing.B) {
nums := make([]int, 100)
for i := range nums {
nums[i] = i
}
b.ResetTimer()
for i := 0; i < b.N; i++ {
u.Intersperse(nums, 0)
}
}

View file

@ -1,10 +1,7 @@
package underscore
// Last returns the last element of the slice.
// Panics if the slice is empty.
// Last returns the last element of the slice
func Last[T any](values []T) T {
if len(values) == 0 {
panic("underscore.Last: empty slice")
}
return values[len(values)-1]
n := len(values)
return values[n-1]
}

View file

@ -53,7 +53,7 @@ func BenchmarkParallelMap(b *testing.B) {
b.Run(fmt.Sprintf("workers=%d", workers), func(b *testing.B) {
b.ResetTimer()
for i := 0; i < b.N; i++ {
_, _ = u.ParallelMap(ctx, data, workers, func(_ context.Context, n int) (int, error) {
u.ParallelMap(ctx, data, workers, func(_ context.Context, n int) (int, error) {
return n * 2, nil
})
}
@ -76,7 +76,7 @@ func BenchmarkMapVsParallelMap(b *testing.B) {
b.Run("ParallelMap", func(b *testing.B) {
for i := 0; i < b.N; i++ {
_, _ = u.ParallelMap(ctx, data, 0, func(_ context.Context, n int) (int, error) {
u.ParallelMap(ctx, data, 0, func(_ context.Context, n int) (int, error) {
return n * 2, nil
})
}

View file

@ -1,92 +0,0 @@
package underscore
import (
"context"
"runtime"
"sync"
)
// ParallelReduce applies a reduction function in parallel using a worker pool.
// The operation must be associative and commutative for correct results.
// If workers <= 0, defaults to GOMAXPROCS.
// On error, the first error is returned and processing is canceled.
//
// Note: Order of operations is not guaranteed, so use only with associative/commutative operations.
func ParallelReduce[T, P any](ctx context.Context, values []T, workers int, fn func(context.Context, T, P) (P, error), acc P) (P, error) {
if workers <= 0 {
workers = runtime.GOMAXPROCS(0)
}
if len(values) == 0 {
return acc, nil
}
type task struct {
idx int
val T
}
tasks := make(chan task)
results := make(chan P, len(values))
ctx, cancel := context.WithCancel(ctx)
defer cancel()
var wg sync.WaitGroup
var once sync.Once
var firstErr error
// Workers
wg.Add(workers)
for i := 0; i < workers; i++ {
go func() {
defer wg.Done()
for t := range tasks {
select {
case <-ctx.Done():
return
default:
}
result, err := fn(ctx, t.val, acc)
if err != nil {
once.Do(func() {
firstErr = err
cancel()
})
return
}
results <- result
}
}()
}
// Send tasks
go func() {
for i, v := range values {
select {
case <-ctx.Done():
close(tasks)
return
default:
tasks <- task{idx: i, val: v}
}
}
close(tasks)
}()
wg.Wait()
close(results)
if firstErr != nil {
return acc, firstErr
}
// Combine results
for result := range results {
// This is a simplified combination - in practice, you'd need a combiner function
acc = result
}
return acc, nil
}

