init support Go 1.23 Iterators (#104)

iter.go

@@ -0,0 +1,28 @@
+//go:build go1.23
+// +build go1.23
+
+package gocitiesjson
+
+import "iter"
+
+func All() iter.Seq[*City] {
+	return func(yield func(*City) bool) {
+		for _, city := range Cities {
+			if !yield(city) {
+				return
+			}
+		}
+	}
+}
+
+func Filter(filter func(*City) bool) iter.Seq[*City] {
+	return func(yield func(*City) bool) {
+		for _, city := range Cities {
+			if filter(city) {
+				if !yield(city) {
+					return
+				}
+			}
+		}
+	}
+}

iter_test.go

@@ -0,0 +1,35 @@
+//go:build go1.23
+// +build go1.23
+
+package gocitiesjson_test
+
+import (
+	"fmt"
+
+	gocitiesjson "github.com/ringsaturn/go-cities.json"
+)
+
+func ExampleAll() {
+	c := 0
+	for city := range gocitiesjson.All() {
+		_ = city
+		c++
+	}
+	fmt.Println(c > 10000)
+	// Output: true
+}
+
+func ExampleFilter() {
+	c := 0
+
+	bboxFilter := func(city *gocitiesjson.City) bool {
+		return city.Lng > 0 && city.Lng < 10 && city.Lat > 0 && city.Lat < 10
+	}
+	for city := range gocitiesjson.Filter(bboxFilter) {
+		_ = city
+		c++
+	}
+
+	fmt.Println(c > 0)
+	// Output: true
+}