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comp / comp.lang.lisp / .Re: simple lisp function

SubjectAuthor
* .Re: simple lisp functionB. Pym
+* Re: .Re: simple lisp functionHenHanna
|`- Re: .Re: simple lisp functionsteve g
`- Re: .Re: simple lisp functionB. Pym

1
Subject: .Re: simple lisp function
From: B. Pym
Newsgroups: comp.lang.lisp
Organization: A noiseless patient Spider
Date: Thu, 6 Jun 2024 10:38 UTC
Path: eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail
From: No_spamming@noWhere_7073.org (B. Pym)
Newsgroups: comp.lang.lisp
Subject: .Re: simple lisp function
Date: Thu, 6 Jun 2024 10:38:54 -0000 (UTC)
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Pascal Bourguignon wrote:

> > this simple function i'm trying to write is giving me headaches!
> > basically i want to do something that does:
> > (variations 'x '(y z)) -> ((x y z) (y x z) (y z x))
> >
> > i come from a procedural programming background and find functional
> > programming very confusing (especially recursion). can someone give
> > me some hints? my attempts at this make no sense so pasting them here
> > would only confirm my newbish forray into LSIP. thanks for any help!
>
> (defun variations (item list)
> (if (null list)
> (list (list item))
> (cons (cons item list)
> (mapcar (lambda (rest) (cons (car list) rest))
> (variations item (cdr list))))))

Gauche Scheme:

(use srfi-1) ;; split-at
(use srfi-42) ;; list-ec

(define (variations x lst)
(list-ec (: i (+ 1 (length lst)))
(receive (a b) (split-at lst i)
`(,@a ,x ,@b))))

(variations '- '(a b c))
===>
((- a b c) (a - b c) (a b - c) (a b c -))

(variations '- '(a))
===>
((- a) (a -))

(variations '- '())
===>
((-))

Subject: Re: .Re: simple lisp function
From: HenHanna
Newsgroups: comp.lang.lisp
Organization: novaBBS
Date: Thu, 6 Jun 2024 20:21 UTC
References: 1
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From: HenHanna@dev.null (HenHanna)
Newsgroups: comp.lang.lisp
Subject: Re: .Re: simple lisp function
Date: Thu, 6 Jun 2024 20:21:06 +0000
Organization: novaBBS
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B. Pym wrote:

> Pascal Bourguignon wrote:

>> > this simple function i'm trying to write is giving me headaches!
>> > basically i want to do something that does:
>> > (variations 'x '(y z)) -> ((x y z) (y x z) (y z x))
>> >
>> > i come from a procedural programming background and find functional
>> > programming very confusing (especially recursion). can someone give
>> > me some hints? my attempts at this make no sense so pasting them
>> here
>> > would only confirm my newbish forray into LSIP. thanks for any help!
>>
>> (defun variations (item list)
>> (if (null list)
>> (list (list item))
>> (cons (cons item list)
>> (mapcar (lambda (rest) (cons (car list) rest))
>> (variations item (cdr list))))))

> Gauche Scheme:

> (use srfi-1) ;; split-at
> (use srfi-42) ;; list-ec

> (define (variations x lst)
> (list-ec (: i (+ 1 (length lst)))
> (receive (a b) (split-at lst i)
> `(,@a ,x ,@b))))

> (variations '- '(a b c)) ===> ((- a b c) (a - b c) (a b - c) (a b
> c -))
> (variations '- '(a)) ===> ((- a) (a -))
> (variations '- '()) ===> ((-))

I remember writing this in Lisp and Python. a few years ago.

Is Scheme (or Gauche) used outside of the Academia?

What kind of people (other than Grad students, Researchers in
Prog.Lang design)
would know about Split-at and List-ec and Receive
?

