feat: add ForEachConcurrent

slice/slice_concurrent.go

@@ -8,6 +8,47 @@ import (
 	"sync"
 )
 
+// ForEachConcurrent applies the iteratee function to each item in the slice concurrently.
+// Play: todo
+func ForEachConcurrent[T any](slice []T, iteratee func(index int, item T), numThreads int) {
+	sliceLen := len(slice)
+	if sliceLen == 0 {
+		return
+	}
+
+	if numThreads <= 0 {
+		numThreads = 1
+	}
+
+	var wg sync.WaitGroup
+
+	chunkSize := (sliceLen + numThreads - 1) / numThreads
+
+	for i := 0; i < numThreads; i++ {
+		start := i * chunkSize
+		end := start + chunkSize
+
+		if start >= sliceLen {
+			break
+		}
+
+		if end > sliceLen {
+			end = sliceLen
+		}
+
+		wg.Add(1)
+		go func(start, end int) {
+			defer wg.Done()
+
+			for j := start; j < end; j++ {
+				iteratee(j, slice[j])
+			}
+		}(start, end)
+	}
+
+	wg.Wait()
+}
+
 // MapConcurrent applies the iteratee function to each item in the slice concurrently.
 // Play: todo
 func MapConcurrent[T any, U any](slice []T, iteratee func(index int, item T) U, numThreads int) []U {

slice/slice_example_test.go

@@ -429,6 +429,23 @@ func ExampleForEach() {
 	// [2 3 4]
 }
 
+func ExampleForEachConcurrent() {
+	nums := []int{1, 2, 3, 4, 5, 6, 7, 8}
+
+	result := make([]int, len(nums))
+
+	addOne := func(index int, value int) {
+		result[index] = value + 1
+	}
+
+	ForEachConcurrent(nums, addOne, 4)
+
+	fmt.Println(result)
+
+	// Output:
+	// [2 3 4 5 6 7 8 9]
+}
+
 func ExampleForEachWithBreak() {
 	numbers := []int{1, 2, 3, 4, 5}
 

slice/slice_test.go

@@ -410,6 +410,73 @@ func TestForEach(t *testing.T) {
 	assert.Equal([]int{3, 4, 5, 6, 7}, result)
 }
 
+func TestForEachConcurrent(t *testing.T) {
+	t.Parallel()
+
+	assert := internal.NewAssert(t, "TestForEachConcurrent")
+
+	t.Run("single thread", func(t *testing.T) {
+		numbers := []int{1, 2, 3, 4, 5, 6, 7, 8, 9}
+		result := make([]int, len(numbers))
+
+		addOne := func(index int, value int) {
+			result[index] = value + 1
+		}
+
+		ForEachConcurrent(numbers, addOne, 1)
+
+		expected := []int{2, 3, 4, 5, 6, 7, 8, 9, 10}
+		assert.Equal(expected, result)
+	})
+
+	t.Run("normal", func(t *testing.T) {
+		numbers := []int{1, 2, 3, 4, 5, 6, 7, 8, 9}
+		result := make([]int, len(numbers))
+
+		addOne := func(index int, value int) {
+			result[index] = value + 1
+		}
+
+		ForEachConcurrent(numbers, addOne, 4)
+
+		expected := []int{2, 3, 4, 5, 6, 7, 8, 9, 10}
+		assert.Equal(expected, result)
+	})
+
+	t.Run("negative threads", func(t *testing.T) {
+		numbers := []int{1, 2, 3, 4, 5, 6, 7, 8, 9}
+		result := make([]int, len(numbers))
+
+		addOne := func(index int, value int) {
+			result[index] = value + 1
+		}
+
+		ForEachConcurrent(numbers, addOne, -4)
+
+		expected := []int{2, 3, 4, 5, 6, 7, 8, 9, 10}
+		assert.Equal(expected, result)
+	})
+
+	t.Run("high number threads", func(t *testing.T) {
+		numbers := make([]int, 1000)
+		for i := range numbers {
+			numbers[i] = i
+		}
+
+		result := make([]int, len(numbers))
+
+		addOne := func(index int, value int) {
+			result[index] = value + 1
+		}
+
+		ForEachConcurrent(numbers, addOne, 50)
+
+		for i, item := range numbers {
+			assert.Equal(item+1, result[i])
+		}
+	})
+}
+
 func TestForEachWithBreak(t *testing.T) {
 	t.Parallel()