Hi,
On Aug 4, 2:32 am, Yang Dong <ydong.pub...@gmail.com> wrote:
> Thank you! I have just another question not related about this topic:
>
> ;during bootstrap we don't have destructuring let, loop or fn, will
> redefine later
> (def
> ^{:macro true
> :added "1.0"}
> let (fn* let [&form &env & decl] (cons 'let* decl)))
>
> In Clojure 1.2.0, the preceding definition of let taks the strange
> argument of `&form' and `&env'. What are they?
user=> (defmacro foo [x y] (prn &form) (prn &env) `(+ ~x ~y))
#'user/foo
user=> (let [x 5] (foo x 6))
(foo x 6)
{x #<LocalBinding clojure.lang.compiler$localbind...@13f991>}
11
&form contains the form how the macro was called. &env contains local
bindings in the macro environment. (At least this is what my little
test shows...) These magic parameters are given to all parameters, but
usually hidden. It's probably safe to ignore them if you don't know
what they really do.
Sincerely
Meikel
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