Subject: Re: .Re: simple lisp function
From: B. Pym
Newsgroups: comp.lang.lisp
Organization: A noiseless patient Spider
Date: Thu, 6 Jun 2024 23:31 UTC
References: 1
Path: eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail
From: No_spamming@noWhere_7073.org (B. Pym)
Newsgroups: comp.lang.lisp
Subject: Re: .Re: simple lisp function
Date: Thu, 6 Jun 2024 23:31:05 -0000 (UTC)
Organization: A noiseless patient Spider
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On 6/6/2024, B. Pym wrote:

> Pascal Bourguignon wrote:
>
> > > this simple function i'm trying to write is giving me headaches!
> > > basically i want to do something that does:
> > > (variations 'x '(y z)) -> ((x y z) (y x z) (y z x))
> > >
> > > i come from a procedural programming background and find functional
> > > programming very confusing (especially recursion). can someone give
> > > me some hints? my attempts at this make no sense so pasting them here
> > > would only confirm my newbish forray into LSIP. thanks for any help!
> >
> > (defun variations (item list)
> > (if (null list)
> > (list (list item))
> > (cons (cons item list)
> > (mapcar (lambda (rest) (cons (car list) rest))
> > (variations item (cdr list))))))
>
> Gauche Scheme:
>
> (use srfi-1) ;; split-at
> (use srfi-42) ;; list-ec
>
> (define (variations x lst)
> (list-ec (: i (+ 1 (length lst)))
> (receive (a b) (split-at lst i)
> `(,@a ,x ,@b))))
>
> (variations '- '(a b c))
> ===>
> ((- a b c) (a - b c) (a b - c) (a b c -))
>
> (variations '- '(a))
> ===>
> ((- a) (a -))
>
> (variations '- '())
> ===>
> ((-))
>

Gauche or Racket Scheme:

(use srfi-42) ;; list-ec for Gauche
or
(require srfi/42) ;; list-ec for Racket

(define (variations item seq)
(list-ec (: i (+ 1 (length seq)))
`(,@(take seq i) ,item ,@(drop seq i))))

Subject: Re: .Re: simple lisp function
From: steve g
Newsgroups: comp.lang.lisp
Date: Sat, 10 Aug 2024 17:33 UTC
References: 1 2
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NNTP-Posting-Date: Sat, 10 Aug 2024 17:33:15 +0000
From: sgonedes1977@gmail.com (steve g)
Newsgroups: comp.lang.lisp
Subject: Re: .Re: simple lisp function
References: <v3s3jt$1fhlp$1@dont-email.me>
<806cc1215afc0176956ea8bfdb3cbcff@www.novabbs.com>
Date: Sat, 10 Aug 2024 13:33:15 -0400
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HenHanna <HenHanna@dev.null> writes:

> B. Pym wrote:
>
< > Pascal Bourguignon wrote:
>
< >> > this simple function i'm trying to write is giving me headaches!
< >> > basically i want to do something that does:
< >> > (variations 'x '(y z)) -> ((x y z) (y x z) (y z x))
< >> >
< >> > i come from a procedural programming background and find functional
< >> > programming very confusing (especially recursion). can someone give
< >> > me some hints? my attempts at this make no sense so pasting them
< >> here
< >> > would only confirm my newbish forray into LSIP. thanks for any help!
< >> (defun variations (item list)
< >> (if (null list)
< >> (list (list item))
< >> (cons (cons item list)
< >> (mapcar (lambda (rest) (cons (car list) rest))
< >> (variations item (cdr list))))))
>
< > Gauche Scheme:
>
< > (use srfi-1) ;; split-at
< > (use srfi-42) ;; list-ec
>
< > (define (variations x lst)
< > (list-ec (: i (+ 1 (length lst)))
< > (receive (a b) (split-at lst i)
< > `(,@a ,x ,@b))))
>
< > (variations '- '(a b c)) ===> ((- a b c) (a - b c) (a b - c) (a b
< > c -))
< > (variations '- '(a)) ===> ((- a) (a -))
< > (variations '- '()) ===> ((-))
>
>
> I remember writing this in Lisp and Python. a few years ago.
>
>
> Is Scheme (or Gauche) used outside of the Academia? What kind of people
> (other than Grad students, Researchers in
> Prog.Lang design)
> would know about Split-at and List-ec and Receive ?

lisp programmers?

CL-USER> (mapcon #'list '(X 1 2 3 4))
((X 1 2 3 4) (1 2 3 4) (2 3 4) (3 4) (4))

1

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