Deduction guides¶
If possible, concurrent_hash_map constructors support class template argument deduction (since C++17).
Copy and move constructors, including constructors with an explicit allocator_type argument,
provide implicitly-generated deduction guides.
In addition, the following explicit deduction guides are provided:
template <typename InputIterator,
typename HashCompare = tbb_hash_compare<iterator_key_t<InputIterator>>,
typename Allocator = tbb_allocator<iterator_alloc_value_t<InputIterator>>>
concurrent_hash_map( InputIterator, InputIterator,
HashCompare = HashCompare(),
Allocator = Allocator() )
-> concurrent_hash_map<iterator_key_t<InputIterator>,
iterator_mapped_t<InputIterator>,
HashCompare,
Allocator>;
template <typename InputIterator,
typename Allocator>
concurrent_hash_map( InputIterator, InputIterator, Allocator )
-> concurrent_hash_map<iterator_key_t<InputIterator>,
iterator_mapped_t<InputIterator>,
tbb_hash_compare<iterator_key_t<InputIterator>>,
Allocator>;
template <typename Key, typename T,
typename HashCompare = tbb_hash_compare<std::remove_const_t<Key>>,
typename Allocator = tbb_allocator<std::pair<const Key, T>>>
concurrent_hash_map( std::initializer_list<std::pair<Key, T>>,
HashCompare = HashCompare(),
Allocator = Allocator() )
-> concurrent_hash_map<std::remove_const_t<Key>,
T,
HashCompare,
Allocator>;
template <typename Key, typename T,
typename Allocator>
concurrent_hash_map( std::initializer_list<std::pair<Key, T>>,
Allocator )
-> concurrent_hash_map<std::remove_const_t<Key>,
T,
tbb_hash_compare<std::remove_const_t<Key>>,
Allocator>;
Where the type aliases iterator_key_t, iterator_mapped_t, and iterator_alloc_value_t
are defined as follows:
template <typename InputIterator>
using iterator_key_t = std::remove_const_t<typename std::iterator_traits<InputIterator>::value_type::first_type>;
template <typename InputIterator>
using iterator_mapped_t = typename std::iterator_traits<InputIterator>::value_type::second_type;
template <typename InputIterator>
using iterator_alloc_value_t = std::pair<std::add_const_t<iterator_key_t<InputIterator>,
iterator_mapped_t<InputIterator>>>;
These deduction guides only participate in the overload resolution if the following requirements are met:
The
InputIteratortype meets theInputIteratorrequirements described in the [input.iterators] section of the ISO C++ Standard.The
Allocatortype meets theAllocatorrequirements described in the [allocator.requirements] section of the ISO C++ Standard.The
HashComparetype does not meet theAllocatorrequirements.
Example
#include <oneapi/tbb/concurrent_hash_map.h>
#include <vector>
int main() {
std::vector<std::pair<const int, float>> v;
// Deduces chmap1 as oneapi::tbb::concurrent_hash_map<int, float>
oneapi::tbb::concurrent_hash_map chmap1(v.begin(), v.end());
std::allocator<std::pair<const int, float>> alloc;
// Deduces chmap2 as oneapi::tbb::concurrent_hash_map<int, float,
// tbb_hash_compare<int>,
// std::allocator<std::pair<const int, float>>>
oneapi::tbb::concurrent_hash_map chmap2(v.begin(), v.end(), alloc);
}