# Deduction guides

If possible, `concurrent_vector` constructors support class template argument deduction (since C++17). The following constructors provide implicitly-generated deduction guides:

- Copy and move constructors, including constructors with explicit `allocator_type` argument

- Constructors, accepting `std::initializer_list` as an argument

In addition, the following explicit deduction guide is provided:

    template <typename InputIterator,
              typename Allocator = tbb::cache_aligned_allocator<iterator_value_t<InputIterator>>>
    concurrent_vector( InputIterator, InputIterator,
                       Allocator = Allocator() )
    -> concurrent_vector<iterator_value_t<InputIterator>,
                         Allocator>;

Where type alias `iterator_value_t` defines as follows:

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

This deduction guide 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.

Example

    #include <oneapi/tbb/concurrent_vector.h>
    #include <array>
    #include <memory>

    int main() {
        std::array<int, 100> arr;

        // Deduces cv1 as oneapi::tbb::concurrent_vector<int>
        oneapi::tbb::concurrent_vector cv1(arr.begin(), arr.end());

        std::allocator<int> alloc;

        // Deduces cv2 as oneapi::tbb::concurrent_vector<int, std::allocator<int>>
        oneapi::tbb::concurrent_vector cv2(arr.begin(), arr.end(), alloc);
    }