[Clojure] 空リストか否か

Clojure では nil と空リストは同じではない。

  (= nil '()) => false

よって、再帰の停止条件などでは空リストか否かを返す述語 empty? を使う。

  (defn sum [lst]
    (if (empty? lst)
      0
      (+ (first lst) (sum (rest lst)))))

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Deprecated: Creation of dynamic property WP_Term::$category_count is deprecated in /usr/home/bugyo/public_html/b-log/wp-includes/category.php on line 379

Deprecated: Creation of dynamic property WP_Term::$category_description is deprecated in /usr/home/bugyo/public_html/b-log/wp-includes/category.php on line 380

Deprecated: Creation of dynamic property WP_Term::$cat_name is deprecated in /usr/home/bugyo/public_html/b-log/wp-includes/category.php on line 381

Deprecated: Creation of dynamic property WP_Term::$category_nicename is deprecated in /usr/home/bugyo/public_html/b-log/wp-includes/category.php on line 382

Deprecated: Creation of dynamic property WP_Term::$category_parent is deprecated in /usr/home/bugyo/public_html/b-log/wp-includes/category.php on line 383
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