Scheme - Scheme idiom or Scheme extension?

Author

Scheme idiom or Scheme extension?

Marco Antoniotti

2004-03-27, 12:25 am

Hi

I was going through Sussman's "Structure and Implementation of Classical
Mechanics" (http://www-swiss.ai.mit.edu/~gjs/69...html/index.html)
and came upon the following idiom:

(define ((L-free-particle mass) local)
(let ((v (velocity local)))
(* 1/2 mass (dot-product v v))))

AFAIK this ain't R^nRS. What is the semantics of the above? I tried to
look around nearby links, but then I decided it'd be easier just to ask.

Cheers

marco

Jean-François Trevien

2004-03-27, 12:25 am

"Marco Antoniotti" <marcoxa@cs.nyu.edu> a écrit dans le message de
news:CW%5c.105$IJ5.80720@typhoon.nyu.edu...
> Hi
>
> I was going through Sussman's "Structure and Implementation of Classical
> Mechanics" (http://www-swiss.ai.mit.edu/~gjs/69...html/index.html)
> and came upon the following idiom:
>
> (define ((L-free-particle mass) local)
> (let ((v (velocity local)))
> (* 1/2 mass (dot-product v v))))
>
> AFAIK this ain't R^nRS. What is the semantics of the above? I tried to
> look around nearby links, but then I decided it'd be easier just to ask.
>
It has been in R3RS as far as i remenber. In R5RS it must be written:
(define (L-free-particle mass)
(lambda (local)
(let ((v (velocity local)))
(* 1/2 mass (dot-product v v)))))

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