163 lines
3.4 KiB
C++
163 lines
3.4 KiB
C++
#ifndef seafire__common__traits_hxx_
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#define seafire__common__traits_hxx_
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#include <optional>
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#include <tuple>
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#include <type_traits>
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namespace seafire::common::traits
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{
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// is_optional
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//
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template<typename T>
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struct is_optional
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: std::false_type
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{};
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template<typename T>
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struct is_optional<std::optional<T>>
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: std::true_type
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{};
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template<typename T>
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constexpr bool is_optional_v{is_optional<T>::value};
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// remove_optional
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//
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template<typename T>
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struct remove_optional
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{
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using type = T;
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};
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template<typename T>
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struct remove_optional<std::optional<T>>
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{
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using type = T;
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};
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template<typename T>
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using remove_optional_t = remove_optional<T>::type;
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// add_optional
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//
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template<typename T>
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std::optional<remove_optional_t<T>>
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add_optional(remove_optional<T>&& non_optional)
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{
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return std::optional<remove_optional<T>>{non_optional};
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}
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// function_traits
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//
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template<typename>
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struct function_traits;
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template<typename Ret, typename... Args>
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struct function_traits<Ret(Args...)>
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{
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static constexpr std::size_t arity = sizeof...(Args);
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using return_type = std::decay_t<Ret>;
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using argument_tuple = std::tuple<std::decay_t<Args>...>;
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};
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template<typename Ret, typename Class, typename... Args>
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struct function_traits<Ret (Class::*)(Args...)>
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{
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static constexpr std::size_t arity = sizeof...(Args);
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using return_type = std::decay_t<Ret>;
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using class_type = Class;
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using argument_tuple = std::tuple<std::decay_t<Args>...>;
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};
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template<typename Ret, typename Class, typename... Args>
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struct function_traits<Ret (Class::*)(Args...) const>
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{
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static constexpr std::size_t arity = sizeof...(Args);
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using return_type = std::decay_t<Ret>;
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using class_type = Class;
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using argument_tuple = std::tuple<std::decay_t<Args>...>;
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};
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template<typename Ret, typename... Args>
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struct function_traits<Ret(*)(Args...)>
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{
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static constexpr std::size_t arity = sizeof...(Args);
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using return_type = std::decay_t<Ret>;
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using argument_tuple = std::tuple<std::decay_t<Args>...>;
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};
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// return_type_t
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//
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template<typename F>
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using return_type_t = typename function_traits<F>::return_type;
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// first_arg
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//
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template<typename F>
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struct first_arg
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{
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using function_traits = traits::function_traits<F>;
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using type = std::tuple_element_t<0, typename function_traits::argument_tuple>;
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};
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template<typename F>
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using first_arg_t = first_arg<F>::type;
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// function_arg_n
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//
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template<
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typename F,
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std::size_t arg,
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std::size_t arity = function_traits<F>::arity
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>
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struct function_arg_n;
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template<
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typename F,
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std::size_t arg
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>
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struct function_arg_n<F, arg, 0>
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{
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using function_traits = traits::function_traits<F>;
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using type = void;
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};
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template<
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typename F,
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std::size_t arg
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>
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struct function_arg_n<F, arg, 1>
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{
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using function_traits = traits::function_traits<F>;
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using type = std::tuple_element_t<arg, typename function_traits::argument_tuple>;
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};
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template<
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typename F,
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std::size_t arg
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>
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struct function_arg_n<F, arg, 2>
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{
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using function_traits = traits::function_traits<F>;
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using type = std::tuple_element_t<arg, typename function_traits::argument_tuple>;
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};
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template<
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typename F,
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std::size_t arg
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>
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using function_arg_n_t = function_arg_n<F, arg>::type;
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} // namespace seafire::common::traits
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#endif
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