View file

@ -1,171 +0,0 @@
package underscore_test
import (
"context"
"errors"
"testing"
"time"
"github.com/stretchr/testify/assert"
u "github.com/rjNemo/underscore"
)
func TestParallelReduce(t *testing.T) {
nums := []int{1, 2, 3, 4, 5}
ctx := context.Background()
// Note: This is a simplified test - ParallelReduce needs work for proper reduction
result, err := u.ParallelReduce(ctx, nums, 2, func(ctx context.Context, n int, acc int) (int, error) {
return n + acc, nil
}, 0)
assert.NoError(t, err)
// Result may vary due to parallel execution
assert.Greater(t, result, 0)
}
func TestParallelReduceEmpty(t *testing.T) {
ctx := context.Background()
result, err := u.ParallelReduce(ctx, []int{}, 2, func(ctx context.Context, n int, acc int) (int, error) {
return n + acc, nil
}, 42)
assert.NoError(t, err)
assert.Equal(t, 42, result)
}
func TestParallelReduceDefaultWorkers(t *testing.T) {
nums := []int{1, 2, 3, 4, 5}
ctx := context.Background()
// Test with workers <= 0 to use GOMAXPROCS
result, err := u.ParallelReduce(ctx, nums, 0, func(ctx context.Context, n int, acc int) (int, error) {
return n + acc, nil
}, 0)
assert.NoError(t, err)
assert.Greater(t, result, 0)
}
func TestParallelReduceNegativeWorkers(t *testing.T) {
nums := []int{1, 2, 3}
ctx := context.Background()
// Negative workers should default to GOMAXPROCS
result, err := u.ParallelReduce(ctx, nums, -1, func(ctx context.Context, n int, acc int) (int, error) {
return n + acc, nil
}, 0)
assert.NoError(t, err)
assert.Greater(t, result, 0)
}
func TestParallelReduceError(t *testing.T) {
nums := []int{1, 2, 3, 4, 5}
ctx := context.Background()
expectedErr := errors.New("processing error")
_, err := u.ParallelReduce(ctx, nums, 2, func(ctx context.Context, n int, acc int) (int, error) {
if n == 3 {
return 0, expectedErr
}
return n + acc, nil
}, 0)
assert.Error(t, err)
assert.Equal(t, expectedErr, err)
}
func TestParallelReduceContextCancellation(t *testing.T) {
nums := make([]int, 100)
for i := range nums {
nums[i] = i
}
ctx, cancel := context.WithCancel(context.Background())
// Cancel after a short delay
go func() {
time.Sleep(10 * time.Millisecond)
cancel()
}()
_, err := u.ParallelReduce(ctx, nums, 4, func(ctx context.Context, n int, acc int) (int, error) {
// Slow processing to allow cancellation
time.Sleep(5 * time.Millisecond)
select {
case <-ctx.Done():
return 0, ctx.Err()
default:
return n + acc, nil
}
}, 0)
// Should either complete or get cancelled
if err != nil {
assert.ErrorIs(t, err, context.Canceled)
}
}
func TestParallelReduceContextTimeout(t *testing.T) {
nums := make([]int, 20)
for i := range nums {
nums[i] = i
}
ctx, cancel := context.WithTimeout(context.Background(), 50*time.Millisecond)
defer cancel()
_, err := u.ParallelReduce(ctx, nums, 2, func(ctx context.Context, n int, acc int) (int, error) {
// Simulate slow work
time.Sleep(100 * time.Millisecond)
if ctx.Err() != nil {
return 0, ctx.Err()
}
return n + acc, nil
}, 0)
// Should timeout
if err != nil {
assert.ErrorIs(t, err, context.DeadlineExceeded)
}
}
func TestParallelReduceSingleElement(t *testing.T) {
ctx := context.Background()
result, err := u.ParallelReduce(ctx, []int{42}, 2, func(ctx context.Context, n int, acc int) (int, error) {
return n + acc, nil
}, 0)
assert.NoError(t, err)
assert.Greater(t, result, 0)
}
func TestParallelReduceManyWorkers(t *testing.T) {
nums := []int{1, 2, 3, 4, 5}
ctx := context.Background()
// More workers than elements
result, err := u.ParallelReduce(ctx, nums, 10, func(ctx context.Context, n int, acc int) (int, error) {
return n + acc, nil
}, 0)
assert.NoError(t, err)
assert.Greater(t, result, 0)
}
func BenchmarkParallelReduce(b *testing.B) {
nums := make([]int, 100)
for i := range nums {
nums[i] = i
}
ctx := context.Background()
b.ResetTimer()
for i := 0; i < b.N; i++ {
_, _ = u.ParallelReduce(ctx, nums, 4, func(ctx context.Context, n int, acc int) (int, error) {
return n + acc, nil
}, 0)
}
}

View file

@ -1,17 +0,0 @@
package underscore
// Replicate creates a slice containing count copies of value.
// Returns an empty slice if count is less than or equal to 0.
//
// Example: Replicate(3, "hello") → ["hello", "hello", "hello"]
func Replicate[T any](count int, value T) []T {
if count <= 0 {
return []T{}
}
res := make([]T, count)
for i := range res {
res[i] = value
}
return res
}

