template<typename Ch, typename A> 
  std::size_t hash_value(std::basic_string<Ch, std::char_traits<Ch>, A> const& val);

Description

Generally shouldn't be called directly by users, instead they should use boost::hash, boost::hash_range or boost::hash_combine which call hash_value without namespace qualification so that overloads for custom types are found via ADL.

Notes: Overloads for other types supplied in other headers.

This is an extension to TR1

Returns: hash_range(val.begin(), val.end())