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From: "B. Pym" <No_spamming@noWhere_7073.org>
Newsgroups: comp.lang.lisp
Subject: Re: Loopy
Date: Thu, 13 Jun 2024 03:13:11 -0000 (UTC)
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On 6/10/2024, B. Pym wrote:

> Peter Seibel wrote:
> 
>  >   (loop for x across array-of-numbers
>  >         minimizing x into min
>  >         maximizing x into max
>  >         summing x into total
>  >         counting t into count
>  >         finally (return (list min max (/ total count))))
> 
> 
> In Gauche Scheme, it's a one-liner.
> 
> (use gauche.sequence)
> 
> (define v #(0 2 -3 99 48 35 86 27 50 18))
> (define count (vector-length v))
> 
> 
> `(,(find-min v) ,(find-max v) ,(/ (fold + 0 v) count))
>   ===>
> (-3 99 181/5)

Another way.

(define v #(0 2 -3 99 48 35 86 27 50 18))
(define count (vector-length v))

(let ((r (mul-vec-reduce (list + max min) v)))
  (reverse (cons (/ (pop! r) count) r)))

  ===>
(-3 99 181/5)

Given:

(use srfi-43) ;; vector-fold

(define (mul-vec-reduce konses vec)
  (let ((len (length konses)))
    (vector-fold
      (lambda (i accum x)
        (if (null? accum)
          (make-list len x)
          (map
            (lambda (f a b) (f a b))
            konses
            (make-list len x)
            accum)))
      '()
      vec)))