On 13 Nov., 17:07, Rich Hickey <richhic...@gmail.com> wrote:
> This kind of do-nothing microbenchmarking demonstrates nothing.
> Protocol dispatching is significantly faster than multimethod
> dispatching, and I haven't even looked into call-site optimization.
> Protocol dispatch is not as fast as interface dispatch, and may or may
> not become so with call-site caching. But, protocols :on interfaces
> are precisely as fast when called with instances of the :on interface
> as calls to the :on interface.
Forget what I said about Performance, I didn't realize that the
functions could be mapped to interface-methods. When mapped to an
interface they get JITed to awesome speeds :-)
> I wouldn't want to key anything off of fn identity. It would make
> mixins quite difficult.
This was just a minor thought of mine, if it impedes with this awesome
literal mixin concept then I gladly take those mixins.
(def composed-mixin (merge mixin-a mixin-b mixin-c))
seems absolutely logical and natural
>
> .......
>
> Admittedly, it is a difference from multimethods. With protocols, both
> protocols and their functions/methods are immutable. Redefining or
> extending a protocol modifies only the protocol and fn vars. I prefer
> that, and don't consider the above behavior a problem. What do others
> think?
>
> Rich
that was a bad Example probably...
hypothetical example for impementing the type function as a
Protocolfn:
(defprotocol Typed (my-type [obj] "Doc.."))
Typed
(extend Object Typed {:my-type (fn [obj] (.getClass obj))})
nil
(defmulti foo my-type)
#'user/foo
(extend clojure.lang.IObj Typed {:my-type (fn [obj] (if (:type ^obj)
(:type ^obj) (.getClass obj)))})
now our foo multifn woudn't work as expected (by me at least).
I just didn't expect that (extend <sth> <Type> <fn-map>) would
redefine some Vars.
extend has to mutate something, but I think that redefining some Vars
is wierder (and thus should be explicit via a visible (def ...))
than mutating the "generic function" (I may be biased by CLOS of
course)
Alex
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