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Re: general lazy list facility for Emacs Lisp?
From: |
Tassilo Horn |
Subject: |
Re: general lazy list facility for Emacs Lisp? |
Date: |
Wed, 23 Mar 2011 20:10:27 +0100 |
User-agent: |
Gnus/5.110016 (No Gnus v0.16) Emacs/24.0.50 (gnu/linux) |
Tassilo Horn <address@hidden> writes:
> I think for "real" memoization, you need clojures. However, I think
> you can simulate memoization with a macro like that (tested only very
> briefly).
>
> (defmacro memoize (name fun)
> (let ((map-name (gensym "memo-map"))
> (args-name (gensym))
> (val-name (gensym)))
> `(progn
> (defvar ,map-name (make-hash-table :test 'equal))
> (defun ,name (&rest ,args-name)
> (let ((,val-name (gethash ,args-name ,map-name)))
> (if ,val-name
> ,val-name
> (puthash ,args-name (apply (quote ,fun) ,args-name)
> ,map-name)))))))
Just a short remark on what I've had in mind with "real" memoization: If
elisp had closures (not clojures ;-)), then one could write memoize as
function, just like the variant in the clojure source code below:
--8<---------------cut here---------------start------------->8---
(defn memoize
[f]
(let [mem (atom {})]
(fn [& args]
(if-let [e (find @mem args)]
(val e)
(let [ret (apply f args)]
(swap! mem assoc args ret)
ret)))))
--8<---------------cut here---------------end--------------->8---
Bye,
Tassilo
- general lazy list facility for Emacs Lisp?, Ted Zlatanov, 2011/03/23
- Re: general lazy list facility for Emacs Lisp?, Tassilo Horn, 2011/03/23
- Re: general lazy list facility for Emacs Lisp?, Ted Zlatanov, 2011/03/23
- Re: general lazy list facility for Emacs Lisp?, Thierry Volpiatto, 2011/03/23
- Re: general lazy list facility for Emacs Lisp?, Ted Zlatanov, 2011/03/23
- Re: general lazy list facility for Emacs Lisp?, Thierry Volpiatto, 2011/03/23
- Re: general lazy list facility for Emacs Lisp?, Ted Zlatanov, 2011/03/23
- Re: general lazy list facility for Emacs Lisp?, Ted Zlatanov, 2011/03/23
- Re: general lazy list facility for Emacs Lisp?, Tassilo Horn, 2011/03/23
- Re: general lazy list facility for Emacs Lisp?,
Tassilo Horn <=
- Re: general lazy list facility for Emacs Lisp?, Ted Zlatanov, 2011/03/23
- Re: general lazy list facility for Emacs Lisp?, Eric Schulte, 2011/03/24
- Re: general lazy list facility for Emacs Lisp?, Ted Zlatanov, 2011/03/24
- Re: general lazy list facility for Emacs Lisp?, Eric Schulte, 2011/03/25
- Re: general lazy list facility for Emacs Lisp?, Stefan Monnier, 2011/03/23
- Re: general lazy list facility for Emacs Lisp?, Jason Earl, 2011/03/23
- Re: general lazy list facility for Emacs Lisp?, Tassilo Horn, 2011/03/23
- Re: general lazy list facility for Emacs Lisp?, Tassilo Horn, 2011/03/23
- Re: general lazy list facility for Emacs Lisp?, Tassilo Horn, 2011/03/23
- Re: general lazy list facility for Emacs Lisp?, Stefan Monnier, 2011/03/23