Function hash

Function hash_value

boost::hash_value — Implementation of the hash function.

Synopsis

std::size_t hash_value(int val);
std::size_t hash_value(unsigned int val);
std::size_t hash_value(long val);
std::size_t hash_value(unsigned long val);
std::size_t hash_value(float val);
std::size_t hash_value(double val);
std::size_t hash_value(long double val);
template<typename T> std::size_t hash_value(T* const& val);
template<typename T, unsigned N> std::size_t hash_value(T (&val)[N]);
template<typename T, unsigned N> std::size_t hash_value(const T (&val)[N]);
template<typename Ch, typename A> 
  std::size_t hash_value(std::basic_string<Ch, std::char_traits<Ch>, A> const& val);
template<typename A, typename B> 
  std::size_t hash_value(std::pair<A, B> const& val);
template<typename T, typename A> 
  std::size_t hash_value(std::vector<T, A> const& val);
template<typename T, typename A> 
  std::size_t hash_value(std::list<T, A> const& val);
template<typename T, typename A> 
  std::size_t hash_value(std::deque<T, A> const& val);
template<typename K, typename C, typename A> 
  std::size_t hash_value(std::set<K, C, A> const& val);
template<typename K, typename C, typename A> 
  std::size_t hash_value(std::multiset<K, C, A> const& val);
template<typename K, typename T, typename C, typename A> 
  std::size_t hash_value(std::map<K, T, C, A> const& val);
template<typename K, typename T, typename C, typename A> 
  std::size_t hash_value(std::multimap<K, T, C, 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:

This is an extension to TR1

Throws: Only throws if a user supplied version of hash_value throws for an element of a container, or one of the types stored in a pair.

Returns:

Types	Returns
`int`, `unsigned int`, `long`, `unsigned long`	`val`
`float`, `double`, `long double`	An unspecified value, except that equal arguments shall yield the same result.
`T*`	An unspecified value, except that equal arguments shall yield the same result.
`T val[N]`, `const T val[N]`	`hash_range(val, val+N)`
`std:basic_string<Ch, std::char_traits<Ch>, A>`, `std::vector<T, A>`, `std::list<T, A>`, `std::deque<T, A>`, `std::set<K, C, A>`, `std::multiset<K, C, A>`, `std::map<K, T, C, A>`, `std::multimap<K, T, C, A>`	`hash_range(val.begin(), val.end())`
`std::pair<A, B>`	size_t seed = 0; hash_combine(seed, val.first); hash_combine(seed, val.second); return seed;