Those of you following the clojure repo on GitHub may have noticed this commit:
http://github.com/richhickey/clojure/commit/29389970bcd41998359681d9a4a20ee391a1e07c Now you can do things like this: user=> (defn funkymonkey [x y z & {:keys [a b c]}] [x y z a b c]) #'user/funkymonkey user=> (funkymonkey 1 2 3) [1 2 3 nil nil nil] user=> (funkymonkey 1 2 3 :b 5) [1 2 3 nil 5 nil] user=> (funkymonkey 1 2 3 :c 6 :a 4 :b 5) [1 2 3 4 5 6] Very nice! It feels smoothly integrated with the general destructuring infrastructure. You can also supply default values with the :or binder: user=> (defn funkymonkey [x y z & {:keys [a b c] :or {a -1 b -2 c -3}] [x y z a b c]) #'user/funkymonkey user=> (funkymonkey 1 2 3) [1 2 3 -1 -2 -3] user=> (funkymonkey 1 2 3 :b 5) [1 2 3 -1 5 -3] The great thing about :keys is that it cuts down on redundancy: you specify a symbol only once and it is dually interpreted as a map keyword and a lexically bound symbol. Since :keys already expects a flat sequence of symbols rather than arbitrary nested binding forms (otherwise this trick of dual interpretation wouldn't work), you could further cut down on the redundancy in the above :keys/:or idiom (which I expect would become commonplace with named arguments) by letting :keys elements optionally be two-element vectors with the second element supplying the default value: user=> (defn funkymonkey [x y z & {:keys [[a -1] [b -2] [c -3]]] [x y z a b c]) What do you think? I hacked this into my local version of core.clj's destructure and it feels very natural to me. -Per -- You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en To unsubscribe from this group, send email to clojure+unsubscribegooglegroups.com or reply to this email with the words "REMOVE ME" as the subject.
