{"id":2188,"date":"2018-12-01T20:32:58","date_gmt":"2018-12-01T11:32:58","guid":{"rendered":"https:\/\/mattyan.net\/blog\/?p=2188"},"modified":"2018-12-01T20:32:58","modified_gmt":"2018-12-01T11:32:58","slug":"c17%e3%81%a7fizzbuzz%e3%82%92%e6%9b%b8%e3%81%84%e3%81%a6%e3%81%bf%e3%81%9f","status":"publish","type":"post","link":"https:\/\/mattyan.net\/blog\/?p=2188","title":{"rendered":"C++17\u3067fizzbuzz\u3092\u66f8\u3044\u3066\u307f\u305f"},"content":{"rendered":"\n

C++\u306e\u30e1\u30bf\u30d7\u30ed\u30b0\u30e9\u30df\u30f3\u30b0\u306e\u7df4\u7fd2\u3067\u4ed5\u4e8b\u4e2d\u306b\u6687\u306a\u6642\u9593\u4f7f\u3063\u3066<\/del>izzbuzz\u3092\u66f8\u3044\u3066\u307f\u305f\u3002
\u66f8\u3044\u305f\u611f\u60f3\u306f\u300c\u9b54\u6cd5\u304b\u3053\u308c?\u300d\u3068\u300c\u4f55\u3060\u3053\u306e\u30af\u30c3\u30bd\u30ad\u30e2\u3044\u30b3\u30fc\u30c9\u2026\u2026\u300d
<\/p>\n\n\n\n\n\n\n\n

struct Fizz {\n    constexpr static char value[5] = "Fizz";\n};\nstruct Buzz {\n    constexpr static char value[5] = "Buzz";\n};\nstruct Fizzbuzz {\n    constexpr static char value[9] = "FizzBuzz";\n};\ntemplate <int num>\nstruct Num {\n    constexpr static int value = num;\n};\ntemplate <bool Cond, class Then, class Else>\nstruct if_c;\n\ntemplate <class Then, class Else>\nstruct if_c<true, Then, Else> {\n    using type = Then;\n};\n\ntemplate <class Then, class Else>\n    struct if_c<false, Then, Else> {\n    using type = Else;\n};\n\ntemplate <int n, typename T = typename if_c <n % 15 == 0, Fizzbuzz,\n        typename if_c <n % 5 == 0, Buzz,\n            typename if_c <n % 3 == 0, Fizz,\n                Num<n> >::type>::type>::type>\nstruct FizzBuzz: public T {};\n\n#include <iostream>\ntemplate <int n> void fizzbuzz() {\n    fizzbuzz<n - 1>();\n    std::cout << FizzBuzz<n>::value << std::endl;\n}\ntemplate <> void fizzbuzz<0>() {\n    std::cout << 0 << std::endl;\n}\nint main() {\n    fizzbuzz<150>();\n    return 0;\n}\n<\/code><\/pre>\n\n\n\n
\u69cb\u9020\u4f53 Fizz, Buzz,Fizzbuzz, Num\u306f\u8868\u793a\u3059\u308b\u5024\u3092\u683c\u7d0d\u3059\u308b\u69cb\u9020\u4f53\u3002
Fizz, Buzz, Fizzbuzz\u306f\u305d\u308c\u305e\u308c\u56fa\u5b9a\u5024\u3060\u3051\u3069\u3001Num\u306f\u30c6\u30f3\u30d7\u30ec\u30fc\u30c8\u5f15\u6570\u3067\u3082\u3089\u3063\u305f\u5024\u3092value\u306b\u683c\u7d0d\u3002
\u69cb\u9020\u4f53 if_c\u306f\u30c6\u30f3\u30d7\u30ec\u30fc\u30c8\u7279\u6b8a\u5316\u3092\u4f7f\u3063\u3066FizzBuzz\u69cb\u9020\u4f53\u306e\u6d3e\u751f\u5143\u3092\u6c7a\u5b9a\u3059\u308b\u3082\u306e\u3002
bool Cond\u304ctrue\u3060\u3063\u305f\u3089\u3001<\/p>\n\n\n
template <class Then, class Else>\nstruct if_c<true, Then, Else> {\n    using type = Then;\n};\n<\/code><\/pre>\n\n\n\n
\u304c\u9069\u7528\u3055\u308c\u3066\u3001Then\u306e\u578b\u304ctype\u306b\u5165\u3063\u305fif_c\u304c\u4f5c\u6210\u3055\u308c\u308b\u3002
false\u3060\u3063\u305f\u3089<\/p>\n\n\n
template <class Then, class Else>\nstruct if_c<false, Then, Else> {\n    using type = Else;\n};\n<\/code><\/pre>\n\n\n\n
\u3053\u3063\u3061\u304c\u5b9f\u4f53\u5316\u3055\u308c\u3066\u3001Else\u306e\u578b\u304ctype\u306b\u5165\u3063\u305fif_c\u304c\u4f5c\u6210\u3055\u308c\u308b\u3002
\u3067
<\/p>\n\n\n
template <int n, typename T = typename if_c <n % 15 == 0, Fizzbuzz,\n    typename if_c <n % 5 == 0, Buzz,\n        typename if_c <n % 3 == 0, Fizz,\n            Num<n> >::type>::type>::type>\nstruct FizzBuzz: public T {};\n<\/code><\/pre>\n\n\n\n
\u306f\u30c6\u30f3\u30d7\u30ec\u30fc\u30c8\u5f15\u6570\u3067\u3082\u3089\u3063\u305fn\u3067Fizz\u304bBuzz\u304bFizzbuzz\u304b\u5224\u5b9a\u3057\u3066FizzBuzz\u306e\u6d3e\u751f\u5143T\u3092\u6c7a\u5b9a\u3002
<\/p>\n\n\n
std::cout << FizzBuzz<n>::value << std::endl;<\/code><\/pre>\n\n\n\n
