diff --git a/list.cpp b/list.cpp
index 937e7a7..009ed9a 100644
--- a/list.cpp
+++ b/list.cpp
@@ -4,6 +4,7 @@
  */
 
 #include <cstdio>
+#include <iostream>
 #include <cstdlib>
 
 template <typename T>
@@ -34,6 +35,15 @@ List<T> *append(List<T> *lst, T value)
   return lst;
 }
 
+template <typename T>
+std::ostream& operator<<(std::ostream& ostream, const List<T> *lst)
+{
+  if (lst == NULL)
+    return ostream;
+  ostream << "|" << lst->value << lst->next;
+  return ostream;
+}
+
 int main(void)
 {
   return 0;