View file

@ -1,29 +0,0 @@
package underscore_test
import (
"testing"
"github.com/stretchr/testify/assert"
u "github.com/rjNemo/underscore"
)
func TestReplicate(t *testing.T) {
result := u.Replicate(3, "hello")
assert.Equal(t, []string{"hello", "hello", "hello"}, result)
}
func TestReplicateZero(t *testing.T) {
result := u.Replicate(0, 42)
assert.Equal(t, []int{}, result)
}
func TestReplicateNegative(t *testing.T) {
result := u.Replicate(-5, 42)
assert.Equal(t, []int{}, result)
}
func TestReplicateOne(t *testing.T) {
result := u.Replicate(1, 100)
assert.Equal(t, []int{100}, result)
}

18
scan.go
View file

@ -1,18 +0,0 @@
package underscore
// Scan is like Reduce but returns all intermediate accumulator values.
// Also known as prefix scan or cumulative fold.
//
// Example: Scan([]int{1,2,3,4}, 0, func(acc, n int) int { return acc + n }) → [1, 3, 6, 10]
func Scan[T, P any](values []T, acc P, fn func(P, T) P) []P {
if len(values) == 0 {
return []P{}
}
res := make([]P, 0, len(values))
for _, v := range values {
acc = fn(acc, v)
res = append(res, acc)
}
return res
}

View file

@ -1,68 +0,0 @@
package underscore_test
import (
"testing"
"github.com/stretchr/testify/assert"
u "github.com/rjNemo/underscore"
)
func TestScan(t *testing.T) {
nums := []int{1, 2, 3, 4}
result := u.Scan(nums, 0, func(acc, n int) int { return acc + n })
assert.Equal(t, []int{1, 3, 6, 10}, result)
}
func TestScanEmpty(t *testing.T) {
result := u.Scan([]int{}, 0, func(acc, n int) int { return acc + n })
assert.Equal(t, []int{}, result)
}
func TestScanSingleElement(t *testing.T) {
result := u.Scan([]int{5}, 0, func(acc, n int) int { return acc + n })
assert.Equal(t, []int{5}, result)
}
func TestScanMultiplication(t *testing.T) {
nums := []int{2, 3, 4}
result := u.Scan(nums, 1, func(acc, n int) int { return acc * n })
assert.Equal(t, []int{2, 6, 24}, result)
}
func TestScanStrings(t *testing.T) {
words := []string{"hello", "world", "!"}
result := u.Scan(words, "", func(acc, s string) string { return acc + s })
assert.Equal(t, []string{"hello", "helloworld", "helloworld!"}, result)
}
func TestScanMax(t *testing.T) {
nums := []int{3, 1, 4, 1, 5, 9, 2}
result := u.Scan(nums, 0, func(acc, n int) int {
if n > acc {
return n
}
return acc
})
assert.Equal(t, []int{3, 3, 4, 4, 5, 9, 9}, result)
}
func TestScanDifferentTypes(t *testing.T) {
nums := []int{1, 2, 3}
result := u.Scan(nums, 0.0, func(acc float64, n int) float64 {
return acc + float64(n)*2.5
})
assert.Equal(t, []float64{2.5, 7.5, 15.0}, result)
}
func BenchmarkScan(b *testing.B) {
nums := make([]int, 1000)
for i := range nums {
nums[i] = i
}
b.ResetTimer()
for i := 0; i < b.N; i++ {
u.Scan(nums, 0, func(acc, n int) int { return acc + n })
}
}

View file

@ -1,23 +0,0 @@
package underscore
// Sliding creates a sliding window view of the slice with the specified window size.
// Returns an empty slice if size is less than or equal to 0.
// Returns an empty slice if size is greater than the slice length.
//
// Example: Sliding([]int{1,2,3,4,5}, 3) → [[1,2,3], [2,3,4], [3,4,5]]
func Sliding[T any](values []T, size int) [][]T {
if size <= 0 || size > len(values) {
return [][]T{}
}
windowCount := len(values) - size + 1
res := make([][]T, 0, windowCount)
for i := 0; i <= len(values)-size; i++ {
window := make([]T, size)
copy(window, values[i:i+size])
res = append(res, window)
}
return res
}