\u3053\u308c\u3067\u683c\u7d0d\u3057\u305fvalue\u3092\u51fa\u529b\u3057\u3066\u7d42\u4e86\u2026\u2026
<\/p>\n\n\n
template <int n> void fizzbuzz() {\nfizzbuzz<n - 1>();\n    std::cout << FizzBuzz<n>::value << std::endl;\n}\n\ntemplate <> void fizzbuzz<0>() {\n    std::cout << 0 << std::endl;\n}\n\nint main() {\n    fizzbuzz<150>();\n    return 0;\n}\n<\/code><\/pre>\n\n\n\n
\u3053\u308c\u3067\u3001\u30c6\u30f3\u30d7\u30ec\u30fc\u30c8\u5f15\u6570n\u3092\u304b\u30891\u5f15\u304d\u306a\u304c\u3089\u3069\u3093\u3069\u3093\u3068\u518d\u5e30\u3057\u3066\u3044\u3063\u3066\u3001n=0\u306b\u306a\u3063\u305f\u30890\u3092\u51fa\u529b\u3002\u3042\u3068\u306f\u5404FizzBuzz::value\u3092\u51fa\u529b\u3059\u308b\u3053\u3068\u3067\u4efb\u610f\u306e\u6570\u306eFizzBuzz\u3092\u51fa\u529b\u3059\u308b\u3088\u3046\u306b\u3057\u305f\u3002
\u6700\u7d42\u7684\u306b(\u4e00\u5fdc)if\u3082for\u3082\u306a\u3044FizzBuzz\u304c\u51fa\u6765\u4e0a\u304c\u3063\u305f\u3002\u306a\u3093\u3060\u30b3\u30ec\u9b54\u6cd5\u304b?
\u30b3\u30f3\u30d1\u30a4\u30eb\u306f
<\/p>\n\n\n
g++ -std=c++17 fizzbuzz.cpp -o fizzbuzz.exe\n<\/code><\/pre>\n\n\n\n
\u6ce8\u610f\u70b9\u3068\u3057\u3066\u306f\u3001main()\u306efizzbuzz<150>();\u306e\u5024\u3092\u3042\u307e\u308a\u5927\u304d\u304f\u3057\u3059\u304e\u308b\u3068\u3001\u30cd\u30b9\u30c8\u304c\u6df1\u304f\u306a\u308a\u3059\u304e\u3066\u30b3\u30f3\u30d1\u30a4\u30e9\u304c\u30b3\u30f3\u30d1\u30a4\u30eb\u3092\u62d2\u5426\u3059\u308b\u3002
\u3042\u3068\u30d0\u30a4\u30ca\u30ea\u304c\u3067\u304b\u3044\u3002
\u524d\u306b\u6d3e\u9063\u5148\u306e\u9762\u8ac7\u3067\u300cFizzbuzz\u66f8\u3051\u307e\u3059\u304b?\u300d\u3063\u3066\u8a00\u308f\u308c\u305f\u3068\u304d\u306b\u666e\u901a\u306bfor\u3068if\u4f7f\u3063\u3066C++\u3068PHP\u3067\u66f8\u3044\u3066\u901a\u3063\u305f\u3051\u3069\u3001\u3053\u306e\u30c6\u30f3\u30d7\u30ec\u30fc\u30c8\u30de\u30b7\u30de\u30b7\u306e\u30b3\u30fc\u30c9\u66f8\u3044\u305f\u3089\u3069\u3046\u3044\u3046\u53cd\u5fdc\u3059\u308b\u3093\u3060\u308d\u3046\u304b\u2026\u2026<\/p>\n\n\n\n
2023\/04\/03\u66f4\u65b0: \u30d7\u30e9\u30b0\u30a4\u30f3\u5909\u66f4\u306b\u4f34\u3046\u30c7\u30b6\u30a4\u30f3\u5d29\u308c\u306b\u5bfe\u5fdc<\/p>\n","protected":false},"excerpt":{"rendered":"
C++\u306e\u30e1\u30bf\u30d7\u30ed\u30b0\u30e9\u30df\u30f3\u30b0\u306e\u7df4\u7fd2\u3067\u4ed5\u4e8b\u4e2d\u306b\u6687\u306a\u6642\u9593\u4f7f\u3063\u3066izzbuzz\u3092\u66f8\u3044\u3066\u307f\u305f\u3002\u66f8\u3044\u305f\u611f\u60f3\u306f\u300c\u9b54\u6cd5\u304b\u3053\u308c?\u300d\u3068\u300c\u4f55\u3060\u3053\u306e\u30af\u30c3\u30bd\u30ad\u30e2\u3044\u30b3\u30fc\u30c9\u2026\u2026\u300d<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[3],"tags":[],"class_list":["post-2188","post","type-post","status-publish","format-standard","hentry","category-3"],"_links":{"self":[{"href":"https:\/\/mattyan.net\/blog\/index.php?rest_route=\/wp\/v2\/posts\/2188","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/mattyan.net\/blog\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/mattyan.net\/blog\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/mattyan.net\/blog\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/mattyan.net\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=2188"}],"version-history":[{"count":0,"href":"https:\/\/mattyan.net\/blog\/index.php?rest_route=\/wp\/v2\/posts\/2188\/revisions"}],"wp:attachment":[{"href":"https:\/\/mattyan.net\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=2188"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/mattyan.net\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=2188"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/mattyan.net\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=2188"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}