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Re: list-set! Wrong type argument in position 1 (expecting mutable pair)
From: |
Linus Björnstam |
Subject: |
Re: list-set! Wrong type argument in position 1 (expecting mutable pair) |
Date: |
Wed, 26 Aug 2020 22:43:32 +0200 |
User-agent: |
Cyrus-JMAP/3.3.0-232-g4bdb081-fm-20200825.002-g4bdb081a |
Literals are immutable. (list-set! '(1 2 3) 1 0) -> error.
(list-set! (list 1 2 3) 1 0) -> works
--
Linus Björnstam
On Wed, 26 Aug 2020, at 22:12, mbcladwell@stihie.net wrote:
>
> Hi,
> One shortcoming I find working with Guile is the limited number of
> examples of how to use code. Consider list-set!. The only reference in
> the entire Guile manual is the definition in section 6.6.9.6 List
> Modification. If I google I find
> https://docs.racket-lang.org/reference/pairs.html which gives me the
> example (list-set '(zero one two) 2 "two") ==> '(zero one "two") which
> is what I deduced from the Guile manual. If I try something similar
> in Guile:
>
> scheme@(guile-user)> (list-set! '("zero" "one" "twooooo") 2 "two")
> ice-9/boot-9.scm:1669:16: In procedure raise-exception:
> In procedure set-car!: Wrong type argument in position 1 (expecting
> mutable pair): ("twooooo")
>
> Entering a new prompt. Type `,bt' for a backtrace or `,q' to continue.
> scheme@(guile-user) [1]> ,bt
> 1 (list-set! ("zero" "one" "twooooo") 2 "two")
> In ice-9/boot-9.scm:
> 1669:16 0 (raise-exception _ #:continuable? _)
>
> Could someone provide me with an example of how to use list-set! ?
> Alternatively what I really need is how to modify a specified element
> in a list.
> Thanks
> Mortimer
>
>
>