View file

@ -1,90 +0,0 @@
package underscore_test
import (
"testing"
"github.com/stretchr/testify/assert"
u "github.com/rjNemo/underscore"
)
func TestSliding(t *testing.T) {
nums := []int{1, 2, 3, 4, 5}
result := u.Sliding(nums, 3)
expected := [][]int{{1, 2, 3}, {2, 3, 4}, {3, 4, 5}}
assert.Equal(t, expected, result)
}
func TestSlidingEmpty(t *testing.T) {
result := u.Sliding([]int{}, 3)
assert.Equal(t, [][]int{}, result)
}
func TestSlidingSizeOne(t *testing.T) {
nums := []int{1, 2, 3}
result := u.Sliding(nums, 1)
expected := [][]int{{1}, {2}, {3}}
assert.Equal(t, expected, result)
}
func TestSlidingSizeEqualLength(t *testing.T) {
nums := []int{1, 2, 3}
result := u.Sliding(nums, 3)
expected := [][]int{{1, 2, 3}}
assert.Equal(t, expected, result)
}
func TestSlidingSizeGreaterThanLength(t *testing.T) {
nums := []int{1, 2, 3}
result := u.Sliding(nums, 5)
assert.Equal(t, [][]int{}, result)
}
func TestSlidingSizeZero(t *testing.T) {
nums := []int{1, 2, 3}
result := u.Sliding(nums, 0)
assert.Equal(t, [][]int{}, result)
}
func TestSlidingSizeNegative(t *testing.T) {
nums := []int{1, 2, 3}
result := u.Sliding(nums, -1)
assert.Equal(t, [][]int{}, result)
}
func TestSlidingTwoElements(t *testing.T) {
nums := []int{1, 2, 3, 4}
result := u.Sliding(nums, 2)
expected := [][]int{{1, 2}, {2, 3}, {3, 4}}
assert.Equal(t, expected, result)
}
func TestSlidingStrings(t *testing.T) {
words := []string{"a", "b", "c", "d"}
result := u.Sliding(words, 2)
expected := [][]string{{"a", "b"}, {"b", "c"}, {"c", "d"}}
assert.Equal(t, expected, result)
}
func TestSlidingDoesNotMutate(t *testing.T) {
original := []int{1, 2, 3, 4}
result := u.Sliding(original, 2)
// Modify a window
result[0][0] = 999
// Original should be unchanged
assert.Equal(t, 1, original[0])
}
func BenchmarkSliding(b *testing.B) {
nums := make([]int, 100)
for i := range nums {
nums[i] = i
}
b.ResetTimer()
for i := 0; i < b.N; i++ {
u.Sliding(nums, 10)
}
}

View file

@ -1,17 +0,0 @@
package underscore
// TakeWhile returns elements from the beginning of the slice while the predicate returns true.
// It stops at the first element where the predicate returns false.
func TakeWhile[T any](values []T, predicate func(T) bool) []T {
for i, v := range values {
if !predicate(v) {
res := make([]T, i)
copy(res, values[:i])
return res
}
}
// All elements satisfy predicate
res := make([]T, len(values))
copy(res, values)
return res
}

View file

@ -1,55 +0,0 @@
package underscore_test
import (
"testing"
"github.com/stretchr/testify/assert"
u "github.com/rjNemo/underscore"
)
func TestTakeWhile(t *testing.T) {
nums := []int{1, 2, 3, 4, 5, 6, 7, 8, 9}
result := u.TakeWhile(nums, func(n int) bool { return n < 5 })
assert.Equal(t, []int{1, 2, 3, 4}, result)
}
func TestTakeWhileEmpty(t *testing.T) {
result := u.TakeWhile([]int{}, func(n int) bool { return n < 5 })
assert.Equal(t, []int{}, result)
}
func TestTakeWhileNoneMatch(t *testing.T) {
nums := []int{5, 6, 7, 8, 9}
result := u.TakeWhile(nums, func(n int) bool { return n < 5 })
assert.Equal(t, []int{}, result)
}
func TestTakeWhileAllMatch(t *testing.T) {
nums := []int{1, 2, 3, 4}
result := u.TakeWhile(nums, func(n int) bool { return n < 10 })
assert.Equal(t, []int{1, 2, 3, 4}, result)
}
func TestTakeWhileSingleElement(t *testing.T) {
result := u.TakeWhile([]int{5}, func(n int) bool { return n < 10 })
assert.Equal(t, []int{5}, result)
}
func TestTakeWhileStrings(t *testing.T) {
words := []string{"apple", "banana", "cherry", "date"}
result := u.TakeWhile(words, func(s string) bool { return len(s) < 6 })
assert.Equal(t, []string{"apple"}, result)
}
func BenchmarkTakeWhile(b *testing.B) {
nums := make([]int, 1000)
for i := range nums {
nums[i] = i
}
b.ResetTimer()
for i := 0; i < b.N; i++ {
u.TakeWhile(nums, func(n int) bool { return n < 500 })
}
}

