Hi Pierre,

> On May 20, 2015, at 3:35 PM, Pierre Thibault <pierre.thibau...@gmail.com> 
> wrote:
> 
> Is possible to use the operator '@' alone? In the Joy Of Clojure book it is 
> presented as '~@'. I would like an example.

There are multiple contexts in which @ could be used. One is syntactic sugar 
for the deref function; @x is just (deref x), where x is some reference type 
like an atom.

~@, unquote-splice, is an entirely different beast. It is used inside 
syntax-quote (a backtick, `) in macros to mean “take all of these forms and put 
them into this form”, e.g.:

(let [xs ‘(1 2 3 4)]
  `(+ ~@xs))

turns into:

(+ 1 2 3 4)

… so the difference between it and just ~ is the “splicing”; regular unquote 
(~) would get you:

(+ [1 2 3 4])


hth
lvh


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