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From: "B. Pym" <Nobody447095@here-nor-there.org>
Newsgroups: comp.lang.lisp,comp.lang.scheme
Subject: Re: Learning Lisp in Linux?
Date: Sun, 22 Jun 2025 20:44:57 -0000 (UTC)
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B. Pym wrote:

> Pascal Costanza wrote:
> 
> > > I'm not advocating tail-recursion instead of specialized iteration
> > > mechanisms closer to the problem domain.  I'm just saying tail-
> > > recursion code isn't anywhere as low-level as you're making it up to
> > > be.
> > 
> > It actually is, and your posting below shows it very nicely.
> > 
> > >> Here is a nice example using loop:
> > > > 
> > >> (loop for (key value) on property-list by #'cddr
> > >>        unless (member key excluded-keys)
> > >>        append (list key value)) ; [1]
> > 
> > As a function:
> > 
> > (defun filter (excluded-keys property-list)
> >    (loop for (key value) on property-list by #'cddr
> >          unless (member key excluded-keys)
> >          nconc (list key value)))
> > 
> >  > (filter '(c d) '(a 1 b 2 b 3 c 4 d 5 c 6))
> > (A 1 B 2 B 3)
> > 
> > The result is a correct property list
> 
> Gauche Scheme
>  
> (define (remove-props bad-keys prop-list)
>   (concatenate
>     (remove (^p (member (car p) bad-keys))
>       (slices prop-list 2))))
> 
> (remove-props '(c d) '(a 1 b 2 b 3 c 4 d 5 c 6))
>   ===>
> (a 1 b 2 b 3)

Using "is":

(define (remove-props bad-keys prop-list)
  (concatenate
    (remove (is car member bad-keys)
      (slices prop-list 2))))


Given:

(define is
  (case-lambda
    [(x) (lambda(y) (equal? y x))]
    [(pred x) (lambda(y) (pred y x))]
    [(key pred x) (lambda(y) (pred (key y) x))]))