Merge pull request #15 from calvinbrown085/adding-map-filter

Adding MapFilter for transform and filter

slices/examples_test.go

@@ -118,6 +118,21 @@ func ExampleMap() {
 	// Output: [8 16 30 32 46 84]
 }
 
+func ExampleMapFilter() {
+	s := []int{4, 8, 15, 16, 23, 42}
+	isEven := func(t int) (string, bool) {
+		if t%2 == 0 {
+			s := fmt.Sprintf("%d", t)
+			return s, true
+		} else {
+			return "", false
+		}
+
+	}
+	doubled := slices.MapFilter(s, isEven)
+	fmt.Println(doubled)
+	// Output: [4 8 16 42]
+}
 func ExampleMapAsync() {
 	pages := slices.MapAsync(
 		[]string{"google.com", "go.dev", "golang.org"},

slices/slice_func.go

@@ -191,6 +191,18 @@ func Map[S ~[]T, T any, G any](items S, f func(el T) G) []G {
 	return result
 }
 
+// Map applies F to all elements in slice of T and returns slice results as pointers, and will filter out the non-nil ones.
+func MapFilter[S ~[]T, T any, G any](items S, f func(el T) (G, bool)) []G {
+	result := make([]G, 0, len(items))
+	for _, el := range items {
+		r, b := f(el)
+		if b {
+			result = append(result, r)
+		}
+	}
+	return result
+}
+
 // Reduce applies F to acc and every element in slice of T and returns acc
 func Reduce[S ~[]T, T any, G any](items S, acc G, f func(el T, acc G) G) G {
 	for _, el := range items {

slices/slice_func_test.go

@@ -1,6 +1,7 @@
 package slices_test
 
 import (
+	"fmt"
 	"testing"
 
 	"github.com/life4/genesis/slices"
@@ -164,6 +165,25 @@ func TestMap(t *testing.T) {
 	f([]int{1, 2, 3}, []int{2, 4, 6})
 }
 
+func TestMapFilter(t *testing.T) {
+	is := is.New(t)
+	f := func(given []int, expected []string) {
+		isEven := func(t int) (string, bool) {
+			if t%2 == 0 {
+				s := fmt.Sprintf("%d", t)
+				return s, true
+			} else {
+				return "", false
+			}
+
+		}
+		actual := slices.MapFilter(given, isEven)
+		is.Equal(expected, actual)
+	}
+	f([]int{}, []string{})
+	f([]int{1}, []string{})
+	f([]int{1, 2, 3, 4}, []string{"2", "4"})
+}
 func TestReduce(t *testing.T) {
 	is := is.New(t)
 	f := func(given []int, expected int) {