Revision of Funny CPP

anduin revised this gist 1758103075. Go to revision

1 file changed, 75 insertions

wired.cpp(file created)

		@@ -0,0 +1,75 @@
1	+	#include <iostream>
2	+	#include <vector>
3	+	#include <array>
4	+	#include <string>
5	+	#include <algorithm>
6	+	#include <ranges>
7	+	#include <utility>
8	+
9	+	// 1. 正常人类 (C++98)
10	+	void print_evens_c98(int arr[], int size) {
11	+	for (int i = 0; i < size; i++) {
12	+	if (arr[i] % 2 == 0) {
13	+	std::cout << arr[i] << " ";
14	+	}
15	+	}
16	+	}
17	+
18	+	// 2. 稍微不正常 (C++11)
19	+	void print_evens_c11(const std::vector<int>& nums) {
20	+	std::for_each(nums.begin(), nums.end(), [](int n) {
21	+	if (n % 2 == 0) {
22	+	std::cout << n << " ";
23	+	}
24	+	});
25	+	}
26	+
27	+	// 3. 再不正常一点 (C++20)
28	+	void print_evens_c20(const std::vector<int>& nums) {
29	+	for (int n : nums \| std::views::filter([](int n) { return n % 2 == 0; })) {
30	+	std::cout << n << " ";
31	+	}
32	+	}
33	+
34	+	// 4. 特别不正常 (C++20 纯编译期)
35	+	template <size_t... Is>
36	+	constexpr auto get_even_numbers_string_helper(const std::array<int, sizeof...(Is)>& arr, std::index_sequence<Is...>) {
37	+	auto filter_and_convert = [&](auto index) constexpr {
38	+	if (arr[index] % 2 == 0) {
39	+	// Returns an empty string literal to avoid runtime heap allocation
40	+	return std::to_string(arr[index]) + " ";
41	+	}
42	+	return std::string("");
43	+	};
44	+	return (filter_and_convert(Is) + ...);
45	+	}
46	+
47	+	template <size_t N>
48	+	void print_even_in_array(const std::array<int, N>& arr) {
49	+	std::cout << get_even_numbers_string_helper(arr, std::make_index_sequence<N>{});
50	+	}
51	+
52	+	int main() {
53	+	int arr[] = {5, 2, 8, 1, 6};
54	+	std::vector<int> nums_vec = {5, 2, 8, 1, 6};
55	+
56	+	constexpr std::array<int, 5> nums_arr_constexpr = {5, 2, 8, 1, 6};
57	+
58	+	std::cout << "1. 正常人类 (C++98):" << std::endl;
59	+	print_evens_c98(arr, 5);
60	+	std::cout << "\n\n";
61	+
62	+	std::cout << "2. 稍微不正常 (C++11):" << std::endl;
63	+	print_evens_c11(nums_vec);
64	+	std::cout << "\n\n";
65	+
66	+	std::cout << "3. 再不正常一点 (C++20):" << std::endl;
67	+	print_evens_c20(nums_vec);
68	+	std::cout << "\n\n";
69	+
70	+	std::cout << "4. 特别不正常 (C++20 纯编译期):" << std::endl;
71	+	print_even_in_array(nums_arr_constexpr);
72	+	std::cout << "\n";
73	+
74	+	return 0;
75	+	}

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