Does anybody else feel that (fnil) should delay evaluation of its argument?
Maybe I've been abusing mutability a bit too much, but for a map which
refers to mutable object instances, I've found this useful:
(defmacro fnil*
"Delayed evaluation version of fnil, where the default expression
gets
evaluated every time it is required."
([f x]
`(fn
([a#] (~f (if (nil? a#) ~x a#)))
([a# b#] (~f (if (nil? a#) ~x a#) b#))
([a# b# c#] (~f (if (nil? a#) ~x a#) b# c#))
([a# b# c# & ds#] (apply ~f (if (nil? a#) ~x a#) b# c# ds#))))
([f x ~y]
`(fn
([a# b#] (~f (if (nil? a#) ~x a#) (if (nil? b#) ~y b#)))
([a# b# c#] (~f (if (nil? a#) ~x a#) (if (nil? b#) ~y b#) c#))
([a# b# c# & ds#] (apply ~f (if (nil? a#) ~x a#) (if (nil? b#) ~y
b#) c# ds#))))
([f x ~y ~z]
`(fn
([a# b#] (~f (if (nil? a#) ~x a#) (if (nil? b#) ~y b#)))
([a# b# c#] (~f (if (nil? a#) ~x a#) (if (nil? b#) ~y b#) (if (nil?
c#) ~z c#)))
([a# b# c# & ds#] (apply ~f (if (nil? a#) ~x a#) (if (nil? b#) ~y
b#) (if (nil? c#) ~z c#) ds#)))))
--
You received this message because you are subscribed to the Google
Groups "Clojure" group.
To post to this group, send email to [email protected]
Note that posts from new members are moderated - please be patient with your
first post.
To unsubscribe from this group, send email to
[email protected]
For more options, visit this group at
http://groups.google.com/group/clojure?hl=en
