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comp / comp.lang.scheme / Re: applying macros

Subject: Re: applying macros
From: B. Pym
Newsgroups: comp.lang.lisp, comp.lang.scheme
Organization: A noiseless patient Spider
Date: Thu, 19 Sep 2024 07:32 UTC

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From: Nobody447095@here-nor-there.org (B. Pym)
Newsgroups: comp.lang.lisp,comp.lang.scheme
Subject: Re: applying macros
Date: Thu, 19 Sep 2024 07:32:45 -0000 (UTC)
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Rainer Joswig wrote:

> (defun average-function (list)
> (assert list (list)
> "List should not be empty.")
> (loop for i from 0
> for item in list
> sum item into result
> finally (return (/ result i))))

It's shorter in Gauche Scheme.

(define (average-function lst)
(let1 n 0
(/ (fold (lambda (x sum) (inc! n) (+ x sum)) 0 lst)
n)))

Subject: Re: applying macros
From: B. Pym
Newsgroups: comp.lang.lisp, comp.lang.scheme
Organization: A noiseless patient Spider
Date: Thu, 19 Sep 2024 08:45 UTC
References: 1

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From: Nobody447095@here-nor-there.org (B. Pym)
Newsgroups: comp.lang.lisp,comp.lang.scheme
Subject: Re: applying macros
Date: Thu, 19 Sep 2024 08:45:16 -0000 (UTC)
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B. Pym wrote:

> Rainer Joswig wrote:
>
> > (defun average-function (list)
> > (assert list (list)
> > "List should not be empty.")
> > (loop for i from 0
> > for item in list
> > sum item into result
> > finally (return (/ result i))))
>
> It's shorter in Gauche Scheme.
>
> (define (average-function lst)
> (let1 n 0
> (/ (fold (lambda (x sum) (inc! n) (+ x sum)) 0 lst)
> n)))

Another way.

(define (average-function lst)
(let1 n 0
(/ (@ fold x sum : (inc! n) (+ x sum) : 0 lst)
n)))

Given:

(define-syntax @-aux
(syntax-rules (:)
;; No parameters given; use "cut".
[(_ func () ((e0 e ...)) : stuff ...)
(func (cut e0 e ...) stuff ...)]
[(_ func vars (e0 e ...) : stuff ...)
(func (lambda vars e0 e ...) stuff ...)]
[(_ func vars (e0 e ...) expr more ...)
(@-aux func vars (e0 e ... expr) more ...)]
[(_ func vars () : expr more ...)
(@-aux func vars (expr) more ...)]
[(_ func (vars ...) () var more ...)
(@-aux func (vars ... var) () more ...)]))

(define-syntax @
(syntax-rules ()
[(_ func stuff ...)
(@-aux func () () stuff ...)]))

Subject	Author
Re: applying macros	B. Pym
Re: applying macros	B. Pym