doc: add doc and examples for lom.Filter

Author: samber

README.md

@@ -334,10 +334,15 @@ Mutable: like `lo.Filter()`, but the slice is updated in place.
 import lom "github.com/samber/lo/mutable"
 
 list := []int{1, 2, 3, 4}
-lom.Filter(list, func(x int) bool {
+newList := lom.Filter(list, func(x int) bool {
     return x%2 == 0
 })
-// []int{2, 4, 6, 8}
+
+list
+// []int{2, 4, 3, 4}
+
+newList
+// []int{2, 4}
 ```
 
 ### Map

mutable/slice_example_test.go

@@ -2,6 +2,32 @@ package mutable
 
 import "fmt"
 
+func ExampleFilter() {
+	list := []int{1, 2, 3, 4}
+
+	newList := Filter(list, func(nbr int) bool {
+		return nbr%2 == 0
+	})
+
+	fmt.Printf("%v\n%v", list, newList)
+	// Output:
+	// [2 4 3 4]
+	// [2 4]
+}
+
+func ExampleFilterI() {
+	list := []int{1, 2, 3, 4}
+
+	newList := Filter(list, func(nbr int) bool {
+		return nbr%2 == 0
+	})
+
+	fmt.Printf("%v\n%v", list, newList)
+	// Output:
+	// [2 4 3 4]
+	// [2 4]
+}
+
 func ExampleMap() {
 	list := []int{1, 2, 3, 4}
 

mutable/slice_test.go

@@ -10,16 +10,20 @@ func TestFilter(t *testing.T) {
 	t.Parallel()
 	is := assert.New(t)
 
-	r1 := Filter([]int{1, 2, 3, 4}, func(x int) bool {
+	input1 := []int{1, 2, 3, 4}
+	r1 := Filter(input1, func(x int) bool {
 		return x%2 == 0
 	})
 
+	is.Equal(input1, []int{2, 4, 3, 4})
 	is.Equal(r1, []int{2, 4})
 
-	r2 := Filter([]string{"", "foo", "", "bar", ""}, func(x string) bool {
+	input2 := []string{"", "foo", "", "bar", ""}
+	r2 := Filter(input2, func(x string) bool {
 		return len(x) > 0
 	})
 
+	is.Equal(input2, []string{"foo", "bar", "", "bar", ""})
 	is.Equal(r2, []string{"foo", "bar"})
 }