12
tap.go
View file

@ -1,12 +0,0 @@
package underscore
// Tap applies a function to each element for side effects (like debugging/logging)
// and returns the original slice unchanged. Useful for debugging pipelines.
//
// Example: Tap([]int{1,2,3}, func(n int) { fmt.Println(n) }) → [1,2,3] (and prints each)
func Tap[T any](values []T, fn func(T)) []T {
for _, v := range values {
fn(v)
}
return values
}

View file

@ -1,22 +0,0 @@
package underscore_test
import (
"testing"
"github.com/stretchr/testify/assert"
u "github.com/rjNemo/underscore"
)
func TestTap(t *testing.T) {
nums := []int{1, 2, 3}
sum := 0
result := u.Tap(nums, func(n int) { sum += n })
assert.Equal(t, nums, result)
assert.Equal(t, 6, sum)
}
func TestTapEmpty(t *testing.T) {
result := u.Tap([]int{}, func(n int) {})
assert.Equal(t, []int{}, result)
}

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@ -1,25 +0,0 @@
package underscore
// Transpose flips a matrix over its diagonal, swapping rows and columns.
// Returns an empty slice if the input is empty.
// Assumes all rows have the same length (uses the length of the first row).
//
// Example: Transpose([[1,2,3], [4,5,6]]) → [[1,4], [2,5], [3,6]]
func Transpose[T any](matrix [][]T) [][]T {
if len(matrix) == 0 || len(matrix[0]) == 0 {
return [][]T{}
}
rows := len(matrix)
cols := len(matrix[0])
result := make([][]T, cols)
for i := range result {
result[i] = make([]T, rows)
for j := range matrix {
result[i][j] = matrix[j][i]
}
}
return result
}

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package underscore_test
import (
"testing"
"github.com/stretchr/testify/assert"
u "github.com/rjNemo/underscore"
)
func TestTranspose(t *testing.T) {
matrix := [][]int{{1, 2, 3}, {4, 5, 6}}
result := u.Transpose(matrix)
expected := [][]int{{1, 4}, {2, 5}, {3, 6}}
assert.Equal(t, expected, result)
}
func TestTransposeEmpty(t *testing.T) {
result := u.Transpose([][]int{})
assert.Equal(t, [][]int{}, result)
}
func TestTransposeSquare(t *testing.T) {
matrix := [][]int{{1, 2}, {3, 4}}
result := u.Transpose(matrix)
expected := [][]int{{1, 3}, {2, 4}}
assert.Equal(t, expected, result)
}

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package underscore
// Unzip splits a slice of tuples into two separate slices.
// The inverse operation of Zip.
//
// Example: Unzip([Tuple{1,"a"}, Tuple{2,"b"}]) → ([1,2], ["a","b"])
func Unzip[L, R any](pairs []Tuple[L, R]) ([]L, []R) {
if len(pairs) == 0 {
return []L{}, []R{}
}
lefts := make([]L, len(pairs))
rights := make([]R, len(pairs))
for i, pair := range pairs {
lefts[i] = pair.Left
rights[i] = pair.Right
}
return lefts, rights
}

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@ -1,26 +0,0 @@
package underscore_test
import (
"testing"
"github.com/stretchr/testify/assert"
u "github.com/rjNemo/underscore"
)
func TestUnzip(t *testing.T) {
pairs := []u.Tuple[int, string]{
{Left: 1, Right: "a"},
{Left: 2, Right: "b"},
{Left: 3, Right: "c"},
}
lefts, rights := u.Unzip(pairs)
assert.Equal(t, []int{1, 2, 3}, lefts)
assert.Equal(t, []string{"a", "b", "c"}, rights)
}
func TestUnzipEmpty(t *testing.T) {
lefts, rights := u.Unzip([]u.Tuple[int, string]{})
assert.Equal(t, []int{}, lefts)
assert.Equal(t, []string{}, rights)
}