On Wed, Jan 27, 2010 at 8:52 AM, Jules <jules.gosn...@gmail.com> wrote:
>
> I have all the ctor arg types in my hand as well and went on to think
> that I could actually write a
>
> (defn make-ctor [class types] ...)
>
> which would return me :
>
> (fn [#^type1 arg1 #^type2 arg2...#^typen argn]...)
>
> then pass this off as the to-be-called-frequently fn mentioned above,
> but my efforts to write this still all ended up returning a fn that
> used eval, as above......
Both eval and reflection could solve your problem, but for
maximum performance you want to avoid doing either inside your
tight loop. I think you're on the right track with make-ctor,
but I'll call my make-factory, since it creates a fn that calls
ctors, not a fn that is a ctor:
(defn make-factory [class & arg-types]
(let [args (map #(with-meta (symbol (str "a" %1)) {:tag %2})
(iterate inc 1)
arg-types)]
(eval `(fn [...@args] (new ~class ~...@args)))))
Note that to use it, you need to pass in symbols for classes, not
classes themselves:
(def newInteger (make-factory 'Integer 'String))
Do that, and therefore the eval, outside your tight loop. Now
you have a nice, fast, non-reflective factory function you can
call inside your tight loop:
(newInteger "5")
;=> 5
Hope that helps.
--Chouser
http://joyofclojure.com/
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