Requests for a "more general" threading macro are usually met with a
link to the thread where Rich says this is not needed and we should
not encourage functions that need threading anywhere except the first
or last position. I don't have the link handy (sorry).
The usual objection centers around the fact that whatever symbol is
used for the binding position then becomes a "varying" thing within
the expression:
(-newthread-> "x"
(str "y" :? "z")
(str "a" :? "b")
println)
Here :? means two different things which seems counter to how Clojure
works elsewhere...
Sean
On Mon, Jul 18, 2011 at 5:10 PM, Andreas Kostler
<[email protected]> wrote:
> Maybe you might find this useful
>
> (defmacro ->
> ([x] x)
> ([x form] (if (seq? form)
> (with-meta (replace {:? x} form) (meta form))
> (list form x)))
> ([x form & more] `(-> (-> ~x ~form) ~@more)))
>
> This allows for a more flexible threading operation:
>
> user> (-> "c"
> (third-param "a" "b" :? "d")
> println)
> first a second b third c fourth d
> nil
>
> Cheers
> Andreas
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