array.hpp

/*
 * Copyright (c) 2024 The RefValue Project
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#pragma once
 
#include <algorithm>
#include <array>
#include <concepts>
#include <cstddef>
#include <type_traits>
 
namespace essence {
    template <typename T>
    struct is_std_array : std::false_type {};
 
    template <typename T, std::size_t N>
    struct is_std_array<std::array<T, N>> : std::true_type {};
 
    template <typename T>
    inline constexpr bool is_std_array_v = is_std_array<T>::value;
 
    template <typename T>
    concept std_array = is_std_array_v<T>;
 
    template <auto GetArray, auto Predicate>
        requires std::predicate<decltype(Predicate), typename decltype(GetArray())::value_type>
    struct filter_array {
        using value_type = typename decltype(GetArray())::value_type;
 
        static constexpr auto value = [] {
            constexpr auto array       = GetArray();
            constexpr auto actual_size = std::count_if(array.begin(), array.end(), Predicate);
 
            std::size_t index{};
            std::array<value_type, actual_size> result{};
 
            for (auto&& item : array) {
                if (Predicate(item)) {
                    result[index++] = item;
                }
            }
 
            return result;
        }();
    };
 
    template <auto GetArray, auto Predicate>
        requires std::predicate<decltype(Predicate), typename decltype(GetArray())::value_type>
    inline constexpr auto filter_array_v = filter_array<GetArray, Predicate>::value;
} // namespace essence