Update ex7_06.h

15801491881 · Jun 24, 2015 · c638184 · c638184
1 parent e9005ef
commit c638184
Showing 1 changed file with 2 additions and 2 deletions.
diff --git a/ch07/ex7_06.h b/ch07/ex7_06.h
@@ -13,9 +13,9 @@
 #include <iostream>
 
 struct Sales_data {
-    std::string isbn() const { return bookNo; };
+    std::string const& isbn() const { return bookNo; };
     Sales_data& combine(const Sales_data&);
-    
+
     std::string bookNo;
     unsigned units_sold = 0;
     double revenue = 0.0;