9.5.2 catch¤Èthrow¤ÎÎã

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(defun search-foo ()
  (catch 'loop
    (let ((i 0))
      (while (< i 10)
        (let ((j 0))
          (while (< j 10)
            (if (foo i j)
                (throw 'loop (list i j)))
            (setq j (1+ j))))
        (setq i (1+ i))))))

foo¤¬¤¢¤ë»þÅÀ¤Çnil°Ê³°¤òÊÖ¤¹¤È¡¢ ¤¿¤À¤Á¤Ë»ß¤Þ¤Ã¤Æi¤Èj¤Î¥ê¥¹¥È¤òÊÖ¤·¤Þ¤¹¡£ foo¤¬¤Ä¤Í¤Ënil¤òÊÖ¤¹¤È¡¢ catch¤ÏÄ̾ï¤É¤ª¤ê¤ËÌá¤Ã¤Æ¡¢¤½¤ÎÃͤÏnil¤Ç¤¹¡£ ¤È¤¤¤¦¤Î¤Ï¡¢while¤Î·ë²Ì¤Ïnil¤À¤«¤é¤Ç¤¹¡£

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(defun catch2 (tag)
  (catch tag
    (throw 'hack 'yes)))
⇒ catch2

(catch 'hack 
  (print (catch2 'hack))
  'no)
-| yes
⇒ no

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(defun catch2 (tag)
  (catch tag
    (throw 'hack 'yes)))
⇒ catch2

(catch 'hack
  (print (catch2 'quux))
  'no)
⇒ yes

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