add iterable

iterable.cc

@@ -0,0 +1,23 @@
+#include <iostream>
+#include <memory>
+
+#include "main.h"
+
+int main() {
+	auto c1 = std::make_shared<Circle>(3.0);
+	auto c2 = std::make_shared<Circle>(5.0);
+	auto c3 = std::make_shared<Circle>(7.0);
+
+	c1->set_next(c2.get());
+	c2->set_next(c3.get());
+
+	std::cout << "Forward:\n";
+	for (auto& shape : c1->traverse<IShape::forward>()) {
+		shape.draw();
+	}
+
+	std::cout << "\nBackward:\n";
+	for (auto& shape : c1->traverse<IShape::backward>()) {
+		shape.draw();
+	}
+}