Boost C++ Libraries: Ticket #9755: Simple way to get hash.

Boost C++ Libraries: Ticket #9755: Simple way to get hash. https://svn.boost.org/trac10/ticket/9755 When writing custom hash_value functions, it is often useful to forward to the hash of another value. However, there is currently no short and simple way to do this. Consider: template<class T> struct C { <blockquote> some_complex_mpl_expression<T>::type value; friend std::size_t hash_value() { <blockquote> First attempt: requires knowledge of the type of the value to hash. return boost::hash<some_complex_mpl_expression<T>::type>()(this->value); </blockquote> </blockquote> <blockquote> <blockquote> Second attempt: two lines, not recommended. using namespace boost; return hash_value(this->value); </blockquote> </blockquote> <blockquote> <blockquote> Third attempt: works, but requires three lines of code and doesn't yield the same hash as the first two attempts. std::size_t seed = 0; boost::hash_combine(seed, this->value); return seed; </blockquote> } </blockquote> }; I propose the addition of a simple function to calculate the hash of any arbitrary value, defined below: template<class T> std::size_t get_hash(T const& v) { <blockquote> return hash<T>()(v); </blockquote> } This would allow me to write the above hash_value function with a single line of simple and correct code: <blockquote> friend std::size_t hash_value() { <blockquote> return boost::get_hash(this->value); </blockquote> } </blockquote> en-us Boost C++ Libraries /htdocs/site/boost.png https://svn.boost.org/trac10/ticket/9755 Trac 1.4.3