On 8 déc, 23:13, "Michael Reid" <[EMAIL PROTECTED]> wrote:
> Then I of course write the implementations for various different
> types. Then, because the multi-method names don't look nice, I wrote a
> macro which transformed the regular operators into calls on the
> multi-methods, i.e.:
>
> (macroexpand-1 '(extended-math (* 3 A))) --> (mul 3 A)
>
> Its still not as clean as a having the operators defined as
> multi-methods from the get-go, but you don't have to muck with
> overriding the core names.
I was trying to do it with namespace but :
ns scratch
(:refer-clojure :exclude [+ - * /])
(:use clojure.contrib.def))
(defalias * clojure.core/*)
(* 2 5) ; 10
(defalias / clojure.core//)
;; #<Exception java.lang.Exception: Invalid token: scratch//>
Didn't find why it work in core.clj ???
> One reason to leave the core operators alone is performance.
> Multi-method dispatch is far more expensive than a regular dispatch. I
> don't have this in front of me to get some real numbers, but when I
> tested, the same operations with the multi-methods were about 10x
> slower than the direct dispatch.
Yes, but it give you some nice abstractions :
sort fallback to Comparable interface.
If not you would use sort-by and provide a function.
An other example :
public interface IPersistentVector extends Associative, Sequential,
IPersistentStack, Reversible
seq & co make Clojure nice and efficient.
But I didn't see a simple way to do it in Clojure (it self).
May be :
(gen-type
:name AType
:extends [Types...]
:methods [aMethode names...])
(gen-instance
:name AnInstance
:extends [AType Types...])
(defmethod aMethode [#^AnInstance param]
(print (param any:)))
(def aVar (AnInstance. {any: "Data"}))
(aMethode (aVar))
Some day, I would try to do it.
pierre
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