add Chapter18

Chapter18/cib/libs/stdx/functional.hpp

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+#pragma once
+
+#include <stdx/type_traits.hpp>
+
+#include <functional>
+#include <type_traits>
+
+#if __cpp_lib_bind_front < 202306L or __cpp_lib_bind_back < 202306L
+#if __cplusplus >= 202002L
+#include <stdx/tuple.hpp>
+#else
+#include <tuple>
+#endif
+#endif
+
+namespace stdx {
+inline namespace v1 {
+
+template <typename F> struct with_result_of : F {
+    using R = std::invoke_result_t<F>;
+    // NOLINTNEXTLINE(google-explicit-constructor)
+    constexpr operator R() const
+        noexcept(noexcept(static_cast<F const &>(*this)())) {
+        return static_cast<F const &>(*this)();
+    }
+    // NOLINTNEXTLINE(google-explicit-constructor)
+    constexpr operator R() noexcept(noexcept(static_cast<F &>(*this)())) {
+        return static_cast<F &>(*this)();
+    }
+};
+
+#if __cpp_deduction_guides < 201907L
+template <typename F> with_result_of(F) -> with_result_of<F>;
+#endif
+
+namespace detail {
+#if __cpp_lib_bind_front < 202306L or __cpp_lib_bind_back < 202306L
+#if __cplusplus >= 202002L
+template <typename... Ts> using bind_tuple_t = stdx::tuple<Ts...>;
+using stdx::get;
+#else
+template <typename... Ts> using bind_tuple_t = std::tuple<Ts...>;
+using std::get;
+#endif
+#endif
+} // namespace detail
+
+#if __cpp_lib_bind_front >= 201907L
+using std::bind_front;
+#else
+namespace detail {
+template <typename...> struct bind_front_t;
+
+template <typename F, std::size_t... Is, typename... BoundArgs>
+struct bind_front_t<F, std::index_sequence<Is...>, BoundArgs...> {
+    F f{};
+    bind_tuple_t<BoundArgs...> t{};
+
+    template <typename... Args>
+    constexpr auto operator()(Args &&...args) const & {
+        return f(get<Is>(t)..., std::forward<Args>(args)...);
+    }
+    template <typename... Args> constexpr auto operator()(Args &&...args) & {
+        return f(get<Is>(t)..., std::forward<Args>(args)...);
+    }
+    template <typename... Args> constexpr auto operator()(Args &&...args) && {
+        return std::move(f)(get<Is>(std::move(t))...,
+                            std::forward<Args>(args)...);
+    }
+};
+} // namespace detail
+
+template <typename F, typename... Args>
+constexpr auto bind_front(F &&f, Args &&...args) {
+    return detail::bind_front_t<stdx::remove_cvref_t<F>,
+                                std::make_index_sequence<sizeof...(Args)>,
+                                std::decay_t<Args>...>{
+        std::forward<F>(f), {std::forward<Args>(args)...}};
+}
+#endif
+
+#if __cpp_lib_bind_front < 202306L
+namespace detail {
+template <auto, typename...> struct bind_front_value_t;
+
+template <auto F, std::size_t... Is, typename... BoundArgs>
+struct bind_front_value_t<F, std::index_sequence<Is...>, BoundArgs...> {
+    bind_tuple_t<BoundArgs...> t{};
+
+    template <typename... Args>
+    constexpr auto operator()(Args &&...args) const & {
+        return F(get<Is>(t)..., std::forward<Args>(args)...);
+    }
+    template <typename... Args> constexpr auto operator()(Args &&...args) & {
+        return F(get<Is>(t)..., std::forward<Args>(args)...);
+    }
+    template <typename... Args> constexpr auto operator()(Args &&...args) && {
+        return F(get<Is>(std::move(t))..., std::forward<Args>(args)...);
+    }
+};
+} // namespace detail
+
+template <auto F, typename... Args> constexpr auto bind_front(Args &&...args) {
+    return detail::bind_front_value_t<
+        F, std::make_index_sequence<sizeof...(Args)>, std::decay_t<Args>...>{
+        {std::forward<Args>(args)...}};
+}
+
+#endif
+
+#if __cpp_lib_bind_back >= 202202L
+using std::bind_back;
+#else
+namespace detail {
+template <typename...> struct bind_back_t;
+
+template <typename F, std::size_t... Is, typename... BoundArgs>
+struct bind_back_t<F, std::index_sequence<Is...>, BoundArgs...> {
+    F f{};
+    bind_tuple_t<BoundArgs...> t{};
+
+    template <typename... Args>
+    constexpr auto operator()(Args &&...args) const & {
+        return f(std::forward<Args>(args)..., get<Is>(t)...);
+    }
+    template <typename... Args> constexpr auto operator()(Args &&...args) & {
+        return f(std::forward<Args>(args)..., get<Is>(t)...);
+    }
+    template <typename... Args> constexpr auto operator()(Args &&...args) && {
+        return std::move(f)(std::forward<Args>(args)...,
+                            get<Is>(std::move(t))...);
+    }
+};
+} // namespace detail
+
+template <typename F, typename... Args>
+constexpr auto bind_back(F &&f, Args &&...args) {
+    return detail::bind_back_t<stdx::remove_cvref_t<F>,
+                               std::make_index_sequence<sizeof...(Args)>,
+                               std::decay_t<Args>...>{
+        std::forward<F>(f), {std::forward<Args>(args)...}};
+}
+#endif
+
+#if __cpp_lib_bind_back < 202306L
+namespace detail {
+template <auto, typename...> struct bind_back_value_t;
+
+template <auto F, std::size_t... Is, typename... BoundArgs>
+struct bind_back_value_t<F, std::index_sequence<Is...>, BoundArgs...> {
+    bind_tuple_t<BoundArgs...> t{};
+
+    template <typename... Args>
+    constexpr auto operator()(Args &&...args) const & {
+        return F(std::forward<Args>(args)..., get<Is>(t)...);
+    }
+    template <typename... Args> constexpr auto operator()(Args &&...args) & {
+        return F(std::forward<Args>(args)..., get<Is>(t)...);
+    }
+    template <typename... Args> constexpr auto operator()(Args &&...args) && {
+        return F(std::forward<Args>(args)..., get<Is>(std::move(t))...);
+    }
+};
+} // namespace detail
+
+template <auto F, typename... Args> constexpr auto bind_back(Args &&...args) {
+    return detail::bind_back_value_t<
+        F, std::make_index_sequence<sizeof...(Args)>, std::decay_t<Args>...>{
+        {std::forward<Args>(args)...}};
+}
+
+#endif
+} // namespace v1
+} // namespace stdx