update comments

examples/hash_std.h

@@ -20,7 +20,8 @@ struct Person
 namespace std
 {
     // inject specialization of std::hash for Person into namespace std
-    // ----------------------------------------------------------------
+    // An alternative is to provide a hash_value() friend function (see hash_value.h)
+    // ------------------------------------------------------------------------------
     template<> struct hash<Person>
     {
         std::size_t operator()(Person const &p) const

examples/hash_value.h

@@ -12,6 +12,9 @@ struct Person
         return _first == o._first && _last == o._last && _age == o._age; 
     }
 
+    // Demonstrates how to provide the hash function as a friend member function of the class
+    // This can be used as an alternative to providing a std::hash<Person> specialization
+    // --------------------------------------------------------------------------------------
     friend size_t hash_value(const Person &p) 
     {
             return phmap::HashState().combine(0, p._first, p._last, p._age);