+/* Class hash_map is a hash-value based container mapping objects of
+ KeyId type to those of the Value type.
+ Both KeyId and Value may be non-trivial (non-POD) types provided
+ a suitabe Traits class. A few default Traits specializations are
+ provided for basic types such as integers, pointers, and std::pair.
+ Inserted elements are value-initialized either to zero for POD types
+ or by invoking their default ctor. Removed elements are destroyed
+ by invoking their dtor. On hash_map destruction all elements are
+ removed. Objects of hash_map type are copy-constructible but not
+ assignable. */
+