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comp / comp.lang.lisp / Re: applying f to f n times - best argument order?

SubjectAuthor
* Re: applying f to f n times - best argument order?B. Pym
`* Re: applying f to f n times - best argument order?Jeff Barnett
 `- Re: applying f to f n times - best argument order?Madhu

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Subject: Re: applying f to f n times - best argument order?
From: B. Pym
Newsgroups: comp.lang.lisp
Organization: A noiseless patient Spider
Date: Sun, 25 Aug 2024 10:04 UTC
Path: eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail
From: Nobody447095@here-nor-there.org (B. Pym)
Newsgroups: comp.lang.lisp
Subject: Re: applying f to f n times - best argument order?
Date: Sun, 25 Aug 2024 10:04:49 -0000 (UTC)
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Kaz Kylheku wrote:

> You want to bounce the arguments down into the recursive call, not a
> list of them as one argument, right?
>
> Is this what you are looking for:
>
> (defun ncall (f n &rest data)
> (loop repeat n
> for result = (apply f data) then (funcall f result)
> finally (return result)))
(define (feedback func init bottom-i :optional (top-i #f))
(let ((result init))
(if top-i
(do ((i bottom-i (+ 1 i)))
((> i top-i) result)
(set! result (func result i)))
(dotimes (i bottom-i)
(set! result (func result))))
result))

;; factorial
(feedback (lambda (prod i) (* i prod)) 1 1 5)
===>
120

(feedback (lambda (prod) (* 2 prod)) 1 8)
===>
256

;; Newton square root
(let ((x 99.0))
(feedback
(lambda (guess) (/. (+ guess (/. x guess)) 2.0))
1.0 8))
===>
9.9498743710662

(sqrt 99)
===>
9.9498743710662

Subject: Re: applying f to f n times - best argument order?
From: Jeff Barnett
Newsgroups: comp.lang.lisp
Organization: A noiseless patient Spider
Date: Sun, 25 Aug 2024 18:50 UTC
References: 1
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From: jbb@notatt.com (Jeff Barnett)
Newsgroups: comp.lang.lisp
Subject: Re: applying f to f n times - best argument order?
Date: Sun, 25 Aug 2024 12:50:21 -0600
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On 8/25/2024 4:04 AM, B. Pym wrote:
> Kaz Kylheku wrote:
>
>> You want to bounce the arguments down into the recursive call, not a
>> list of them as one argument, right?
>>
>> Is this what you are looking for:
>>
>> (defun ncall (f n &rest data)
>> (loop repeat n
>> for result = (apply f data) then (funcall f result)
>> finally (return result)))
>
> (define (feedback func init bottom-i :optional (top-i #f))
> (let ((result init))
> (if top-i
> (do ((i bottom-i (+ 1 i)))
> ((> i top-i) result)
> (set! result (func result i)))
> (dotimes (i bottom-i)
> (set! result (func result))))
> result))

Isn't this where you usually jump in and loudly proclaim "SHORTER!"? You
might as well repeat it hear since you are not shorter a significant
amount of the time.

Off topic question: Any job offers recently?

> ;; factorial
> (feedback (lambda (prod i) (* i prod)) 1 1 5)
> ===>
> 120
>
>
> (feedback (lambda (prod) (* 2 prod)) 1 8)
> ===>
> 256
>
>
> ;; Newton square root
> (let ((x 99.0))
> (feedback
> (lambda (guess) (/. (+ guess (/. x guess)) 2.0))
> 1.0 8))
> ===>
> 9.9498743710662
>
> (sqrt 99)
> ===>
> 9.9498743710662
--
Jeff Barnett

Subject: Re: applying f to f n times - best argument order?
From: Madhu
Newsgroups: comp.lang.lisp
Organization: Motzarella
Date: Mon, 26 Aug 2024 05:04 UTC
References: 1 2
Path: eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail
From: enometh@meer.net (Madhu)
Newsgroups: comp.lang.lisp
Subject: Re: applying f to f n times - best argument order?
Date: Mon, 26 Aug 2024 10:34:31 +0530
Organization: Motzarella
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memo: there's no glory in trolling WJ

* Jeff Barnett <vafudd$220kj$1@dont-email.me> :
Wrote on Sun, 25 Aug 2024 12:50:21 -0600:

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