支持Filter方法函数 (#104)

slicex/README.md

@@ -52,4 +52,7 @@ func SymmetricDiff(slices ...[]T) []T
 
 // Intersect 计算交集
 func Intersect(slices ...[]T) []T
+
+// Filter 返回符合 f 的元素组成的新切片
+func Filter(s []T, f func(T) bool) []T 
 ```

slicex/filter.go

@@ -0,0 +1,13 @@
+package slicex
+
+// Filter 返回符合 f 的元素组成的新切片
+func Filter[T any](s []T, f func(T) bool) []T {
+	// var result []T
+	result := make([]T, 0) // 保证不是 nil
+	for _, v := range s {
+		if f(v) {
+			result = append(result, v)
+		}
+	}
+	return result
+}

slicex/filter_example_test.go

@@ -0,0 +1,23 @@
+package slicex
+
+import (
+	"fmt"
+)
+
+func ExampleFilter() {
+	numbers := []int{1, 2, 3, 4, 5}
+	even := Filter(numbers, func(n int) bool {
+		return n%2 == 0
+	})
+	fmt.Println(even)
+
+	words := []string{"go", "java", "c", "python"}
+	longWords := Filter(words, func(s string) bool {
+		return len(s) > 2
+	})
+	fmt.Println(longWords)
+
+	// Output:
+	// [2 4]
+	// [java python]
+}

slicex/filter_test.go

@@ -0,0 +1,77 @@
+package slicex
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestFilter(t *testing.T) {
+	testCases := []struct {
+		name     string
+		input    []int
+		filterFn func(int) bool
+		want     []int
+	}{
+		{
+			name:     "filter even numbers",
+			input:    []int{1, 2, 3, 4, 5, 6},
+			filterFn: func(i int) bool { return i%2 == 0 },
+			want:     []int{2, 4, 6},
+		},
+		{
+			name:     "filter all",
+			input:    []int{1, 2, 3},
+			filterFn: func(i int) bool { return true },
+			want:     []int{1, 2, 3},
+		},
+		{
+			name:     "filter none",
+			input:    []int{1, 2, 3},
+			filterFn: func(i int) bool { return false },
+			want:     []int{},
+		},
+		{
+			name:     "empty input",
+			input:    []int{},
+			filterFn: func(i int) bool { return i > 0 },
+			want:     []int{},
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			got := Filter(tc.input, tc.filterFn)
+			assert.Equal(t, tc.want, got)
+		})
+	}
+}
+
+func TestFilterStrings(t *testing.T) {
+	testCases := []struct {
+		name     string
+		input    []string
+		filterFn func(string) bool
+		want     []string
+	}{
+		{
+			name:     "length > 2",
+			input:    []string{"go", "java", "c", "rust"},
+			filterFn: func(s string) bool { return len(s) > 2 },
+			want:     []string{"java", "rust"},
+		},
+		{
+			name:     "empty input",
+			input:    []string{},
+			filterFn: func(s string) bool { return len(s) > 0 },
+			want:     []string{},
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			got := Filter(tc.input, tc.filterFn)
+			assert.Equal(t, tc.want, got)
+		})
+	}
+}