On Fri, Jul 31, 2015 at 1:57 PM, Eduardo Aquiles Affonso Radanovitsck <
eduardoaquiles...@gmail.com> wrote:
> Not sure if this is expected or not:
>
> (map (fn [v] {:k v}) #{1 2 3})
> => ({:k 1} {:k 3} {:k 2})
> (map #({:k %}) #{1 2 3})
> ArityException Wrong number of args (0) passed to: PersistentArrayMap
> clojure.lang.AFn.throwArity (AFn.java:429)
>
The same behavior is visible in earlier versions of clojure and has to do
with how the #(...) syntax is parsed. The workaround is #(do {:k %}).
Basically, whatever occurs between the #( and the ) is spliced into a list,
so if you have just one single expression, it turns into a function call:
user=> (defmacro p [k] (println k))
#'user/p
user=> (p #({:k %}))
(fn* [p1__7143#] ({:k p1__7143#})) ;; <---- attempting to invoke a map
with zero args
nil
user=> (p #(do {:k %}))
(fn* [p1__7144#] (do {:k p1__7144#}))
nil
--
Ben Wolfson
"Human kind has used its intelligence to vary the flavour of drinks, which
may be sweet, aromatic, fermented or spirit-based. ... Family and social
life also offer numerous other occasions to consume drinks for pleasure."
[Larousse, "Drink" entry]
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