Deduction guides

If possible, concurrent_unordered_set 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 Hash = std::hash<iterator_value_t<InputIterator>>,
          typename KeyEqual = std::equal_to<iterator_value_t<InputIterator>>,
          typename Allocator = tbb::tbb_allocator<iterator_value_t<InputIterator>>>
concurrent_unordered_set( InputIterator, InputIterator,
                          set_size_type = {},
                          Hash = Hash(),
                          KeyEqual = KeyEqual(),
                          Allocator = Allocator() )
-> concurrent_unordered_set<iterator_value_t<InputIterator>,
                            Hash,
                            KeyEqual,
                            Allocator>;

template <typename InputIterator,
          typename Allocator>
concurrent_unordered_set( InputIterator, InputIterator,
                          set_size_type,
                          Allocator )
-> concurrent_unordered_set<iterator_value_t<InputIterator>,
                            std::hash<iterator_value_t<InputIterator>>,
                            std::equal_to<iterator_value_t<InputIterator>>,
                            Allocator>;

template <typename T,
          typename Hash = std::hash<T>,
          typename KeyEqual = std::equal_to<T>,
          typename Allocator = tbb::tbb_allocator<T>>
concurrent_unordered_set( std::initializer_list<T>,
                          set_size_type = {},
                          Hash = Hash(),
                          KeyEqual = KeyEqual(),
                          Allocator = Allocator() )
-> concurrent_unordered_set<T,
                            Hash,
                            KeyEqual,
                            Allocator>;

template <typename T,
          typename Allocator>
concurrent_unordered_set( std::initializer_list<T>,
                          set_size_type,
                          Allocator )
-> concurrent_unordered_set<T,
                            std::hash<T>,
                            std::equal_to<T>,
                            Allocator>;

template <typename T,
          typename Allocator>
concurrent_unordered_set( std::initializer_list<T>,
                          Allocator )
-> concurrent_unordered_set<T,
                            std::hash<T>,
                            std::equal_to<T>,
                            Allocator>;

template <typename T,
          typename Hash,
          typename Allocator>
concurrent_unordered_set( std::initializer_list<T>,
                          set_size_type,
                          Hash,
                          Allocator )
-> concurrent_unordered_set<T,
                            Hash,
                            std::equal_to<T>,
                            Allocator>;

Where the set_size_type type refers to the size_type member type of the deduced concurrent_unordered_set and the type alias iterator_value_t is defined as follows:

template <typename InputIterator>
using iterator_value_t = typename std::iterator_traits<InputIterator>::value_type;

These deduction guides only participate in the overload resolution if the following requirements are met:

  • The InputIterator type meets the InputIterator requirements described in the [input.iterators] section of the ISO C++ Standard.

  • The Allocator type meets the Allocator requirements described in the [allocator.requirements] section of the ISO C++ Standard.

  • The Hash type does not meet the Allocator requirements.

  • The KeyEqual type does not meet the Allocator requirements.

Example

#include <oneapi/tbb/concurrent_unordered_set.h>
#include <vector>
#include <functional>

struct CustomHasher {...};

int main() {
    std::vector<int> v;

    // Deduces s1 as concurrent_unordered_set<int>
    oneapi::tbb::concurrent_unordered_set s1(v.begin(), v.end());

    // Deduces s2 as concurrent_unordered_set<int, CustomHasher>;
    oneapi::tbb::concurrent_unordered_set s2(v.begin(), v.end(), CustomHasher{});
}

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