add Chapter18
This commit is contained in:
Amar Mahmutbegovic
228
Chapter18/cib/libs/stdx/concepts.hpp
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228
Chapter18/cib/libs/stdx/concepts.hpp
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#pragma once
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#include <stdx/type_traits.hpp>
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#if __has_include(<concepts>)
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#include <concepts>
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#endif
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#if __cpp_lib_concepts < 202002L
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#include <functional>
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#include <type_traits>
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#include <utility>
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namespace stdx {
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inline namespace v1 {
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#if __cplusplus < 202002L
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// Before C++20 we can't use concepts directly, but we can still allow the
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// names to be used in constexpr contexts
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template <typename T> constexpr auto integral = std::is_integral_v<T>;
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template <typename T>
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constexpr auto floating_point = std::is_floating_point_v<T>;
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template <typename T>
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constexpr auto signed_integral = integral<T> and std::is_signed_v<T>;
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template <typename T>
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constexpr auto unsigned_integral = integral<T> and std::is_unsigned_v<T>;
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template <typename From, typename To>
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constexpr auto convertible_to = std::is_convertible_v<From, To>;
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template <typename T, typename U>
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constexpr auto derived_from =
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std::is_base_of_v<U, T> and
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std::is_convertible_v<T const volatile *, U const volatile *>;
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template <typename T, typename U>
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constexpr auto same_as = std::is_same_v<T, U> and std::is_same_v<U, T>;
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template <typename T, typename U>
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constexpr auto same_as_unqualified =
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is_same_unqualified_v<T, U> and is_same_unqualified_v<U, T>;
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// NOLINTBEGIN(bugprone-macro-parentheses, cppcoreguidelines-macro-usage)
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#define DETECTOR(name, expr) \
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namespace detail::detect { \
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template <typename T, typename = void> constexpr auto name = false; \
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template <typename T> \
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constexpr auto name<T, std::void_t<decltype(expr)>> = true; \
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}
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// NOLINTEND(bugprone-macro-parentheses, cppcoreguidelines-macro-usage)
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DETECTOR(eq_compare, (std::declval<T>() == std::declval<T>()))
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DETECTOR(neq_compare, (std::declval<T>() != std::declval<T>()))
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template <typename T>
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constexpr auto equality_comparable =
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detail::detect::eq_compare<T> and detail::detect::neq_compare<T>;
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DETECTOR(lt_compare, (std::declval<T>() < std::declval<T>()))
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DETECTOR(lte_compare, (std::declval<T>() <= std::declval<T>()))
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DETECTOR(gt_compare, (std::declval<T>() > std::declval<T>()))
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DETECTOR(gte_compare, (std::declval<T>() >= std::declval<T>()))
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template <typename T>
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constexpr auto totally_ordered =
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equality_comparable<T> and detail::detect::lt_compare<T> and
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detail::detect::lte_compare<T> and detail::detect::gt_compare<T> and
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detail::detect::gte_compare<T>;
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namespace detail::detect {
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template <typename... Args> struct arg_list {
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template <typename F>
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using invoke_result_t = std::invoke_result_t<F, Args...>;
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};
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template <typename F, typename Args, typename = void>
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constexpr auto invocable = false;
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template <typename F, typename Args>
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constexpr auto invocable<
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F, Args, std::void_t<typename Args::template invoke_result_t<F>>> = true;
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} // namespace detail::detect
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template <typename F, typename... Args>
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constexpr auto invocable =
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detail::detect::invocable<F, detail::detect::arg_list<Args...>>;
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template <typename F, typename... Args>
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constexpr auto predicate =
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invocable<F, Args...> and
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std::is_convertible_v<std::invoke_result_t<F, Args...>, bool>;
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template <typename T> constexpr auto callable = is_callable_v<T>;
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template <typename T, template <typename> typename TypeTrait>
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constexpr auto has_trait = TypeTrait<T>::value;
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#undef DETECTOR
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template <typename T> constexpr auto structural = is_structural_v<T>;
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#else
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// After C++20, we can define concepts that are lacking in the library
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template <typename T>
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concept integral = std::is_integral_v<T>;
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template <typename T>
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concept floating_point = std::is_floating_point_v<T>;
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template <typename T>
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concept signed_integral = integral<T> and std::is_signed_v<T>;
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template <typename T>
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concept unsigned_integral = integral<T> and std::is_unsigned_v<T>;
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template <typename From, typename To>
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concept convertible_to = std::is_convertible_v<From, To> and
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requires { static_cast<To>(std::declval<From>()); };
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template <typename T, typename U>
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concept derived_from =
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std::is_base_of_v<U, T> and
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std::is_convertible_v<T const volatile *, U const volatile *>;
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template <typename T, typename U>
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concept same_as = std::is_same_v<T, U> and std::is_same_v<U, T>;
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template <typename T, typename U>
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concept same_as_unqualified =
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is_same_unqualified_v<T, U> and is_same_unqualified_v<U, T>;
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template <typename T>
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concept equality_comparable = requires(T const &t) {
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{ t == t } -> same_as<bool>;
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{ t != t } -> same_as<bool>;
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};
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namespace detail {
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template <typename T>
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concept partially_ordered = requires(T const &t) {
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{ t < t } -> same_as<bool>;
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{ t <= t } -> same_as<bool>;
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{ t > t } -> same_as<bool>;
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{ t >= t } -> same_as<bool>;
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};
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} // namespace detail
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template <typename T>
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concept totally_ordered =
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equality_comparable<T> and detail::partially_ordered<T>;
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template <typename F, typename... Args>
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concept invocable = requires(F &&f, Args &&...args) {
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std::invoke(std::forward<F>(f), std::forward<Args>(args)...);
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};
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namespace detail {
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template <typename B>
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concept boolean_testable_impl = stdx::convertible_to<B, bool>;
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template <typename B>
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concept boolean_testable = boolean_testable_impl<B> and requires(B &&b) {
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{ not std::forward<B>(b) } -> boolean_testable_impl;
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};
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} // namespace detail
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template <typename F, typename... Args>
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concept predicate = invocable<F, Args...> and
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detail::boolean_testable<std::invoke_result_t<F, Args...>>;
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template <typename T>
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concept callable = is_callable_v<T>;
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template <typename T, template <typename> typename TypeTrait>
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concept has_trait = TypeTrait<T>::value;
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template <typename T>
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concept structural = is_structural_v<T>;
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#endif
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} // namespace v1
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} // namespace stdx
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#else
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// C++20 concept library exists, so use that
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namespace stdx {
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inline namespace v1 {
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using std::floating_point;
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using std::integral;
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using std::signed_integral;
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using std::unsigned_integral;
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using std::convertible_to;
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using std::derived_from;
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using std::same_as;
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using std::equality_comparable;
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using std::totally_ordered;
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using std::invocable;
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using std::predicate;
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template <typename T>
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concept callable = is_callable_v<T>;
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template <typename T, template <typename> typename TypeTrait>
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concept has_trait = TypeTrait<T>::value;
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template <typename T, typename U>
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concept same_as_unqualified =
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is_same_unqualified_v<T, U> and is_same_unqualified_v<U, T>;
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template <typename T>
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concept structural = is_structural_v<T>;
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} // namespace v1
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} // namespace stdx
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#endif
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