add Chapter18

Chapter18/cib/libs/stdx/algorithm.hpp

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+#pragma once
+
+#include <functional>
+#if __cplusplus >= 202002L
+#include <stdx/tuple.hpp>
+#else
+#include <tuple>
+#endif
+
+namespace stdx {
+inline namespace v1 {
+namespace detail {
+#if __cplusplus >= 202002L
+template <typename... Ts> using result_tuple_t = stdx::tuple<Ts...>;
+#define CONSTEXPR_INVOKE constexpr
+#else
+template <typename... Ts> using result_tuple_t = std::tuple<Ts...>;
+#define CONSTEXPR_INVOKE
+#endif
+} // namespace detail
+
+template <typename O, typename... Is>
+using transform_result = detail::result_tuple_t<O, Is...>;
+
+template <typename InputIt, typename OutputIt, typename Operation,
+          typename... InputItN>
+CONSTEXPR_INVOKE auto transform(InputIt first, InputIt last, OutputIt d_first,
+                                Operation op, InputItN... first_n)
+    -> transform_result<OutputIt, InputIt, InputItN...> {
+    while (first != last) {
+        *d_first = std::invoke(op, *first, *first_n...);
+        static_cast<void>(++first), (static_cast<void>(++first_n), ...),
+            ++d_first;
+    }
+    return {d_first, first, first_n...};
+}
+
+template <typename InputIt, typename Size, typename OutputIt,
+          typename Operation, typename... InputItN>
+CONSTEXPR_INVOKE auto transform_n(InputIt first, Size n, OutputIt d_first,
+                                  Operation op, InputItN... first_n)
+    -> transform_result<OutputIt, InputIt, InputItN...> {
+    while (n-- > 0) {
+        *d_first = std::invoke(op, *first, *first_n...);
+        static_cast<void>(++first), (static_cast<void>(++first_n), ...),
+            ++d_first;
+    }
+    return {d_first, first, first_n...};
+}
+
+template <typename InputIt, typename Operation, typename... InputItN>
+CONSTEXPR_INVOKE auto for_each(InputIt first, InputIt last, Operation op,
+                               InputItN... first_n) -> Operation {
+    while (first != last) {
+        std::invoke(op, *first, *first_n...);
+        static_cast<void>(++first), (static_cast<void>(++first_n), ...);
+    }
+    return op;
+}
+
+template <typename InputIt, typename Size, typename Operation,
+          typename... InputItN>
+CONSTEXPR_INVOKE auto for_each_n(InputIt first, Size n, Operation op,
+                                 InputItN... first_n) -> Operation {
+    while (n-- > 0) {
+        std::invoke(op, *first, *first_n...);
+        static_cast<void>(++first), (static_cast<void>(++first_n), ...);
+    }
+    return op;
+}
+
+#undef CONSTEXPR_INVOKE
+} // namespace v1
+} // namespace stdx