1 files changed, 3 insertions, 0 deletions
diff --git a/number.h b/number.h
index e7eebb5..8489453 100644
--- a/number.h
+++ b/number.h
@@ -1,6 +1,7 @@
 #pragma once
 
 #include <list>
+#include <ostream>
 
 #include <cstdint>
 
@@ -77,3 +78,5 @@ private:
      /* First item is the least significant. */
     std::list<std::uint64_t> _operands;
 };
+
+std::ostream &operator<<(std::ostream &, const number &);