[The Little Schemer]or

「The Little Schemer」P.21 ～

 

(or (null? '()) (atom? '(d e f g))) ;; => #t

 

(or (null? '(a b c)) (null? '())) ;; => #t

 

• or likes SQL's Coalesce.

 

(or (null? '(a b c)) (null? '(atom))) ;; => #f

 

• (or ...
  • asks two quesstions, one at a time. If the first one is true it stops and answers true. Otherwise it asks the second question and answers with whatever the second question answers.
  • 一度に二つの質問をしたとする。もし最初の一つがtrueであれば質問をやめ、trueを返す。そうでなければ、二つ目の質問をし、二つ目の質問の解を返す。