{"categories":["Haskell"],"provider_url":"https://hatena.blog","blog_url":"https://kazu-yamamoto.hatenablog.jp/","url":"https://kazu-yamamoto.hatenablog.jp/entry/20100601/1275367421","published":"2010-06-01 13:43:41","blog_title":"\u3042\u3069\u3051\u306a\u3044\u8a71","provider_name":"Hatena Blog","html":"<iframe src=\"https://hatenablog-parts.com/embed?url=https%3A%2F%2Fkazu-yamamoto.hatenablog.jp%2Fentry%2F20100601%2F1275367421\" title=\"Y\u30b3\u30f3\u30d3\u30cd\u30fc\u30bf\u306e\u307e\u3068\u3081 - \u3042\u3069\u3051\u306a\u3044\u8a71\" class=\"embed-card embed-blogcard\" scrolling=\"no\" frameborder=\"0\" style=\"display: block; width: 100%; height: 190px; max-width: 500px; margin: 10px 0px;\"></iframe>","author_url":"https://blog.hatena.ne.jp/kazu-yamamoto/","image_url":null,"type":"rich","title":"Y\u30b3\u30f3\u30d3\u30cd\u30fc\u30bf\u306e\u307e\u3068\u3081","author_name":"kazu-yamamoto","width":"100%","version":"1.0","height":"190","description":"\u4e0d\u52d5\u70b9 \u95a2\u6570 f :: a -> a \u306b\u5bfe\u3057\u3066\u3001f x == x \u3068\u306a\u308b x \u3092\u300c\u95a2\u6570 f \u306e\u4e0d\u52d5\u70b9\u300d\u3068\u3044\u3046\u3002\u3082\u3057\u3001\u95a2\u6570 f \u3092\u5165\u529b\u3068\u3057\u3066\u53d6\u308a\u3001\u95a2\u6570 f \u306e\u4e0d\u52d5\u70b9\u3092\u8fd4\u3059\u95a2\u6570 Y \u304c\u3042\u308b\u3068\u3059\u308c\u3070\u3001\u95a2\u6570 f \u306e\u4e0d\u52d5\u70b9\u3092 Y f \u3068\u8868\u73fe\u3067\u304d\u308b\u3002\u3053\u3053\u3067\u3001Y \u306e\u578b\u3092\u8abf\u3079\u308b\u3002\u5f15\u6570 f \u306e\u578b\u306f a -> a\u3001Y \u306f\u4e0d\u52d5\u70b9\u3092\u8fd4\u3059\u304b\u3089\u8fd4\u308a\u5024\u306e\u578b\u306f a\u3002\u3088\u3063\u3066\u3001Y :: (a -> a) -> a \u3068\u306a\u308b\u3002\u4e0d\u52d5\u70b9 x = Y f \u3092 f x == x \u306b\u4ee3\u5165\u3059\u308b\u3068\u3001Y f == f (Y f) \u3068\u306a\u308b\u3002\u3053\u308c\u3092 Haskell \u3067\u5b9f\u88c5\u3059\u308b\u3068\u3001\u95a2\u6570\u540d\u306b\u5927\u6587\u5b57\u304c\u4f7f\u3048\u308b\u3068\u3057\u3066\u3001\u4ee5\u4e0b\u306e\u3088\u3046\u306b\u306a\u308b\u3002 Y x = x (Y x\u2026"}